The best Dynaco preamp
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Marantz 500
Active Member
AFAIK, ths Pas2 and 3 are very similar, the main difference being the front plate and knobs. They look different but are constructed the same way. The Pas3x has tone controls which are completely defeated when set to zero. My Pas3x sounds good, not sure if it's better or worse than the Pas2 and 3. And of course many people choose to eliminate the tone controls completely for better sound quality. I prefer keeping it original, though!
mhardy6647
Lunatic Member
There is a cottage industry devoted to PAS-2/3 modifications.
jaymanaa
RIP 1961-2018
Yep, and FWIW, if you decide to use the original boards, they should be stripped and cleaned as they tend to be awfully leaky otherwise. I've found when slightly modified and freshened up, the PAS 2 (and I'm sure 3) are very capable preamps.
dividebytube
Well-Known Member
don't forget running dual PAM-1s!
mhardy6647
Lunatic Member
I am slowly but surely freshening one for AKer "iambiglou"...
ducati_EL34
Addicted Member
This is my modified PAS. The phono in and out wiring is now 22/2 shielded cable. The tone controls are no longer in the circuit. Neither is the blend, balance, or any of the filter switches. The volume pot is new as well. I also leave the top off...
The boards are new reproductions.
The boards are new reproductions.
Attachments
The PAS 3X is the best of the bunch. With the tone control knobs centered, the tone controls are effectively removed from the circuit and the output impedance is lower. These are good sounding tube preamplifiers, IMHO, even in their stock form and as has been said before, there are plenty of modifications available.
Kegger
R.I.P. 1/12/1966 - 6/1/2017
My opinion, and it's just that MY opinion is stray away from the pas2/3 preamps.
Week power supplies including tranny and a good bit of mods to make it decent.
By the time you've bought one/modded/rebuild it I personally feel you could get
much more for the money/time spent on one of the Pas Pre's.
Week power supplies including tranny and a good bit of mods to make it decent.
By the time you've bought one/modded/rebuild it I personally feel you could get
much more for the money/time spent on one of the Pas Pre's.
ducati_EL34
Addicted Member
But you would have the fun and satisfaction of DIY. As for the weak power transformer, get rid of the indicator bulb and go solid state. That would take some of the load off of it.
Kegger
R.I.P. 1/12/1966 - 6/1/2017
I have no problem with DIY, as a matter of fact quite like it, and prefer Tube rectification.
Problem is by the time I was to buy a pas and completely redo the whole darn thing it's a
different preamp altogether (Nothing left of the pas but the shell) and probably $600.oo+
invested, I'd rather buy something different or do a whole new "scratch" build instead of
modding/mangling the Pas. (I don't mind hacking to bits if it gets me somewhere I like)
Problem is by the time I was to buy a pas and completely redo the whole darn thing it's a
different preamp altogether (Nothing left of the pas but the shell) and probably $600.oo+
invested, I'd rather buy something different or do a whole new "scratch" build instead of
modding/mangling the Pas. (I don't mind hacking to bits if it gets me somewhere I like)
SpruceMoose
Super Member
see, here's what i dont get: in the case of ducati's PAS, (not to pick on you, but as a for instance), what of the original PAS is still there? the box. the transformer. or was it also replaced? the I/O jacks. oh yeah, the tubes!
it has always seemed to me like the story of the guy that bought george washington's original ax that he used to chop down the cherry tree. the head was replaced three times, and the handle twice. there's darn near nothing left of the PAS. if it were me (and it isn't) i would either leave the PAS alone (which is what i am doing with mine) or build an open-top preamp using those upgrade parts. (which i would love to do, eventually.)
no offense intended, but donning my flame suit anyway.
it has always seemed to me like the story of the guy that bought george washington's original ax that he used to chop down the cherry tree. the head was replaced three times, and the handle twice. there's darn near nothing left of the PAS. if it were me (and it isn't) i would either leave the PAS alone (which is what i am doing with mine) or build an open-top preamp using those upgrade parts. (which i would love to do, eventually.)
no offense intended, but donning my flame suit anyway.
ducati_EL34
Addicted Member
see, here's what i dont get: in the case of ducati's PAS, (not to pick on you, but as a for instance), what of the original PAS is still there? the box. the transformer. or was it also replaced? the I/O jacks. oh yeah, the tubes!
it has always seemed to me like the story of the guy that bought george washington's original ax that he used to chop down the cherry tree. the head was replaced three times, and the handle twice. there's darn near nothing left of the PAS. if it were me (and it isn't) i would either leave the PAS alone (which is what i am doing with mine) or build an open-top preamp using those upgrade parts. (which i would love to do, eventually.)
no offense intended, but donning my flame suit anyway.
Bruce221 and Moose,
It is probably one othe more modded PAS preamps, that still retains the original circuit. The transformer is original. The tone pots were very rough, and one channel was weaker than the other. The phono and preamp boards come prestuffed from "vintage electron" on ebay. They are $115.
I do not pretend this is still a Dynaco PAS. I bought it to get back into vacuum tube audio, when I bought the ST-70. I have performed certain mods to the circuit to increase the gain, along with the tone control removal. I just get a kick out of seeing how much I can change this unit.
My goal has been to make this PAS as good as possible and still retain the original circuit. I have been reading up on and performing mods that have been done to these units over the last ~30 years.
SpruceMoose
Super Member
i guess i was lucky to find a PAS that was ready to run. after i used it for awhile, the xfmr went bad. kinda strange. i stashed it for several years, as there were no replacement transformers out there. i looked off and on for quite awhile. i just replaced it with a new one from triode electronics. now i have a channel imbalance issue to track town. no big deal.
i do like having the tone controls, as my speakers are not in optimal, similar positions, and are not movable. so the left one gets a bit of bass boost. i also like having the loudness switch, for low-level listening. i like having a bit of bass kick at low levels.
but i would also love to build an open-top pre, possibly based on one of the modified phono boards, no line inputs, nickel-plated chassis. i love the look of my st70 without the cage. we shall see...
i do like having the tone controls, as my speakers are not in optimal, similar positions, and are not movable. so the left one gets a bit of bass boost. i also like having the loudness switch, for low-level listening. i like having a bit of bass kick at low levels.
but i would also love to build an open-top pre, possibly based on one of the modified phono boards, no line inputs, nickel-plated chassis. i love the look of my st70 without the cage. we shall see...
shelly_d
Not An Audiophool
IF you really want to go with a Dynaco understand that - as been mentioned already - the PAS2 and PAS3 are exactly the same circuit and you can expect exactly the same performance / issues / service expense from them. The PAS3X has a slightly different circuit that removes them from the circuit when centered.
I know a few people that really like the stock Dynacos but there are many that want to modify them as Kegger or Ducati_EL34 suggest / have done.
You need to decide which way you are likely to go. If its the mod route you might want to look into something like a bottlehead kit instead www.bottlehead.com. THat way for about the same cost as a highly modded 40 year old unit with new guts you instead get a brand new unit you build yourself with a very modern circuit and design layout. On the other hand if it’s the just clean it up and make it dependable route the Dynaco will certainly keep the costs down:yes: Either way I'm sure that you will enjoy the music.
Shelly_d
pilotputz
Super Member
I have an interesting mod on my PAS3X. The tone controls have been routed through the filter switch: When the switch is off, the tone controls are by-passed. When the filter switch is on, the tone controls are functional.
I can see why people simply remove them from the circuit: I seldom if ever need to use the tone controls.
I can see why people simply remove them from the circuit: I seldom if ever need to use the tone controls.
SpruceMoose
Super Member
mine is balanced at 930 or so. i think the problem popped up after i deoxited the pots. i tbhbink i will give them another shot before i jumper them.
