New Dynaco PAS Boards

MRC1991

New Member
Good Morning,

I bought an old Dynaco PAS3X from eBay a while back and got it running to the point and have enjoyed it for the last few months. I an now ready to perform a complete over haul on it.

So far I have by passed the tone blend and filter controls, upgraded the power supply to the tubes4hifi version, installed a new transformer and replaced the volume and balance pots with ALPS.

I am looking for opinions on new PCB's for the Dynaco, I am leaning towards the Zmod upgrade from Tubes4hifi. I will also be replacing the rear jacks and selector switch.

Has anyone had any luck with these boards or recommend another route?

I am hesitant to pull the trigger until I hear some opinions on the sound. I have search and only saw 2 reviews on these. (1 positive, 1 negative) I also purchased the ALPS volume pot from them and have had some issues (100K instead of 250K, only even through both channels at max volume). The power supply worked perfect though.

Tech support from them has been awesome and I'm overall happy with their products.
 
The original board design just isn't that bad. Actually it's quite good. The only problem with the PAS is it's old and needs a wicked good cleanup. Like you are doing. New volume pot, switches, jacks, etc....

If the board is in good shape leave it. Maybe recap it at best. You will loose that "sound" by removing it and all the components. If that's what your goal is then go for it. I would bypass all those filter and sterero mono switches!!!

Personally I would invest in a good selector and volume control from Gold Point, replace the jacks and clean it up and enjoy. Don't mod the crap out of it before you've listened to it as it was mostly intended to be.

It really is a nice little preamp stock. But it seems to be a victim of tweakers.
 
The original board design just isn't that bad. Actually it's quite good. The only problem with the PAS is it's old and needs a wicked good cleanup. Like you are doing. New volume pot, switches, jacks, etc....

If the board is in good shape leave it. Maybe recap it at best. You will loose that "sound" by removing it and all the components. If that's what your goal is then go for it. I would bypass all those filter and sterero mono switches!!!

Personally I would invest in a good selector and volume control from Gold Point, replace the jacks and clean it up and enjoy. Don't mod the crap out of it before you've listened to it as it was mostly intended to be.

It really is a nice little preamp stock. But it seems to be a victim of tweakers.

I understand your point, I'm starting to lean that way.

I did by-pass all of those switches and am happy with the results. That gold point volume pot looks pretty awesome. I will look into that.

Would you perform the RIAA upgrade or anything to the stock phono board?
 
For now I WOULD order a selector switch from Gold Point. It makes a HELL of a difference!!!! Later on get the volume control. Again WELL worth the investment.

Do you have a part number on either of those? I really appreciate the help!

I am going to stick with stock boards and do a re cap. Does anyone have a capacitor list?
 
[Qhttp://www.goldpt.com/UOTE="MRC1991, post: 10314709, member: 241684"]Do you have a part number on either of those?[/QUOTE]

Just email the owner of Gold Point and tell him what you need. It's a very personal and friendly place. I've dealt with him several times and the owner has always been very helpful and obliging.
 
In my PAS thread I also asked about the ZMod boards. I got little response about them, as well. However, I did get many other great opinions/suggestions regarding my PAS Project.
I want to jump in on this thread because I, too, have questions regarding pots/attenuators.
Starting with the current essentially stock PAS I just acquired, I'm looking to replace the pot with an ALPS or TKD unit. For simplicity's sake I was to use a 250k item as it matches the original. I often see 100k units offered/suggested. At the Goldpoint site it says it makes little difference which value you use.So given that I plan to remove the tone controls to lower the impedance (don't know if that even matters for pot selection) what am I looking for when choosing a value for my pot?
I am also going to start with a PAS chassis and go with an Aikido line amp and some sort of PC6 phono circuit. These are designed to drop into the PAS chassis with all that goes with it. So does this imply I should stay with the a 250k attenuator (in this case) or some other, lower value? Do I need to take potential amps into account?
Thanks!
 
The limit of 250k for volume pot is due to the ability of the riaa to feed both the volume pot AND the tape-out, considering that tape-out is loaded with a typical tube-input ( > 250k )
Replacing the riaa will trow all bets off.
A question: if you buy a PAS and then throw it out, wouldn't it be cheaper and more convenient to start
with a new box and have all limitations removed ??? Using the PAS as a chassies but replacing boards and power
seems odd to me..
 
@peterh That is exactly why I bought a new chassis. Since i was going to use an Aikido line stage and ph10 phono board I couldnt see gutting an existing PAS for this. If your going to shell out for a complete PAS, then gut it you might as well just buy a shiny new chassis and build it like want. Doing the math it comes out about the same cost. Including a custom face plate.
 
I was not clear- My second PAS for my project is a bright, shiny, new chassis from Dynakits. with this I will be starting from scratch with an Aikido board and some sort of PC 6 in this chassis. I can choose ANY attenuator I want. I just don't know what I want. Or why I should want what I want.
Does it matter where in the circuit you apply the attenuator as to the value you might choose?
As far as the stock PAS, if I don't need a tape out, and I Don't that open up my options for the pot value? 100k? 50k? 10k?!! I'm not looking for a reason to change the value, I just want make an enlightened decision as to correct pot/attenuator to use..
 
The instructions for mine was to put the volume pot between the source and line stage. So from the output of the selector switch to the line stage. If you dont find a custom face plate you like say from Dynakit, FM3 zone will make whatever you want, holes, lettering and lettering color and color of faceplate too for the same price. i went with the PH10 phono board like the one tubes4hifi sells only on a smaller board to fit the pas chassis. Uses two 12ay7's or equivalent. Kegger sold me a nice set of mil. Spec. tubes for it and Iit sounds very nice.
 
[Qhttp://www.goldpt.com/UOTE="MRC1991, post: 10314709, member: 241684"]Do you have a part number on either of those?

Just email the owner of Gold Point and tell him what you need. It's a very personal and friendly place. I've dealt with him several times and the owner has always been very helpful and obliging.[/QUOTE]

Awesome thank you! I am going to test different reistances of volume pots before I order.
 
Okay great, I removed the loudness controls already and the blend switch. With the 100k pot I bought I noticed my turntable hum was alot worse. Plus the POT channels were only balance all the way turned up. I am going to switch back to a 250k ALPS and see if it changes. On my SS equipment my turntable hum is only audable at 3/4 volume
 
I totally strip both boards and soak them in acetone, and denatured alcohol, and scrub them with a brush. This gets rid of any voltage leaking round on the board. Then I use the RIAA out of the RCA tube manual with a 47k load. The selector switches were poor when new, so it get's tossed. You can get creative with the line stage, such as EF86s or EL95s, stuff like that. I usually bump the rectifier up to the 6CA4 too, and definitely a larger PT.
 
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