My first amp attempt...

[SMOTH]

I have recently purchased a pair of PMC GB1i's and they sound bloody amazing! the problem is, my current amp is just not up to snuff. PMC recommends Bryston amplifiers, which I can't really afford after blowing a ton of cash on the PMC's. I've entertained the idea of trying to clone a 2B SST, but I don't think I have enough training or experience to pull that off since I'm just a hobbyist. My background consists of a bit of guitar tube amp building/repair, primitive analog synths, a Theremin and some fuzz boxes...

I know there are probably some good kits out there, but I want the satisfaction of learning something along the way (my fabrication skills are already quite good). I've read G. Randy Slone's Audiophile's Source book, but it seems to me all the schematics are pretty much standard 70's designs. Does anyone know if any of them actually sound really good?

I've recently been considering chip amps as a possible mid ground. I know there's some debate about integrated vs. discrete, but if something like a LME49830‏ driving a MOSFET output stage could approach sounding as good as a Bryston, than perhaps it would be something I should pursue (sonic transparency is the goal here).

Regardless, I've already started work on the power supply for whatever I end up building; It will have separate toroidal transformer supplies for each channel (+ and - 30V I think, the transformers I scavenged put out 66.6V AC unloaded. I only need about 100 Watts). I'm also considering making four amps total so I can bi amp the PMC's.

Anyway, any feedback or suggestions on these ideas would be much appreciated! I'd hate to waste my time on the impractical!

Thanks,

Smoth

[AndrewT]

Get some practice in on a single channel power amplifier.
Learn how to put it together. Learn how to test it. Learn how to work with mains electricity safely. Learn how it works.
Don't bother with an expensive chassis. Don't buy specialist components, ordinary commercial/industrial grade components are good enough.

Listen to that, while you work out what your next learning & building project is going to be.

[Nico Ras]

Why not read and build APEX amp on this thread, nothing wrong with it and it will provide the power you need.
100W Ultimate Fidelity Amplifier

[sgrossklass]

Before going into "ARGH - PANIC - I need a new amp!" mode, it is always a good idea to take a look at the technical details of the speakers at hand. Here's what I found for the PMC GB1i:
* Nominal impedance 8 ohms, measured minimum = 5.5 ohms (looks uncritical)
* Nominal sensitivity 87 dB SPL / 1 W / 1 m, measured 85.3 dB / 2.83 V (fair enough)
* Peak output level: >100 dB SPL

So you will need an amp that can deliver, at the very least, 12.6 Vrms or 29 W into 5.5 ohms. Having a bit of headroom won't hurt, but it seems to me that a decent 80..120 wpc unit should do just fine. In case you should decide not to go ahead with building one yourself, there's only like a gazillion of these on the (used) market.

It is a very good idea to go with a proven PCB layout. In case Mr Slone's book did not touch on the subject, Douglas Self's most definitely does (and I'd be surprised if Bob Cordell's didn't).

I'm not sure whether the transformers will be suitable. It sounds like there is just a single secondary at 66.6 VAC unloaded?! You either need a split secondary transformer or two separate ones, but in the latter case the DC supplies may turn out a little high.