UcD400 Gain Issue

PHilgeman · 3rd May 2007, 11:05 AM

I got a UcD400 back from repair a few days ago, hooked it up today, and it has very low gain. I checked all of the gain setting resistors. This is using a SE input, with the - input grounded.

Everything functions perfectly, except it is quite a bit quieter than any other UcD400 I have in house right now.

Any ideas on this? I am stumped after about 2 hours of swapping cables, checking all connections etc.

Thanks,
Paul

BWRX · 3rd May 2007, 12:40 PM

Measure the gain of the modules to find out for sure.

PHilgeman · 3rd May 2007, 12:51 PM

Not sure what you mean by that... just input voltage to output voltage....

That I can tell with my ears, around 10dB less on this particular module.

-Paul

BWRX · 3rd May 2007, 01:00 PM

10dB is a pretty significant difference!

If they have the same gain setting resistors then they should have the same voltage gain (the modules and power supply are exactly the same otherwise right?). Just use a 1V test tone and measure the output voltage. If the voltage gains are significantly different, which they should be according to what you're hearing, send your information to Hypex. Something clearly isn't right there.

Pierre · 3rd May 2007, 01:50 PM

Why did they fail? I mean, why did you send them for repair?

PHilgeman · 3rd May 2007, 02:35 PM

Fixed it, lifted the trace on the - input underneath the opamp when I was swapping.

I am not sure why it broke....

-Paul

3rd May 2007, 11:05 AM	#1
PHilgeman diyAudio Member Join Date: Dec 2003 Location: Arlington Heights, IL	UcD400 Gain Issue I got a UcD400 back from repair a few days ago, hooked it up today, and it has very low gain. I checked all of the gain setting resistors. This is using a SE input, with the - input grounded. Everything functions perfectly, except it is quite a bit quieter than any other UcD400 I have in house right now. Any ideas on this? I am stumped after about 2 hours of swapping cables, checking all connections etc. Thanks, Paul

3rd May 2007, 12:40 PM	#2
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	Measure the gain of the modules to find out for sure. __________________ Brian

3rd May 2007, 01:00 PM	#4
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	10dB is a pretty significant difference! If they have the same gain setting resistors then they should have the same voltage gain (the modules and power supply are exactly the same otherwise right?). Just use a 1V test tone and measure the output voltage. If the voltage gains are significantly different, which they should be according to what you're hearing, send your information to Hypex. Something clearly isn't right there. __________________ Brian

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
UcD400 Q & A	classd4sure	Class D	1756	23rd November 2010 01:22 PM
Gain Blockwith Variable Loop Gain	Bonsai	Solid State	17	11th July 2008 02:40 PM
UCD400 Amp	john65b	Swap Meet	4	12th November 2007 11:08 PM
Heretical Unity Gain line stage PLUS a little gain ?	yagas	Tubes / Valves	7	24th January 2006 01:30 PM
Unity Gain Operation (or low gain)	Tomo	Chip Amps	12	22nd January 2004 01:47 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

3rd May 2007, 12:51 PM	#3
PHilgeman diyAudio Member Join Date: Dec 2003 Location: Arlington Heights, IL	Not sure what you mean by that... just input voltage to output voltage.... That I can tell with my ears, around 10dB less on this particular module. -Paul

3rd May 2007, 01:50 PM	#5
Pierre Banned Join Date: Nov 2004 Location: Paris	Why did they fail? I mean, why did you send them for repair?

3rd May 2007, 02:35 PM	#6
PHilgeman diyAudio Member Join Date: Dec 2003 Location: Arlington Heights, IL	Fixed it, lifted the trace on the - input underneath the opamp when I was swapping. I am not sure why it broke.... -Paul

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read