Does anyone care to ask an amplifier designer a technical question? My door is open.

@stargazer3   OP do you believe in the burn in process of an amp that over time the sound will settle and finally focus on a cohesive musical experience or is it to your opinion all in our brain that is adjusting to the sound of the component? When I mention burn in process its regard to periods of 300hrs and more (eg Naim or Simaudio Moon amps).

Speakers for sure. The are mechanical devices that have to loosen up. I hook up my woofers and drive them hard for a few days and can measure the resonant frequency drop a few Hz.

Amplifiers, only the tubes. When it comes to electronics and wire I believe the listener is becoming accustomed to the change. 

For those who will likely disagree: If burn in exists in these devices why did we not know about it until recently. I find no references to burn in in the 50s 60s 70s.. when did it start? 

I know the manufacturers love the idea because it gives them a reason for you to get used to the product. They are certainly going to promote the idea. 

With digital devics I really have to wonder what is burning in. The digits?

We always burn in amplifiers to find infant mortality. We would rather have an amplifier break in our shop than in your home. This process is well documented and 24 hours usually does the trick. The failures are very rare and most often just a tube. We even cycle the amps on and off many times to temperature cycle the glass which is what usually fails but its just 1 out of 100 tubes.

With tubes  I always set the idle current (bias) 10 % low because I know it will come up a little in the first 100 hours. 

@ieales 

minimize artifacts occurring from the interconnect cable between the preamp and amp.

A second reason is that a preamp can provide a fairly high impedance load for the source

Source output 22R, amp inputs 23k5 or 100K. Adding a preamp with attendant switching, circuitry, noise and additional cables is little more than a subtle tone control. It maybe different, but it may not be better.

I agree with ieales and not the answer given above his, but then you all know that. What are these artifacts, are they Egyptian?

@apogee141516 apogee141516176 posts12-07-2018 5:25amThis is kind of an obtuse question, but why do some amplifier manufactures say to use a preamp between their amplifiers and the streamer when you are only using a streamer and power amp, no vinyl and no other sources. I understand the need for a volume control and to have the impedance's low for the streamer/DAC and high for the power amp. My streamer/Dac is <100 ohms and the power amp is 47K. There is an implication that the preamp does other things that affect the SQ. Any idea what those are? An Allegri+ addresses the impedance problem and give a volume control and is extraordinarily transparent on my Ribbon Speakers.  My amp and steamer is very high end. Is there more?

 

Perhaps the amplifier maker hopes you will buy his preamp. You are correct, there is no need for one.

Sorry this post is gonna look strange. The operation of this app is wonky, but its free.



 

@bdp24

@ramtubes, Here's a question for you Roger regarding a matter that was being discussed amongst Maggie owners on The Planar Speaker Asylum forum yesterday. One poster said of hearing from tube amps something I too hear, and that is of a sound stage that begins in front of the loudspeakers.

I heard that for the first time when Bill Johnson played an LP of Holst's The Planets (in 1973 at Audio Arts in Livermore, after he finished setting up his complete system in the shops really good room), a recording made in a large hall. The front of the orchestra was clearly located between myself and the front plane of the Magneplanar Tympani T-I's, and the rear of the orchestra was waaay back behind the speakers, sounding as if it was actually further away than was the wall behind the Maggies. I could hear the delicate triangle in the rhythm section, elevated on risers, playing in the quieter sections of the piece. It was thrilling!

Prior to that experience, at Sound Systems in Palo Alto I had heard a pair of the original Infinity Servo-Static ESL's, powered by the then-new line of SAE electronics. Through that system I did NOT hear the image "thrown" forward of the speakers. I have subsequently heard the forward image (and great depth) from other systems (including my own), but only when the electronics are tubed.

So my question is, why is it tubes are able to do that? Is it a matter of tubes being lowest in distortion at lower-signal levels (where imaging resides?), and transistors in their curves highest?

Thanks for throwing the ball my way.  

I would like to say its a property of tubes but I rather think its a property of how well the system was set up. I dont feel ampifiers have much to do with imaging. I don't see how they can. However I think they sound better than SS and therefore the system sounds better. When the system sounds better all sorts of nice things happen.

If you want to hear great imaging like you have never heard before find someone with properly set up Beveridge ESLs., the Direct Drive ones. They have 180 degree dispersion at all frequencies and properly set up FACE each other sending sound directly to you, directly to the middle and directly to the back wall which must be at least 6 feet away. Not many rooms will allow these set up distances. Ideally the room is 11 ft wide and 24 feet long or longer. Then the back of the sound stage is 2x6 feet or 12 feet deep. Its really cool. 

@krelldreams My verdict, with this passive unit, in my system is as follows: The system with the passive has clear high and mid frequencies, good space, and sounds spacious... but it is a bit brighter, a bit leaner, and is less pleasant to listen to than with the preamp. I’d call the sound with the preamp “smoother” and “warmer”. The vocals through the preamp were slightly veiled compared to the passive though, which annoyed me. So.. after this exercise, I believe that either a better quality passive, or a more transparent preamp, is what I’d want. What design elements could improve the sound of a passive device? Clio wrote about a phono preamp with passive level control and aux inputs. What a great idea!

We make those phono preamps with a aux for people who appreciate that kind of thing. One other advantage is that you only power the phono section when you need it. Otherwise it is completely off, thus saving the tube life.

From a pure business sense I should talk preamp up and passives down, however that is not my truth. Passives are a great solution when used properly which is: dont load them with a lot of cable and dont load the source. This is easy today with low impedance sources.

Of course an active preamp is going to add a little distortion. Typically you can count on about 0.1 % per volt of output if there is no feedback. We dont know how every preamp colors the sound because we dont know what the designer is doing inside, perhaps intentionally. Some designers cheat the game by intentionally making something colored. They know someone will love it. Dont go assuming all preamps are designed on a level playing field, especially these days.

As someone said here he likes the microphonics of his 6SN7 preamp and calls it euphonic. Microphonics can pay a large role in preamp sound. Go tap on some tube preamps and see what comes out.

The thing that intersts me is that most complain that the bass of passives is usually lacking. However the bass of passives goes to DC with no phase shift. Tube preamps do not go to DC and at 40 Hz will start to have some phase shift. Is the phase shift what they like?

Is the phase shift what they like?

Could very well be Roger, that’s why I posted this as the possible explanation.

Especially in this case with a 0.47uf Wima coupling cap on the output of the Mani phono which is then loaded with his 5kohm pot to ground, it’s a high pass that’s -3dB @ 67hz, and if it’s 1uf still -3db @ 32hz.
The fix: Pot should be 10kohm or even 20kohm and the cap 1uF or more.

Mani top https://ibb.co/WsFNvhk

Mani bottom https://ibb.co/RyV6Gmt

Cheers George

I have a technical question regarding a PP EL86 tube amp I am modifying. I would like to upgrade the power supply. The current power supply is very, very simple and while simplicity is good I think a more robust supply could help sound quality.

A couple of questions and these should also have application for many others here.

1) All filaments are AC heated! Not DC. No filtering, no rectifier....Love you hear your comments on this. Would converting to a CLC filter with possible voltage regulation be worth doing?

2) 5U4 rectifier Tube receives 350 VAC and post tube VDC of 476 with no load. The plate supply is a simple RC only. 100 ohm resistor followed by two 680uf electrolytic caps in series. This feeds the vintage Scott output trannys. If I wanted to add a choke where should it be placed and how do I determine the value correctly. Like to know how you would design the plate supply for this simple PP el84 amp.

I ask your opinion of SS voltage regulation on both filament and plate supplies. Is it something you regard as very important? 

Thanks in advance.

@ramtubes

For those who will likely disagree: If burn in exists in these devices why did we not know about it until recently. I find no references to burn in in the 50s 60s 70s.. when did it start?

And if burn in occurs in cabling, why don’t we see people producing these measurable results between a new and burned in cable? The suspicious thing is that when most cable manufacturers are hyping either the technical reasons why their cables produce better sound, or telling you the cables need burn in, they are always appealing to some objective, technical phenomena whose existence is known because it was measurable. "Here’s a technical problem with cables you need to know about, that we have solved via our manufacturing process!"

But when they tout that they have "solved" one or more objective technical problems in cable design, they typically don’t demonstrate they’ve solved the problem in any measurable way. Instead, the results go straight to hype, marketing and the subjective impressions of audiophiles and reviewers. Same with burn in. Funny that.

As I’ve mentioned before in such discussions, audiophiles think everything changes substantially with "burn in," fuses, resistors, cables. And yet companies like Vishay and others - responsible for selling cabling, resistors etc to professional industries - industrial, computer, and incredibly spec-sensitive applications in avionics, military and aerospace design - don’t go on about "burn in." If the specs actually changed that much over time of a cable or resistor or fuse from when it was delivered new to in-use, this is something customers employing them in sensitive applications would need to know (and it would obviously be very problematic if those industries could not rely on a product actually meeting the stated specs, out of the gate).

And, again, you see (as far as I know) none of this "please burn our product in for 100 hours before application, as the specs will change" when the rubber hits the road, when you sell these things to engineers who can identify B.S. from marketing.

So my question is, why is it tubes are able to do that? Is it a matter of tubes being lowest in distortion at lower-signal levels (where imaging resides?), and transistors in their curves highest?

Back in the 90's when emulating gear in digital, we found that adding even order harmonic distortion brought the image forward and wider, i.e. more tube like. Odd order made the image deeper and more triangular, i.e. more SS like. By careful adjustment of O/E ratios, we could alter the sound stage. We were using 24bit digital and adding distortion at the 16th bit or 0.0015%.

Mani phono pre [only for example, not a slur against Schiit]

In the upper left corner is a 3 terminal voltage regulator. These devices are notorious for varying between manufacturers and within manufacturers as die changes are implemented or offshored. Additionally, these are active devices with feedback and as such can have horrific impedance and phase characteristics which affect the sound of the circuit powered therefrom. On the same DUT, the regulator can make it sound boxy, shrill, dull, warm, etc. With the same regulator, circuit changes which alter the current draw can cause the same sonic changes.

I find no references to burn in in the 50s 60s 70s.. when did it start?

I first heard of it, when the first burn in CD was produced to suck the gullible in so the makers could make some bucks, as they weren't cheap, I think it was Monster that did it to "burn in" their cables

The only thing that "may" burn-in with 20hz lf  tones, is the roll-surround on speaker drivers, that's more of a softening rather than "burn-in"

Cheers George 

Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?

Amplifiers, only the tubes. When it comes to electronics and wire I believe the listener is becoming accustomed to the change.

I must admit that I personally in my limited experience of owning new HiFi components I never experienced this  marked change of sound during 'burn in process'.  When you confirm that in regard solid state amplifiers it is the listener who is becoming accustomed to the change thats quite an assertion  when you consider the host of people (professional and non professional) who claim to have actually heard and experienced the change of sound during the claimed burn in process.  Its fascinating that such a divide exists among normal music lovers.

If burn in exists in these devices why did we not know about it until recently. I find no references to burn in in the 50s 60s 70s.. when did it start?

It's my belief that connectors are the largest culprit. As components became more modular, more connectors. Once I have a system I plan to keep for a while, I remove ALL internal connectors. More than once I've rejuvenated a system by re-plugging ALL connectors, both internal and external.

In the studio, we regularly cleaned all connectors, patch cords. Tracking setup required every mic cable be re-plugged 3x to ensure an unoxidized contact. All multitrack cards and console modules were R&R'd. AFAIK, this was SOP in some places going back to the 50's for mics and 70's as consoles and tape decks became more modular.

Cable burn-in? Bunkum!

Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?

It takes electrolytic capacitors no time at all to form (certainly not days or weeks) with the correct polarizing voltage, and if they have zero or don’t have the correct polarizing voltage, it was a bad design.

Cheers George

@prof  And if burn in occurs in cabling, why don’t we see people producing these measurable results between a new and burned in cable? The suspicious thing is that when most cable manufacturers are hyping either the technical reasons why their cables produce better sound, or telling you the cables need burn in, they are always appealing to some objective, technical phenomena whose existence is known because it was measurable. "Here’s a technical problem with cables you need to know about, that we have solved via our manufacturing process!"

Nicely done all of it. To the part quoted the reason we dont see measurable changes is that there arent any. Of course the people who believe in burn in and such will just go to the default "well you cant measure everything".  If you measure the things we can measure they will stay the same. 

We all need decent cables, thats fine. Decent cables need not cost much and are very easy to make. Up until Monster came on the scene most people made their own speaker cables out of zip cord, which is an excellent choice, very low capacitance, resistance as low as you want just buy more copper. High capacitance speakers have been known to blow up SS amps as they cause the amplifier to go into oscillation. Ive seen a Levinson smoke.

@grannyring  I have a technical question regarding a PP EL86 tube amp I am modifying. I would like to upgrade the power supply. The current power supply is very, very simple and while simplicity is good I think a more robust supply could help sound quality.

A couple of questions and these should also have application for many others here.

1) All filaments are AC heated! Not DC. No filtering, no rectifier....Love you hear your comments on this. Would converting to a CLC filter with possible voltage regulation be worth doing?

2) 5U4 rectifier Tube receives 350 VAC and post tube VDC of 476 with no load. The plate supply is a simple RC only. 100 ohm resistor followed by two 680uf electrolytic caps in series. This feeds the vintage Scott output trannys. If I wanted to add a choke where should it be placed and how do I determine the value correctly. Like to know how you would design the plate supply for this simple PP el84 amp.

I ask your opinion of SS voltage regulation on both filament and plate supplies. Is it something you regard as very important?

EL 86 is an interesting tube. I think of it as an EL84 with half the screen voltage so Ultralinear is generally out. What is the circuit like? Most people dont realize the screen supply is more important than the plate for hum. So how are the screens connected?

No need to DC heat power tube filaments, better not to. If you have hum in the front end DC heaters may fix that. 

The 5U4 is a good rectifier but does have a larger voltage drop than a cathode tube like a 5AR4. They put the 100 ohm resistor to reduce the plate peak current. Even a 5AR4 doesnt like to see more than 40 uF. All that information is on the data sheet. Tube rectifiers were useful in their day, I see no need for them now.

As to filtering, you really have only one cap and thus a fair amount of ripple. C L C filtering is the best and make the last C large so the bass can draw on it and not sag. There are lots of power supply emulator programs out there. Duncan Amps has a nice one. 

Regulation for filaments is easy so use a 3 terminal regulator for that. B+ regulation is difficult. Dont try to do too much too soon in the learning process.

@ieales  More than once I've rejuvenated a system by re-plugging ALL connectors, both internal and external.

YES, YES, YES.  Ive fixed so many things just doing that. Flat screen TVs, my Sony ES player many times, Its used up 6 of its 9 lives. 

Its sad how many components, expecially CD players end up on the scrap heap that could be fixed in 10 minutes. Dont forget the ribbon running to the laser head. That one needs the most attention. Use some logic. If the player cant read a CD go for that one. If some of the display is out or buttons dont work go for the one going to the front panel. Its really simple and you have nothing to lose. CD players cannot shock you. Do unplug them however. (I dont). 

When I open a unit with lots of those ribbon connectors inside I know it has limited life. All connectors oxidize. Oxides also form rectifiers in the signal chain and distortion.  

The old Polk Audio Cobra cables were a very high capacitance design, and caused some amps to become unstable.

@ramtubes. 

   It is very likely that what I’m hearing with this preamp vs passive thing is a less than perfect passive, against preamp distortions which “smooth” the sound. I’d like to know more about your suggested solution to this issue, but contact outside of this discussion is probably best.

   I do have technical questions regarding cabling and AC outlet use though! I’m not excited about super expensive cables (I’ve tried many with very little in the way of difference), but there are electrical differences (capacitance, inductance) in wire. Also, there are different metals and connectors used. What should one look for in terms of material (copper, silver, etc), and electrical properties (capacitance, etc) when choosing wire?
 
  Regarding AC outlet use, how does one best work out the unavoidable need to plug various components into a two outlet wall plate? I had an electrician run a dedicated 30A, 10AWG line to the duplex behind my system location to isolate the stereo components, and to provide enough amperage for the amplifier’s initial turn on draw (it was tripping the 20A breaker). I have seven components that need power. I plug my power amp into one of the outlets, and a “high end” six outlet power bar to the other outlet. Is there something special, and necessary about power strips for stereo components? If so, what does one look for when choosing between them?

@twoleftears  Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?

Electrolytic caps do need to form and the form time is related to how long they have been off or stored. This is why smart tech bring up old equipment on a variac, to let the caps form. If power caps are just hit with full voltage they will draw DC leakage current as they form. If they get too hot in the process they explode. The process is regenerative so it goes very fast at the end. Many people destroy otherwise good caps by just turning things on for too long. 

If people want to know there is a lot to be said about these caps and I have studied them in depth. I made a current limited "former" that will prevent the overheating runaway. Sometimes old caps are better than what is being made now. I know because Ive tested them. 

It takes about a day to fully form a 10 year old cap. They often form to much higher voltage than the rating. The old man at Mallory explained it all to me.  In large quantities where we spec what we want, the voltage written on the cap is more often the voltage on the purchase order rather than what the cap was made for. 

For example we ordered 1000 pcs of 150 uf 315 volt caps at Beveridge. I tested them and found them good to over 500 volts, therefore I would say they could have been marked 450 but we ordered 315V. We got more than we paid for, but one has to TEST these things to know. 

He also told me that stored at cool temperatures 10 years takes only a month off the life of a cap. Basically nothing. Its all about the water inside staying inside. 

I am sad to report that modern caps from good makers are having other problems that prevent this kind of testing. Recently I found some good caps flashed over at slightly above rating because the edge margins on the paper had been reduced to shrink the cap's size. Now that is sad. 

My advice, heed this well, If you have old lytics that are working fine, DO NOT REPLACE THEM. The new ones may not last nearly as long. I have 30 year old caps in RM-9s that are doing just fine. I don't think modern caps are going to last 30 years. 

Oh, perhaps I forgot to mention, Im really into finding out why parts fail. One has to care to make long lasting equipment.

@bdp24 The old Polk Audio Cobra cables were a very high capacitance design, and caused some amps to become unstable

.

We briefly sold those cables till we found out if you step on them they short out. Weaving magnet wire into a snake skin is a really bad idea.

@krelldreams

   I do have technical questions regarding cabling and AC outlet use though! I’m not excited about super expensive cables (I’ve tried many with very little in the way of difference), but there are electrical differences (capacitance, inductance) in wire. Also, there are different metals and connectors used. What should one look for in terms of material (copper, silver, etc), and electrical properties (capacitance, etc) when choosing wire?
 
  Regarding AC outlet use, how does one best work out the unavoidable need to plug various components into a two outlet wall plate? I had an electrician run a dedicated 30A, 10AWG line to the duplex behind my system location to isolate the stereo components, and to provide enough amperage for the amplifier’s initial turn on draw (it was tripping the 20A breaker). I have seven components that need power. I plug my power amp into one of the outlets, and a “high end” six outlet power bar to the other outlet. Is there something special, and necessary about power strips for stereo components? If so, what does one look for when choosing between them?

Not sure what I can do about the passive thing but you can write Tony at tubeaudiostore@gmail and he will forward to me. 

The capacitance and inductance in a power cord is vanishingly small and can be ignored. Some platings are nice. DeOxit is a good cleaner and cleaning may help more than anything. 

I would have had the electrician put in several duplex outlets so no power strip is needed. Power strips vary in cost and quality but the expensive ones with big claims are just marketing. You have nice 10 Ga wire in the wall and then what?

Heres something Ive done. Get a bunch of reasonable power cords, like $20 each of various lengths. Cut off all the male plugs strip and hardwire the cut end directly to the 10 GA wire with a bussbar. Solder good solder lugs to the wires and screw them with a star washer to the bussbar. THe star washers are important. Now you have direct power cords and have eliminated one connection.  Make some extras of course.  The ones you arent using just coil them up.

I had custom power cords made that are 8 ft long, very flexible, supple, drape nicely and wont pull  your smaller devices off the shelf. We have them if you need some. 

Bottom line here. Its not the wire that matters. You have hundreds of feet of ordinary magnet wire in every transformer. What you gonna do bout that? :). All this power cord and power strip is just foolishness. Why do we need powercords that are a pain to run?

Thanks for the question. I hope people can see that throwing dollars at something is not always the best solution. 

@stargazer   I must admit that I personally in my limited experience of owning new HiFi components I never experienced this marked change of sound during 'burn in process'. When you confirm that in regard solid state amplifiers it is the listener who is becoming accustomed to the change thats quite an assertion when you consider the host of people (professional and non professional) who claim to have actually heard and experienced the change of sound during the claimed burn in process. Its fascinating that such a divide exists among normal music lovers.

It is quite an assertion that I made. We know not what they heard, we know not what posessed them to make such claims. I assert that the change is so subtle as to be entirely imaginary. I have said to many who report such " Wow you have a really good imagination"

Look at it this way. There are professionals and non professionals who assert they have golden ears and they must say these things to support their ears. We dont know what someone is hearing. 

As I have posted previously ive been in a room with some golden ears where the system was "broken" and they didnt hear it. Given that who is really hearing what?

Roger, why did you switch the input to the 12AT7 from the 12AX7 on the Ram10 mkll?

@jlhaudio Roger, why did you switch the input to the 12AT7 from the 12AX7 on the Ram10 mkll?

Along with changing the bias system from fixed to cathode bias and changing the B+ I found the 12AT7 was a better choice. It has a lower saturation voltage than a 12AX7 and higher current. As far as we can determine the amps sound the same. We want them to. 

My pre-amps are unusual in many ways as they use only six subminiature tubes, are a voltage regulated design with no fuse/breaker necessary and have the stepped attenuator out of the signal path but operates by bleeding off voltage to ground to attenuate the volume. That’s what the manufacturer told me. Sounds as good or better than an EAR 912 with tubes rated for 100,000 hours and non-microphonic. The phono pre-amp is similarly designed without the attenuator.

I think it was Monster that did it to "burn in" their cables

When I consulted with Monster Pro in the 80s & 90s,AFAIR burn-in was never mentioned.

The first I heard of it was in the early naughts, but I had been in AA [Audiophile Anonymous] for a few years.

Apparently some people just cannot restrain themselves or have difficulty with reading comprehension

-Or there might be a third explanation.

minimize artifacts occurring from the interconnect cable between the preamp and amp.

A second reason is that a preamp can provide a fairly high impedance load for the source

Source output 22R, amp inputs 23k5 or 100K. Adding a preamp with attendant switching, circuitry, noise and additional cables is little more than a subtle tone control. It maybe different, but it may not be better.

I agree with ieales and not the answer given above his, but then you all know that. What are these artifacts, are they Egyptian?

If you've heard cables sound different from one to another, that is an artifact. Cables have capacitance, inductance and characteristic impedance (hence the 600 ohm standard used with balanced lines for several decades).

The thing that intersts me is that most complain that the bass of passives is usually lacking. However the bass of passives goes to DC with no phase shift. Tube preamps do not go to DC and at 40 Hz will start to have some phase shift. Is the phase shift what they like?

It would be interesting to see if it is indeed phase shift. Many preamps don't have any phase shift right to 20Hz but I suspect that passives often do- not because the passive itself does of course, but because it in tandem with certain sources might.

A preamp need not have DC response to have immeasurable phase shift at 20Hz. For that it only need to go 2Hz.

Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?

Electrolytic capacitors do need to be formed. Most of this is done at the factory, simply by charging the cap to the forming voltage (and is actually the difference *in some cases* between two voltage ratings). This is to prevent the cap from being damaged at installation! However the caps are shipped without charge and can sit unused. They do need to form up properly again when installed.  In some of our larger amps, we often see the amp blow a fuse during turn-on (due to current inrush) that it won't ever blow later after the caps have formed up properly (which seems to take a week or so of intermittent use). 

More than once I've rejuvenated a system by re-plugging ALL connectors, both internal and external.

+1

@atmasphere 

If the capacitance of a cable causes rolloff, is that an artifact?

I used to think that power was power with only minor differences in the sound.  However in trying to decide on the best amplifier for my Thiel 2.4s I've auditioned the Bel Canto m600s (their current production monblock), the Bryston 4 cubed stereo amp, and the Pass x150.8.  They were PROFOUNDLY different.  The Bel Canto rather oddly was very recessed the dark sounding, the Bryston was a little shrill with very little mid range "meat" on the bones but the Pass was JUST RIGHT.  Honestly, I'm being a little sarcastic here but these were not subtle differences.  I left the experience feeling that the "electrical" handshake between the power amp and the speaker is considerably more complicated than I originally imagined.  Thoughts?

If the capacitance of a cable causes rolloff, is that an artifact?

Of course.

@pwhinson The Thiel is a low impedance speaker, below 4Ω for most of the range with two steep peaks in the bass. https://www.stereophile.com/content/thiel-cs24-loudspeaker-measurements

An amp to drive these speakers should be happy with a 2Ω load.

And what speaker wire do you use?

NO amp is happy with a 2 ohm load, or at least it’s far happier seeing a higher impedance. When did all these very-low impedance loudspeakers start appearing, and why? The original Magneplanar Tympani T-I was a nominal 8 ohm load, which soon was changed to 4 ohms. 4 ohms coupled with a ss amp makes for more power getting to the speaker, but why go lower? Speakers with wildly-varying impedances (many ESL’s) are a real problem, especially with the typically-high output impedance tube amps. The Music Reference RM-200 being the rare exception, of course ;-) .

The answer is that the industry cares more about power than nuance. As well many speaker designers don't realize the relationship between amp and speakers so they don't realize that by making the speaker lower impedance, the amp will make more distortion. In high end audio, its more about nuance than power, and higher impedance loads do that with greater ease.

Or there might be a third explanation.
Attainment of the tipping point of your cortex?

Or there might be a third explanation.
Attainment of the tipping point of your cortex?

Simpler than that.


This is a public forum. Anyone who wishes can post anywhere on the forum, including this thread as long as they are a member.


I've been here since its inception.


I'm also an engineer, an amplifier designer and I answer questions.


But here's the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts. This is against the Audiogon rules, but because I and others are posting here as well, the entire thread doesn't have to be taken down.

I notice on this account that Georgehifi isn't being taken to task; although while he is a manufacturer, he's not an amp designer. But this thread has drifted to the topic of preamps on occasion and on that account he's been posting too.

I've been here since its inception.

Does that give you the right to be a self proclaimed forum cop.

This thread was put up as a promotional device.

That's the pot calling the kettle black

I notice on this account that Georgehifi isn't being taken to task;

Wow, you've really got something up you this morning, must be the bagging Class-D's getting on the other thread, and you keep saying (promoting) your is coming soon and it will fix all the problems with Class-D. 

Does that give you the right to be a self proclaimed forum cop.

Of course not- neither am I attempting to enforce any rules.

That's the pot calling the kettle black

Oh- can you point me to a thread I've created on this site? Meanwhile, irony is still a thing, huh?

Wow, you've really got something up you this morning, must be the bagging Class-D's getting on the other thread, and you keep saying (promoting) your is coming soon and it will fix all the problems with Class-D.

?? Did I promote such a thing on that thread? I did provide info but IIRC no information whatsoever about what we're up to.

I greatly value Ralph Karsten’s forthright yet tactful comments. I learn something with out being belittled.  He dignifies the other person by doing that. Thank you Ralph, Almarg and others like that.

Did I promote such a thing on that thread?

Not on that specific thread, but you have numerous times, what was it that was said???oh yes!!!
"LET HIM AMONG US, WHO IS WITHOUT SIN, CAST THE FIRST STONE"
Think that was it, I remember reading it somewhere, "How to survive in the Australian outback" or something,  correct me if I'm wrong. 

He dignifies the other person by doing that. Thank you Ralph

Really!!! by saying this about Roger, who is helping others with their questions with this thread.

"But here’s the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts."

I think you have that totally "arse about face", marqmike

Cheers George

But here’s the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts. This is against the Audiogon rules, but because I and others are posting here as well, the entire thread doesn’t have to be taken down.

A promotional device in what manner? Do you think Roger is using this thread to try and sell more products? Since you called out Roger on this I will say you are walking a fine line here Ralph, especially given what you once told me in a conversation we had about marketing. The thread was started so that Roger can share his knowledge and experience with the community. He has requested that other designers not respond to the questions asked of him, and from my perspective it’s not that you don’t bring value to the discussion (and I get it’s a public forum), but when you bring up the self promotion stuff, I have to agree with George that it is the pot calling the kettle black.

You consistently promote balanced differential designs, not always mentioning products specifically, although correct me if I am wrong, but you have mentioned the MP-1 was one of the first balanced preamps in high end audio on more than one occasion. I have read many threads where you reference how your preamps solve the issue of cable artifacts coloring the sound, that you make them unity gain with a buffered output, and you have mentioned or alluded to your amplifier designs many a time as well. Granted you do so in a gentlemanly manner and as a means to educate. However, isn’t that what Roger is doing as well?

Here is an example from 12/26/2017:

Our MP-3 preamp is based on the first balanced preamp circuit ever sold to high end audio (our MP-1). It has a direct-coupled output (despite being a tube preamp) and has bandwidth to about 400KHz.

Here is an older example:

How the MP-1 works is it has a direct-coupled output. The output impedance is low enough that it can drive 32-ohm headphones easily. It is designed to drive 600 ohms without effort; obviously its output impedance has to be well below that in order to do so.

Because its outputs are direct-coupled, the output impedance is flat from 1Hz to 200KHz or thereabouts. So it really can drive 200 foot interconnects without difficulty.

It my opinion that getting rid of the output coupling caps is the single best thing you can do with a tube preamp to improve transparency and bandwidth.

The MP-1 was/is the first balanced line preamp for high end audio.

Roger is being very generous with his time (as you have over the years) and trying to answer as many questions as possible. Is he self promoting? His experience for sure. Does he mention his products? Yes. Does he push them? Not in my opinion. From my perspective he references them to supplement responses relevant to his experience or in direct response to questions about that product from other members posting on this thread. I see nothing wrong with that, especially since you have done the same on Audiogon.

I have enjoyed posts by Ralph and Ramtubes on this forum. They are both highly qualified as designers and manufacturers. They both provide  answers to technical questions about gear. Sometimes, they include opinions based on their understanding of the science behind gear. Nevertheless, their posts are almost always informative to the membership here. Occasionally, they are self referential, although I do not view their contributions as self promotion that should be banned such as posts by Audiotroy which usually contain rank self promotion and, at other times, stealth promotion under the guise of informing the Audiogon community of his opinion ( almost always favoring the gear he sells) based upon his vast experience which he claims is more valuable than the opinions of other dealers who are out for the money--- while he is out to help the Audiogon community. 
Of course, these are extreme comparisons about what should and should not be permitted here. I suspect the line should be drawn somewhere in between the services provided by Ralph and Ramtubes and the disservice provided by Audiotroy. Might I add that Ralph and Ramtubes are not close to that line IMHO. 
     

I couldn't agree more with both clio09 and gpgr4blu. Thanks guys.

@pwhinson 
I used to think that power was power with only minor differences in the sound.  However in trying to decide on the best amplifier for my Thiel 2.4s I've auditioned the Bel Canto m600s (their current production monblock), the Bryston 4 cubed stereo amp, and the Pass x150.8.  They were PROFOUNDLY different.  The Bel Canto rather oddly was very recessed the dark sounding, the Bryston was a little shrill with very little mid range "meat" on the bones but the Pass was JUST RIGHT.  Honestly, I'm being a little sarcastic here but these were not subtle differences.  I left the experience feeling that the "electrical" handshake between the power amp and the speaker is considerably more complicated than I originally imagined.  Thoughts?

Those are all big amplifiers. Given the low impedance in Thiels you want the amp with the most current. 

I would only listen to one amp at a time with one as a referene in a strict A/B test. Swapping amps has to much time between, levels are often not matched. I wish dealers had A/B boxes but its a lot of work and they dont want that kind of testing. You may find out the less expensive amp sounds the same or better. When you compare good amps with good specks they really cant sound much different, can they?

Now throw in a high distortion, low damping amp and you will hear that.

@fleschler  EAR 912 with tubes rated for 100,000 hours and non-microphonic.

I have looked at the rating of many tubes, last I looked Tim was using 7DJ8s. Those are 10,000 hour tubes If you get 10,000 be happy. 

Most tubes are rated for 10,000 hours and 10,000 turn-ons .So watch that. 

@grgr4blu I have enjoyed posts by Ralph and Ramtubes on this forum. They are both highly qualified as designers and manufacturers. They both provide answers to technical questions about gear. Sometimes, they include opinions based on their understanding of the science behind gear. Nevertheless, their posts are almost always informative to the membership here. Occasionally, they are self referential, although I do not view their contributions as self promotion that should be banned such as posts by Audiotroy which usually contain rank self promotion and, at other times, stealth promotion under the guise of informing the Audiogon community of his opinion ( almost always favoring the gear he sells) based upon his vast experience which he claims is more valuable than the opinions of other dealers who are out for the money--- while he is out to help the Audiogon community. Of course, these are extreme comparisons about what should and should not be permitted here. I suspect the line should be drawn somewhere in between the services provided by Ralph and Ramtubes and the disservice provided by Audiotroy. Might I add that Ralph and Ramtubes are not close to that line IMHO.

I toatlly agree about not promoting ones product and plan to watch it carefully. I would like to see people make some simple A/B boxes and will tell them how  for no charge. If I make one for someblody its a one off and not a product, just a tool, and a very good one. Perhaps I can make one and we can pass it around to those really interested and can convince me they can properly perform the experiment.

I will remind everyone that this thread is to answer and discuss technical topics. If you want me to answer personally pease direct the question to me.

Furthermore If anyone wants to debate a topic, be sure to have vetted sources to support your premise or be good at supporting it yourself. We have had a few on here that went on an on with no support, clairty or sensiblity. 

@atmasphere    But here's the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts. This is against the Audiogon rules, but because I and others are posting here as well, the entire thread doesn't have to be taken down.

I notice on this account that Georgehifi isn't being taken to task; although while he is a manufacturer, he's not an amp designer. But this thread has drifted to the topic of preamps on occasion and on that account he's been posting too.

Ralph, Im sad to have to say all this but you have a very different about the owner ship of threads on Audiogon. of course it is a public forum, however it appears that most threads respect the OP as the moderator of his thread. 

 I think the original post is pretty clear. I am here to answer questions, educate and share the results of my experiments that I encourage others to have a go at some experiment that they may find very enlightening. 

I never imagined other amplifier designers would want to answer questions directed to me. If you think one of my answers is wrong you are wellcome to chime in but not with your paradigm or unsupported theories. I dont welcome any unsupported theories, poorly vetter answers from flawed articles.

Perhaps its time for you to start you own similar thread, Anyone who wants to ask Ralph a question can easily find him. 

You have a paradigm to promote with which I totally disagree. When I bring up that a widely varying impedance speaker will not sound as the designer intended, you bring your paradigm.. Perhaps your amp provides a tone control some like. I have 2 m-60s in my shop right now in my A/B test rack, anyone is welcome to come listen. One is stock one is my mod with feedback. It appears you have abandoned feeback on some psychological level rather than listening. We are just listening. 

So please dont bring your, not vettet, paradigm to a scientific discusstion which is in general disagreement with it. That is self promoting to a high degree. Why post here when you have known for years we disagree about damping, distortion, current, tube applications and a host of other things?  Ive read your paper over and over again and it makes little sense.

You are the only outside designer who has entered this thread.

When you answer questions from your point of view I have to deal with that and it makes more work for me. We already know what you are going to say you have said it 6,798 times.