It's the BOM for the amplifier...all the data you need about the resistors and all other components...
and if you use 0.25W resistors where François ( the designer ) suggests 0.6W ..it might well work but....long term stability of the resistor value will very probably change and funny things will happen.
There is a very good example of this in the UGS pre amp...the earth return resistor had to be upgraded to 2 W because switch on transients were degrading it so much that value changed completely.
It's not only stable running conditions that have to be considered but very especially the abnormal ones like switch on as well.
...hope this helps more
C
and if you use 0.25W resistors where François ( the designer ) suggests 0.6W ..it might well work but....long term stability of the resistor value will very probably change and funny things will happen.
There is a very good example of this in the UGS pre amp...the earth return resistor had to be upgraded to 2 W because switch on transients were degrading it so much that value changed completely.
It's not only stable running conditions that have to be considered but very especially the abnormal ones like switch on as well.
...hope this helps more
C
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I have now spent a few weeks living with the UGS preamp and I love it. It's driving a Sympatico from Twisted Pear at the moment, into a pair of Frugal Horns. There is super control, great clarity, detail and power. The background is so inky black quiet.
So I'm now thinking UP, or F5 balanced Turbo. Does anyone have any UP boards spare?
On the other hand the Sympatico is sounding very very good. Would UP sound different? Advice welcome.
So I'm now thinking UP, or F5 balanced Turbo. Does anyone have any UP boards spare?
On the other hand the Sympatico is sounding very very good. Would UP sound different? Advice welcome.
Comparing tha Simpatico to the UP isnt really fair....the UP is at another level.
Read some of François initial comparison test with his first prototype of the UP against his own Aleph X clone i think and the UP come out on top.....it's worth reading a bit.
Hello,
Some time ago I finished my copy of the U.P. The pcb’s came from one of the French group buys and I followed the instructions given in the French document during the assembly.
I haven’t listen to the amp very much until recently. I took my Aleph-J and U.P to a friend over the weekend and we did a lot of A-B test. I was not really happy with the sound of the amp. Well compared to the A-J the total presentation is brighter and thinner. The soundstage is not as big and it’s difficult to pinpoint instruments and musicians.
During the this tests we switched between two types of speakers. One regular 2-way box spkr and a tangband 4” in a TL. Source was UGS pre-amp and DAC-END connected to a squeezebox.
What the amp is phenomenal at is bass. Tight, fast and with great authority.
When I assembled the amp I didn’t use the best possible matched mosfets. I bought them already matched but didn’t measure them until after I powered the amp. I measure between 0.09-0.14V across the source resistors. I didn’t match any of the transistors for the front end…
I expected the "sound" to be better then the A-J. Could the mismatched mosfets be the "problem"?
Some time ago I finished my copy of the U.P. The pcb’s came from one of the French group buys and I followed the instructions given in the French document during the assembly.
I haven’t listen to the amp very much until recently. I took my Aleph-J and U.P to a friend over the weekend and we did a lot of A-B test. I was not really happy with the sound of the amp. Well compared to the A-J the total presentation is brighter and thinner. The soundstage is not as big and it’s difficult to pinpoint instruments and musicians.
During the this tests we switched between two types of speakers. One regular 2-way box spkr and a tangband 4” in a TL. Source was UGS pre-amp and DAC-END connected to a squeezebox.
What the amp is phenomenal at is bass. Tight, fast and with great authority.
When I assembled the amp I didn’t use the best possible matched mosfets. I bought them already matched but didn’t measure them until after I powered the amp. I measure between 0.09-0.14V across the source resistors. I didn’t match any of the transistors for the front end…
I expected the "sound" to be better then the A-J. Could the mismatched mosfets be the "problem"?
Attachments
it's easy to test matching issue :
using light load ( 4" tangband) ,try with disconnected (pulled from circ , easiest with desoldering one end of source and one end of gate resistor per mosfet) all but one output mosfet per quadrant (so having just 4 per channel) ....... if sound is the same , regarding mid and highs , matching isn't problem
however - generally speaking for amp , be sure that you're having all operating points exactly where they need to be ( currents , voltages)
using light load ( 4" tangband) ,try with disconnected (pulled from circ , easiest with desoldering one end of source and one end of gate resistor per mosfet) all but one output mosfet per quadrant (so having just 4 per channel) ....... if sound is the same , regarding mid and highs , matching isn't problem
however - generally speaking for amp , be sure that you're having all operating points exactly where they need to be ( currents , voltages)
Thanks Zen Mod,
I'll try eliminate mismatch problem first.
Then to find operating pionts may be a bit more challenging. I think I remember Cheff posted a picture from a sim with voltages and current for the UGS front ends. But I think it was using a few different parts and I can't find it now..
I'll try eliminate mismatch problem first.
Then to find operating pionts may be a bit more challenging. I think I remember Cheff posted a picture from a sim with voltages and current for the UGS front ends. But I think it was using a few different parts and I can't find it now..
Hi everyone,
I have just put together one channel of UP but have hit a snag and need help. I have carefully followed the manual v2. Everything was going according to spec until I installed the 22000 caps and output devices. On power up, the manual says to check voltage va where I should be getting 24v. I did so up to this point, however now I'm only getting about 9v! Is there a likely cause?
Your help would be very much appreciated
Thanks
I have just put together one channel of UP but have hit a snag and need help. I have carefully followed the manual v2. Everything was going according to spec until I installed the 22000 caps and output devices. On power up, the manual says to check voltage va where I should be getting 24v. I did so up to this point, however now I'm only getting about 9v! Is there a likely cause?
Your help would be very much appreciated
Thanks
