Transform your aging classic into a Modern Classic!

Musical Concepts opened the doors in 1979 featuring a modification for the Hafler DH-101 preamp, so some of you may think Musical Concepts ‘comes from’ solid-state. Not so! For years prior to establishing Musical Concepts the devotion to tubed amps and preamps was alive and well. Bridging the once wide sonic gap between the technologies is a point of pride at Musical Concepts. John Hillig, our designer, used a pair of highly modified Dyna MK IIIs for years. Frankly, he’d still be happy to use them today. Time has gifted us with dramatically improved component parts which weren’t available to the designers of Dynaco amplifiers. Our carefully selected component parts bring a level of refinement that could only be dreamt of by the Dynaco designers. Part and circuit enhancements such as capacitors, resistors, rectifiers and so much more to help us improve on already solidly designed older amplifiers.

Power supply upgrades include superior capacitors and film bypass caps. The redesign of the bias supply makes it quieter, stiffer and more stable. It is very important to remember that the amplifier’s output stage does not know the difference between drive signal and bias supply noise and non-linearity. Both are reproduced equally by the output stage. A much improved, larger main power supply reservoir yields more solid, clean bass and rock solid imaging. You can retain the tube rectifier or elect to use Soft-Recovery Rectifiers which allows for a power boost to as much as 45 Watts/ch for ST-70 and over 70 Watts/ch for MK-III.

Driver circuitry is refined with all new sonically selected coupling caps and many resistor/capacitor upgrades to improve noise figures and inherent drive linearity. Sadly it is not uncommon to see a 7199 driver tube, even a brand new one, that is too weak to produce a credible sine wave at anywhere near full output. We make sure you have low distortion right up to the clipping point.

The sound is more refined, detailed and even more natural. Listeners have always lauded the dynamic range, liquidity and three-dimensional imaging qualities of our modifications. You’ll enjoy imaging beyond simple depth. Now there is pinpoint imaging in the field of depth and height. The feeling that each individual image has a physical shape and sense of presence of it’s own will excite you. You won’t be disappointed.

These modifications are installed only - no kits are available:

Dynaco ST-70: $499, $579 with new, tightly matched EL-34 tubes

Dynaco Mono Amps, MK. III, etc (exc. MK-VI): $599/pr, $679 with new tubes 

Dynaco MK-VI Mono Amps: $899/pr, $1099 with new EL-34 tubes, since the original 8417 tubes are generally unavailable.

Custom Mods: Consult with us. Some examples below.

See our "Connector" page for hi-quality RCA connectors and binding posts!

A Musical Concepts History Tour:

This elegant Dyna MK III upgrade was performed recently. The owner wanted an all-out custom modification. New driver and power supply boards were selected for the project.

Our power supply upgrade retains the original tube rectifier to send voltage to the first B+ cap, the black capacitor at the upper right corner. It’s a 30uF/600V dry polypropylene film part, really superb for the purpose - quick, clean, natural. The filtered voltage is sent to the new power supply board for significant additional filtering, high frequency bypassing and voltage division. Power supply caps and resistors were carefully chosen for their sonic prowess. The power supply upgrade delivers solid imaging, clean bass, amazing speed and a delicate lucidity that’s a treat to the ear.

The first amplifier stage is a classic 12AU7 cascoded amplifier. The driver stage is a very linear 12BH7 long tail pair. To extract superb clear detailing Mundorf Silver/Oil and ZN capacitors were chosen along with specially selected resistors. Feedback compensation is optimized for superior imaging and a sweet, extended quality. Improved ventilation for enhanced cooling is an integral part of the modification.

This Dynaco MK III modification finishes with a new IEC power cord socket, Cardas Copper binding post and OFC RCA jack so nothing would remain to hinder the sonic qualities. This is an amplifier you can listen to as long as you like without a moment of fatigue. You might regret that you have to turn it off and go to bed though.


Here is an oldie to remind you that Musical Concepts has been in business since 1979. This Dynaco MK III sports a specially designed driver board produced in the 1980s at Musical Concepts. That’s when these things were laid out with black tape type material by the way. You gotta love computers. Topologically it is really very similar to the amp board above, but with some provision for power supply atop the driver board. It has separate bias pots for each tube so you don’t really have to buy matched tube pairs. A local customer brought this amplifier in for some service recently. I hadn’t seen one in a few years. Our customer has owned this pair for 15 years and wouldn’t dream of a new amp.

This picture was taken before the refurbishment so you can see the original 80s retro style.

This is still a great circuit so our refurbishment was mainly in replacing all the electrolytic caps and tubes. Upon completion it sounded superb and was ready for many years of continued enjoyment.

Dynaco Power Amplifier Modifications