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4.5 Pre-amp part numbers

#1

I have a 4.5 pre-amp that has a bad input selector switch. I called customer service and was told that no parts lists or schematics were available for that unit. The representative also told me that that design had been contracted out to a 3rd party company, which made my request even more difficult. It seems very odd to me that PS Audio would not have a parts list for units it sold.

The dealer who sold the unit says he cannot service them, and he does not have any schematics or parts lists either. No one else in San Diego seems to have that information. I really love the preamp because of the fabulous sound using straight wire gain and the moving coil section, so I’d like to continue to use it.

Can anyone at PS Audio supply the part number for the Lorlin switch on the 4.5 preamp input selector?

Thank you in advance!

Best Regards,

Jeff Thayer

San Diego

#2

I’m thinking out loud … was Cullen Circuits involved? The man behind that has retired but his son has a similar business and may have some information. He sells power cords, interconnects, and speaker wire. Cullen Cable is the name I think. I’m not sure if Paul was involved with the company at time either, can’t speak for any of the other current PS Audio employees.

#3

Rick Cullen, Patrick’s father, built all of these products for us back in the day. Rick was our production manager.

The Lorlin switches haven’t been made in decades, unfortunately. There is no replacement I am aware of. Sorry. The one thig that can be done is to replace the switch with a good selector, like a CTS or any decent rotary switch. Then, hand wire from the switch to the PCB. It’s tedious, takes skill, but it can be done.

Wish I had better news.crying_gif

#4

I found an old post from 11/08 on the diyAudio Forum, from mightydub, with part numbers and a schematic for the PS Audio 4.6 pre-amp.

http://www.diyaudio.com/forums/

Mightydub supplied me with fantastic information, enabling me to fix my PS Audio 4.5 pre-amp. It had the 4.5/4.6 common problem, worn out selector switches. They are Lorlin switches, and contrary to information on the PS Audio Forum, the parts are still made, and readily available.

mightydub’s info was specific to the 4.6 pre-amp, but the 4.5 and 4.6 pre-amps shared many parts. The switch part numbers are the same, and worked on my 4.5 pre-amp.

I love the sound of the PS Audio 4.5 pre-amp using the Straightwire setting, which bypasses the line level amp. If your source has a high enough output, you can select Straightwire, which bypasses the entire pre-amp, using only the volume potentiometer. Thus you are only listening to your CD or digital source output, and not the pre-amp. For vinyl records, you can choose to use only the PS Audio phono section, bypassing the line level amp. That assumes the use of a moving coil cartridge with a moderate or high output level. Pretty neat design.

I ordered the switches from Allied Electronics:
http://www.alliedelec.com/lorlin-pt6422/70749355/

MANY thanks to mightydub!

Here’s the information mightydub sent me:

Here's the schematic and data sheet on the switches. The switches are a modular system, you start with the basic switch then you can add additional wafers to it. The output, tape feed, and source switches are 2 pole, 5 way though only the input selector uses all 5. The output and tape feed have a stop pin that limits it to 4 positions. The balance switch is two 12 pole wafers. The schematic is hard to follow but it all makes sense once you take the preamp apart and study it a bit.
I found the switches at Allied Electronics, you could also try Farnell in the UK. I just did a google search and see availability at a variety of places.
http://uk.farnell.com/lorlin/pt6434-bmh/switch-1pole-12-pos-tht-0-5a-250v/dp/1123674
http://www.newark.com/lorlin/pt6422-bmh/switch-2pole-5-pos/dp/24M6507
http://uk.rs-online.com/web/p/rotary-switches/0352301/
http://uk.rs-online.com/web/p/rotary-switches/0352294/
1 Lorlin SWITCH + 1P 12W Mfr's Part#: PT6434
3 Lorlin PCB SWITCH MECHANISM Mfr's Part#: PT6422
2 Lorlin PCB 2 POLE 5 WAY Mfr's Part#: PT602-003
2 Lorlin PCB 1 POLE 12 WAY Mfr's Part#: PT602-001
#5
I have a faulty PS Audio 4.5 and need the schematic for repair work. It would be appreciated if any of you can send me a scanned one on my email all@bio-root.com Thanks