Any Dynaco/kit owners here, former, now? Kit builders, fans, haters?

I hate to wade into the sonics of the Dynaco line - especially their tube gear which I have tons of experience with. But here I go:

A fully functioning stock Dynaco 70 - recapped, tested 7199s, Mullard output tubes and rectifiers is a good amplifier that can make some beautiful music. But I would never call it state of the art. For example - my (now departed) Eico HF-60s with the Acro TO-330 output transformers was leaps ahead in SQ - no roll-off in the treble, way less muddy sounding, and bass control that could compete (and yes, even beat!) my Threshold S/500 250WPC solid-state amplifier. The Eico was an amazing piece of kit, that unfortunately also liked to chew through output tubes if biased at the factory recommendations.

I've heard many amplifiers over the years - all of them sounding quite different to me - and I would put the ol' venerable Dynaco 70 in the middle of the pack. I preferred the Mark IIIs - bigger iron, more power, and - with the right input board - a higher bandwidth sound. But to my ears the '70 does sound better than a whole number of 1970s and even some 1980s solid-state gear. Whatever sins the Dynaco 70 has, however, are ones of omission. It is a thoroughly pleasant amplifier that can actually help with bad source material. Partnered up with a stock (but recapped) Dynaco PAS will give you a warm, golden sound that is highly addictive. A true budget piece that opens up the idea of vacuum tubes to a person raised on solid-state. The Dynaco 70 was my "gateway" amplifier and I'm sure it has been for countless others.

 

I have a Dynaco SCA-35 that I bought stock about 5 or 10 years ago. I got it cheap, and upgraded it as I got the money. I replaced the boards and power supply caps, added a choke and did the so-called Enhanced Fixed Bias mod, which gives some control over the cathode voltage and runs the tubes a lot cooler. It has enough power to drive my B&W DM602's just fine. I think it sounds pretty spectacular, though of course there is always something better. But probably not for the $300 or so I put into it.

 

Built a PAT4 and Stereo 80 when I was 16. My father built the SCA-80Q at the same time.a lot of fun. My pair went to college and was stolen, my father upgraded his along the way and used it until he passed. I found out that he not only bought the kits we built, but another PAT4 kit and Stereo 80 kit. I have both those now in unopened boxes in my closet. Thought it would be fun to build with my son, but he took his summer earnings and bought a NAD3020D instead. Probably will put the NOS kits up for sale and see if any wants the fun.

 

It may have been average in the 60s in comparison to all the other tube equipment at the time, but it takes a pretty penny to equal them today. I have collected and restored vintage tube for 25 years and in my stable I have both the Stereo 70 and Stereo 35 amps which I completely tore down and restored with all carbon comp resistors and original circuit design. They are very good sounding amps indeed although I much prefer my Scott 299 and 222 which are my daily drivers. I think their solid state stuff was not even close to the tube stuff, although at the time it was better than average for sure as most solid state gear from the 70s is unlistenable today.

 

My SCA35 still serves me, never topped by any other amp, valve or solid state I tried.

Only upgrade: each powervalve it's own cathode elco/resistor. From 1967 on.
Phono or CD's all gorgious !!!

 

What's an elco? Isn't that a locomotive?

 

By the time you get a ST70 going properly today you have spent six to nine hundred dollars if you buy everything new. So it is not a cheap way to go, although it is true modern high end units from the name makers can be a lot more. If you buy them used you can resell them without huge loss. I have found that come resale time no matter how much you put into a ST70, it's still worth no more than a stock ST70.

It's ironic you mention carbon comp resistors: in the 80s I summarily diked out and disposed of barrels of them because I thought they sounded bad. I still do, but people wnt them now.

 

Nope - that would be Alco...



https://www.flickr.com/photos/lightning72/3967690041/

 

True you will not get that money back, and the prices in the past few years have become too high for sure. When I started in the vintage game in the late 80s it was like knowing a secret that nobody else seemed to have a clue about, you could get things literally for next to nothing. Fishers, Dynacos, Scotts, Heathkits, all in the low hundred range often less than a hundred. Marantz and Mac even 300-500. I used the carbon comps not because they are better, certainly they aren't measuarbly but to retain as much as the original sound as possible. When you start in with too much metal film it can change the sound unpredictability. I do use some metal films in critical areas where I like the sides of the amp to be closely matched. I've had so much of the stuff over the past 2 decades that I kind of decided what amps I like the best and kept those and completely rebuilt them so what I have now I plan on going to the finish line with.

 

Not true, not even close to being true unless you are paying a shop retail price for some ridiculous labor rate; it only costs a little more than what you suggest to have a trumpet properly re-lacquered and aligned (the Musicians here will know what that comparison means and what it entails) Don't paint such a generalized picture when there are those who do their own work and those who have to pay someone else to do it; that is not the ST-70's fault

You need to spend an afternoon perusing the Audiogon classifieds

That is a baseless remark as well as it is an obscene over genralization

"Barrels" of resistors? "Barrels"? Really?
Sorry, but I find that incredible; do you have any photos of any those "barrels" of resistors?

As for carbon comps, they had and still have their place in many circuits; you have to know how and where to use them..........that's why people "now" want them

 

You really need to stop drinking the dyna-koolaid and get off your dyna-horse.

Triode electronics Kit: over $900
Dynakit: $675
Tubes4Hifi: $839

None of those prices include assembly labor. Burt's statements are accurate. Yours are bizarre.

 

That's not entirely true. If a trusted technician brought it into spec, people might go a little higher in price.

From what I see, stock (but serviced) St-70s go for between $300 and $400. Fresh builds with modern driver boards tend to go for around $600 to $800. Some optimists try to get closer to a grand, but I notice that their ads tend to stick around for a long, long time.

Given the labor involved, it's a far cry from a profitable business. Heck, it looks like a money loser just on parts cost if you're assembling brand new kits.

 

Well it depends on what one means by getting one "going properly," but I think Burt's actually lowballing the cost of getting a used ST-70 up to the best it can perform today; and even lowballing the cost of getting one to just sound like a stock one but in modern working order.

Like @kfringe notes, for a kit builder -- not a tech nor a guy with a garage full of drill presses for fabricating chassis -- but for the kind of person who once built or is likely to rebuilt a ST-70 today, a new kit with the original circuit on a durable PC and a modern power transformer will cost you, minimum $700, not accounting for your own labor.

Used units on eBay seem to be selling on average for around $525 (looks like that's the trending eBay price but of course the range of condition of units you see on eBay is enormous). An improved power transformer for Triode or Dynakit Parts will cost you $140 plus shipping. A new PC with the original circuit (though I don't know why you'd use that if you're rebuilding one completely, but OK), and parts will cost you around $100 from Curcio (and there's no way you're going to be able to use that toasted old board and get the thing "going properly"). You can get a direct can cap replacement for $40, or better a circuit board for someone with more filter capacticane and solid state rectification and a bias power supply for $65 and up. So that's around $800-830 in parts alone (not including tubes and miscellaneous resistors that will probably need to be replaces, and of course not accounting for one's time) to get an old one up to original spec.

You can get some different driver circuit boards from anywhere from $90 up to Curcio's excellect cascode differential driver with CCS for $300 including parts. If you want to go for the Van Alstine kit, and you're not going to fabricate your own PC, the kit will cost you $450 from Frank. If you want the full monty Curcio driver and regulated power supply you'll need not just the three bills for PC but another 3 for the power supply PC and parts. In those cases you'll have a much more modern sounding (and I think much better sounding amp), but you'll have spent upwards of $1,000 in parts alone.

Now, that $750 - $1,200 depending on how far you want to in terms of restorting vs altering a ST70, is still maybe cheaper than anything new (and even the commonly encountered used stuff) from most of the high end hifi tube amp manufacturers, though there's current production stuff from Rogue (which I haven't heard) starting at like $1,200 or $1,300 I think. But that's the real world cost of the ST-70 and it's variants for the average kit builder in 2015.

Of course, if you have a full scale shop at home, and you're a tech and can rebuild the ST70 from the spare parts you have lying around, your cost is going to be lower, but you also could do what Burt's always suggesting and build an even better amp from scratch.

The bottom line is that the ST70 has its pluses and minuses, and it has long been a good platform for major improvement that can turn it into a much better sounding amp, but all that playing around and tweaking was one thing when you could pick up a ST70 for $50 even $100, with good iron and good original Mullard and Sylvania tubes, it's a bit of another thing at today's prices.

 

An elco is an electrolytic capacitor. I'm sorry I used the Dutch word, elco, electrolytic condensator.

 

Try reading/quoting my entire post if you sincerely disagree or have another take on things, but please refrain from lifting, OUT OF CONTEXT the little pieces you need to demonstrate your affinity for "Burt"

Current CLONE KITS are not the same thing as an ST-70 proper (authentic/original) That is the direction my remarks were directed

When "Burt" remarked "everything new" that would give recognition to the opposite option (that there was one), don't you think?

I am certain "Burt" appreciates you clearing that all up for him as well as your defending his credibility and supporting his position! (but I really don't think he needs it; if you still want to do so, at least do it accurately)

You are a good friend!

 

Any Dynaco/kit owners here, former, now? Kit builders, fans, haters?

 

I agree on your points of fact (what people are charging for things is high); but there's nothing stopping even the most casual of hobbyists from availing themselves of the benefits of a good schematic, of both "stock" and "improved" circuit varieties, both of which are readily available (many of which are free) and the resources of Mouser, Digi-Key and others...........one is not obligated to buy the price inflated "kits"

There is no rule that mandates you take the "convenience" path

Wouldn't go that route even if I had money to burn; you can buy better parts for less money; just takes a little more effort (i.e.: time) to put it all together

If one is to rely on the choices made by those who package "turnkey" solutions, then why bother? Just put your faith in a manufacturer and buy a new amplifier

Besides, there is nothing to stop anyone from "reverse engineering" any of these kit solutions in every detail; only part of it that many would be better off (cost effective) purchasing retail would be PC boards (and even those are doable for the DIYer) OR can be executed as hardwired with a little planning and thought

 

I would love to build a pair of "MKIII monoblocks". I use quotes because I'm sure mine would be considerably modified from an original version... ...and a kit version for that matter. Those who roll their own know what I'm talking about.

 

GO FOR IT! DO IT!
And don't forget to post pics, lots and lots-o-pics!

 

I don't get the slam against carbon comp resistors. They have "a sound" just like carbon film, metal film, tantalum, etc. I would think them going out of spec over time would be the main concern; but, what do I know??? Sounded bad? Wtfarg? I, personally, have never had anyone ask for film or tantalum, ever. If they ask at all, it's for carbon comp resistors and PIO or mustard caps; whether or not it's solid state or tube rectified. No one's ever asked for "tight tolerances" or what the percentage was. But, like I said... ...I don't know jack.

 

Don't worry; he doesn't either

 

They can have a sound. They don't need to. What they do have is higher noise than metal film, wandering levels of contact noise, and values that tend to drift more quickly. Everything really depends on the the circuit. If you're looking for low noise (phono stage, preamp, amplifier input), you're probably not looking too closely at carbon comps. If you're looking for some specific behavior at higher voltages or a certain old-school performance (power amp output, guitar amp), then a carbon comp might be just the ticket for you.

You can chase good sound with carbon comps. If you're using big carbon comps in your input stages, though, you're definitely not chasing low noise.

 

You finally have me over a , well, a barrel.

In reality it was not barrels of them I cut out, it was probably a few of the 100 foot 35mm film spool cans I used a lot of back then.

 

You could. I have little experience with the transformer they use but would suspect it's better than the ST70 one: I think it predates the patent the ST70 one is covered by.

 

It really doesn't take all that much to build your own from scratch. The big thing now more than in the past is having a place to set up to do it. it's astonishing how much free stuff in the way of tools you can get on Freecycle now.

Recommend everyone get a 60s or 70s copy of the ARRL Handbook for Radio AMateurs: any good library has one. Morgan Jones' books on building valve amplifiers are also worth a read.