Does anyone care to ask an amplifier designer a technical question? My door is open.
I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.
I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer. . Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.
I like to tell true stories of my experience with others in this industry.
I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.
On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.
I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.
Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.
krelldreams I primarily listen to LPs, but I do have a DAC (Cambridge DacMagic Plus)
What would your phono stage be, hopefully I can find it’s output impedance and if it has capacitor coupling and if that’s big enough, to work into a 5kohm Alps pot., if not it will roll off the bass prematurely, "creating a leaner sound"
As far as the DacMaigic goes (at<50ohm output impedance) there’s no problem for it to see, your 5kohm Alps pot. But it has an output coupling cap also and with the 5kohm Alps pot that coupling cap has to be at least 5uf in size to be -3db at 10hz if smaller than this it could prematurely roll off the bass also, "creating a leaner sound".
Thanks for the link.. I’ll check it out. My comment regarding the phono preamp with aux inputs and level control was made selfishly because I am very much interested in outstanding LP playback, and only listen to my digital sources casually (for background music, or if I’m not in the mood to flip records). Therefore a high quality phono preamp with a couple auxiliary inputs and a volume control is very attractive to ME
Sorry, I had mentioned my sources in a previous post, but this thread has many, many posts by many people! I primarily listen to LPs, but I do have a DAC (Cambridge DacMagic Plus), and an Audioquest Beetle to stream Spotify over Bluetooth. I initially entered this thread to ask Roger his opinion about using a tube amp with my Maggies, but realized, after considering my system, that my preamp is likely the weak link. That realization lead me to learn more about improving the switching and level control functions... whether by a traditional preamp, or by using the combination of a passive device with a dedicated phono preamp. I had a passive in a different system, so I tried it in the main system to check it out.
Yes his amps are loved by passives and with my customers that use them.
My power amp is a CJ Evolution 2000 its input impedance is 100k ohms, and input sensitivity is 900 mV to full output. It should also love passives, with that 0.9v input sensitivity. And that 100k input impedance you could of had a 20k Alps passive, not just 5k,
A 20k Alps pot would have been fine for just about any source then, which by the way you have not told what you have as the source.?? because if it has high’ish output impedance it won’t be comfortable with that 5kohm Alps pot as it will load down it's output and also create a voltage divider.
Thanks George. I like the idea of a passive control device, and I’m trying to learn about the system matching aspect so I can try an appropriate unit. I did appreciate the clarity, but was distracted by what I’ll call an overly etched, and leaner presentation. I can accept the fact that there may be more going on here than the “passive vs active” thing. The only passive I have was ordered for a very different application... level control for a CD player into a vintage tube amp for a second system. To be honest, it sounded pretty good despite the fact that it was MUCH less expensive than my preamp (1/10 the cost). Mr. Modjeski seems to endorse passives, and I’d like to at least explore this avenue with the right unit (for my system). My power amp is a CJ Evolution 2000 which was upgraded/updated by Bill Thalmann of Music Technology (formerly of CJ). Its input impedance is 100k ohms, and input sensitivity is 900 mV to full output. I’d like some flexibility with whatever I choose as a source switch/level control in case I decide to use a different power amp.
Passives should be at least 10kohm to suit "most" situations
It depends on the source output impedance what the passive resistance should be. If the output impedance is < 500Ω, a 5k pot is fine.
Pots have a different sound than stepped resistor controls. IMO, P&G pots were more musical than Alps when I used passive level controls in the studio. Additionally pots, especially log, track nowhere near as well as stepped resistors.
Clio wrote about a phono preamp with passive level control and aux inputs. What a great idea!
Whether it is a great idea depends on the topology and to what it is connected.
krelldreams my passive across the input to the output as you requested. It measures 1.21kohm, which is as written on the bottom of the case.
If your Alps pot’s passive pre, input to output measures 1.21kohm then you have a 5kohm Alps pot. Your source may well be doing it hard into this 5k load, and making things "leaner". Passives should be at least 10kohm to suit "most" situations. Or higher (>10kohm) if the amp is also >50kohm or more.
I measured the impedance of my passive across the input to the output as you requested. It measures 1.21kohm, which is as written on the bottom of the case. I opened the case and found an Alps volume pot, two resistors, and wiring. I played lots of music through it, using my phono preamp as the source, and I periodically placed my preamp back in the system for comparison. 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!
Hi, My Nakamichi Compact ! Receiver has a FM tuner. How do I connect it to my Rotel A14 integrated amp? The Nakamichi has Pre output , main input and Aux available. Rotel has aux and pre output/
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).
@bdp24
I also remember The RM-5 and the Audible Illusions Modulus 2 were considered THE bargain tube pre-amps to choose between. I found the AI Mod's 30dB of line stage gain unfortunate and ill-advised, as well as it's dual-mono volume controls. The Modulus is still in production (in updated form, of course), so Roger, any thoughts of offering a contemporary RM-5 type pre?
Thanks for the memories... who sung that? The Modulus and RM-5 present a great example of dueling designers. Art did not put feedback around the line tube as I did. I also made it variable with dip switches for many gain settings from 0 to 30 dB which is the full gain of the tube. He later put a cathode bypass disconnect to lower the gain but that is a Very bad idea as it raises the output impedance to about 10K. The feedback in my line stage lowered the output impedance to about 1K. Im surprised people didnt hear the difference more easily. Again, that would have showed up in an A/B which is just not done is it?
Where I did volume and balance Arthur liked his dual controls. Other than that the preamps were pretty except for the power supply. His blew up, mind didnt.
Problem was, Arthur was not an engineer and the preamp was the work of many people. I think he bought the company from Bruce Moore. Hope Im not bragging on mine too much, just the facts Madam.
He claims in the TAS book to have sold 25,000 units. His tech, Meserve. was my tech in the 1980s and said theres no way. We sold 960 over the 15 years we made it. All sonically and ciruits wise the same.. Only thing that changed was the jacks as better ones came alone. If you can find a MKIV that was the nicest as we put on a phono tube off switch, heavier metal, nicer jacks. We only made 50 so good luck. The MKIII is more available and just as good except for those two things.
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.
Some volume controls in DACs are actually far more than subtle in their operation. Stripping bits isn't the best way to control volume. For that reason the buffered volume control that can be in an active line section could be more neutral.
One thing is certain: when it comes to preamps, passive volume controls or running direct, because there are so many different products and approaches to this problem no generalization about the matter could be seen as true.
I can’t imagine living without my dual Kozmo pots now that I have them. I will never own another preamp without some sort of balance, preferably dual volume pots.
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.
@ieales, agreed, but the Modulus pots (Noble?) were not that precise. I have no interest in resetting the channel balance every time I adjust the volume!
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.
The answer is highly system dependent of course, but one reason is that a preamp is or should be designed to minimize artifacts occurring from the interconnect cable between the preamp and amp. Sometimes digital sources are not very good at this. A second reason is that a preamp can provide a fairly high impedance load for the source, meaning that the latter does not have to work as hard to make its signal. This could result in lower distortion- and no place better in the system to get things right!
@bdp24 - dual controls are not too fiddly if they are 1db or less stepped
@apogee14151617 - all components active and passive alter the sound. There is no electrical reason to have a preamp if the source has output level control or the amp has input level control. I use a passive 1db stepped resistor of my own design. It has a sound, but everything does.
This 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?
@ramtubes, oh yeah Roger, now I remember Dick Olsher's review of the RM-9 Mk.2. I found Olsher to be a reviewer from the Gordon Holt school (a school I approve of ;-), and he loved the amp. I believe his closing line was something like "Who needs an MC75 (the classic Mac amp) when we have the RM-9 Mk.2?"
I also remember The RM-5 and the Audible Illusions Modulus 2 were considered THE bargain tube pre-amps to choose between. I found the AI Mod's 30dB of line stage gain unfortunate and ill-advised, as well as it's dual-mono volume controls. The Modulus is still in production (in updated form, of course), so Roger, any thoughts of offering a contemporary RM-5 type pre?
RIP Charley I was a friend of some small depth on Facebook and a BIG fan of his VXR amp....countless hours of musical enyoyment. Peace and grace for his family and a lasting legacy of greatness is my prayer...
@almarg
That’s interesting to hear, Roger. Although to be precise I’m pretty certain that the 8 and 8B were both single-chassis stereo amps.
I’ve never heard an 8 or 8B but during the 1990s I owned a pair of Model 9 monoblocks and a pair of Model 2 monoblocks. And I greatly preferred the sound of the 2s to the 9s, although in fairness I can’t exclude the possibility that condition may have been a factor in that.
The 2 was similar in some respects to the 8 and 8B, which came later of course. Although in addition to being monoblocks the 2 employed tube rectification, while the 8 and 8B used solid state rectification, and the 2 used 12AX7 input tubes while the others used 6BH6s.
I’ve commented here in the past that at least when used in conjunction with speakers having benign impedance characteristics and not requiring more than the 18 or 20 watts or so that the 2s were capable of in triode mode, in that mode the 2s were one of the best sounding amps I’ve ever heard.
I never got my hands on a 2 but I studied the 5 (half of an 8) in great detail and I saw how they did the tertiary feedback winding. I had to do a lot of experimenting to make that work out but its a trick I have rarely seen in other amplifiers.
The separate feedback winding makes the amp more stable into reactive loads. Perhaps few know that we made all the transformers for the RM-9. I cut my teeth on the design of that output transformer.
The 9 was quite a departure from the 8, far more complex, perhaps better specs, but when you take specs too seriously (as in too much feedback) things can go downhill.
...BTW Saul told me that around the shop they firmly preferred a pair of Mono 8s to the famous Model 9.
That’s interesting to hear, Roger. Although to be precise I’m pretty certain that the 8 and 8B were both single-chassis stereo amps.
I’ve never heard an 8 or 8B but during the 1990s I owned a pair of Model 9 monoblocks and a pair of Model 2 monoblocks. And I greatly preferred the sound of the 2s to the 9s, although in fairness I can’t exclude the possibility that condition may have been a factor in that.
The 2 was similar in some respects to the 8 and 8B, which came later of course. Although in addition to being monoblocks the 2 employed tube rectification, while the 8 and 8B used solid state rectification, and the 2 used 12AX7 input tubes while the others used 6BH6s.
I’ve commented here in the past that at least when used in conjunction with speakers having benign impedance characteristics and not requiring more than the 18 or 20 watts or so that the 2s were capable of in triode mode, in that mode the 2s were one of the best sounding amps I’ve ever heard.
@bdp24
I have for years heard accusations from audiophiles about TAS and now Stereophile requiring advertising from any company wanting one of their products reviewed. I have never seen any proof of that, and have to point of that though I have never seen an ad from Music Reference in Stereophile, a review of the RM-200 by Michael Fremer has twice appeared in the mag; once of the original version, a second of the Mk.2. That the Arma-Sphere M60 and/or MP-3 have not been reviewed is ridiculous. They review all kinds of over-priced status symbols, why not some high-value mid-priced pieces (the stuff most of us are interested in owning)?
True, I have never advertised in Stereophile. I run a different ship than most. I was offered to share the front cover for the Fremer review but declined. I want my amps to sell on their merit not advertising. The people who know will find me, its never been a problem.
I find Stereophile and JA the most unbiased folks in the industry. TAS is and always has been a joke technically. Harry made the best of it as the self acclaimed "Audio Pusher". I read a few issues over the summer and saw that their current model is the "two page review" Every review was two facing pages. How boring. Where do the reviewers find all those words? TAS will never measure anything and what am I supposed to learn from all those words.
Stereophile also reviewed the RM-5 and RM-9 in the 80s. Im quite sad where things have gone in this industry I have devoted my life to. Need I say more?
@krelldreams
You mentioned, that in the RM 9, two KT120 or KT150 output tubes could be substituted for four EL34s in each channel. Is there an advantage to using fewer higher output tubes as opposed to using double the number of lower output power tubes, or vice versa? In other words, is the former following a “simpler” path than the latter?
The advantage lies in fewer tubes to fool with, a little less heater draw so the power transformer will run cooler and you get away from the tight matching of 4 tubes. The path is the same. The idle current will be the same. Might have to shift the bias a little. I know the 120s work. We have had several people do it. If I get a chance I will give the 150s a try in an RM-9. Might look cool having 4 x 150s in the front row.
not all things that matter are amenable to testing.
Indeed we cant test for everything. However we can test for the big three and include that information in our listening. For instance if one amplifier produces a lot more bass from a speaker which amp is right. If the person prefers more bass then he buys that one. However usually when there is more bass the bass is not as good. Its uneven, boomy, the extreme being the "one note" bass. Now if we measure the amp with more bass and find it has poor damping we can say to the first order that is due to the poor damping.
What gets interesting is when we have two very good measuring amps that sound fairly alike and one is tube and one is SS then we have to start wondering as Charlie did, What is it tubes do differently?
I hope someday I make a better amp than what i have made so far. An RM-9 is hard to beat. So are all the Marantz tube amps. Perhaps I have equaled the Marantz 8B, Saul's favorite. Perhaps I have better bass because now we have much larger filter caps than he had. Other than that not much has changed. BTW Saul told me that around the shop they firmly preferred a pair of Mono 8s to the famous Model 9.
I have for years heard accusations from audiophiles about TAS and now Stereophile requiring advertising from any company wanting one of their products reviewed. I have never seen any proof of that, and have to point of that though I have never seen an ad from Music Reference in Stereophile, a review of the RM-200 by Michael Fremer has twice appeared in the mag; once of the original version, a second of the Mk.2. That the Arma-Sphere M60 and/or MP-3 have not been reviewed is ridiculous. They review all kinds of over-priced status symbols, why not some high-value mid-priced pieces (the stuff most of us are interested in owning)?
Great comment (on hearing)! I believe our hearing mechanism is somewhat of a “moving target”, so to speak. I’ve wondered why sometimes music through my system sounds great to me, and other times, not as good. Even when playing the same recordings at the same volume. The disparity is occasionally such that I think something is “broken”. Fortunately it sounds good much more frequently than it does not.
You mentioned, that in the RM 9, two KT120 or KT150 output tubes could be substituted for four EL34s in each channel. Is there an advantage to using fewer higher output tubes as opposed to using double the number of lower output power tubes, or vice versa? In other words, is the former following a “simpler” path than the latter?
In a separate post your "intake guy" Clio-something really gave me the
business about being a troll and not having anything technical to add.
Actually, I said you bring zero value. The statement wasn't referring to just technical value. Perhaps you got confused with the other part of the paragraph where I said you lack the knowledge or credibility to refute anything Roger says. I was in fact referring to your lack of technical knowledge in that instance, but of course you already copped to that previously.
Well, it turns out that it was my friend Ralph (we have never met, I simply call him my friend) who misspelled Charley's name.
He did the measurements of our old M-60 kit for Glass Audio. I met him and hung out back when he was still Avalon Loudspeakers. Different world... nice guy. He is missed.
Well, it turns out that it was my friend Ralph (we have never met, I simply call him my friend) who misspelled Charley's name.
It is in no way an excuse for bad specs- and in fact our amps have some pretty good specs (if proper measurement technique is used, which means **don’t ground a speaker terminal during testing**, which is the mistake that almost everyone except Charles Hanson made/makes). I suspect you didn’t read the paper at the link very carefully, since you claimed that you read it, yet still with the remonstrations!
Sorry. Now back to my sorely missed idol, the great Charles Hansen. He gave an interview to S'Phile back in October 2016 (or at least, published in that issue) and said this;
I didn't really understand it for a long time. When I first made the Ayre MX-R amps and KX-R preamp, I thought, Okay we've done it. We've made stuff that is so good it's as good as tubes—why would you bother with tubes? But I would still get customers and manufacturers who would say, "Yeah, that's nice, but I'm still sticking with my tube piece, because you haven't got there yet." And one of my weaknesses, for better or worse, is that I have such a big ego, I don't have to listen to other kit. I just listen to my own designs. If I had, I would have known what they were talking about.
When we made the KX-R Twenty, we took all our ideas we had been working on for 20 years, and getting feedback from people who were able to teach me how to listen better, and what to listen for—20 years of hard work. And then I hooked up the KX-R Twenty and I went, "Holy cow! This is what they were talking about. No wonder they didn't want to listen to solid-state—this is what they wanted to hear." It just hit me: This is what all those tube nuts were talking about. I would send stuff off to these dyed-in-the-wool tube guys, and they would say, "Nope, it's gotta have a tube in it or it's never going to work right. No, it's just sand. How can it sound right?"
My point being that here we have this great engineer who thought he had engineered a product that tested well and sounded great and then he had an epiphany of sorts that something better was indeed out there and attainable. I continue to believe that old maxim that we're all tired of reciting let alone hearing; not all things that matter are amenable to testing. In a separate post your "intake guy" Clio-something really gave me the business about being a troll and not having anything technical to add. He's kind of right and kind of wrong IMHO. I may not have technical expertise but I will never believe that JA's measurements trump listening impressions. Roger-the Roger that I have metaphysically shaken hands with-enthusiastically too-you have endorsed JA's measurement techniques again and again and yet the fact of the matter is that JA has never given any tubed amp an enthusiastic endorsement from the standpoint of measurements. If your amp is an exception, than fine, that would be one instance of my "never" being incorrect. He may have given that monster hybrid integrated by Musical Fidelity-a known S'Phile darling-a thumbs up from a measurement perspective as well. So that would be two exceptions. Btw, go back to the full link of Charley Hansen's interview and see what he said about finding a power cord laying against the carpet at a show and finding that one wood block cured his perceived dissonance. What do you have to say about that? That it was in his mind?
Perhaps I was not clear in my original posting that this is a thread to ask the OP a question and have it answered by the OP. It was not an open invitation for other designers to answer questions or give their opinions on my answers. The whole point is to give the public some insight on how I design things and how I evaluate my own and other equipment.
If you notice John Atkinson and I have similar views on what an amplifier ought to do.
If other designers want to have such a thread all the better. I would not care to comment on their thread because those are their answers, their views.
In the end I hope to educate. As far as selling anything I am happy to share the workings of my A/B test set up for no charge or build one for someone if they want to get into A/B testing.
I am most happy to discuss interactions in equipment, how I go about designing, how I listen. Far down the list is the sound of particular tubes or brands of the same tube. I will talk about what different tubes can and cannot do well. I can talk about how some circuits are more sensitive to tube rolling and some are much less so.
I made a few Zero Feedback amps in the 1970s, Still have one, perhaps I should dust it off and have a listen. Like Charlie I maintained the big 3 targets. If you don't you will have created an amplifier that is very speaker dependent.
I am likely one of a very few designers that actually will repair others
equipment. I do this because I like to see others work, how they make
things, how their things perform. I have tested over 400 amps and
preamps and can tell you all about what is going on in them.
Well there's another thing we share. I put myself through college doing consumer electronics repair. I got the job right out of high school in 1974. I enjoy seeing how things are built and how problems were solved. We don't see much gear shipped to us, but we do a lot of local repairs on competitors equipment, as well as guitar amps, semi-pro and pro audio.
@ptss
@ OP. How do you feel about Spectral Audio designing amps with extreme bandwidth? Are there benefits for solid state amps?
When I went to Vegas in 1978 Spectral was playing B&W video through their line stage. The volume control thus because the contrast control which they encouraged everyone to play with. The picture was ok so it was at least a few MHz of bandwidth. I guess they liked bandwith. Their designs were, in my opinion, excellent.
I dont see how it makes a difference to go that far and it is an invitation for RFI to be passed on to the power amp.
After a certain point slew rate and bandwidth are just for bragging rights.
In output transformer tube amps wide bandwidth, maintaining stability and getting the big 3 parameters reasonable, is the greatest challenge
@krelldreams
I’d like to add this: I appreciate the fact that there are two professionals contributing here, despite the fact that there is tension that’s been created by disagreement. I’m trying to read through the commentary to the points being made, the examples being given, and the facts. The reality is, there are many ways to arrive at the same destination. I’ve listened to, and owned A LOT of gear in my life, though none, so far, by either of these designers. Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless.
I appreciate your balanced view on two designers, with very different viewpoints, airing their design thoughts in public. Im fine with it and I hope readers understand that sometimes a statement is so shocking to me that I get a little worked up about it.
I have experienced and previously stated where cartridge loading makes large difference. I love to do things on the fly with minimum time between evaluations. Therefore I built a 6 position load box for my Denon 103 from 10 to 200 ohms, including no load. I can just dial through and listen. The Denon is a cartridge that needs loading otherwise it is bright and harsh. Around 100 ohms it sounds good to me. Below that it gets kinda dead sounding. On the other hand we did the same with the Lyra and no load sounded the best. We had a switch of 12 loads from 3 ohms to no load. From 10 ohms up we heard no difference. The audience was 40 people who generally agreed and were surprised at what they heard.
I fully agree and have stated before that each of us have a system that is "his sound". It can be fun to visit and listen to others sound. Now what does one do when (and this is a horribly delicate situation which I have encountered too many times) one visits a friend and while the owner thinks things are fine the system is actually broken. When I found the bad 6SN7 in the Oppo the owner said it had probably been like that for a month. When we find a speaker out of phase it might have been that way for half a year. When I hear a distorted amplifier and I put it on the bench and find it way out of spec what has the listener been doing?
I visited another audiophile who had $100,000 of good gear in a cubic room about 14x14x14 feet with all hard surfaces and no treatment at all. The room was so live I couldn't even carry on a conversation. I politely said.. "Hey its nice outside can we go sit in the sun and chat" When we came back in to listen he asked me what I though of his system. I told him, Sorry I cant hear the system I can only hear the room. Once again he though because he had good equipment that it had to sound good.
Of course we should trust our ears but where is our reference? How many high end systems are being listened to with something out of wack.
I am likely one of a very few designers that actually will repair others equipment. I do this because I like to see others work, how they make things, how their things perform. I have tested over 400 amps and preamps and can tell you all about what is going on in them.
I feel one of the great benefits of tube products is the limited
bandwidth eliminates susceptibility to much of the higher frequency ac
noise. Comments?
You can have plenty of bandwidth and not have noise problems. Noise is best handled by proper power supply design and good grounding technique. I find also that fully balanced differential circuits are handy for noise rejection as well. This means that you can have a wide bandwidth tube amplifier and have it be very quiet, even though it may not be shielded by a chassis.
Some products allow the music to communicate to you, some don’t, and a
combination of components may speak to me, but not to you. I know this
isn’t a technical question, but I felt compelled to write it
nevertheless.
Dr Herbert Melcher showed that there are tipping points in the brain. Normally music is processed by the limbic system. But when things audio go amiss, the processing is unconsciously transferred to the cerebral cortex. At that point the music 'subjectively' loses its 'soul'. For this reason, its really important to know how the ear/brain system perceives sound, so as not to violate its perceptual rules (if you want the gear to be emotionally involving). Once you know that, it becomes and engineering task that is fairly mundane.
He made excellent equipment and I can see from JAs measurements he did a
good job on the three major characteristics of a good amplifier, one
that would drive a wide variety of speakers well. On this I am in
complete agreement with Charley. Im not sure why I need to listen to his
amps, I am confident they sound find. Charley and I are on the same
page with what is important.
Charles made **zero feedback** amps and IMO his are some of the best solid state amps made. What I like about his approach is that he solved the issue of an amp that acts as a voltage source while also lacking the usual coloration of brightness caused by the distortion of added feedback. The industry needs this sort of diversity and he is missed.
I feel one of the great benefits of tube products is the limited bandwidth eliminates susceptibility to much of the higher frequency ac noise. Comments?
Also, while I don’t recall the exact numbers, Ralph has stated in some
past threads that he has observed remarkably high levels of energy
emanating from LOMC cartridges at ultrasonic or RF frequencies.
@almarg The Hagerman site shows a 30db(!) peak. I can confirm that.
About 35 years ago I used to subscribe to the cartridge-needing-a-load theory. I set out to build a device that would come up with the correct loading so as to eliminate guesswork on the part of the user, which I was hoping to build and sell.
What I found when ringing the cartridges was that they really didn't ring until you got to some very high frequencies well past audio! This is easy to understand- if you pass a squarewave through one, there isn't much inductance to mess with the squareware at audio frequencies.
So if the brightness of an unloaded cartridge isn't due to ringing, what is doing it? I was lucky- a serendipitous event caused me to realize that the preamp played the bigger role. At that point it became a simple engineering task to insure that a phono preamp design would be resistant to this sort of problem. In a way, I did get what I set out to achieve- being able to sort out the correct load, which for all LOMC cartridges is 47K. What is needed is a preamp that is unperturbed by a 30 db peak 100KHz or above into the low MHz.... Not that hard once you know what's afoot.
I think you are mistaken. I don't recall ever entering into any debate of any kind let alone some type of trolling-skirmish with you. IMO, you are once again confused. Let me ask you this Roger; other than one of Ralph's amps, which modern era top-tier tube amps have you actually sat down and listened to with not just your own planar speakers, but also modern coned speakers across a decent spectrum? I ask because as I have said previously in this thread, you keep referencing ancient amplifiers of the remote past which you conveniently choose to piss all over. Others have asked you this same question too and you have not responded. Are you living in a cave? I re-entered because I could not resist. I saw that your irascible behavior has continued and not just towards me, so I felt better about re-entering. I do respect you and your knowledge base, but it also pays to be a gentleman. Towards the end of his life, Charley Hansen (you misspelled his name a few posts ago-shame on you) was very vocal about MQA and his debate with JA on another forum became quite heated. Throughout that give and take, both managed to remain polite and civil. You could take a lesson from them. I brought up Charley Hansen's interview towards the end of his life about his latest iteration of amps finally-in his opinion-capturing the sound of the best modern tube amps. Have you sat down to listen to any of his amps? Have you analyzed why they might sound as they do from an engineering standpoint? I am into vinyl, thank you. I am the proud owner of a Manley Steelhead, which I bought new. I love it and love Manley. I wish the aesthetics of their amps suited me more. I acknowledge that letting aesthetics get in the way of a purchase decision seems silly. I also acknowledge that Ralph's views on cartridge loading differ from my own. But as you quoted me (accurately), I have 1% of your engineering knowledge and his too. But I have years and years of empirical experience and based upon that, I have chosen to disregard Ralph's views on cartridge loading as simply not applicable to my particular system and experience.
Perhaps I have mistaken you for someone, however your last post was rather heavy handed. But lets shake hands and move on.
I hope to be brief because this is not on topic. I do not think I have ever mentioned Charley Hansen in any post. Please correct me if I am wrong. I would like to read an interview that you particularly like, could you please provide a link? He made excellent equipment and I can see from JAs measurements he did a good job on the three major characteristics of a good amplifier, one that would drive a wide variety of speakers well. On this I am in complete agreement with Charley. Im not sure why I need to listen to his amps, I am confident they sound find. Charley and I are on the same page with what is important. Though some may take objection to the following here is what I have found:
If you compare several amplifiers that meet the three criterion of damping, low distortion, good current delivery then these are what I call good amplifiers. Good performing amplifiers tend to sound very similar because they are GOOD. Now if we take one of those ampifiers and compare it to amplifiers that do not meet the three criterion (there are more than 3 but the first 3 are the most obvious) in an A/B setup, levels matched, the differences can be quite alarming and immediately obvious on either pink noise or the proper choice of source material. This has been my experience over 45 years of doing this. I invite others to get their opinion. I invite you to come listen, bring any amp you like and lets have a go at it.
In the current setup I am using QUAD 57s and a few cone speakers. I prefer ESLs and find them more revealing. I think everyone knows I moved to Santa Barbara from VIrginia specificaly to work with Harold Beveridge in 1978. As I recall he paid me $500 a month plus royalties on my preamp. I didnt do it for the money I did it to apprentice to a master.
In the past year I have repaired and listened to a Reference Line SS amp, A big 833 SE amp. Several Single ended 45, 2A3, 300B. Of course I listen to all of mine and aways to the strict A/B.
As to modern amps, on some we are going backwards. The Cary SLI 150 is an example. While it measured badly it sounded fine to Herb because he played it at the low range of power where the distortion is low. This is a very common occurance at Stereophile. Once a broken EAR amp got a great sonic review and upon test it was discovered to be very distorted about a few watts. However below that level where the reviewer used it there was no appreciable distortion. It is clear to me that most reviewers do not put a high power amp through its paces. Its just not how they listen.
These days anyone who can get an amp to work at all and has the ability to get it to market ends up doing so.
Eveanna Manley is a close friend, I have stayed at her home when David was still around. I have sold them EI EL84s. I know the stingray well from the point of supplying tubes. The bias control range is rather narrow, Have you had any trouble getting tubes that will not bias up in the range of the pot? We had do do selecting for some customers.
Also, FWIW, I’ll mention that Keith Herron, whose company and products
(especially his phono stage) are about as non-controversial and highly
regarded as they come, suggests that with his particular phono stage no
loading whatsoever will often be found to be preferable with LOMCs,
regardless of the cartridge type. (The LOMC input of his phono stage is
FET-based, and it applies a load resistance to the cartridge that is
nearly infinite when load resistors are not connected externally, to RCA
jacks that are provided for that purpose). And I have found that to be
the case in my own system, with an AT-ART9 cartridge having a
recommended load of "100 ohms minimum."
I am glad this has been brought up. I met Keith at an audio show (IIRC the last THE SHOW Las Vegas held at St. Tropez). He had his phono stage there and because I didn't see any loading capability on it assumed it was MM only. He quickly corrected me by pointing out the cartridge he was using. When I asked him why no loading feature he provided an eloquent response that went over my head, but after my own testing, from that day forward I have never loaded a MC cartridge, regardless of the cartridge manufacturer's recommendation. Keith added a loading feature in the next design iteration and continues to offer it today and we can probably guess why.
I’d like to add this: I appreciate the fact that there are two professionals contributing here, despite the fact that there is tension that’s been created by disagreement. I’m trying to read through the commentary to the points being made, the examples being given, and the facts. The reality is, there are many ways to arrive at the same destination. I’ve listened to, and owned A LOT of gear in my life, though none, so far, by either of these designers. Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless.
(although I am unclear if the phone company developed the standard which I have heard referred to as the 600 ohm standard).
The 600 ohm aspect has to do with the spacing of the lines on telephone poles. You've seen them many times - that spacing causes the resulting transmission line to have a characteristic impedance of 600 ohms. This means that if terminated by a 600 ohm load, there will be no reflections at the termination in the transmission line- its not that the impedance of the transmission line is 600 ohms. So output transformers driving a balanced line were set up to drive a 600 ohm load. When the balanced line system was brought into studio and radio station applications, the 600 ohm became a standard which stood for many years and many pro audio components still support it.
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