High End, Super-chimy Amps?

ICBM

Here's a challenge for you, given that I know you're an analogue electronics engineer…

Go back to absolutely first principles, ignore everything that's been done over the past fifty years, and design a solid-state amp from the ground up using the same type of circuit topology used in valve amps - ie not using any of the now-standard solid-state 'building blocks', especially in the power stage. It should have AC-coupled single-transistor stages, a single-rail power supply and an output transformer. (All things you will be reading about relating to valve amps.)

Then see what it sounds like.

Sorry, thread diversion .

thomasross20

I bet it sounds like sh!t - I'm not yet up to speed on valves but I read that a simple valve circuit can only be barely mimicked by a much more complicated SS circuit. I need to analyse valve characteristics. I read they result in plentiful even order harmonics which is pleasing to the ear. Apparently the sag in some valve amps sounds great and sh!tty carbon composite resistors sound great because (!) of their voltage coefficient! E.g. you want natural compression when you hit hard. Though I read brunetti used metal film resistors.

Honestly, for an IC designer, BJTs (which we use in automotive applications) are outdated but valves..  lol... that's like the stone ages. But I'm loving this! And a lot of the principles are the same so this isn't TOO difficult a read. That RDH4 book is mammoth, though. 

I know a lot of audio IC guys in Edinburgh - I wonder if any of them would be interested in a super amp project. I wonder what background folk from blackstar, Yamaha etc have who do all their modeling.. 

Anyway, lots of reading to do yet!

thomasross20

For me, the interesting part is how all these components turns into perceived sound

ICBM

thomasross20 said:

I bet it sounds like sh!t - I'm not yet up to speed on valves but I read that a simple valve circuit can only be barely mimicked by a much more complicated SS circuit. I need to analyse valve characteristics. I read they result in plentiful even order harmonics which is pleasing to the ear.

No . That's why I think it needs trying. I don't really have the kit to do it though.

You're probably as well-placed as anyone to try something like this given that you use 'outdated' solid-state technology and have no audio experience yet.

thomasross20

I could probably bread-board something once I read up some more. Surely this has been done..

thomasross20

Just to note, I'm not dissing older tech... there are people doing 12nm stuff now that I haven't touched at all. It's all good. Funnily, and as you may assume, all the electronics in oil & gas is ancient due to reliability reasons.

Everything has a purpose and is interesting in its own right  

Would be interesting to take an inverse FFT of a bunch of harmonics you select to see what makes a good sound. I must check what references there are  for this!

ICBM

thomasross20 said:

I could probably bread-board something once I read up some more. Surely this has been done..

No, not as far as I know. Even the very earliest transistor amps (eg the Vox T60 of 1963/64) don't use exact valve-amp topology, although similar - but still no output transformer. These also sound very nice, but were unreliable largely due to the primitive germanium transistors which were all that was available then.

After that, more sophisticated designs started being used which have been up to the present day in Class AB amps, but these have very different power-stage characteristics. My guess is that the reason they don't sound 'right' to guitarists is because of this, but I've never been able to confirm it.

thomasross20

Doesn't the helix effectively map the frequency response of different amps + cabs? That's the ultimate - no wonder they apparently sound so good.

Nowadays you might almost be able to afford to design a custom IC and PCB for it to go on.. I'd love to try that - all integrated..

ICBM

thomasross20 said:

Doesn't the helix effectively map the frequency response of different amps + cabs?

It might, but that's not what I want .

I want a proper analogue solid state amp that works and sounds like a valve one. And I believe it can be done…

You really need to hear an original, un-blown-up T60 to understand, possibly . I have, and it's amazing for a solid-state amp - not *quite* like a Vox valve amp, but much closer than you would ever expect given that it's essentially Mk1 as far as solid-state goes.

thomasross20 said:

Nowadays you might almost be able to afford to design a custom IC and PCB for it to go on.. I'd love to try that - all integrated..

No - that would make it effectively unrepairable in the future, which is something I would want to avoid.

martinw

ICBM said:

thomasross20 said:

Nowadays you might almost be able to afford to design a custom IC and PCB for it to go on.. I'd love to try that - all integrated..

No - that would make it effectively unrepairable in the future, which is something I would want to avoid.

You see, this is what happens when you let proper electronics engineers at it!

I too would like to see if it could be achieved. Some of the nicest solid state amps are those earlier designs that didn't try to mimic valve sounds exactly, but did their own thing. I prefer those to the fake valve simulators that came later and don't sound valve-like anyway to me.

thomasross20

Understand !! 
Sorry, been out all day - actually away from the screen for once!!

stickyfiddle

Well today I was driving past Coda so thought I'd pop in and make sure really did like the Cub while I had the chance! Thankfully @DougCoda is a proper gent and dragged a head & can down from the warehoused or me to try.

 It's AWESOME and exactly what I'm after. I'll probably want an attenuator for maximum flexibility but the K-Master works really well and it does that brilliant chewy, chimey, not-quite-clean thing absolutely perfectly. 

In in other good news I tried a spectacular Masterbuilt Strat that was genuinely both brilliant and only fractionally better than my own bitsa strat, which is a lovely feeling. 

Also had a quick bash on a Gibson ES-275 which was very nice, and saw an LP Custom Classic Lite (I think) like @fretmeister just bought which also looked reeeeally good.