Dynaco PAS 2 value and difference to PAS 3?

I run a Dynaco PAS-3X in my 'second' system (McIntosh 250 / Dynaco PAS / Dynaco AF-6 tuner / KEF Q60 speakers / Panasonic linear turntable and Pioneer CD player). The PAS is a very pleasant preamplifier and with a SDS Power Supply board, new coupling capacitors and tone control bypass it does a competent job. As mentioned above, it isn't exactly the most detailed or revealing preamplifer, but it is very musical. Perfect for less-than-stellar recordings and less than perfect audio systems.

They do have a high output impedance and work better with an amplifier of higher input impedance.

Again, there is no need to bypass the tone controls on the Pas 3x because the tone controls are bypassed when set to the neutral position. The Pas2 and Pas 3 do not have this tone defeat circuit, so you may want to bypass tone controls on those units.

I would respectfully differ on that point based on personal experience. If you jumper the PC-5 circut board, you will avoid all of the crap wire, and solder joints, running to the tone controls themselves. Trace the board and you will see that the signal runs from the board, to the tone controls and then back to the board. The tone controls can effectively take their wipers out of the circuit, but they can't take the wire running back and forth to the board out. Try it. I did on my PAS 3X, and was quite surprised. Not the difference made my bypassing the blend and balance controls, but good none the less.

I've been doing mods on the PAS preamps for 30 years. There is **plenty** of reason to bypass the tone controls! Even if set flat, the stock line stage lacks bandwidth and resolution. However the line stage circuit can be seriously upgraded such that the unit will easily keep up with many modern high end preamps.

The phono section is only good for high output MM cartridges, but it too responds readily to upgrade. If you have no plans of using it for tape, the EQ components can be moved to the PCB and the middle wafer on the input selector swich can be eliminated. There are also improved EQ values, and one of the coupling caps at the output of the phono can be easily eliminated too.

They are, IOW, great preamps if you plan to tinker or update. In stock form they are OK but nothing special. The 3 and 3x look a little nicer and that is the only reason to pay any more for them. The filter caps, both high voltage and filament, should be replaced regardless of your plans. I usually replace the filament rectifiers as well- the old selinium units are nasty.

Have fun!

I just picked up a Pas 2 that looks just like a Pas 3 so I assume it is a later production model. IMHO bypassing the tone controls is a instant upgrade.It eliminated a lot of noise and it is so easy to do anyone with any soldering skills can do it in no time at all.The benefits are huge!
I plan on doing many upgrades to mine,but first will be the potentiometer and the power supply.The power supply upgrade is very inexpensive and makes it a much safer piece,not to mention (from what I understand having not done it yet) a sonic improvement.
This is my first tube component in over 30 years of solid state sterility. So far it is nothing but fun to hack on and sounds amazing.Old and funky?sure, but it is cheap and fun for hacking and the sound is way better than any SS preamp I have ever heard.

btw Viridian and Ralph Atmos are very experienced and are guys to listen to.

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