PS Audio 4.5

My PS Audio 4.5 (from the '80’s) lost the left channel in phono mode. Any ideas?

Yup. My guess is that the electrolytic caps are toast. Mine even coughed up some fluid onto the circuit board. It is probably time to re-cap the whole thing or move on. I re-capped mine and still use it as a line level preamp for running the bass side of my system.

If it’s only the one channel it could also be the selector switch not making contact too. Wiggle the switch and see if it comes back at all. I would also take wglen’s advice on the caps too.

Contact enhancers like Caig Pro Gold can also help rejuvenate old switches, if that’s the problem. Did wonders for my old Fisher 400 tube receiver.

Another thing, after thirty years, the RCA jacks can come loose from the board and lose connection. Give them a wiggle to see if the channel comes back.

Thanks, all, for the suggestions. I’ll do the cap replacement if that’s what it takes. But one question: is it possibly the selector switches? When I turn the selector knob to the various input settings, I get some noise. Also, when I get to the Phono selection, even the one channel isn’t clear unless I turn the selector a bit, then the right channel settles in. Which first made me think it was oxidation in the switch. I took off the top and sprayed the two disks with contact cleaner, but no improvement.

It absolutely could be the switches. They were rather notorious in these older units. Some spray cleaner and lube might be just what you need. Though, I see you’ve tried this - you might wiggle them around to see if it comes back - or try a better cleaner.

On my old PS IVH not only the switches, but as mentioned, the RCA jacks would either corrode or lose contact slightly, either form slight corrosion or the contacts lost their force on the corresponding interconnect plug. I’d have to jiggle the RCA jacks every few months to get the thing to make contact again. You can probably fix this by opening up the preamp chassis and, using a small tool, see if you can bend the center contact up for each RCA jack so it has more force on the cable’s center contact.

I’ve tried the wiggling suggestions, but no results.

Question: if it is the selector switch, is it possible to replace it? It seems proprietary, being soldered into the circuit board.

It wasn’t proprietary and you can still find them around on occasion. They were made by a British company, Lorlin. They can be replaced with anything else if you wish. Some have carefully removed the switch, replaced it with wires connected to a rotary selector switch.

I’ve been looking all over and just realized PS Audio has a forum, so I might as well check here.

I have a PS Audio 4.5 Preamp that I enjoyed for many years. While listening to some LPs one evening the preamp visibly (and olfactory) let the magic blue smoke out. The damage was visibly to a resistor presumably on the left channel phono pre or related as it took out the left channel of my phono cartridge at the same time.

I replaced the resistor but it, too, smoked (with nothing plugged in - eliminating the cart as a possible cause). Is there a source for a schematic on this preamp somewhere to aid in troubleshooting?

Thanks in advance.


Please contact our service department on Tuesday and we can fix you up with a schematic. Sorry about that blue smoke escaping!

Paul McGowan said

Please contact our service department on Tuesday and we can fix you up with a schematic. Sorry about that blue smoke escaping!

Thanks Paul. Will do.

Enjoying your YouTube channel BTW. I worked for Dolby Laboratories in the 90’s and a colleague of mine had a set of IRS Betas that I was always jealous of. I can only imagine what you’re listening room sounds like.

Happy New Year.


Same to you!

Paul McGowan said

Please contact our service department on Tuesday and we can fix you up with a schematic. Sorry about that blue smoke escaping!

Just wanted to post to close out the thought in case someone else comes along with a similar issue. I really want to thank the PS Audio guys for getting back to me. Unfortunately, I guess there are no documents before the P300 Power Plant. Duncan from PS Audio offered me a very generous offer on trade in credit for the non-functioning preamp. Unfortunately, I need to settle on a new permanent preamp/phono cartridge solution and PS Audio doesn’t really have anything for me in that regard. I’m more of a second-hand HiFi guy in that regard anyway (or at least my wallet is).

Maybe someday I’ll win the lottery and be able to play with the big boys. PS Audio gear would definitely be in the running in that case!

Thanks again. Keep up the videos Paul.

The power supply of my 4.5 preamp buzzes pretty bad. Is it worth fixing?

It would likely need a new transformer which might be hard to source.

Bummer, ok i’ll power it off then…Thanks from another former (unfortunately) SLO resident.

Hi Paul, I have the PS preamp 4.5 as well but I lost the power supply during the move.I believe PS does not have the power supply in stock any more. Would you able to send me the requirements of the power supply and the circuitry so I can make one myself. Thanks.

56v (AC) center tapped transformer. Bigger the better.