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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Need PS Audio PS IV schematic
Need PS Audio PS IV schematic
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Old 6th April 2016, 04:15 AM   #21
Didhefocus is offline Didhefocus  United States
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I have some hand drawn schematics, some custom, some stock, but I created easier to read computer drawn schematics from them. PM me with your email and I'll be happy to give you what I have.

I've got my PSIV preamp almost fixed. I had noise in the Phono stage and the gain section. The gain section had a bad transistor but I still haven't found the culprit in the Phono stage. I'd be happy to swap notes!
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Old 6th April 2016, 06:16 AM   #22
rss388 is offline rss388  United States
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I also have a PSIV that I picked up on FleaBay. The line section is hissy so I am running it passive for now. The phono amp is actually quite OK. Now I am thinking of recapping the amp, clean the sticking controls and fix the hissing. Sure would be great to swap notes.
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Old 9th April 2016, 08:04 PM   #23
Didhefocus is offline Didhefocus  United States
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Passive has enough gain for me but I still haven't found the noise in the phono section, which sounds awesome BTW!
I have already re-cap'd mine and about half were bad or marginal, but it made little to no difference to the noise I'm getting.
The transistors used throughout the preamp are not both readily available. MPS8099(G) are still available at Newark.com but I couldn't find MPS8599. I got MPSA56RLRMG as a replacement which seems to work fine!
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Old 10th April 2016, 08:48 AM   #24
AndrewT is offline AndrewT  Scotland
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You could replace the front end transistors with types that are not equivalent.

Low gain types that are known to work properly will be nearly as low in low noise as good working high gain types. Most of the noise comes from the front end.

If after replacing you find no change in noise then you know it was not the old transistors. test them and put them back.

If the noise is much improved, then you know the old ones were damaged. Look for good replacement types.
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Old 10th April 2016, 05:53 PM   #25
Didhefocus is offline Didhefocus  United States
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Changing transistors one by one on this preamp is not practical since the solder side of the PCB is not accessible unless the whole thing is disassembled. Each board is soldered to another and all rear connectors and front controls and PCBs must be removed together. I found desoldering and re-soldering caused too much damage to the fragile traces than I'd care to deal with.
I have been cutting the transistor legs and replacing them one by one from the component side.

Thank you for your tip on noise usually coming from the front-end transistors. When I get back into this project I'll start there.

Do you have recommendations for different transistor replacements that would work properly? I find cross referencing very confusing!
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Old 19th November 2016, 01:43 AM   #26
redz06 is offline redz06
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Default PS Audio IVH preamp

Let me apologize in advance for tagging onto this thread. I felt that doing so might allow me to reach folks who can really help me.

I pulled a PS Audio IVH preamp out of my closet recently. I am the original owner and I am guessing it is somewhere around 34 years old. It still works and I am using it with my original Amber 70 power amp (also pulled out of the same closet). Both still sound pretty good. My preamp has a small problem though and I am looking for advice on how to fix it. Often when I switch it on, only the right channel is working. All I have to do is give it a sharp rap on the cover and the left channel starts working. Sounds great, no hum, etc. Eventually the left channel drops out.

I have had the cover off and nothing looks amiss. I am wondering if the problem could be a poor ground on the central ground bolt. Does anyone have any other suggestions for me to follow up on? Warning, I am a mechanical engineer, not an electronics technician.

Currently I am using this equipment to replace an Altec-Lansing powered speaker system with my desktop computer. Listening to MP3 files, it sounds 100 times better than the Altec ever did, using an old pair of Mordaunt Short bookshelf speakers, also rescued from my closet.
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Old 27th April 2018, 07:04 PM   #27
Zen Mod is online now Zen Mod  Serbia
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Need PS Audio PS IV schematic
Boyz, I'm in need of PS Audio 5.6 preamp schmtc, for troubleshooting purposes

I reckon , maybe any of earlier preamps schm could be helpful ........

so , if you have one , please send it to >zenmodiyaudio@gmail.com<

TIA
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Old 9th May 2018, 01:14 PM   #28
samchen is offline samchen  Taiwan
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Hi Greg,
Very interisting,can you send a copy for me,my email:a0958302508@gmail.com
Thank you so much
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Old 10th May 2018, 04:20 AM   #29
Greg Stewart is offline Greg Stewart  United States
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Need PS Audio PS IV schematic
Will get to you in nest few days
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Old 12th May 2018, 11:01 AM   #30
samchen is offline samchen  Taiwan
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Hi Greg.,
Thank you very mush!
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