Dynaco PAS 2 value and difference to PAS 3?

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'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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Emorrisiv, here are some tips if you are interested:

try to retain the rectifier tube. Replace all the filter capacitors. Replace the selenium filament rectifiers with 3A low voltage silicon devices.

Tape has become more popular, but usually the tape machines have their own playback EQ. So its a nice trick to move all the EQ components for the phono off of the switch and onto the bottom of the board. You can also wire the phono input directly to the phono board as a result. This eliminates the need for the middle wafer on the selector switch.

I've made 24-position stepped volume controls for the PAS that have worked out quite well! If everything is done right this preamp can challenge a lot of modern preamps, but it will not do LOMC without a stepup device.

Have fun!