Transform your aging classic into a Modern Classic!

John Hillig, founder of Musical Concepts, always admired tubed electronics. It was a challenge from a friend to make his solid-state Hafler DH-101 preamp sound like a tube preamp that launched Musical Concepts, but that’s another story. John used a highly modified Dynaco PAS-3X for years. Some of you may recall the Trevor Lees mod for the famous Dyna preamp. John used the T-Lees with his own additional mods, such as passive RIAA, better power supply, etc as a phono stage. Frankly, he’d still be happy to use it today.

Now lets talk about your Dyna PAS.

The Upgraded Power Supply: Robust power power supply upgrades are needed for outstanding performance. Filament voltages are filtered more heavily and wideband noise issues are banished. Yes, all the noise of our daily lives such as WiFi, Cell phones, cordless phones, etc. is everywhere! You’d rather not have that stuff crawling around on your DC power supplies, don’t you agree. You can keep your 12X4 tube rectifier since we are implementing a relatively efficient circuit in place of the original. Higher voltages become available for the phono and line stages since the large power supply caps reduce the need for large pi section filter resistors. B+ capacitance is enlarged and dramatically enhanced with high frequency bypass techniques.  

A New Line Stage: A complete line stage redesign is required to drive modern amplifiers adequately. An unusual SRPP line stage with 20dB gain in a quiet, incredibly simple, low output impedance configuration was chosen. With even  inexpensive 12AU7 tubes this line stage will produce stunningly natural sound. This is a simple, but elegant design. It has superb soundstage recreation, wide dynamics, very powerful bass extension and clean, natural tonal qualities! It’s an inexpensive, foot tapping sort of miracle.  Tone controls and filters are eliminated!

The Classic Phono Stage: The venerable basic design retains the 12AX7. The two-stage 12AX7 redesign incorporates a passive RIAA mode and complete operating point redesign taking it beyond the basics. All new resistors and capacitors complete the picture. Your treasured tubes will provide extended, robust sound and high gain to accommodate medium output phono cartridges.

The Sound: If you’re looking for a simple refurbishment, a PAS with more modern parts, then look elsewhere. Though the PAS-3X was great in its day, this isn’t its day. Its day was an all tube time. Tubed amplifiers are much easier for an original PAS-3X to drive. Solid-state amplifiers are another story. Our modification is a major REDESIGN of a classic circuit to accommodate both solid-state and tubed amplifiers. The Musical Concepts modified PAS-2/3 series represents a modern high performance standard well beyond the achievable results of 1950s technology. You will be thrilled with the sense of wide dynamic range, lucid soundstaging, subtle sonic shadings and the sense of neutrality.

PAS-2/3 Line Stage Mod is $499.00 installed (phono stage remains stock)

PAS-2/3 Complete Mod including "Phono Stage" $699 installed

PAS-2/3 Elite Line Stage Mod is $699 installed with Schottky and Soft-Recovery Rectifiers, added power supply bypass caps, etc.

PAS-2/3 Elite Complete Mod is $899 for complete, phono + line, installed mod

Custom Mods - Consult with us. See some examples below!

—––––New tubes extra with all mods–––––––-

A Musical Concepts Custom Tour:

A dedicated audiophile who really likes his PAS-3X decided to give it the custom luxury treatment. This was about a year ago when BlackGate caps were not unobtianium.

The power supply is built around a pair of dual-section BlackGate caps fed from IXYS FRED diodes. We rebuilt the filament supply with regulation. Oh yes, notice the new externally mounted transformer. It’s such a simple idea that opens up the interior and practically makes it look spacious in there.

The phono stage retained the dual 12AX7 configuration with a redesign including passive RIAA compensation, new operating points and all new quality parts. That second control from the left is the highly regarded PEC volume control for those that don’t recognize it. It’s a beautiful thing with gold solder lugs. It is totally sealed to the environment. It sounds great too.

The line stage has been modified to use 12AU7 tubes in SRPP mode. The circuit is like our Musical Design SP-2B which uses the 6922 tube. It’s a bit hard to see but those are our Platinum Grade resistors in the line stage. Mundorf Silver-in-Oil caps have a superb, extended and detailed quality that is truly unique. The Mundorf caps have a sense of soundstage illumination without drifting towards brightness - a light airy quality, but with authority. Then we went and replaced the Mundorfs with the Aura-T Teflon caps after this picture for another upgrade level. We replaced several of the original RCA jacks with the silver-plated Deltron connectors from England. They don’t look fancy, but wow they sound neutral.  All circuits operate at 300VDC.

If you have great eyes you might notice the switch with the white tape under it. That is a ‘Home Theater Bypass’ switch we implemented. Oh yeah, the original LOUDNESS switch has been converted to a mute switch.

Maybe you are seeing this and thinking you might like to have one. Well the BlackGates are gone unless you supply them, but a set of Jensen four-pole caps would be unstoppable too. You could do just the line stage or heck just a phono - we can build a killer phono with three or four tubes if you just want an outboard phono stage. Come to think of it we can probably stuff a phono stage in a PAT-4 or PAT-5 if you really want to shock your friends.


Here’s another great sounding PAS-3X. We were tasked to deliver a middle sort of price. Still I wasn’t surprised at how great it sounded - another foot-tapper is born. Actually this is similar in design to our new Chameleon preamp(standard version).

The power supply utilizes our Musical Design SP-2B power transformer. Voltage is rectified by IXYS FRED rectifiers and fed to the five electrolytic caps on the board to the left of the transformer. Separate voltage regulators are provided for line and phono stages. The filament supply uses Schottky rectifiers, has a good chunk of capacitance(twin capacitors mounted on the chassis to the right) and is also regulated.

The line stage is comprised of a single 6DJ8/6922 tube operating as a Plate Follower for a gain of 20dB and low output impedance under 1K Ohms. You’ll see the famous SILMIC II caps used for cathode bypasses in both line and phono stages. There’s that great PEC volume pot again. Oops, where’s that other tube? Don’t need it, the single 6922 does a great job just like it does in our Chameleon preamp!

The phono stage uses a pair of 6DJ8/6922 tubes in grounded cathode amplifier mode with a passive RIAA compensation circuit. In order to get the needed gain the cathode resistors are bypassed on each stage. Of course, it has the added benefit of lower output impedance too. Again this stage is very similar to our optional phono stage for the Chameleon preamp.

Summing it up, we liked it, the customer liked it and the wife was impressed too if memory serves. We are the builders of domestic tranquility, yeah.


Dynaco Tube Preamps - PAS-2 and PAS-3