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

What do you think of Parasound’s new integrated amplifier?

Not sure if this has been covered on this thread.  In regard to BiWiring speakers from the amplifier, does this seperate route of connection in general improve the sound of the speakers or is it just one of those HiFi myths (pure BS?).

"...does this separate route of connection in general improve the sound of the speakers or is it just one of those HiFi myths (pure BS?)."

In my experience, it is not a myth and it does incrementally improve the sound quality. My understanding of the technical reason is it reduces the negative affects of the crossover by (almost) directly connecting the amplifier to the drivers. 

In regard to Bi-Wiring speakers from the amplifier, does this separate route of connection in general improve the sound of the speakers or is it just one of those HiFi myths

As in all things HiFi, the devil is in the details.

For a technical look at Bi-Wiring, please see  http://ielogical.com/Audio/CableSnakeOil.php/#BiWire Please note that these are Spice models and not actual system measurements.

This thread is going way to fast for me.. Way back, power cables was mentioned.. For those that said that they don't make a difference, does speaker cables and interconnects make a difference ? I felt that if the latter two makes a difference then the power cables do to.. I swear when installed Audioquest's Hurricanes it improved the sound.. Maybe its just me thinking that ??.. I need one more to complete the full loom (4pcs).. I'll try 4 $100 cables after the complete loom and see..

@ffzz My speakers are 93db sensitive (1w/1m) with 8 ohm impedance (7ohm min).With a listening distance of 8 feet, it seems 15w will be more than enough to produce 100db or so loudness that Symphonic music peaks into from time to time.Assuming 100db is my max need, will there be any advantage of using, say, a 30w amp rather than a 15w amp? What if the amp is class AB rather than A?

I think thats a little light on power. 8 feet is more than double a meter so 9db loss there but 3 gain for stereo so lets make it minus  6 dB on your sensitivity. You are going to get 87 db per watt. 10 watts will get you 97 and 20 watts will get you 100. If that is peak, not average then 30 watts is barely ok. If your room is absortive then more power is needed. 

100 db is a high level, have you checked with an SPL meter.  I listen no louder than 90 peak. A 30 watt amp is fine for me and most people but they dont listen at 100 dB

The class of amp will make no difference. 

@oem  This thread is going way to fast for me.. Way back, power cables was mentioned.. For those that said that they don't make a difference, does speaker cables and interconnects make a difference ? I felt that if the latter two makes a difference then the power cables do to.. I swear when installed Audioquest's Hurricanes it improved the sound.. Maybe its just me thinking that ??.. I need one more to complete the full loom (4pcs).. I'll try 4 $100 cables after the complete loom and see..

We can slow down, no problem. 

Audio cables make a difference no doubt. However after $100 I think there is little to gain. Cables have measureable and predictable effects of capacitance, inductance etc. 

Just because they make a difference it does not follow that a power cord does. In power cables there is not much to measure and a lot of other wire to consider. 

In my experience, it is not a myth and it does incrementally improve the sound quality. My understanding of the technical reason is it reduces the negative affects of the crossover by (almost) directly connecting the amplifier to the drivers.

The best crossover is no crossover. When are we going to stop piddling around with tiny effects when we can bi amp and do someting that really makes a difference.

Many of these cables and little tweaky things cost more than a good electronic crossover and a second amp.

@tinear   Richard... I am enjoying the heck out of this forum and am learning quite a lot.  I am interested in your thoughts and insight into Bob Carver’s latest tube amps

I heard the amps were very light weight, had tiny transformers in those big cans. He has to be cutting corners somewhere at those prices. Check the weight of the 275. Wheres the measurement?

Roger

My understanding of the technical reason is it reduces the negative affects of the crossover by (almost) directly connecting the amplifier to the drivers.

Bi-Wiring has no effect on the crossover. In an electronic circuit, when current flows through a resistance, voltage is developed. In a Mono-Wire system the tweeter connection is modulated by the woofer current. By providing a direct path to the low impedance amplifier output, the tweeter is not modulated by the woofer circuit current. On some program material, it is quite evident, not so much on others. YMMV.

The best crossover is no crossover. When are we going to stop piddling around with tiny effects when we can bi amp and do something that really makes a difference.

As mentioned earlier, the devil is in the details. Some speaker crossovers are more complex in their action than a symmetric electronic one. My dbx223 sits in the cupboard because the dual 4th order did not sound as well as the 4th/2nd passive on the mains or the electronic 3rd / passive 1st for the sub.

Digital may have promise, but at this stage, new hardware elicits no interest.

For a technical look at Bi-Wiring, please see  http://ielogical.com/Audio/CableSnakeOil.php/#BiWire Please note that these are Spice models and not actual system measurements.

He was doing fine till he got here on #1..   

  To go back to our marble and donut example, a higher frequency would be represented by inserting a marble faster in the tube, with a correspondingly fast-moving donut. So with a multi-frequency signal such as music, the higher frequencies entering the cable reach the other end earlier than the lower frequencies.

  Also as we saw, the “signal” moves down the wire’s outer circumference, and not in the wire. Therefore, the velocity of propagation of the signal (versus the velocity of the actual electrons) is determined by the dielectric or insulation material that the electromagnetic wave is predominantly traveling through. The slowing effect of the dielectric varies with frequency, throwing another variable into velocity of propagation—but giving us a way to play with it.

Do they higher frequencies get there sooner, i think not. The second part is skin effect which has pretty well been delt with as a no go in reasonablely small conductors. Dielectric on a 8 ohm cable is ludirus. Hes just measuring inductance for that time thing.

Whenever people start talking about time, they suck in the audiophiles and make big errors in logic.

Sorry I cant read anymore without ruining my day.

 In an electronic circuit, when current flows through a resistance, voltage is developed.

Most would say when a voltage is applied aross a resistance a current flows. An ampifier supplies a voltage and the current is determined by the load. Tere is no current till there is a load.

However in designing a preamp (the most difficult thing to get right) is that we drop voltages across resistors to get our operating points. Has anyone thought why preamps have so many more resistors than anything else?

But I am still thinking about voltages not so much currents till I get to the output stage of a power amp.

As mentioned earlier, the devil is in the details. Some speaker crossovers are more complex in their action than a symmetric electronic one. My dbx223 sits in the cupboard because the dual 4th order did not sound as well as the 4th/2nd passive on the mains or the electronic 3rd / passive 1st for the sub

.

Digital may have promise, but at this stage, new hardware elicits no interest.

The RM-3 crossover I use is all discrete push pull followers in the high end, op amps in the low. DIgital crossovers are not recommended. Too may A/D and D/A coversions to be done well at a price. Then there is the code that runs them. 

Analong crossovers are available, why get a digital one?

Good drivers need no correction because they are good, look at the response curves. No one is going to convince me that a bunch of coils (some with iron) capacitors, lossy resistors is better than a direct connection to the drivers.

Audiophiles will spend copiouis dollars on cables that have minimal effects and ignore the real powerful effects because they are daunted by the thought of bi amping. Get some help, read some books, do something important.

Is there a bi-amping group somewhere on this forum? I'd rather go there and help them. Seems all I get here is disagreement.

HAPPY NEW  YEAR, Make a resolution to do something important to your system. At a minimum make a bi amp speaker, even a little one. Crossover kits are available for less than the price of a bi wire.

Regarding differences in cable propagation velocity as a function of frequency, the following paper (which I and another member had referenced in posts here a few years ago) appears to me to be credible as well as informative:

http://www.audiosystemsgroup.com/TransLines-LowFreq.pdf

See Figure 2 of that paper, although it addresses a coaxial cable rather than speaker cables. It can be seen that propagation velocity does decrease considerably at low audio frequencies compared to high audio frequencies. However, even at 20 Hz the propagation velocity, while much slower than at higher frequencies, is still about 5,000,000 meters per second, easily fast enough to be utterly inconsequential in the context of a home audio system, despite claims in some marketing literature to the contrary.

As Ralph aptly said in another context here not long ago, where there is an effect there is snake oil for it. I would add that is particularly likely to be true when the claimed effect is not or cannot be looked at in a quantitative manner.

... the velocity of propagation of the signal (versus the velocity of the actual electrons) is determined by the dielectric or insulation material that the electromagnetic wave is predominantly traveling through.

I believe that this statement is correct, and is unrelated to skin effect. Cable propagation velocities are usually somewhere between around 50% and 95% or so of the speed of light in a vacuum, and are dependent on the dielectric constant of the insulating material surrounding the conductors. Numerous references can be found on the web in support of that.

The reason is that signal energy is conveyed in the form of an electromagnetic wave (rather than by the associated but vastly slower "drift velocity" of electrons), and for the most part that wave propagates outside of the conductors, within the dielectric (aside from a small fraction of that energy that is absorbed by the resistance of the cable itself).

Again, though, whether an audio signal propagates from one end of an audio cable to another at 1 nanosecond per foot (close to the speed of light in a vacuum) or at 2 nanoseconds per foot, or somewhere in between, is utterly inconsequential. And if a 1 ns/foot cable sounds different than a 2 ns/foot cable, the reason is something else.


Regards,
-- Al

Just because they make a difference it does not follow that a power cord does. In power cables there is not much to measure and a lot of other wire to consider.

I would not base an assessment of a power cord on the effects of interconnects or speaker cables. Ohm's Law works much better :)
You can measure the voltage drop of the power cord with a simple DVM.
As to its effects, its easier to see how it affects the equipment to which its connected. Some gear is more sensitive to AC input voltage than others, but in general, measure power output, output impedance and distortion. These will vary according to power cords, but not according to the cost of those cables  :)

Nelson Pass is now offering a kit version of his nice First Watt B4 active electronic x/o at an irresistible price. It provides 1st/2nd/3rd/4th-order high-pass and low-pass filers (6-12-18-24 dB/octave) in 25Hz increments from 25Hz to 3200Hz, via discrete circuitry (no opamps, no ic's, purely analog). A speaker unusably easy to bi-amp with a x/o such as the B4 is the .6 and earlier Maggies. For instance, one can simply use the B4 in place of the outboard x/o included with the 3.6; the B4 filters the bass out of the signal sent to the amp used on the woofer drivers from the amp driving the midrange drivers and tweeters, and visa versa. The improvement is huge! This is possible with the 3.6 because the speaker's x/o is a parallel design; in the 3.7, Magnepan unfortunately switched to a series x/o, so bi-amping is not possible with performing internal surgery on the speaker.

Why can’t people stay focused? Ramtubes started this discussion about amplifiers and it looks like it fell into the cable whole again! 
Start your own thread about cables of any different kind and stay out of the ones that have nothing to do with it!

Hole not whole. I want to learn about amplifiers

@bdp24 - where can I find that B4 crossover kit you referenced. Haven’t been able to locate it on the Internet.

Clio

The B4 is a First Watt product, it is a stereo active crossover with adjustable frequencies, slopes, and level, uses Jfets with no feedback.

@clio09, I read awhile back on a DIY forum that the assembled First Watt B4 was being discontinued, and Nelson was by that time providing info on the kit version. I just looked on the First Watt site, and the B4 is still listed. That doesn’t necessarily mean it is still available, of course, but give Reno Hi-Fi a call, maybe they have one left. It retailed for $1500.

Yes was aware it was a First Watt product just never saw it advertised as a kit. Nelson does have a crossover kit on the DIY Audio store but it's an analog version of the digital crossover used by Ziegfried Linkwitz, who asked Nelson to design it. I actually have the stuffed boards for this crossover as Nelson made them available at the recent Burning Amp.

Roger, 
           Thanks for this great thread! It is one of the best threads I have ever read on this website! Your time educating us non-technical prople is greatly appreciated. I still own the original Beveridge Model 2׳s and have a couple questions after reading your earlier comments about these speakers. You mentioned in an earlier post that the perfect room for these speakers is one that is 11’ W by 24’ long. You mentioned that they needed to be at least 6 feet from the rear wall facing each other. Then you commented on their amazing imaging saying that they should be 2 times 6ft or 12 feet area for imaging. Were you just saying that both speakers were 6 feet away from the rear wall or were you saying the speakers should be pulled 12 feet from the rear wall in this perfect room?

The original Beveridge amplifiers uses solid state inputs much like your RM-200. Is this because the high voltage needed for the speakers? It These Beveridge amplifiers weakness is their power transformers which I have had a few go bad on me. For this reason I keep a stash of these amps. Could you recommend a source for rewinding these power transformers because Jack at Electroprint has very little interest because of the enormous demand on the power transformer. Could you comment on this? I believe you might have come up with a work around for this issue. 
 Lastly, i have stayed away from your RM-1 (and RM-2 Power supply) Beveridge preamp because I have been told that the preamp is very hard on tubes used in it. This seems very much counter to your later works. Is this true or myth about the RM-1/2? If so, is there a later fix for this issue or should I just buy a later preamp of yours. I have used many preamps with the Beveridge 2’s. Currently I am using an old PS Audio 4 preamp in the passive mode. I obviously am
a fan of your work!

Roger,
           Thanks for this great thread! It is one of the best threads I have ever read on this website! Your time educating us non-technical prople is greatly appreciated. I still own the original Beveridge Model 2׳s and have a couple questions after reading your earlier comments about these speakers. You mentioned in an earlier post that the perfect room for these speakers is one that is 11’ W by 24’ long. You mentioned that they needed to be at least 6 feet from the rear wall facing each other. Then you commented on their amazing imaging saying that they should be 2 times 6ft or 12 feet area for imaging. Were you just saying that both speakers were 6 feet away from the rear wall or were you saying the speakers should be pulled 12 feet from the rear wall in this perfect room?

The speaker will be 6 feet from the rear wall. 12 feet is the depth of the image which is 6 ft to the wall and 6 more for the sound to return to the speaker. a 12 mSec delay feels like 12 feet.

Very nice speaker, hold on to it. I hope visitors appreciate it.

Lastly, i have stayed away from your RM-1 (and RM-2 Power supply) Beveridge preamp because I have been told that the preamp is very hard on tubes used in it. This seems very much counter to your later works. Is this true or myth about the RM-1/2? If so, is there a later fix for this issue or should I just buy a later preamp of yours. I have used many preamps with the Beveridge 2’s. Currently I am using an old PS Audio 4 preamp in the passive mode. I obviously am
a fan of your work!

The early runs of the preamp ran hot even though I ran the tubes at one half dissipation. I reduced it to 1/4 rated dissipation. We upgraded many but there are some high current ones out there.12 tubes makes some heat so it needs free air and not in a rack or stack. Many of them come to me with Ram tubes so I can tell last time we sold the customer tubes. Its typically 3 years. Now a tube can get noisy at any time and its a very low noise preamp so people use the MM input for cartridges  0,5 mV and up.. Therefore they would run the line higher and a noisy tube would be obvious.

Lets say this. For its 1978 vintage it something few can do. Its DC coupled, no output capacitor, many features for phono lovers. Try one out. Clean or better yet, replace the 12 pin connector from the power supply. 

If people want to know about RM-1s I will write up a white paper. If it was still in production I would be sending on to Stereophile for JA to bench text. There would be no drop off in the bottom or top end at any load, even a ohm. Output impedance is 100 ohms, very rare for tubes of the day.

I would say it rivals an SP10 in many ways and perhaps more reliable. 

More about Beveridge and the company on request. He was my mentor and very out of the box.

Hello Roger, thanks again for this opportunity seeing you worked for Harold Beveridge , I have two questions, 1). I have a pair of Beveridge 2SW's with a panel that has gone south. I am looking to make a jig to tension the mylar film. Can you shed some light on how to rebuild the panels, I have some background info on the mylar but would like to know the tension techniques to properly rebuild.

Question 2), I had purchased a set of Counterpoint SA-4's about 2 years ago needing repair/restoration. One was functional one was not but found one tube had vented, I think it was due to mishandling during transportation.

Can you give info on what to check for, and possible ECO's on this amp so I can proceed with a restoration for a set of Quad 63's I am planning to use them on.

Best Regards,    

Roger,
          Thank you for the comments about Beveridge speakers. Could you also make some mention about the power transformer of these direct drive amps?  Should it be so difficult to find a source to rewind these transformers making the amplifiers operational again? I have had 4 amps where this is an issue (in both Beveridge 2 and 2sw amps.) My original pair model 2’s had this issue upon purchase (long story.)

This power transformer issue and panel issues seem to be what keep these speakers from being more highly coveted today. Thanks again for your generous participation on this thread. 

Re: Beveridge
Hi, Roger,
You'd worked on the Bev DD amps for my Model II's when you were situated in Santa Barbara.  Unfortunately, Rick was unable to complete the restoration process and my panels require attention.  Can you assist?
Thanks for the attention.
Vbr,
Sam

Roger, thanks for your time.
Some of the technical talk on this thread is way over my head so I’ll have to bone up on my tube electronics, which I learned over 50 years ago in college, then became a computer jock so I forgot about them until recently.
I am sold on tubes for analogue audio but am confused by all of the information on power. I see from many posts that tube power need not be very high or as high as the speaker manufacturer claims as a requirement, i.e. a 200 WPC SS amp is needed to drive a speaker with 85db sensitivity (the manufacturer requires a minimum of 75 WPC, but likes at least 100 WPC), yet I have used a tube power amp with 40 WPC on the speakers and it sounds terrific. I have read that it is in the output transformers and SS amps are generally direct coupled.
Will you please explain this phenomenon?

Thanks. Rollin

Well, that just figures, doesn't it? Living way out here in Wyoming, my chances of having a conversation about this is more than rare. Then in the last few weeks, I have an opportunity to tap into 3 different audio engineers, electronic engineer, amp designer. It's funny how that can be.
  So here is something that probably has been asked before, but there are just too many pages for me to go through. Why shouldn't decent tone controls, and maybe even loudness controls come back in fashion? For it is simply that I need them at times, being 61. Now, mind you, I have bought many a product in the past that had such controls that were not worth the solder. Then, I got ahold of a low cost Yamaha integrated that changed my mind about such things. When it came to a loudness control, they chose NOT to increase the bass/treble, but instead to reduce the midrange. Cool idea. Other companys were spot on in the thinking tone controls whose turn over frequency for that particular control could switched to a more desirable frequency to start the correction. So if you were to use the bass control, you might have a choice of adjustment starting at either 100 hz or lower, at 60 hz, for example. The fact that these could be switched out of circuit when not needed, is enough for me to buy such a product.

  Your thoughts...

I hope that Roger will step in at some point and address some more questions but currently there are a couple projects occupying a lot of his time. So he’s had to take a little break from here.

@4krow - Roger has often talked to me about the difficulty in doing tone controls right. I know there are some C4 preamps of his out there with tone controls that owners have found very useful. He was often asked how to use the controls and his stock response was use the setting that sounds best to you.

In addition, Roger designed and for a while offered the two knob EQ for speakers that lack bass in the 320, 160 or 80 Hz range. You could choose between these frequencies and dial in exactly how much you want to boost, up to + 6 dB if I recall. Roger designed it in part because he listens to a lot of Leon Redbone and noticed the vocals never quite sounded right on most of the speakers he listened to. So the EQ corrected for that. He’s one of the few people I know that consistently uses the bass control on his RM3 crossover. Me, I’m set it and forget it with my RM3, but Roger fiddles with his to get the sound to his liking.

@c1ferrari (it’s been a while Sam, we met at Newport in my room there as you had interest in demoing the Lightspeed attenuator). I will talk to Roger about your situation and see what we can do to help (same for you Baranyi). We do stock the mylar for the panels if you need some.

I am sold on tubes for analogue audio but am confused by all of the information on power. I see from many posts that tube power need not be very high or as high as the speaker manufacturer claims as a requirement, i.e. a 200 WPC SS amp is needed to drive a speaker with 85db sensitivity (the manufacturer requires a minimum of 75 WPC, but likes at least 100 WPC), yet I have used a tube power amp with 40 WPC on the speakers and it sounds terrific. I have read that it is in the output transformers and SS amps are generally direct coupled.
Will you please explain this phenomenon?

@rollintubes
With all amplifiers its all about frequency response and distortion as to how they are going to sound. Solid state amps tend to have the flattest frequency response, but the difference between that and a good tube amp is slight and on many speaker loads may not even be measurable. Yet the solid state amp often sounds brighter and harsher, even though its got flat frequency response.

The reason is distortion. Our ears detect sound pressure by detecting the presence of higher ordered harmonics in any sound (likely because pure sine waves are extremely rare in nature). Solid state amps typically make more of these higher ordered harmonic distortions than tube amps do.

So when you are trying to make power, this really comes into play in a number of ways. As you push an amplifier towards full power, tubes and transistors behave differently- at clipping (anything over full power) transistor amps produce a large amount of higher ordered harmonics. Tubes don't, until they are over-driven really hard (and thus their distortion becomes audible as break-up).

So a smaller tube amp can act like its a lot bigger than it seems compared to a transistor amp. This is because music has lots of transients, and the distortion may only be showing up on the transients. The ear interacts with these distortions, telling you that the sound is louder. But the tube amp tends to do this in a way that is less noticeable, so essentially its giving you false loudness cues (this is particularly true of SET amplifiers, which is why they are often cited for being so 'dynamic' for how little power they have).


The other thing that comes into play is decibels. A 3db (decibel) increase is not very noticeable to the ear, but it takes twice as much power to do it. Your solid state example of 200 watts is just a little over 6 db more powerful than your 40 watt tube amp. That's not a huge increase volume-wise, so the additional distortion the tube amp makes at or near full power is able to fool your ear.


In a nutshell, tube amps have a more pleasant overload character so you can push them into overload and not even know it. That is why tube power **seems** more powerful than solid state power. Its not, but you might need a sound pressure level meter to see what is happening.

Why shouldn't decent tone controls, and maybe even loudness controls come back in fashion?

@4krow

A really nice tube preamp that had excellent tone controls was the Harmon Kardon Citation 1. If you can find one and have it properly refurbished, problem solved (so long as you don't need low output moving coil capability, although you could solve that with a stepup transformer). It employed switches to execute the tone controls, so when set to flat it really was flat. Its tricky to build a good tone control circuit (which requires an additional gain stage) that does not color the signal beyond the effect of the tone control itself, which is why tone controls went the way in the quest for greater transparency.

Why shouldn't decent tone controls, and maybe even loudness controls come back in fashion?

Fashion is the operative word.

In the recording studio, we had EQ of several flavors: Peak, Shelf, Parametric, Sub-Octave graphic. Various equalizers by Neve, API, Massenberg, UREI, etc. plus console module EQ by Trident, MCI, Neve, API, etc. plus mic 'EQ' for Neumann, AKG, Sony, Shure, etc. plus mic pre EQ from all the aforementioned and more. Each has its own characteristics and colorations to create the palette desired.

The problem with a 'generic' tone control on a HiFi is that 99% of the time, its not in the required frequency range and it's pure serendipity if the chosen frequencies align with source, recording, loudspeaker and room defects.

At our local venue, we have a small 32 channel mixer. EQ is digital and extremely flexible, incorporating most of the functionality of a whole rack of outboard EQ. It does not color tonality in the same manner as individual analog devices, which all add colorations along with level and phase changes. Sometimes a good thing, sometimes not.

I for one would love to have a couple channels built into my CD player that I could control with my phone. I could then save settings in CDP and it would recall them for each disk. A nice feature would be to save templates, e.g. "Sh.tty Columbia Remaster" for easy recall as generic corrections. A reasonable DAC with such flexibility might open my wallet in a heartbeat!

bdp24
 Nelson Pass is now offering a kit version of his nice First Watt B4 active electronic x/o at an irresistible price.

I too would like a link to this kit, I can't find it anywhere???

Cheers George

I too would like a link to this kit, I can't find it anywhere

diyAudio Store has Pass's LX-Mini kit https://diyaudiostore.com/products/analog-crossover-network

It's not as flexible as the B4, but can be customized for user desired Fc and order

The talk I saw about the DIY kit version of the First watt B4 was maybe six months ago, on a Nelson Pass-related DIY Forum site. I’ve been looking through all my folders, but have yet to find it. I’ll keep looking, but a call to Pass Labs may get an answer.

Hi Rodger,

I’m still enjoying your Music Reference RM5 MK-III preamplifier. I think I bought it back in 1994 or there about’s. Still sounds amazing by the way. I was wondering what tubes would you recommend as replacements because I’m sure you have tried many over the years and have some favorites you could recommend.

Again Thanks!

There would be a step beyond desire for the implementation of 'tone' controls, i.e. to weak a control, and nah, give me soup. Too much, but then it becomes my mother. "Do this-do that, this isn't quite right, what about another..." You see, I either listen to the music, or listen to Everything else! Choice ends when the system is set at the positive. All is right with the beat.

@ks2 - When Roger refurbishes an RM-5 the preamp gets computer tested pre-end of Soviet era SLN 6922 tubes. That is the preferred tube and the lowest noise 6922/6DJ8 tube he has tested.

FWIW - I have used them in my RM-5 Mk IV, RM-1 (12 tubes total), RM-4, and the as yet unnamed phono stage/tape head preamp. So I can attest to Roger's findings.

The talk I saw about the DIY kit version of the First watt B4 was maybe six months ago, on a Nelson Pass-related DIY Forum site.

"However, there is progress. The DIY versions of the SL crossover and
a version of B4 should be in the store in a month or so, starting with just
the pcb + Jfets kit, to be followed by more complete w/ parts versions."

Nelson Pass in diyAudio Pass Labs 2018-02-13 : https://www.diyaudio.com/forums/pass-labs/165756-pass-labs-b4-crossover-questions-post5340382.html

@ieales - Thanks for digging that up. From what I read in the link if the B4 kits were to be available in March or so, then they are either quite delayed or perhaps they were made available and sold out. I have the SL kit on a fully populated board but would much prefer a B4 kit.

Question:

What type of sonic issues occur as tubes get old? 


I had a tube in my CJ power amp fail, and the local shop said it was getting time to replace all the tubes.  But what is likely to happen if they are just left and keep on running?  Is it eventual failure?  Or does the sound start to alter in any way? Frequency response?  Dynamics, whatever?

I have the same question for my CJ preamp.  I know one aspect of tubes getting old: it now has a raised background "hiss" that it didn't have years ago when I bought it (so I've just bought replacement tubes).  But other than possible tube noise floor raising...is the actual sound likely to alter in any way as tubes age?

Thanks.

I am very interested in the answer to prof's questions above. Especially as it pertains to what impact aging tubes will have on the sonics of a preamp, other than "hiss"?  I think another way of asking the question is that if you replace a set of aged preamp tubes (having no hiss) with an identical new set, will you hear a difference?

 I’ve been studying electronics and simple circuits. I bought and assembled an $18 DIY speaker kit. It worked first time! It was my first assembly. I wasn’t perfect, before turning it on and I noticed that a 10k was in the wrong place. It was hard taking it out. Anyway after all this discussion, I bought the only remaining DIY audio preamplifier for $525. Just a few minutes ago. Roger, thanks for the inspiration!
Bentunderground
Michael Lent

@ieales, thanks for finding the exact Forum to which I was referring. My six month estimate turns out to have actually been almost a year!

Actually, after looking at the Harmon Kardon Citation 1 pre-amp, I noticed that all of the EQ that was mentioned about it pertained to phono, not tone controls. Yes, there are tone controls, but that is all they are. The adjustment is not flexible except for the plus and minus positions. I would rather have a tone control that can be set to a particular frequency... in fact, once the unit was at my house, maybe then I could determine those needed frequencies and change out capacitors/resistors to adjust to the needed frequency. Or, to get a bit fancier, as i mentioned before, there could be two or three choices, per a switch to choose which turnover frequency that you would want to use. Much better than a 33 band EQ in my opinion, and in some cases even a parametric EQ.

@4krow I believe most of the Japanese integrated amps have tone controls: Luxman, Accuphase and the newer Yamahas. I am a fan personally, my vintage Kenwood sounds so good. There is definitely something undeniably cool about switches, knobs and levers. All this purist approach is fine and good, but its also boring as hell.

But other than possible tube noise floor raising...is the actual sound likely to alter in any way as tubes age?

Yes. If their transconductance falls below the minimum values, the performance will suffer and can affect things like bandwidth, distortion and dynamic qualities. In a nutshell, can sound 'sleepy'.

Much better than a 33 band EQ in my opinion, and in some cases even a parametric EQ.

@4krow
Its **very** tricky to build a 33 band EQ that doesn't mess up the sound! Even a 10-band is challenging. Parametrics have a lot in common with the filters used in analog synthesizers- they are pretty complex circuit-wise and so they are going to have a sonic footprint even when set to flat. 

Thanks atmosphere!!
I'm being a bit lazy in getting around to changing the tubes in my CJ pre, but I'll see if I can note any difference other than (hopefully) lowering of noise floor.

 For the price, I wouldn't hesitate to go with Yamaha again after all those years ago. When I was struggling, I owned an inexpensive Yamaha integrated that really surprised me to be as good as it was and flexible as well. Like I have stated before, 'some' tone controls are flexible enough to be practical, at times anyway. The bulk of them just don't do it for me.

yes, I would be happy to pay for coursework on the subject. What do you offer?