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PAS preamp project

I have a Marantz model 33 preamp I really like. But it does have sliders. And yes they tend to need cleaning more often than stantard pots.
 
While looking for circuit options, I have seen boards, line and phono, by Curcio, Koren, Aikido, even Marantz 7 derived. Has anyone done/heard anything with these circuits? (The Aikido seems to have its fans).
 
ctjetta said:
While looking for circuit options, I have seen boards, line and phono, by Curcio, Koren, Aikido, even Marantz 7 derived. Has anyone done/heard anything with these circuits? (The Aikido seems to have its fans).
Click to expand...
See rennenkamps infopage where the PAS3 phono is superior to at least curicio . The suggested phono in a PAS is pc-6 from dynaco
or any of it's replicas ( yes you can purchase exakt replicas made in modern material)
Any better board needs more power, and that is not available in PAS.
 
peterh said:
See rennenkamps infopage where the PAS3 phono is superior to at least curicio . The suggested phono in a PAS is pc-6 from dynaco
or any of it's replicas ( yes you can purchase exakt replicas made in modern material)
Any better board needs more power, and that is not available in PAS.
Click to expand...
There are power transformers now to replace the original, with. A bit more current to go with the updated power supply. From what ive read the reproduction tranys are quieter too.
 
As I'm starting with a blank chassis my intention is use a regulated PS from either Tube Nirvana or Dynaco Doctor (a Curcio site). This should give me the flexibility to go with any board. I'm leaning toward retaining the 12X4, for nostalgic reasons I imagine, and the LED replacement.. This would be an improvement even with the stock boards, or their clones.
For the the pc6/phono board the rennenkamps circuit is certainly a good way to go. I'm thinking the PH-10 (Tube Nirvana) is also viable, the further I get from stock.
 
petercapo said:
A few things...

If you plan to mix and match, be sure the different boards you want to use are truly compatible with each other. I suggest contacting the sellers to discuss this.

If you want to retain the 12X4, make sure the power supply you plan to install will permit this.

In the case of Mr. Curcio, I'd contact him before sending any money to make sure he is going to be available to support you. He has been MIA from his forum for a while. And, IIRC, there was some question with his regulated power supply http://audioasylum.com/forums/dynaco/messages/12/7790.html
Click to expand...
petercapo, thanks for the heads up on Curcio. And if it hasn't been obvious, I admit to only knowing enough to be dangerous. I've been contacting the vendors on various products.
One of the Tube Nirvana regulated PS's retains the 12X4. The other one doesn't. As you say there's a potential issue with Dynaco Doctor's PS that helps narrow down my choices.
As far as mixing/matching I will definitely inquire about compatibility issues if I source from different vendors.
And all, I appreciate your continued input!
 
I used the tube nervana SS power supply and havnt noticed excessive heat. The repop cover does have slotts on both sides and seems to vent heat well. My temp gun reads 93º most of the time on the top cover. And with the Aikido board there are 6 tubes inside instead of 4.
 
A friend just happened to drop by with a PAS-3 that I modified back around 1979, complete with its custom outboard regulated 375V tube power supply. If there's any interest, I'll be happy to post the PSU schematic.
 
One small tweak I'd make to the original phono circuit is to put the caps on the board vs running them through the switch. This doesn't actually change the circuit in any real way, it just gets rid of some connections in the signal path. Nobody really needs a tape head input these days. Mine still has the inputs running through the switch so I get 3 phono inputs, but if you don't need so many its a small matter to feed input straight to the phono board and rewire the switch to gain some more line level inputs. Doing that would also help clean up the signal path on the phono board a bit.

My PAS has a power supply board from Classic Valve. Won't tell you that you honestly need a regulated power supply, but mine had none of the PSU parts in it except the transformer and it was less expensive to use his board with SS rectification than it would have been to buy a 12X4 and duplicate the stock supply design with boards or individual parts.
 
I like that Harman and Kardon 17S preamp, it would match up with my Citation 18 tuner. Fantastic build quality and classy looks.

BillWojo
 
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