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buzzforb 28th March 2014 01:50 PM

Funny Pre
 
1 Attachment(s)
I have gained much from this forum in terms of both learning and enjoyment and would like to give something back. I do not think it is an equal trade, but i would like to think it will be a nice option. I have been toying with this idea for sometime after enjoying a bastardization of the F6 which was named the Funny^6. The problem with it is that it uses fairly rare SSR100 fets, which drive the cost up substantially. THis in addition to the fact that it is already somewhat expensive due to the dual transformers needed. The preamp version is an attempt to address what I feel may some of thw weaknesses of the amp version. First is cost, second is bass response. First problem will be dealt with by dropping the need for SS. THe second will be dealt with by using a preamp format that can feed the venerable F4/BA output stages available through the forum. I have started the final drawing in order to get the preamp off the breadboard and on to something more official. What I hear so far is promising in its ability to deliever most of what you get with the power amp version. Hopefully with some tweaking, I can take it the rest of the way. Progress will be slow and measurements, slower, but I will try to provide both. What the amp and subsequent preamp does do exceptionally well is deliver a musical presentation that I have fell in love with. For me, it is able to create a stereo image that I have rarely experienced in audio. Imaging and soundstage are just a delight. I will not go into a lengthy description as I suck at language and communication in general, but i do think it will be a worthwhile endeavor for those who take the risk. I will provide any and all layouts for those who wish to try it. I wouls suggest just following along if you are interested until I give an all clear on both the sound and the execution. A little teaser of a half done board. First attempt is single layer for home etching. I may push into a dual layer SMD version for personal use, but I believe this will be the most useful in general.

Zen Mod 28th March 2014 01:56 PM

Quote:

Originally Posted by buzzforb (Post 3871445)
.... I suck at language and communication in general.......

yeah .........

:rofl:

flg 28th March 2014 05:42 PM

Quote:

Originally Posted by Zen Mod (Post 3871452)
yeah .........

:rofl:

But, you have Pepi to help you :D

flg 28th March 2014 06:35 PM

So when might we see the schemo of your funnyness? The layout requires to much brainpower to understand :D
Actually, I was one of the ones who wanted to try the F4 with a step up xfrmr gain config. If It can't cut it, it should have no trouble driving some smaller outputs for a pre or headphone amp :D

buzzforb 28th March 2014 08:16 PM

The transformer is only used to create - and + signals for the output fets. The output fets are responsible for all the gain that is provided by the stage. It is very much like the BA3, but I am able to drop the source resistance on the FE Jfets and have no need for the level shifter. The FE is cascoded. The output bias is provided by low noise zener. It is a f6 with different outputs in balanced/bridged configuration, with a common feedback point. Ill try to pencil in a schematic. I always skip that and just draw teh baords.

evanc 28th March 2014 08:50 PM

I'm interested and will follow along best I can. I've been listening to balanced ba3 front end, f4 ish output with buz 901/906 mosfets. This setup sounds real nice but it would be fun to try something a bit different.
Evan

flocchini 29th March 2014 04:13 PM

buzz

I think this provides a great platform to experiment.

As you know I have enjoyed your Funny for at least 6 months driving my PHL 1130s (300-5k Hz) To my ears the Funny is the most enjoyable amp I have used in my system. This includes the F3, Aleph30, BA3balanced/ 4 crippled F4 boards, F4 with Jensen interstage which is my headphone amp and ZenLite. The Funny provides a wider and deeper soundstage with outrageous imaging.

Is it the transformers, the SS outputs, the "balanced" or symmetric nature, or the combination in the Funny that provides this outstanding listening experience. I think using the Funny pre with a F4 would give some answers to what factor may/could dominate.

Would the Funny pre work with a crippled F4? This summer I could easily replace the BA3b front end with your boards and compare.

Sorry I am rambling - I really appreciate what you are doing and Nelson again many thanks for giving us the F6 platform.

Bob

buzzforb 29th March 2014 05:17 PM

It should have no issue whatsoever driving a crippled F4. It is basically a hybrid Ba3/f6 topology, functioning in almost the same way as the BA3.

GuidoR 8th April 2014 09:00 AM

Hi Buzz,
Thanks for sharing your project, it looks very promising.
Any chance to have a schematic? I don't have the patience :scratch1: to reverse engineer the pcb...
Talking about the transformer, is it a 4 windings 600:600 Jensen as in F6?
I've got a Lundahl LL1540 lying around, is it a suitable choice?

Tks again

Guido

buzzforb 8th April 2014 09:40 AM

I will try to post this weekend. Clearing a GB and waiting on PCB. Gonna etch this one and an F5X preamp, like Euvl's,at the same time and compare the two.


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