F3 Builders Thread

[d to the g]

We found that adjusting r8 had a very large effect on the dc voltage at the output cap. (21v)

To get a 21 volt reading the left channel is a 2.2 bypassed with a 10 ohm and the right channel is bypassed with 20. Feedback is set the same and overall gain was 11db give or take.

My favorite thing about this amp is just how the decay on instruments is very natural. The amp is laid back without being at all slow or mushy. I'm using it with 7000uf of silmics and a pair of altec 604c. My favorite DIY amp so far.

[Dzius]

I have used my F3 since september. After first days I connected it with B1 buffer, as it sounded a bit more dynamic at low power levels.
Recently I found out that even though B1+F3 played very good, could say with a lot of “musicality”, but a little of "air" from concert room was lost
comparing to F3 playing alone. B1+F3 plays more "soft", more "rounded". The difference is just tiny but definately exists.
Anyone have noticed similar effect ?

[djkiwi]

Hi guys, I recently bought a used a Rawson F3 clone to try out on some TAD 4001 horns in an active environment. Because the 4001 is running at 110db+ and only covering 650 hertz and above the F3 isn't even breaking a sweat. I did try the amp using the passive TAD TN2 passive crossover network but the improvement going active and achieving 110+ db was remarkable.

A couple of impressions so far. Firstly it is dead quiet. I have many amps in the house and it is as quiet as my custom SET 45 monoblocks.

Secondly, it has extraordinary clarity and musicality. The TAD 4001 has ruthlessly exposed many so called high end amps. In fact this amp is the closest in sound quality to my reference SET 45 amps and in some areas exceeds them. It's a tribute to Nelson Pass to make such a transducer available to the DIY community.

After reading this thread I'd like to get the best out of the amp I can. Looking at the parts inside they seem to be of good quality but not great so I'd welcome some pointers on upgrades. I read some posts from Nelson about putting a bank of Elna caps but my amp seems to have different parts than the schematic posted. Here is a picture of the inside and has the following:

1. 8 x Nover Caps rated at 10,000 uf 63 volt (This is quite different from the single 1 x 15,000 cap and bank of 220s shown in the schematic.
2. Avel Y236651 250VA 18V+18V Toroidal Transformer

link here:

Avel Y236651 250VA 18V+18V Toroidal Transformer 122-620

For the power supply I'm thinking of replacing the existing one with a piltron. Anyone tried the pitron or other recommended options?

On the caps, I'm not sure what to do? I'm not sure why these are 8 x 10,000 for a start. I'd like to go down the Elna route but would require an army of them to replace 8 x 10k caps.


Cheers
DJ

[Sweetsweetback]

Dj

Your f3 looks like an f5 to me. I could be wrong.

[Zen Mod]

why don't you ask maker for upgrade policy ?

in any case - you profited - you paid for 3 , now you have 5

certainly F5 ( made as drek cheap chinese extending cord , model "Fire in the house")

that guy is not just a thief , he is dangerous ; one day some cheapskate will be burned or electrocuted

[Dzius]

No doubt, that's F5. Switch to other thread then. There are over 1000 posts so you've got a lot to read about it.

[william2001]

Man, I hate seeing exposed mains terminals like that. You could easily lay your hand right across that fuse while tweaking the bias or something. Please at least keep a secured top on it at all times when the kids / pets are around. Real easy to get a nasty shock with that kind of setup. And ONLY the LED wires are twisted, and nothing else? But, you said it's quiet so I guess that's all that matters.

[Zen Mod]

Originally Posted by william2001

....so I guess that's all that matters.

hardly ;

this is the case where someone who owns TAD drivers ( and is most probably used to be informed about price/quality generally ) is willing to skimp on amp quality .

isn't odd to pay for an amp amount of greenies barely enough for a pair of decent 300Bs , and expect that amp in question is of any decent quality ?!

OK - let call buyer nothing more than naive , but TR's "work" is everything but naive .

one day someone will have major troubles because of that ;

and - fact that his amps are so praised on Audiofoolgone and similar "expert & aficionado" gathering places tells us more than enough about overall stupidity of members in question .

[Salas]

Using else than Pass Labs boards or officially Pass approved third party ones is not endorsed by the forum also. Beyond that, avoid personal characterizations please.

[Zen Mod]

mea culpa !

maxima !