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Old 4th October 2006, 07:43 PM   #111
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Quote:
Originally posted by Phill
Sigurd Ruschkow,

I like much the cases of your electronic!
a little relativity in this world of perfection



Phill
Box building is not what I am best at
I am more concerned with what is inside a box.

I do like your box for your preamp:
Click the image to open in full size.

Click the image to open in full size.

Nice work!



Sigurd
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Old 4th October 2006, 08:47 PM   #112
Phill is offline Phill  France
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Sigurd Ruschkow

it is much of compliments!
I am not a good finisher.I am not patient enough, and not enough competant.
I want the best music as fast as possible !

CheffDeGaar builds pretty cases, to put these beautiful electronic... it can do everything!

Phill
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Old 7th October 2006, 08:05 AM   #113
spencer is offline spencer  Hong Kong
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Hi,

Just finished UGS Ver 3 and listening test under way. First impression is that the gain is too low in my system. Resolution is a bit better than Borbely SE pre-amp.

Any suggestion to increase the gain? Reduce input Rin or increase Rfb? Which way is better?

Spencer
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Old 7th October 2006, 08:54 AM   #114
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Hi spencer

You guys are amazing !

You didn't specially make the enclosure to host the ugs, did you ?
Great work ! Is the supply the one I described, or another one ?

It would be better I guess to increase RFB to increase the gain (try 68K
to 100K). That's strange, I never felt the gain was low in my system...
At my normal listening levels at home, the ouput is around 30dB from
full scale, with the 15K/56K gain resistors, but I use it fully balanced...
(Edit : If I remember, you use 47k as RFB ?)

If I may, I have some questions :
What is the gain of the Borbely preamp your'e using ?
Do you use the ugs unbal to bal or fully unbalanced ?
And what is the impedance of the stepped attenuator you're using ?
Did you put it at output, or input ?

Anyway, thanks for teststing, and keep us to date

Cheers,
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Old 7th October 2006, 09:29 AM   #115
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Hi

I made another change in terms of stability.
Now I have 150k feedback resistors and 10k from output to ground.
Also like in the AX amps I put 2 10k resistors from the +/- outputs to the RS1 and RS2 connection and the amp is very stable in terms of offset.
I think it sounds a lot better like this but I donít now if you put the Volume pot at output you get problems with clipping.
The voltage swing could be higher because it now has 5k at the output in stat of 1k.

Rob
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Old 7th October 2006, 10:04 AM   #116
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Hi Rob,

As I stated in the first post of this thread, one of my concerns was to
get rid of these common mode feedback resistors, that impede on the
unbal to bal function, but they sure help a lot to stabilize the absolute offset.

As you own a double trace scope (alas I don't...), could you test
the unbalance between the two outputs when feeding the UGS
unbalanced ? The lower the comon mode fb resistors, the worse
the results. If you can plot V(out+) + V(out-), you should normally
have zero when the unbal to bal conversion is perfect. And in sims,
it was around few tens of mV when the resistors where present.
And that's what I measured with a PC soundcard scope...

You could also test higher resistors values (100K, 200K). Their effect
is still there on offset stability (slightly worse, but workable), and the
unbal to bal conversion is better...

And as I said previoulsy, perhaps you could test back with a 1K Rout,
keeping the "high" feedback resistors. The effect on the closed
loop gain will not be high, and it also might help you stabilizing the
offset.

I will try 100K or 150K resistors as RFB this WE (keeping Rout as 1K),
and report back my impressions.

Thanks for all your tests, and for keeping it up .

Cheers
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Old 7th October 2006, 01:57 PM   #117
spencer is offline spencer  Hong Kong
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Hi Cheff,

I give up my Aleph 1.7 casing and put in the UGS. I only hv two casings with XLR and RCA sockets.

The supply is just a zener and mosfet series regulator, follow NP design. Voltage at about 22.3V.

I use 3.3k Rin now and Rfb 47k, the gain is higher a bit but still not up to my expection. I need to turn to 12:00 for loud level.

The Borbely SE Jfet preamp is about 21 dB gain, I turn to 9:00 for same volume level. Gain is a bit high to me. I believe 10:30 for my loud level is best position to me.

I use 10k ohm volume at input for both amp.

My DAC is unbal output, UGS output is bal to my Aleph 60 diy.

I believe your power amp has higher gain than mine.

Spencer
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Old 7th October 2006, 02:04 PM   #118
spencer is offline spencer  Hong Kong
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Old 7th October 2006, 02:06 PM   #119
spencer is offline spencer  Hong Kong
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My system.
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Old 8th October 2006, 09:08 AM   #120
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Hi Cheff

I measured the unbalanced in and Balanced out with the common mode feedback resistors and you where wright.
There was alot of difference between the +/- outputs.
So I go back to the 1K and do some listening again.

Rob
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