Recommended Modifications/Tweaks for Dynaco PAS-3 Series II Pre-Amp

[Superman]

hi!

a friend is asking me what are some modifications/improvements/tweaks that can be done for a Dynaco PAS-3 series II tube pre-amp...it uses 3 pieces 12ax7 tubes in the line stage stage as well as 3 12ax7 tubes in the phono stage...any website that you can recommend?

many thanks to all!


Superman

 

[Brian Beck]

Norman Koren has done some good work sorting out the feedback and coupling issues of the older Dyna preamps:

http://www.normankoren.com/Audio/

I'm not sure how much of this applies to the Series II, but worth a look.

 

[Robert Morin]

Norman Koren 2nd yes vote

http://www.normankoren.com/Audio/Spice_preamp.html

It amount to almost a total rebuild but the circuit confuguration is a serious winner, used by Hovland, Pultec and Groovetubes.

Have at it and enjoy!

Robert Morin

 

[Ricdelros]

pas3 bass & treble

Hello !

I don't want to totally rebuild my pas3. All i want is to change the pot into a commercial value, because 700k & 400k are nowhere to find. what shall i do without changing the circuit?

 

[Geek]

A certain forum member is an authorized reseller of the Koren boards too 😉

Cheers!

 

[SyncTronX]

Opening it up

Is there a simple way to open this up without removing
every screw in it?

I removed the 3 screws on the face plate thinking the chassis
would slide out, or down. It doesn't.

It feels like the sheet metal is glued together. I tried
knifing along the bottom to break the seal but that
didn't seem to work.

If I keep trying and prying I'll end up ruining it...
any guidance would help....the manual didn't help.

 

[rayma]

Is there a simple way to open this up without removing every screw in it?

First, make sure that you have all the screws out of the cover, on the top (if any), on both sides, and on the rear edges of the cover (if any).
Next, using a wide, flat blade screwdriver, insert the blade under the bottom edge of one side of the cover, between the cover and the chassis.
Twist the blade a little, and you should get a gap opening up. Repeat along that entire side, and also along the other side.
Then use the gap to push the cover up. The problem is that the cover's flange is tightly wedged between the front panel and the chassis.
If you take off the front panel and knobs first, this would be much easier.

 

[SyncTronX]

Oops,

The three screws are on the rear, none on the side or the top.

Series II, the reissue.

I tried to pry it a little but it is stuck, so I took the razor knife
to it but that seemed to slice the finish.

The last thing I want to do is ruin it by jamming a screw driver in
there. Also tried a putty knife, it seemed as though it were glued
or taped along the sides.

Looking for another way in but there doesn't seem to be.

I don't have a problem using the brute force method, but
you know how that goes. I tend to use too much to begin
with so just trying to gently coax it apart.

I great at breaking high end taps in aluminium...go figure.

Will work on it a little bit later after I finish calibrating
my function generator.

Thank you Ray.

 

[rayma]

The last thing I want to do is ruin it by jamming a screw driver in
there. Also tried a putty knife, it seemed as though it were glued
or taped along the sides.

You'll probably have to remove the knobs and front panel to loosen the cover up enough.
If it's like the PAS3 chassis, there's a flange in between.