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I could use some help on this PS Audio Preamp

danbisawsum

danbisawsum

Active Member
Hi fine folks,

I recently purchased a PS Audio 5.5 Preamp and it came to me in a less than favorable operating condition.

Here's my experience with it:

- it works in both straightwire modes
- in active mode, it only outputs on one channel
- if I switch active mode from L-R to the R-L active mode, it switches which channel the output comes out of the unit... the other channel is mute at this time (no hum or weird noises). I've made sure that the unit was in stereo mode.

I think the active mode sounds more pleasing than the straightwire mode, there is a seeming lack of bass in the straightwire mode. So, I'd like to get the active mode working properly because I anticipate really liking the sound I got out of the single channel.

I checked my source and used different sources and checked the wires and used different ones and know for certain that it is the unit and not something up stream or down stream in the gear chain.

I've uploaded some pics for you guys to look at. I can't find a schematic on this unit and don't have a manual either, if anyone can point me to them that would be much appreciated.

My SWAG (scientific wild a$$ guess) is that I'm going to need some new opamps... but which ones? I dunno. Also, it's kind of inconvenient that they are soldered to the board... but we'll get to that when it matters. Do you think I'm barking up the right tree or should I plan on checking caps first? Should I just recap the whole audio path regardless?

Please help, I'm a noob and want to get this unit singing.
 

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Before you swap parts, get the data sheet for the opamps and verify that they are getting correct power.
 
Had a similar weird short in a PS 4.5, never could find it. Sold on eBay as a project so someone else could pound the bench in frustration.
 
I can't find a schematic on this unit and don't have a manual either
Click to expand...
You most likely won't, PS Audio is pretty tight fisted when it comes to service manuals and or tech notes. If you really want to fix it. Send it to PSAudio.
 
Thanks for the comments thus far. I'll contact PS Audio and see if they can estimate a repair.

My hang up is that the wife didn't like me buying it off of fleabay in the first place, then it came in non-functional condition... I thought I'd take the cheap and educational route to try to save some face... we'll see how it all plays out.
 
Boo hoo, PS Audio won't service the unit... any recommendations for techs in the area (Wilmington, Phila, Balt)?

I'm willing to make this a learning experience if someone has advice on how to intelligently go about it. I've got a scope and patience.
 
danbisawsum said:
Thanks for the comments thus far. I'll contact PS Audio and see if they can estimate a repair.

My hang up is that the wife didn't like me buying it off of fleabay in the first place...
Click to expand...

Yep, you need to learn how to lie to your wife.
Hide any new toys that you bring home for at least 6 months. Make sure anything she does see looks like it was dragged through the dirt before it came in the house. If she does ask, tell her you "traded ___________ for it." That will put a plug in the nag hole.
 
If you want to try to do it yourself, take the scope and find the audio in the channel that's working and then go to the other side to find out where it is losing it. Localize the problem. Troubleshooting is a process of elimination.

I take it there is a phono preamp, does it also work on both channels in direct mode ?

One good place to check sometimes is the balance control. Same with the volume. Ideally you want to get right in the middle of the thing to eliminate fully half of it in one fell swoop, but sometimes you do not know where the middle is.

One thing, if you are going to pick brains over the internet, if it has ICs, draw a layout and supply their numbers. Hope they aren't house marked.

This is reverse engineering and it is not going to be easy over the internet. I could do it if you send it over, but then so can quite a few people around here. Actually reverse engineering was one of my strongest points over the years, due to uncooperative manufacturers.

One thing, where is the power transformer ?
 
Hi JURB,

Thanks for the comments, I'll see what I can do in terms of drawing a schematic for this thing as I dig into it. In regards to the transformer, it's in a separate box... that was one of the supposed benefits of this unit. I haven't tried the phono input yet, just the line level inputs (and they all behave the same, as described in the OP).

PS - Mr Marco, thanks for the sage wisdom :)
 
New development, I tried the phono input... it throws my amp into protect mode. More gremlins I guess. Can anyone suggest a good tech in the phila/balt/wilm area that can hook me up here?

I'm not sure if I want to burn more money on it or just find something else at this point.
 
any recommendations for techs
Click to expand...
**** can the whole thing and find something else. I worked on one PSAudio preamp 5.0 or something like that. I will never touch one again.
 
I have a PS audio 5.5 I am trying to sort out, and have found a supplier for the NPD5565 Dual Fet chips- Linear Systems can supply the LS5565, which aside from a very small difference in trans conductance, is a direct replacement in the same package-http://www.linearsystems.com/
 
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