DIY Transistor Amp Using NVA Boards

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ed
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#166 Re: DIY Transistor Amp Using NVA Boards

Post by ed »

couple of points...the James are multi tap so will doubtless suit a setup your playing with.

As Nick says there is no competition, but if it's something to fiddle with then I strongly suggest you build a mofo...I'm sure that will give you something to think about. It will let you turn the wick up a bit more and will be operating in a happy area, just right for your listening space and speakers. As Mike Holmes would say, guess how I know.
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#167 Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr »

ed wrote: Wed Jan 05, 2022 7:00 pm ...but if it's something to fiddle with then I strongly suggest you build a mofo...I'm sure that will give you something to think about. It will let you turn the wick up a bit more and will be operating in a happy area, just right for your listening space and speakers. As Mike Holmes would say, guess how I know.
Cheers Ed,
I'll have a look at the relevant stuff on the Nelson Pass forum on DIYAudio. That'll make three amps, which would be a record in my house. :)
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#168 Re: DIY Transistor Amp Using NVA Boards

Post by Ant »

I think ive got a pair of jlh boards wot our phil (i think) passed on to me and some psu boards that i think came from ray if you want those to build?
That'd be four
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#169 Re: DIY Transistor Amp Using NVA Boards

Post by pre65 »

Steve, I can supply you a pair of the MoFo circuit boards if you want.

And, the microwave oven transformers I got from Ray seem up to the job. :)
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#170 Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr »

Thanks chaps, I'll think about it and PM when I make my mind up. :)
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#171 Re: DIY Transistor Amp Using NVA Boards

Post by steve s »

Cressy Snr wrote: Wed Jan 05, 2022 7:15 pm
That'll make three amps, which would be a record in my house. :)
Only 3..

To add to the positives and thoughts already shared, I too really like your 45 amp, a lovely and sweet sounding amp to me.

I have a couple of pairs of sowters, as you know, and they are doing nothing if you want something to play with.
As Ed says the mofo is always worth a build, but you've heard mine a couple of times now, so you know what they are about.
But they are still little bit of an investment if your starting from scratch.
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#172 Re: DIY Transistor Amp Using NVA Boards

Post by pre65 »

steve s wrote: Wed Jan 05, 2022 8:12 pm
But they are still little bit of an investment if your starting from scratch.
Can be, price up the two heatsinks and chokes before starting.
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#173 Re: DIY Transistor Amp Using NVA Boards

Post by Ray P »

Sorry, a little late to the party...

If a MoFo is of interest I have a couple of almost fullyy populated PCBs you can have for the cost of the postage Steve.

As a variation, how about a power FET device instead of the MosFet of the MoFo?

The LuFo uses the LU1014D device. The original version was around 39W output using a MosFet Cascode but with the power requirements of your speakers you could probably get away with a LuFo-Lite, which was a variant for headphones but capable of delivering a handful of Watts into 8ohms. It's as simple as MoFo but with the lower power you should be able to use smaller heatsinks and chokes = less cost.

https://www.diyaudio.com/community/thre ... mp.374760/

As you'll see on the link, the original power supply was a 19V computer SMPS brick, followed by a Cap multiplier. I can let you have a pair of the LU1014s and I have some PCBs for a cap Mx if that would help, though other power supply arrangements might be more your style.

One thing to remember is that MoFo (and LuFo) don't have voltage gain so you need to provide that upstream with your preamp.
Last edited by Ray P on Wed Jan 12, 2022 9:48 am, edited 2 times in total.
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#174 Re: DIY Transistor Amp Using NVA Boards

Post by Nick »

Being slightly awkward, but also having gone around this loop myself...

Maybe, instead of building multiple valve amps because they do something that the NVA amp doesn't, but then realizing the NVA amp does something the valve amps don;t, so rinse and repeat. How about working out what it is the NVA amp doesn't do and see if a better SS amp would fix the problem. Then if you want a bit more 2nd and 3rd add a valve buffer when required.

Maybe start with this?

https://neurochrome.com/products/modulus-86

I heard one from a bunch of them some years back now and it was generally doing very little wrong.
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#175 Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr »

Thanks chaps. :)
Contrary to what might be the unintended impression I’m giving. I don’t sit there agonising over perceived deficiencies in the quality of the sound that comes out of my speakers. I just find the whole hi-fi thing fascinating. I mean what is the absolute sound anyway?
I don’t believe it is possible to get every single aspect of what I want out of a system at the same time. It’s a hobby that keeps me occupied and it is rewarding in the sense that I like making objects. The feverish amp building of the past was more a physical manifestation of a poor state of mind than it was about anything to do with hi-fi. Trouble is, once it’s out there, it’s out there forever.
I don’t really feel that there is any need to make any more progress beyond what I have at the moment. Some may not understand that attitude, but what I’ve heard at Owston tells me that folks like a wide range of different presentations, some of which I like and others that I couldn’t live with if you paid me.
I’m near enough to what I like, that we are down to minor differences in flavour these days.

If I want solidity and authority, I use the NVA, intimacy and subtlety, I use the 45. A bit of both, a partial feedback SEP/SEUL.
It works for me because I have these options now, whereas before, when it was one amp and no backup, these options didn’t exist.

SS amp with valve buffer might be the way to go at some point. It is something I’ve thought about for years but have never got around to trying. The old WAD Pre II cathode follower type thing looks like a decent proposition. Silent power and heater supplies being a prerequisite of course.
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#176 Re: DIY Transistor Amp Using NVA Boards

Post by steve s »

On an aside, I was very aware of all (all I remember?) the bass sounding soft on many of the solid state powered bass drivers at our last owston meet.

What I mean by that was that the leading edges to bass notes sounded wooly and not real or accurate and the texture was missing from the bass

I put it down to cheap amps used to power the bass drivers, but I could be wrong on that assumption.

But it's still got me wondering why..

What it did prove is the mainstream thinking regarding bass powered by separate ss amps is flawed
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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