I could have sworn I read a thread on here where people discussed the difference between a UCD-400 amplifier and the D200 from Channel Island Audio.
I believe it had to do with a couple of transistors on the output. I don't know. Could someone please help me locate the thread if they know what I am talking about. Thank you.
I believe it had to do with a couple of transistors on the output. I don't know. Could someone please help me locate the thread if they know what I am talking about. Thank you.
tf1216 said:
Well, I have removed the coupling capacitors and removed the current protection alltogether (don't know if the current protection has any sonic benefit, but my speakers are very low impedance). Having very inneficient speakers (Infinity Reference Standard II), it's one of the few amps that really give life to these.
Removing coupling capacitors is a big step forward, and regarding the front-end low voltage supply I'm still looking into it.. Based on others' reports this would be another worthy improvement.
lucpes said:
Excuse me please, which amp do you have?
If it is a UcD, which model ?
When you say Removing coupling capacitors are you referring to input coupling caps?
And how have you removed the current protection ?
Is it easy to perform?
I would accept some risks in order to get a more powerful low end.
Have you any picture of your amp ?
I am extremely curious about UcD 400 implementations.
Thank you so much and kind regards.
beppe
UcD400 (AD)
1) Coupling caps. 22uf. They are between the opamps and the input modulator stage. Removing really clears up things.
2) Current protection. Remove R13 (SMD on the bottom). I wouldn't encourage that as there seems to be not much of a difference. Don't blame me for your modules go poof if you accidentally short the output.
3) Low voltage caps (22uf/50V I believe). Replaced with 47uf/16V Rubycon ZA's. Tighter bass and overall clarity improved.
4) Main voltage caps (470uf/100V). Replaced with 2x680uf Panasonic FC (soldered another pair on the bottom of the boards). Result is deeper bass and more 'sparkle' in the highs.
5) Output filter capacitor. Replaced with .68uf/250V EPCOS polypropylene from Farnell. Opens up things quite a bit.
6) Bootstrap cap (220/16 I think). Replaced with 180uf/16V OSCON SEP. Low impedance is key here.
7) Power supply: dual mono, +/-60VDC, 1000VA, dual bridge, 18000uf, choke, 18000uf, 250uf/160V polyprops per rail/amp. (The 250uf polyprops are huge but they take care of most noise in the supply and seem to help provide a lot of details I was missing before). Adding chokes in the supply really makes things sound 'musical'. Wired with 12Ga teflon silver plated wire.
And most important tweak for difficult loads, direct soldering of the power/output wires on the board (have screw-type main capacitors, I can remove the connectors from there), also added a thick solid copper wire on the module where the ground connections are (measured a tiny drop there during heavy bass passages with my speakers).
Sry, no picture for now.
1) Coupling caps. 22uf. They are between the opamps and the input modulator stage. Removing really clears up things.
2) Current protection. Remove R13 (SMD on the bottom). I wouldn't encourage that as there seems to be not much of a difference. Don't blame me for your modules go poof if you accidentally short the output.
3) Low voltage caps (22uf/50V I believe). Replaced with 47uf/16V Rubycon ZA's. Tighter bass and overall clarity improved.
4) Main voltage caps (470uf/100V). Replaced with 2x680uf Panasonic FC (soldered another pair on the bottom of the boards). Result is deeper bass and more 'sparkle' in the highs.
5) Output filter capacitor. Replaced with .68uf/250V EPCOS polypropylene from Farnell. Opens up things quite a bit.
6) Bootstrap cap (220/16 I think). Replaced with 180uf/16V OSCON SEP. Low impedance is key here.
7) Power supply: dual mono, +/-60VDC, 1000VA, dual bridge, 18000uf, choke, 18000uf, 250uf/160V polyprops per rail/amp. (The 250uf polyprops are huge but they take care of most noise in the supply and seem to help provide a lot of details I was missing before). Adding chokes in the supply really makes things sound 'musical'. Wired with 12Ga teflon silver plated wire.
And most important tweak for difficult loads, direct soldering of the power/output wires on the board (have screw-type main capacitors, I can remove the connectors from there), also added a thick solid copper wire on the module where the ground connections are (measured a tiny drop there during heavy bass passages with my speakers).
Sry, no picture for now.
Thank you so much for your extremely kind and valuable instructions !
As you use the UcD 400 with your Infinity Reference Standard II your experience is very important for me, knowing how difficult are Infinity to drive adequately.
And knowing then that the 400s are able to make them sing speaks for itself.
Nevertheless I am a little scared by the complexity of your solution for the power supply.
I wonder if it is mandatory for nice sound or also a simpler PS could give nice results.
I am not looking for high-end performance, of course.
Anyway thank you very much again.
Kind regards,
beppe
P.S. a solution for the PS
http://www.audio-consulting.ch/HypexPSUKit.htm
As you use the UcD 400 with your Infinity Reference Standard II your experience is very important for me, knowing how difficult are Infinity to drive adequately.
And knowing then that the 400s are able to make them sing speaks for itself.
Nevertheless I am a little scared by the complexity of your solution for the power supply.
I wonder if it is mandatory for nice sound or also a simpler PS could give nice results.
I am not looking for high-end performance, of course.
Anyway thank you very much again.
Kind regards,
beppe
P.S. a solution for the PS
http://www.audio-consulting.ch/HypexPSUKit.htm
lucpes said:
Excuse me just another question.
Is it possible to remove the cap between the opamps and the input modulator stage and install instead an high quality film cap at the input of the op-amps?
At least a film cap should harm the sound much less.
I understand that no cap is much better than any cap, even exotic ones.
Moreover, all the voltage gain is performed by the op-amp ?
(If only I could get a schematic then life would be simpler).
Thanks and regards,
beppe
PS: A simpler PS also gives nice results, no problem 
coupling caps: 2.2uf polyprop(s) at the board's input should suffice. No need if the source (preamp) has output coupling caps.
Attaching link to your other thread for the sake of it: http://www.diyaudio.com/forums/showthread.php?s=&threadid=87818
coupling caps: 2.2uf polyprop(s) at the board's input should suffice. No need if the source (preamp) has output coupling caps.
Attaching link to your other thread for the sake of it: http://www.diyaudio.com/forums/showthread.php?s=&threadid=87818
lucpes said:
PS: A simpler PS also gives nice results, no problem
coupling caps: 2.2uf polyprop(s) at the board's input should suffice.
No need if the source (preamp) has output coupling caps.
Attaching link to your other thread for the sake of it: http://www.diyaudio.com/forums/showthread.php?s=&threadid=87818
Thanks a lot for the very helpful advice.
Kind regards,
beppe
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