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Old 23rd September 2012, 05:18 PM   #1
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Exclamation weak bass output from adcom gfa 5500

I have a new to me adcom gfa 5500...plays loud and clear, just has weak bass responce, is this normal or is there something wrong with it...my other amp it replaced is lower power but has more bass responce than the bigger Adcom, this is my first Adcom amp is this normal for these amps?
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Old 24th September 2012, 10:05 PM   #2
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Anyone??? could this be the big capacitors going bad... or maybe the power supply capacitors??
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Old 29th September 2012, 12:27 AM   #3
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looked around on here, found someone with simular problem...but cant get anywhere with this...any help is appreaciated,thanks
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Old 29th September 2012, 03:45 AM   #4
djoffe is offline djoffe  United States
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Are you able to do any measurements? Weak bass can be caused by an electrolytic in the feedback loop losing value, or perhaps the input capacitor. It could also be caused in the output cap in a preamp went down a lot in value, or if it is kind of small to begin with. What kind of preamp are you driving the amp with?

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Old 29th September 2012, 03:50 AM   #5
jam is offline jam  United States
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Replace the electrolytic capacitors in the feedback network.
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Old 29th September 2012, 11:29 AM   #6
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I jave measured the dc offset at the speaker terminal...was (L) 30mv...(R) 66mv...and the input source is good, swaped another amp in place to make sure and its a lower power amp, and the bass output was better...so Im thinking its the amp.
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Old 29th September 2012, 08:49 PM   #7
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Quote:
Originally Posted by jam View Post
Replace the electrolytic capacitors in the feedback network.
which are these you speak of...the 4 large beer can size caps??..or the 8 smaller onesClick the image to open in full size.
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Old 29th September 2012, 08:57 PM   #8
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it just seems to lack (the punch ) in the bass dept!!, other than this..plays loud and clear...no humm, no pop's or anything else strange..Im at a loss...could it be since the DC offset is a lil high that it maybe needs a (tune up)..I really had high hopes for this amp, it looks so good on paper!
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Old 29th September 2012, 11:04 PM   #9
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Hi, get your Offset issues dealt with (and check Bias while you are at it), then see about next steps such as re-capping.

Offset should be within +/- 10 mv of zero.

Example of a happier camper at this link here

Also - what speakers are you driving? Just curious.
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Old 30th September 2012, 12:45 AM   #10
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speakers are cerwin vega VS150..thanks, I have a nice volt meter, are these things I can do myself...or do I need other equipment to do this sort of stuff
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