DIY Transistor Amp Using NVA Boards

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Cressy Snr
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#346 Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr »

jack wrote: Thu May 11, 2023 8:31 pm Shod.... Hang on!

No... Very nice actually !
🙂
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Nick
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#347 Re: DIY Transistor Amp Using NVA Boards

Post by Nick »

Cressy Snr wrote: Thu May 11, 2023 8:38 pm
Daniel Quinn wrote: Thu May 11, 2023 8:25 pm So long wires are detrimental to sound ?
Dunno to be honest Dan. The opinions seems to be that in a transistor amp, power and signal paths need to be as short as possible, but the amp sounds fantastic as is, so maybe I’m obsessing over nothing.
IMHO it's yet another example of the crap that is talked about hifi to try and make engineering into something closer to magic. The old computer engineering rule that 1 foot is one nano second is worth remembering. 1ns = 1 billionth of a second. Starts to matter at 100Mhz and above.
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#348 Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr »

Nick wrote: Thu May 11, 2023 9:16 pm
Cressy Snr wrote: Thu May 11, 2023 8:38 pm
Daniel Quinn wrote: Thu May 11, 2023 8:25 pm So long wires are detrimental to sound ?
Dunno to be honest Dan. The opinions seems to be that in a transistor amp, power and signal paths need to be as short as possible, but the amp sounds fantastic as is, so maybe I’m obsessing over nothing.
IMHO it's yet another example of the crap that is talked about hifi to try and make engineering into something closer to magic. The old computer engineering rule that 1 foot is one nano second is worth remembering. 1ns = 1 billionth of a second. Starts to matter at 100Mhz and above.
Thanks Nick. That puts things into perspective :)
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izzy wizzy
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#349 Re: DIY Transistor Amp Using NVA Boards

Post by izzy wizzy »

I reckon if the currents are huge and changeable then yes, it might make a difference. Many 100s of watts into super inefficient speaks, I'd want the power supply wiring short especially from the bridge to the caps. There I'd want it real short coz large caps, quite huge current pulses = mucho interference and stuff.

But closer to Class A and smaller amps, prolly not so much.

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Nick
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#350 Re: DIY Transistor Amp Using NVA Boards

Post by Nick »

There I'd want it real short coz large caps, quite huge current pulses = mucho interference and stuff.
Yep, but that's as much a case of using enough copper as the length. And the only way you will get the dv/dt is the 100 Hz switching edges and any resonances generated from that, and I would hope they were addressed by caps across the bridge, as close as possible. But other than that, once it gets to the amp, there may be huge currents, but the frequencies are still going to be low.

Clearly running a unshielded signal wire for 10's of CM close and in parallel with the connection into the power supply caps is going to matter. But the important bit there is more the "parallel" than the length. But I think Steve was thinking about it in a more vague hifi sense of all the sounds arriving at different times.
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#351 Re: DIY Transistor Amp Using NVA Boards

Post by Max N »

I have been reading some of the links posted here recently about current flowing through wiring loops (http://www.valvewizard.co.uk/Grounding.pdf top of page 266 has a good diagram)
The gist is that the transformer, rectifier, reservoir cap loop carries short, heavy pulses of current. So the recommendation is to keep the enclosed area of that wiring loop as small as possible, to minimise the radiated emf.
But I have no idea how important that actually is.....
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#352 Re: DIY Transistor Amp Using NVA Boards

Post by Max N »

Actually, looking at your photos, I reckon you've got that loop pretty small :-)
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#353 Re: DIY Transistor Amp Using NVA Boards

Post by jack »

Folk are always looking for ways to upsell their kit, and finding something that noone else is muttering about is always helpful.

Max has it in a nutshell: is it important or is it BS?

I would go further: is it detectable in any way? Stating the bleeding obvious, my 3 rules are:

1. There are lots (maybe 100s) of processes occurring simultaneously in audio equipment; the key is in identifying those that may cause a detectable (audible) deterioration in resultant audio quality. We'll call these "negative processes" and they should be removed if possible.

2. Processes that improves audio quality, we shall call "positive processes". You can always add positive processes.

3. The remaining "neutral processes" should be ignored, simplified or removed unless they directly or indirectly impact the other processes in a positive way, otherwise they're just a distraction/marketing BS. KISS.

Iterate through 1 -> 2 -> 3 and back to 1 until no further (detectable/significant/worthwhile/cost-effective/...) improvement detected.

For completeness' sake, there can be a symbiotic relationship between positive, negative and neutral processes where the net result is positive - common sense is important - I'm not advocating Muntzing!

NB. "audio quality" is both a quantitative and a qualitive/subjective term. The only interpretation that matters is your own!
Last edited by jack on Fri May 12, 2023 12:26 pm, edited 1 time in total.
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Nick
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#354 Re: DIY Transistor Amp Using NVA Boards

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I would (do) entirly agree with that but I do think the problem is this:
the key is in identifying those that may cause a detectable (audible) deterioration in resultant audio quality
There is a big problem in finding just what is and what isn't audible. This is the hole into which any amount of BS can be inserted. The only real way you can check if something is audible is by listening tests, and they have to be blind, and they have to be a much more complex protocol that simple A/B or A/B/X tests as the brain makes them unreliable for obvious reasons. So to determine if something is really audible is difficult and expensive so is basically never actually done. (Obviously I am not including simple low level problems here, I am assuming we are close to correct and its the last bit we are worried about). And further, even if those tests were done, if we found we could detect a change, how do we go about finding out which side of the change is the deterioration?

So the only rational (it seems to me) way forward is to measure, and try and extrapolate what may be audible, and work at fixing that, but its nowhere as simple as we might hope it was. I got a perfect example of this in my inbox the other day, an advert trying to look reasonable from a cable maker. I will quote:
The mysteries of "cable burn-in" and "settling-in". Can quantum physics provide some answers here?

Are any of you involved in the field, or do you know someone who is?

Then there's the thing where the act of taking a cable from one place to another and installing it in a hi-fi system, somehow makes it not sound fully right until it's settled in over a period of hours or days.

All of this also appears to apply to other parts of a hi-fi chain too...

Naturally cable sceptics and "qualified sound engineers" (the very worst!) will happily tell you that there's no change (it's all in your gullible imagination - confirmation bias and all that).

They will challenge you to prove it with any of the usual crude measurements (which of course you can't).

Only the most sophisticated audio measuring device in the world will tell you about these changes - it's called the human ear/brain interface. And yes it is fallible and sometimes you can't be 100% sure that you've heard changes, but most of the time if you're an experienced listener you will be right...

But the question of why these phenomena happen - now there's a challenge! I believe that the most likely area that may provide some insight is quantum physics. The electrical signal that travels down our cables and through the circuitry inside our hi-fi components is made out of sub-atomic particles called electrons. Anything that is smaller than an atom behaves in odd ways that are counter-intuitive to us. Unlike things that are larger than an atom, they do not obey the laws of Newtonian physics. The study of how they do behave is called quantum physics. Ask a quantum physicist whether individual electrons travel down a cable in the direction of the signal and you will be told that it's actually it's more complicated than that! It may even be misleading to think of them as particles, since subatomic particles often exhibit the expected qualities of both particles and waves!

So the behaviour of electrons is weird. At this point, my understanding runs out. Can this behaviour be modified by the direction and nature of the signals going through them?

I would love to find a quantum physicist who is also an audiophile. Too niche?! Could such a person shed some light on what might be going on here, with "burn-in" and "settling"? Maybe they might be willing to do some research in the area? Are any of you well-versed or involved in quantum physics; or do you know someone who is? Please get in contact with me - maybe we can actually get some scientific answers. Maybe we can even convert some cable-sceptics (ever the optimist!!!).
In the middle of all that spin, is the idea
Only the most sophisticated audio measuring device in the world will tell you about these changes - it's called the human ear/brain interface.
Just stated as a fact that we are expected to agree with when all the evidence we have is its just flat out wrong. Its a variation of the Argument from ignorance, though is closer to "The God of the Gaps".
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#355 Re: DIY Transistor Amp Using NVA Boards

Post by jack »

Wonderful. That advert/spiel is full of pejorative crap:
  • qualified sound engineers" (the very worst!)
  • your gullible imagination
  • crude measurements
  • Anything that is smaller than an atom behaves in odd ways that are counter-intuitive to us
  • ...ad nauseum
Basically, all of it.

The three points I mention are just a condensing of common engineering practice that works for me (not just in audio). The quantitative/qualitative dichotomy is the bit seized upon by the snake-oil merchants. Any opportunity to insert uncertainty into someone's mind and by association, their wallet, is exploited. In short, FUD sells.
Last edited by jack on Fri May 12, 2023 2:04 pm, edited 1 time in total.
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#356 Re: DIY Transistor Amp Using NVA Boards

Post by Daniel Quinn »

That's what this hobby is about cressy🤣
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Nick
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#357 Re: DIY Transistor Amp Using NVA Boards

Post by Nick »

Daniel Quinn wrote: Fri May 12, 2023 1:41 pm That's what this hobby is about cressy🤣
Yep, but without disagreeing with DQ, the problem is "this" in that sentence is somewhat overloaded. Is the hobby:

1. Using HiFi kit to listen to music
2. Making HiFi kit to listen to music

There are others but at least those two.
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#358 Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr »

Nick wrote: Fri May 12, 2023 1:49 pm
Daniel Quinn wrote: Fri May 12, 2023 1:41 pm That's what this hobby is about cressy🤣
Yep, but without disagreeing with DQ, the problem is "this" in that sentence is somewhat overloaded. Is the hobby:

1. Using HiFi kit to listen to music
2. Making HiFi kit to listen to music

There are others but at least those two.
2. That's me. I have about a 10% success rate with amps. However, this is one of the proper successes. Of course the circuit is not mine. As RD was keen to point out, SS is a whole different ball game. I wouldn’t dare try to scratch build a transistor amp.
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Mike H
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#359 Re: DIY Transistor Amp Using NVA Boards

Post by Mike H »

I was just reminded of some years ago about a chap's amplifier where the power supply was in one room, and the amplifier in the next room, and holes through the wall for massive conductors that connected them together – sure it was posted about on here :lol:
 
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#360 Re: DIY Transistor Amp Using NVA Boards

Post by pre65 »

Mike, do you remember the Maplin 50W Mosfet module amp circuit ?

I think you can still get similar on Ebay. A pair of them was very nearly my first amp build.
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