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JKC 27th October 2011 03:36 PM


Sorry, that was my mistake. Correct designators should be R22 and R23 in reference to original schematics. R24 and R25 are correct.


JKC 27th October 2011 03:46 PM


You should look at most recent documentation where all errors are corrected.


barmanekm 28th October 2011 03:50 PM

Hi guys,
Can any of you provide any measurements of FETZilla?
THD, IMD, spectrum and SNR. Friend of mine has done slightly modified FETZilla version
and it sounds pretty damn awesome and so it measure. I would like to compare with yours version...

JKC 28th October 2011 06:08 PM

Can you elaborate more about "slightly modified FETZilla version".


barmanekm 28th October 2011 06:30 PM

he was posting initial schematic several posts before... Actually the differences are
- no output coil
- different mosfet in VAS (but very similar to ZVPxxx)
- 33pF compensation in feedback
- IRFs in the output instead of lateral mosfets...
The THD is not higher than 0.02% at rated power (45W) and it is almost only 2nd harmonic, IMD do not exceed 0.006%...

AFAIR he was posting in original FETZilla thread...

taniknight 28th October 2011 10:44 PM

Transformer wiring question
1 Attachment(s)
Hi everyone,

In hunting down transformers for this project, I found some 200VA, 0-12V x2, toroidals at a clearance price and was considering using 2 per channel wired as shown in the attachment (I'll of course switch and fuse it in practice). The 4 required for a stereo amp are still cheaper than any single 300VA 0-25V x2 transformer I can find, and much cheaper that two 160VA.

Within my limited knowledge of electrical wiring I can't see a problem, unless I must make sure the AC phase is the same at either end... but past the bridge its all one-sided anyway, right?

Does anyone care to comment on this scheme for the FETZilla? Is 24V AC an acceptable voltage to have. Also on sale are 300VA 30-0-30V... if this is not too high it would be cheaper again for me to use 1 per channel.

Many thanks,

AKSA 28th October 2011 11:12 PM

Hi Tani,

That will work very well, no problem at all. You could in fact use each transformer to power the positive supply of EACH module, in fact. That way you'd only need to buy two of them, giving a combined 400VA anyways, more than enough. Separate bridges would ensure galvanic separation and give good results. Just be sure to have one trafo for the positive rails, and the other trafo for the negative rails, otherwise earthing may conflict.

A 30V secondary will give you 42V, which is too much for this design.

Did you visit Laurie at Safety Beach and listen to the VSonics?



taniknight 29th October 2011 12:09 AM

Thanks Hugh,

I'll snap them up. I was sure that 30V was too high, but always worth asking I guess. I think I'll buy a couple of the 300VA anyway, just to have... they're $27! Aussie built with resetting thermal protection.

Yes I met Laurie on Thursday evening... turned out we had quite a bit in common and we were listening and chatting for quite a while... I learnt a lot. I had a good listening session with the VSonics, across wide and varied style of music.

Not wanting to go into details on this thread (I'll write up soon on your website) I'll simply say that the VSonics were outstanding. Furthermore, Laurie believed that the VSonics paired fanatically with the FETZilla, so I would be in for a treat if I ended up with the combination.

Having just bought a house though, I'll need to be putting my pennies aside before I purchase anything in the region of the VSonics. When I'm ready to, hopefully in a few months, I'd have to say that Laurie's design would likely be my choice.


taniknight 29th October 2011 01:21 AM


Originally Posted by taniknight (
the VSonics paired fanatically with the FETZilla


Paired fantastically with the FETZilla.

Sorry about that. Serves me right for blindly accepting the first offer by the spell checker.


Ian Finch 29th October 2011 04:00 AM

Whilst in the sharing mood Tani, would you like to tell us who would be selling 300VA toroids at such a price? What a deal! - I hope not personal customers only.

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