2. amps-preamps
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Preamp sending amp into protect

Hello everyone,
I recently took delivery of a Denafrips Athena preamp and their Apollo power amp, as well as a Lumin U1 Mini and an Ares 2 DAC. When the amp is connected via xlr outs to the preamp, it goes into protect within a few seconds. However, when connected directly to the Ares 2 DAC, everything is working as it should. Before I got the amp in I was using the xlr outs of the preamp to connect a set of powered monitors, which worked fine. I’m confused as to what would cause this issue with the preamp and amp combo. Any help would be appreciated.
jdown88
rodman99999
6,037 posts
 
Then again: some amps have coupling caps, at their inputs.   ie: The early Haflers had a, "C1", for blocking DC, on the driver board's input.     Perhaps a bad one, on the left (if applicable)?
atmasphere's avatar
atmasphere
11,662 posts
 
After going over some tests with Alvin, I have noticed that no matter what combination of outputs I use from the preamp(both sets of XLR outputs, both L/R channels) as long as the left channel of the amp is involved in the mix, it goes into protect when using the preamp. Does not do this coming straight in from the DAC.
Clearly the preamp is making a bit of DC at its output. It may well be that your powered speakers have coupling caps at their inputs. At any rate, the preamp needs service. It likely has 4 output coupling caps as its running balanced and likely also does not support the balanced standard or else it would have output transformers.


Any competent service technician should be easily able to sort this out.
jdown88 OP
3 posts
 
Would that also cause the right channel of the amp to have a problem as well though? When I use any of the preamp outputs on the right channel input of the amp there is no problem. 
atmasphere's avatar
atmasphere
11,662 posts
 
If the amp is stereo, yes, since the protection relay is common to both channels.
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