CheffDeGaar UGS preamp vs other or Borbely

[NYCOne]

I bought the boards to make the CheffDeGaar UGS preamp. In reading through the threads, I came across a few people that didn't like the preamp compared to:

Borbely SE JFET
http://www.borbelyaudio.com/pics/EB-2000-402 final.pdf

Or the Choky and Oly Pumpkin
http://choky.diyaudio.rs/downloads/The Pumpkin & Shunty.pdf

Before I spend the money on the build (the UGS with the shunts will run a fair amount), do folks have experience with the other preamps I've noted?

I'm running an F5 amp and need gain.

Thanks

 

[Zen Mod]

best way is to build all 3 and listen

but - even better is to make what you already have , connect to F5 and enjoy .

who cares what others say - you'll listen with your ears



(with F5 - differences between these three preamps - are just matter of taste; so - no big deal )

 

[NYCOne]

I understand the thought, but time and money don't permit the 3 way taste test.

If one or the other stands out in either direction, it's worthwhile knowing. Afterall, without input from others, we would all have to build everything.

 

[Zen Mod]

I put smiley , when I wrote about building all 3

later I wrote that you proceed with UGS , which you already have

because :

with F5 - differences between these 3 preamps - are just matter of taste; so - no big deal

 

[Melon Head]

I understand the thought, but time and money don't permit the 3 way taste test.

I remember saying the exact same thing a few years ago.
I have now built 6 amps, 2 preamps, and I have at least another 4 more amps I would like to build as well as few of my own designs, as well as an IV, and a few more preamps.

Where do I go for DIYAUDIO anonymous counselling?

 

[jacco vermeulen]

compared to: Borbely SE JFET

Balanced designs only work if they're balanced.

Balanced also implies that the left and right part (aka inverting + non-inverting) operate identical (step two is building left and right channel as close as possible).
Which means that you have to invest in a lot of parts to build a proper one, especially those with local NFB only (Burbely rear ended).
The main reason why commercial products of relative simplicity are very costly, (sale tag also pays for the rejects and the time invested in them)

Nice example is the current Goldmund folly at the SS forum.
Original parts are hard (expensive) to come by, and a Lateral MOSFET output stage of 3-4 complementary pairs without source resistors obligates buying a lot of them for proper matching.
Name something Swiss that cost $25K in 1994, the hurd will scream for boards.
MSRP of a '90s Rolls paid for the hand-painted Golden line on the sides, a dozen scar-free Connolly leather hides, a flashy bird on the radiator.
It also paid for a hand-assembled and blueprinted engine, including the mechanic's signature.

 

[Russellc]

I'm going to try Pumpkin, as soon as ZM's paypal issues are resolved.
How's that going by the way?

Russellc

 

[Zen Mod]

I'm going to try Pumpkin, as soon as ZM's paypal issues are resolved.
How's that going by the way?

Russellc

soon .

even Bank branches have working hours

 

[NYCOne]

Nagging questions as I build preamp(s)

It's taken longer than it should have, but I think I'll have all the parts for a fully balanced system in a few days.

As you may have surmised, I'm new to DIY audio. I found the most difficult part was getting specifics from people that have done it before. I certainly understand a commercial enterprise keeping trade secrets. I seem to have encountered an issue around not being expert enough to warrant specific answers to real questions, or being told to "read the thread". I can tell you, I've read some of these threads 20 times. When you don't understand something new, reading over and over again is not the answer.

Some examples:
I still don't know what the distortion figures are for an F5 with different feedback resistors. Folks point to feeback resistors of 75 ohms and 100 ohms (instead of 50 ohms) as ways of getting more gain, but I haven't seen any analysis of the distortion using those parameters. I don't have access to the equipment to check it myself.

I still don't know how to refigure resistors for a balanced version of the F5 using the IRF outputs. If anyone knows, I'd appreciate a heads up. The electronics expertise to answer this question is beyond my abilities.

And getting back to this thread, I've read about a number of people seeking preamps for their F5. The one's I've listed in this thread seem like naturals for the F5. I would have guessed many people have tried these out and have A vs. B thoughts.

Any input is appreciated.

 

[Zen Mod]

well - I can say that you're given with answer to your question , asked in this thread ;

build Papa Borbely's preamp and enjoy ; it's on par with two other you mention .

regarding other questions ...... ask them one by one ........ here or in any other thread ;

just one thing - do not bother with F5 distortion ; it's certainly better than most amps you can buy for sane amount of greenies ;

distortion numbers will not tell you what's important , on this level of game .
more important thing in changing feedback ratio in F5 , or changing type of outputs is , say , damping factor change , same as distortion harmonics distribution ;
long but short story ;
if you say that you don't have enough electronic knowledge - you can't be filled with knowledge in short ..... you must trust someone to tell you differences in simple terms

speaking of which ...... (game) you didn't tell what speakers you have , room , listening habits ( meaning on SPL ) ;

 

[NYCOne]

ZM -

Thanks for the responses.

From reading the forum, I'm trying to build:

XF5 Balanced (already have "regular" F5 - first build)
Preamp - UGS, Borbely SE Balanced JFET, or Pumpkin
Speakers - OB FF85K and Alpha 15" ala Martin King

Except for the F5, I'm ordering parts and building everything else. In fact, I'm just finishing measuring 220 transistors for their Idss to make matched sets of 8 for each balanced item (amp and preamp).

I guess my most burning question is if anyone is running an "XF5" balanced with the IRF output devices. If so, what resistors are they using? I'd like to see how folks optimized the IRFs in a balanced configuration. I suppose it's possible no one is using the IRFs in the "XF5", but I'd be surprised.

 

[samoloko]

I like to see XF5 - maybe some pics, schematics, measurements, tips
I also would like to build It
Toshiba FETs are supposed to be better than IRFs

 

[Russellc]

I would also like to see F-5X as well. As far as preamp, I'm going to try the Pumpkin, once banks wake up. I've got IRF devices, also have Toshiba, which is what I'm using on next build.

I'm going through the entire F-5 thread again, taking notes as to interesting info, straining out the babbling....

russellc

 

[smyslow]

I like to see XF5 - maybe some pics, ...

Here are some pics of my F5-X:
post #5659
post #5673

In the meantime I installed more powerful toroids (400VA/14VAC per channel) and bought new (and better) speakers.
post #35

At the moment I'm playing around with my third version of an UGS based preamp.

Regards, Uwe

 

[NYCOne]

Uwe-

I'd like to try an XF5 with the IRF outputs. Did you ever try this? Do you have any advice?

 

[samoloko]

I got F5 with 1.6 bias and UGS - very good sound
but I like to get balanced connection between preamp and F5 - now I have grounded negative In and out of UGS
would like to have opinion about best DAC/chip to get balanced DAC
pcm63 OK ?

 

[Zen Mod]

you'll need 2 PCM63s per channel for balanced

 

[samoloko]

Zen Mod I know that
wondering what Is most favored DAC chip solution for balanced DAC

 

[Zen Mod]

sorry

I'm afraid that you'll hear 100 diff opinions from 75 ppl ........

I like balanced with PCM1704 ; passive xformer I/V then SUSY jfet gain stage

- you can count on my opinion as one from 4 ppl at least ......

 

[samoloko]

sounds good
why you prefer 1704 to pcm63
can we do It without xformer I/V

cheers