Review: Classic Dynaco Tube Amps - Upgrades and Mods

Tube be or not tube be... sorry... couldn't resist. The picture you see here shows a pair of restored, original factory assembled Dynaco Mk III amplifiers. I purchased this pair from a neighbor who had them stored in has garage. He needed some cash and I was looking for some tube equipment to sweeten up my stereo system.

With a little help from my friends I cleaned up these amps, replaced old selenium rectifiers, installed new power supply capacitors and of course installed all new tubes. James Demeter and Kevin from DynakitParts.com were both generous in providing their expertise and encouragement. Kevin also supplied replacements for the original Dynaco can type capacitors. These replacements increase the capacitance and voltage rating of the original power supply caps. That makes the power supply safter and it also give you a performance boost. Kevin sells complete kit amps that are excellent replicas of the original Dynakit amps. Like the original Dynakits the prices are reasonable and the quality is first rate.

Dynaco amps were some of the most popular hifi amps ever sold. Their popular models include the Stereo 70, Stereo 35, Mark III, and Mark IV. These amps were sold factory built or as kits. I was fortunate to get a pair of the 60 watt Mk III amps that were factory built. The original workmanship was good and they didn't need a whole lot of work. The sound of these amps is lush and sweet. You know right away these aren't your typical transistor amplifiers. Voices and instruments take on a three dimensional quality that brings the music alive.

There a folks such as self-proclaimed Dynaco guru Dynaco Doctor aka Joe Curcio who will tell you that the Dynaco amps perform poorly unless modded. Curcio audio has for sale a number of "upgrades" that he promises will allow you to realize the "full potential" of your classic Dynaco amp. It makes me wonder how these amps became bestselling classics in the first place without any help at all from Mr. Curcio and his fellow tube gurus. Could it be that they sound pretty darn good with the stock circuitry designed by David Hafler? Are the commercially available mods really going to sound better than the classic Dynaco sound? 

My buddy Dennis and I have, between us, built most of Mr. Curcio's designs and we've each been disappointed with the final results. The tube magic was lost. The modified amps may measure well but they they sound somewhat cold and uninvolving. It's also worth noting here that the Dynaco amps are collectable and that they are most valuable in their stock form. Perhaps monetary value is significant as an indicator of optimal sound quality–it depends on who you listen to.

Curcio is now advertising some newly designed mods. He says these mods will preserve the tube sweetness of the original Dynaco circuits. We exchanged some emails and he persuaded me to place an order. However, after thinking it over, I cancelled the order and opted to keep my Mk III amps stock. The 6922 tube driver stage favored by Curcio may be accurate and may measure well, but 6922 tubes tend to sound cold compared with the original Dynaco drivers. If you're dead set on modding your vintage Dyncaco amps, there are a number of popular mods available these days. You can do some Googling and you will find the commercially available Curcio Audio mods, the Roy Mottram mods and the Poseidon mod plus all kinds of DIY mods. 

In my opinion, David Hafler got some things very right in the original Dynaco designs. Therefore my advice is to do only what is necessary to keep them running well and then sit back and enjoy the magic. (By the way, be warned... when I cancelled my order for Joe Curcio's Mk III upgrades, he deducted a whopping twenty percent "restocking fee" from my refund. When I complained about that his response was adversarial bordering on belligerent. He doesn't deal with returns graciously.)

I'm using a Conrad-Johnson PV5 preamp and my Mk III amps to drive a pair of Thiel CS 2.2 speakers. While Thiel's are not considered to be especially tube friendly these CS 2.2's sound great with the Mk III's. There is plenty of power to spare. 

If you are fortunate enough to own a pair of Klipsch horn loaded speakers, you should seriously consider finding or building a tube amp. Many music lovers consider Dynaco and Klipsch to be the path to musical nirvana. Kevin from Dynakitparts.com tells me the Dynakit Stereo 35 paired with some highly efficient horn speakers is some of the best sound he's ever heard. The Klipsch forums are another good source of info about Dynaco amps.

The original Dynaco designs are among the best tube amps ever made. You can buy better tube amps, but you had better be prepared to spend a whole lot of money. If you absolutely must have the best of the best and you can afford it, then look for some Conrad-Johnson tube hifi gear. If you are willing to believe that you can convert a Dynaco amp into an amp that rivals the very finest amps that money can buy then Joe Curcio and the other Dynaco gurus will be glad to take your money. Although I haven't tried every possible mod, I would urge you to be skeptical of these claims. They sound too good to be true and in my experience that's usually a sign that they probably are too good to be true.

In the meantime consider this: In the world of tube amps, second best is still a darn sight better than just about anything else available. If you are fortunate enough to stumble across an old stereo Dynaco tube amp or a pair of Dynaco tube monoblocks my advice is to restore them, keep them as original as possible, and enjoy them for their classic sweetness and richness. I guarantee you will rediscover your favorite music and hear subtleties and shadings you never noticed before.

As a musician I believe that the perfect is the enemy of the good. Before you blow your hard earned money on expensive "upgrades", hear what the original Dynaco amp designs can do. I'm willing to bet that if you do that, you'll stop right there. It doesn't get much better. So save yourself some money, skip the mods, and spend your extra cash on some new recordings. Music is one of life's greatest pleasures and even more so when you play it through some great classic tube amps like the Dynaco Mk III's.