#dynaco 400

[audio-luddite]

Dynaco Renaissance.

Well sort of.

On a lap through the classified ads I found a clean looking but not functional Dynaco 400 amplifier for $400. That much for not working? Is this an indication of them becoming desirable? Not really, just a generation of audio people dying and things getting into estate sales. I should look into those.

Back in the day I had this exact model I built from a kit. The guy wants $400 bucks for it but it needs major repair. By coincidence I have a full set of parts and pc boards for one of these. Those are spares for my Franken amp if it smoked. The only missing bits are the output transistors, and PS capacitors, I know where to get those. So I could fix it.

It has the right knobs and all the cosmetic bits which are often lost or damaged. The fundamental question is it worth fixing at that price?

It is prettier than a black box for sure. Oh and yes I would want to modify it to Franken status which disables the speaker protection and all that stuff. So strictly in the name of science I go looking for the value of these things fully operational and clean.

The prices on Ebay go from about $260 broken to $2500 CDN with the optional meters, (plus shipping). There are a couple near $600 claimed to be working perfectly. One is in Canada with only 50 bucks for shipping. So a working one for $650 all in. I take that to mean that $400 bucks needing a few hundred in parts and hours on the bench is too much money. The value of these as collectables is to leave them stock. The $2500 unit is with meters and is definitely collectable if that is your thing.

All these date from the early 1970s. The Dynacos were the equal of Crowns and better than Phase Linears according to the golden ears of the era. As is often the case people who have never heard them dislike them cuz they are old etc. This was also the era of Ampzilla and SAE who shared Mr James Bongiorno as the designer with Dynaco. Dynaco was first then SAE, then GAS (Ampzilla). They were good units.

Given the many kits of parts and upgrades and community support a lot of people share my good opinion of them. The base units all had a clever power limiting system that could be turned off, but is thought to degrade the sound a wee bit. The later 410 black boxes were stripped down to just the amplifier with no safety nets. My Franken-amp is from one of those. The mods I made were fairly brute force in the power supply with only capacitor tweaks in the amp circuit and the doubled up output transistors just like the 416. At its heart it is still a Dynaco 400. Well a Dynaco 416.

I can tell you with confidence mine is at least as good and in places better than my high end ARC Classic 60 tube amp dating from 1990. In twenty years the goal posts did not move very far if even at all. As far as I am concerned they still have not moved now in 2024.

[audio-luddite]

SAE 2400L

This is one of the first super amps. Back then a super amp was anything over 100 Watts / side. This was 200 / side. Another was the Phase Linear 400, then 700 (the flame linear). And of course the Dynaco Stereo 400. At roughly the same time (late 70s) there was the Ampzilla which was also 200 / side.

The Phase Linears were designed by Bob Carver.

The Dynaco, SAE and the Ampzilla were designed by James Bongiorno. The Dynaco 400 was done by JB, before he went to SAE. The Ampzilla was after. In any event JB was a prolific audio system engineer. And good at his job.

The 2400 was one of the early SAE products and it was the very first super amp I heard. It may be a refined version of the Dynaco circuit, parts look really similar. A friend working in a stereo shop borrowed one and brought it to our Dorm in college one evening. We hooked it up to my speakers as they were the most resilient ones. That SAE was big and silver and had two huge meters on the front. We could not feed it audiophile quality stuff, but we were still impressed.

As stupid kids we just wanted it loud and it did that effortlessly. It was also what prompted me to buy a Dynaco as it was far more affordable.

The 2400L was a later version with LEDs instead of analog meters but the same amplifier circuit. I almost wish I knew electronics better, but I always dig up circuit diagrams if I can. The circuit design and topology are where the genius lies. Designers have a style. They try this and that. New parts are invented and they will see what can be done. The 2400s had fully complementary circuits. The positive side and negative side wiring and transistors were exactly mirror imaged. On one side NPN and the other PNP. What that means is they flow opposite polarity current. It looks elegant.

Certainly it was well regarded in the day and there are many fans still in Solid State Audiophiles.

James B left SAE to found GAS who made and sold the Ampzilla it was a further refinement of the fully complimentary circuit. It was originally a diagram and list of parts in Popular Electronics magazine. Then GAS made kits and full factory amps eventually. The Ampzilla is a bit strangely packaged, but was very respected by audiophiles.

There may be stages of refinement and improvement through these amplifiers, but all the Bongiorno designs are very similar.

There is a 2400L for sale near me. It is a reasonable price at $650.00. It was checked out and well here I am writing about it so yes it is tempting. Probably better in stock form than my Dynaco in stock form, but the black beast is not stock.

To duplicate the Dynaco tweaks to the 2400 what would I have to do? Well I would need to split the power supply in two. Four new capacitors, two bridge rectifiers, and small bridging caps. That is easy, and as new caps are smaller room could be found. I would also have to change at least 4 and as many as 8 signal path capacitors from polar electrolytic to film in each channel. That may be risky as they may be used as diodes in circuit. I suppose diodes could be added in line. Or I could just use better electrolytics.

A fair bit of messing about is required. The question is it worth it? There is a bit of risk and I do not need another amplifier.