DIY Transistor Amp Using NVA Boards

[Nick]

What does

sonic matrix

mean?

[izzy wizzy]

What does

sonic matrix

mean?

Sumfink like ... the typical traits of presentation for that set of components.

[Nick]

What does

sonic matrix

mean?

Sumfink like ... the typical traits of presentation for that set of components.

Ok, so functionally equivalent to "sound" then

[Cressy Snr]

I couldn’t leave things like this, so made a couple of changes in the SEP to enable the use of KT88s; I have one pair of JJs.
The SEP now puts out nearly 12WPC, which is two watts above the lower power limit of the Mission speakers.

Bass is nice and powerful, that warm, sweet coloration is much reduced, the image is wider and deeper and the amp holds onto rhythms superbly well. Taken as a whole, it is still not as good as the SS amp but is now at least in with a shout and I’m now quite happy to use it as a stand-in when I get around to using what I’ve learned, to build the final version of the solid state amp.

[rowuk]

I would not expect a single ended valve amp to be optimum for a low efficiency speaker. I believe that the secret is the total amount of "control". Efficient speaker drivers have less "compliance", meaning more return force through mechanical means. For any given system the return force is the interaction between damping factor and compliance. I believe that there is a sweetspot. A lower efficiency speaker has greater mechanical compliance and thus needs more amplifier damping factor. Bob Carver told me once that if I wanted to use his transistor amplifiers on a high efficiency speaker, add a 1 ohm resistor in the positive side of the speaker wire to reduce damping factor. I tried it with success - in the bass.
I would imagine with the SEP that a (much) larger OPT would help even more than the output tube.

I couldn’t leave things like this, so made a couple of changes in the SEP to enable the use of KT88s; I have one pair of JJs.
The SEP now puts out nearly 12WPC, which is two watts above the lower power limit of the Mission speakers.

Bass is nice and powerful, that warm, sweet coloration is much reduced, the image is wider and deeper and the amp holds onto rhythms superbly well. Taken as a whole, it is still not as good as the SS amp but is now at least in with a shout and I’m now quite happy to use it as a stand-in when I get around to using what I’ve learned, to build the final version of the solid state amp.

[Cressy Snr]

Hi Rowuk,
I suppose one could argue that as soon as I moved away from the 98dB Fanes, I excluded myself from the low-power SE triode/ultralinear/pentode world, but I’m comfortable with that and happy to learn the skills required to make great sound with transistors.

Not dissing valves. They have brought me much pleasure over the years and I suspect they will continue to do so in one form or another.

[steve s]

I would not expect a single ended valve amp to be optimum for a low efficiency speaker. I believe that the secret is the total amount of "control". Efficient speaker drivers have less "compliance", meaning more return force through mechanical means. For any given system the return force is the interaction between damping factor and compliance. I believe that there is a sweetspot. A lower efficiency speaker has greater mechanical compliance and thus needs more amplifier damping factor

Thats my view too, a smaller efficient speaker with a large enough magnet can be completely self damped, as the magnet decreases or the cone gets larger, the self damping starts to decrease.
In most cases this is clearly audible as the leading edges of notes start to become softer and less accurate, and start to loose realism

I'm pretty convinced that realism is all about how the leading edges of notes are reproduced.

At the last audio show I went to most of the systems suffered ( somewhere in the frequency range - nearly always in the bass) soft woolly leading edges.

Both the amplifier and speakers can have an impact .. rise time in solid state and acceleration, and quite a few other things that can slugg the sound in some designs/components.

[Nick]

I can see that in the case of single drivers. But once you add a xover the low pass will remove those edges anyway. One thing that surprised me about the acrylic ob's was they sound the same with a set as ss. I think that's down to Chris's series inductors keeping the driver's from being driven to where q becomes a problem.

[rowuk]

Thats my view too, a smaller efficient speaker with a large enough magnet can be completely self damped, as the magnet decreases or the cone gets larger, the self damping starts to decrease.
In most cases this is clearly audible as the leading edges of notes start to become softer and less accurate, and start to loose realism

I'm pretty convinced that realism is all about how the leading edges of notes are reproduced.

At the last audio show I went to most of the systems suffered ( somewhere in the frequency range - nearly always in the bass) soft woolly leading edges.

Both the amplifier and speakers can have an impact .. rise time in solid state and acceleration, and quite a few other things that can slugg the sound in some designs/components.

I agree BUT there is also the reality of "exaggerated" articulation. This happens when we take a well damped driver and use an amplifier with very high damping factor. Many times this is perceived as increased "resolution". Nick seems to have found an exception. I would like to know more about those inductors.

[Nick]

I agree BUT there is also the reality of "exaggerated" articulation. This happens when we take a well damped driver and use an amplifier with very high damping factor. Many times this is perceived as increased "resolution". Nick seems to have found an exception. I would like to know more about those inductors.

It was Chris's idea. A 8.2mH in series with the Supravox, and a 0.47mh in series with the Lowther. In both cases to roll off the drivers before the response gets ragged and to improve the match to the next driver up in frequency. A unexpected effect has been to make the speakers play nicely with both a 300b SET and a mosfet SS amp. I was expecting what you describe well as "exaggerated" articulation, but it didn't seem to be there.

[rowuk]

It was Chris's idea. A 8.2mH in series with the Supravox, and a 0.47mh in series with the Lowther. In both cases to roll off the drivers before the response gets ragged and to improve the match to the next driver up in frequency. A unexpected effect has been to make the speakers play nicely with both a 300b SET and a mosfet SS amp. I was expecting what you describe well as "exaggerated" articulation, but it didn't seem to be there.

Interesting, Looking at 8.2mH air core coils available, they seem to have around 1+ ohm DC resistance - exactly what Bob Carver recommended many years ago for his solid state amplifiers. Maybe a couple of things are going on here.

[Nick]

I didn't use air core for the 8.2uH for that reason. The one I used has a DCR of 0.15 ohm. The 0.47mH was a air core, and had a DCR of 0.12R

[steve s]

I agree BUT there is also the reality of "exaggerated" articulation. This happens when we take a well damped driver and use an amplifier with very high damping factor. Many times this is perceived as increased "resolution". Nick seems to have found an exception. I would like to know more about those inductors.

I've heard many 1000s of systems over the years but exaggerated articulation due to excessive damping is a new one on me..

My speakers too seem to perform equally well with any type of amplifier, the quality of the amplifier being the overriding factor

[rowuk]

I've heard many 1000s of systems over the years but exaggerated articulation due to excessive damping is a new one on me..

My speakers too seem to perform equally well with any type of amplifier, the quality of the amplifier being the overriding factor

I do not read much about "articulation" in any of the audio press, but the deficits certainly show up in MANY playback systems. I am a professional trumpet player and spend a lot of time on stage with real acoustic instruments. Articulation is a very important part of an instruments characteristic sound and I have NOT heard many playback systems that get it very close to right. Valve amps with lesser efficient speakers are often on the "inarticulate" side, high efficiency systems like horns or wide band drivers are often on the overly articulate side with high damping factor amplifiers.

In fact most of the "audiophile" systems that I have heard sound more like the latter than the former. Perhaps there is an industry preference for "etched" highs? As I wrote, empirical evidence seems to point towards a sweet spot in total damping.

Personally, I have never heard two different architecture amplifiers that have the same presentation regardless of the speaker used.

[izzy wizzy]

I've never heard that term articulation be it more, less, too much etc.

It sounds an interesting way of describing an attribute to the presentation; a component of the sonic matrix.

Can you expand or point me to what this means in musical terms? Could be the thing that I feel but can't put a word to it.

Thanks.