Hot-Rodded Dynaco PAS

[HF9]

Finally finished up my PAS rebuild, it's been months coming. I chose to use reproductions of the original PAS 3 boards from eBay and rather than recreate the selenium rectifier with standard capacitors, I used the ClassicValve PAS Regulated Power Supply. I/O board and RCAs were sourced from Tubes4HiFi, Transformer from TriodeElectronics, Elma switch from PercyAudio, Alps pots from Mouser, resistors and caps from Sonicraft, etc. etc.

Be sure to check out all the build notes here: http://www.diyaudioblog.com/2011/02/complete-restoration-of-dynaco-pas-pre.html

 

[Grainger49]

Wow!  You used the stock chassis and the transformer (maybe?) replacing just about everything else.  That is a lot of work and very neat.

What circuit modifications did you do?  It looks like the tone controls are out, pots in place but not wired.  

Did Mouser have an Alps balance control (pot)?  

 

[mrarroyo]

Bryan, once again you have outdone yourself. Awesome work, now enjoy it.

 

[HF9]

Thanks Miguel and Grainger The transformer is actually a new one from Triode Electronics. I would have used the old one if it were included with the donor, but alas, the previous owner had something unusual in there. The tone controls were indeed bypassed, those pots are just cheapies I put in to act as knobs holders. I did seek out an old blend switch in decent shape to wire in. The phono was modded to allow a more accurate RIAA curve based on the Curcio Audio tutorial, and the power board is of course new tech.

The balance pot actually came from Roy at Tubes4HiFi. The volume control was from Mouser.

 

[howardnair]

looks very nice--love the interior colors--i am a fan of pas's if they are upgraded --i have a pas2 that i kept the original brass face plate --but new boards -selector rca/s volume  i kept the tone controls in mine-i used sonic craft and jupiter caps -the jupiters in the curcio phono upgrade and in the line stage where i used 1uf-i also used prp resisitors most places-silver teflon wire-etc--mine looks nice and neat  inside and out but its still a dynaco box nothing special-- yours really  puts mine to shame for creativity- very very  nice!!!

 

[Tube Newbie]

Wow!  That is very nice!  I like how clean and sterile that cam out.  It's stuffed with lots of quality components and hard work that's for sure!

Beautiful work!!!

Ron

 

[Grainger49]

This may or may not work for you with a regulated supply on the heaters.  Years ago I read "The Last PAS Mod" in a magazine.  One of the tweaks was to add massive capacitance to the heater supply.  I had stacks of surplus 16V caps and I added 0.9F to the supply. 

The soundstage deepened and spread.  It was beautiful!  Today you can buy large values cheaply.  You might give it a try.  If it doesn't work you can always use extra caps!  Well, I always can.

 

[HF9]

Hah, indeed. I love big caps too. The way Geek designed the regulated PS was with just enough capacitance. Some boards increase it by four fold, but you shorten the life of the little 12X4 rectifier tube.

I'd love to see some pics of your modded PAS Howard, sounds like some great stuff in there

 

[Mikey]

Nice job!

A very clean build.....

 

[HF9]

Looks like I'll be building a second one soon. I secured a set of Norman Koren PAS boards from Geek at ClassicValve