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Dynaco PAS2 Recap/Mods Complete !

Steve-H

Steve-H

Burnin down the house
Gents,
I wrapped up my complete recap and circuit modification of a PAS2 I had purchased about two months ago. It needed the heater circuit redone (someone had replaced the Se rectifier, but did a very poor job of it), along with some minor trouble shooting.

In short, the modifications were:
- RIAA was removed from the switch and placed on-board (Phono Only now)
- RIAA values tweeked
- Ditch all the mica caps and sub in polystyrene (exception - NFB cap)
- Removal of scratch filter
- Sub in larger coupling caps
- Add an output cap to the line stage

Along the way I also replaced all of the caps and any resistors that were out of spec (I found 3...). Additionally, all of the resistors in the RIAA circuit are now metal film types. I also found the usual loose wire, bad joint, etc.
I MUST thank paARt for his help with this project....His help and emails (the thousands...) were a massive help.
While the photo isn't much to look at, I can honestly say that it is like a completely different preamp. It might not be the newest/latest/greatest, but I assure you it does sound pretty damn good. :music::music: If anyone would like the specifics on values, etc - I'd be more than happy to help.
 

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Steve, this looks like a very satisfying project, and one that has been well executed! Beautiful workmanship, I don't believe many of the original units looks as nice and tidy! I'd love for you to bring it over someday so I could hear it!

What valves are you running?
 
Thanks Ed !
The wiring still leaves something to be desired; but I honestly didn't want to open that can of worms. I've seen worse for sure, so I figured that if it works, then so be it.
The tubes are a mix-match right now. I have two Tele's in the linestange, and two baldwinn branded tubes in the phono. Not quite sure what I want to put in there - suggestions ??
 
Pas-2

Nice work! I like the sound of the PAS units. I also removed the RIAA components from the switch and placed them on the PC board, that makes a lot of sense. :thmbsp:
 
Yes that can be a very satisfying preamp when upgraded. I ran a modified PAS for a number years when I was young before finally upgrading to something better.
 
pas upgrades

looks niceand clean,what did you change your coupling caps to?
I've changed the ps to a sds board, and replaced most caps, also bypassed tone controls. I'm looking to change out the selector switch, and have a nice mil.spec three pole six position switch, I don't care about phono stage at all.
Any suggestions
Thanks much,
sk
 
I recapped my PAS2 sometime ago. Then bypassed the tone contols, added the caps to the line out stage, new volume pot and selector switch with the reworking of the functions and RIAA. I am quite pleased with the results especially for the dollars invested. The rewiring for the switch seemed to be straight forward but was more of a PITA than I anticipated. Still, all was worth the effort. Enjoy.
 
Steve-H said:
Gents,
I wrapped up my complete recap and circuit modification of a PAS2 I had purchased about two months ago. It needed the heater circuit redone (someone had replaced the Se rectifier, but did a very poor job of it), along with some minor trouble shooting.

In short, the modifications were:
- RIAA was removed from the switch and placed on-board (Phono Only now)
- RIAA values tweeked
- Ditch all the mica caps and sub in polystyrene (exception - NFB cap)
- Removal of scratch filter
- Sub in larger coupling caps
- Add an output cap to the line stage

Along the way I also replaced all of the caps and any resistors that were out of spec (I found 3...). Additionally, all of the resistors in the RIAA circuit are now metal film types. I also found the usual loose wire, bad joint, etc.
I MUST thank paARt for his help with this project....His help and emails (the thousands...) were a massive help.
While the photo isn't much to look at, I can honestly say that it is like a completely different preamp. It might not be the newest/latest/greatest, but I assure you it does sound pretty damn good. :music::music: If anyone would like the specifics on values, etc - I'd be more than happy to help.
Click to expand...
I would love to have more data on changes to the circuit. Mine (PAS2) won't be phono only but I'd like to know what changes you made to the RIAA, what coupling cap values, and tell me about adding an output cap.

I know it's a pretty old thread but I'm ever hopeful.
 
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