Attached is a teaser picture of a new driver board that will take its place as one of the many variants of the venerable Dynaco ST70. The output transformers (original) were grabbed on E-pay, and will be the only thing left in the design that bears any resemblance to the original.
The chassis is a nice SS pre-punched number offered by Triode Electronics. The output transformers will be stripped and painted metallic cast-iron gray to go with the SS chassis. The power transformer will be an ugly Woodward-Schumacher monster scored on E-pay. This manufacturer had a habit of painting the transformer after the varnish dunk, so that the finish is ugly and lumpy, albeit durable. Hopefully, when I'm finished, it'll sort of match the output iron. Schematics will follow when all is worked out. I'm using 6L6GC instead of the original EL34 outputs, so I'll be working out bias voltages and screen supply from some bench observations. First up in the sockets will be "New Svetlana" 6L6GCs.
Guess the input tube if you can - the input is an LTP, and there are an obscenely liberal amount of Supertex depletion mode fets scattered about the board.
The chassis is a nice SS pre-punched number offered by Triode Electronics. The output transformers will be stripped and painted metallic cast-iron gray to go with the SS chassis. The power transformer will be an ugly Woodward-Schumacher monster scored on E-pay. This manufacturer had a habit of painting the transformer after the varnish dunk, so that the finish is ugly and lumpy, albeit durable. Hopefully, when I'm finished, it'll sort of match the output iron. Schematics will follow when all is worked out. I'm using 6L6GC instead of the original EL34 outputs, so I'll be working out bias voltages and screen supply from some bench observations. First up in the sockets will be "New Svetlana" 6L6GCs.
Guess the input tube if you can - the input is an LTP, and there are an obscenely liberal amount of Supertex depletion mode fets scattered about the board.
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When I find some TO-220 sinks with fins not as long as the ones I had on hand (used on all the other devices), I'll sink the two remaining devices.It won't be important for initial investigations. In the long run, dissipation on those two devices will end up somewhere between 0.6 - 0.8W, so some nominal heat sink will be necessary. I may use some clip-on sinks I have on hand.
That's more like it. I did some looking around at the various readily available dual triodes, and that one won out on the basis of transconductance vs. plate current for a cheap tube. You can get higher transconductance with other dual tubes, but at the cost of drain current per plate >>10ma - no thanks. I disqualified the 6DJ8/6922 from the start, as the trendiness/audiophool factor has jacked up the price of that tube way above sane levels. Besides, I already had some 6BQ7As on hand - a sleeve of nice NOS GEs. People that have experience with this tube, please comment on other brands that might work better for this application, if such is the case.
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I have used the 6BQ7 for LTP. I used a CCS in the tail so I could tweak the current. The pinout is such that there are about 20 tubes that will plug in to the socket and usually work with a twist of the CCS pot. I remember running several 6BQ7's through this amp when I built it and don't remember enough differences to have noted anything.
Some 6BQ7's can be microphonic in high gain applications like a guitar amp, but that was another cheap tube project in a different thread.
My list of pinout compatible tubes. I have tried some, but not all of them. Yes the audiophool 6DJ8 will fit, and I tried them. The 6BQ7 seemed to work just as good.
6AQ8 6BC8 6BK7 6BQ7 6BZ7 6BS8 6BX8 6BZ8 6DJ8 6DT8 6ES8 6FW8 6HK8 6JK8 6KN8 6922 7057 7308 6CG7 6EV7 6FQ7 6GU7 ECC89 7058 7898
Schematic of screen drive test amp. It's from about 5 years ago. My latest experiments with the tubes on this list were all guitar amp related.
Some 6BQ7's can be microphonic in high gain applications like a guitar amp, but that was another cheap tube project in a different thread.
My list of pinout compatible tubes. I have tried some, but not all of them. Yes the audiophool 6DJ8 will fit, and I tried them. The 6BQ7 seemed to work just as good.
6AQ8 6BC8 6BK7 6BQ7 6BZ7 6BS8 6BX8 6BZ8 6DJ8 6DT8 6ES8 6FW8 6HK8 6JK8 6KN8 6922 7057 7308 6CG7 6EV7 6FQ7 6GU7 ECC89 7058 7898
Schematic of screen drive test amp. It's from about 5 years ago. My latest experiments with the tubes on this list were all guitar amp related.
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So why call this a Dynaco ST-70 "Imposter"...?
If I hook an A-470 to the back of my refrigerator will that make it an ST-70 imposter, too? The clone chassis doesn't make it an ST-70 anything either.
You need to retitle this thread to something like... "My unique never before seen design with A-470 iron"...
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How many of the "ST-70" kits out there bear any resemblance to the original ST-70. Some do, some have redesigned driver boards, and some just have shiney plated chassis.
And speaking of ST-70's, which one? There were two audio amps called ST-70 in the 1960's. One was a Dynaco, the other was an Eico. So.....will the real ST-70 please stand up!
Would you go see a KISS tribute band that plays their own stuff but does wear the costume? Or maybe you'd like to buy some DisneyLand tickets ..oh but it's not really DL it's the petting zoo in my backyard but I'll be wearing a Mickey Mouse hat and be your guide.
Wagon hitching for attention.
Because that's exactly what it is! An amplifier with the same chassis layout and same OPT's. A look-alike. I understand perfectly what wrenchone's meaning is. But I don't understand why you're so bent out of shape over it. He's not claiming it to be anything else then an imposter. Could it be that the original ST70 holds a special place in your heart? Remember, imitation can be the sincerest form of flattery.
I also like it, and I own two of them. But IMO most of Haflers stuff of that era were cheap and dirty designs that became very popular and have acquired almost cult status. One couldn't build an amplifier like that with fewer parts and have it work as well. And with a few simple modifications they become much better. That's probably why so many people began modifying them, both for fun and performance.
The kit clones that at least try to duplicate the ST-70 are the real "imposters", the real "impersonators", they try to pass themselves as duplicated Dynaco but they are only "imposters." Genuine imposters.
All the rest are just different amps using the heritage of the ST-70 as a surf board. They're just dune buggies.
I will agree that David Hafler made it as cheap as he could . Triode electronic fix some of that by offering trans that are built up to the task. Over 500,000 unit where sold so it did have a following . Power transformer is marginal at best . the rest is a cheapened copy of DTN Williamson work . This much like kit car they are not the real thing nor cost as much but the best are fun to drive.
I personally never went to see Kiss, nor would I go see a tribute band. I have seen Pink Floyd a few times, and when the Aussie tribute band comes to Miami, I might go see them.....Why? Because they are GOOD.
I had a Dynaco ST-70. I got it at a hamfest for $50 played with it for a while and sold it at another hamfest for $200. Why, because it didn't sound any better than the amps I was making, and I didn't want to hack up an unmolested classic. Unfortunately the guy I sold it to did.
I also had an Eico ST-70. I was very underwhelmed, so I sold that one too.
If someone makes a Dynaclone, does that upset you? Would it if he represented it as an original? That kind of crap goes on in the classic car world all the time. There are more Hemi Cudas in existence today than Plymouth ever made. Some of them must be fakes. Socks for a car that can fetch half a MILLION bucks.
Make whatever you want as long as you represent it as such. Wrench man clearly calls this an imposter, and that is a perfect description. If I mounted some black transformers and PC boards to one of those shiney chrome chassis and called it an ST-150 would that be a crime?
When someone mongrelizes a classic and uses a refrence to the original it's the same as the tribute band analogy I made.
That's an A for the classics.
I'm all for anyone who tries to create reproductions without false claims, exagerations. My objection is about the folks who take an original, mongrelize it and stand back proudly and say, "Look at my wonderful ST-70 I've done so much to to improve... It's SO much better now. The bass isn't so flabby, and mids really punch through. The soundstage is so much wider." They simply have a real vested interest to support to themselves.
"That kind of crap goes on classic car world all the time."
A+. Couldn't have said it better, TL.
"Make whatever you want as long as you represent it as such."
Remove the Dynakit badge from the cage, please.
Can we please get back to the thread now? Since I also make "Imposters" I would like to hear more and see more on the driver board. Hell, I would purchase one if the price isn't excessive.
My suggestion is this.....if you don't like the name of the thread then don't comment on it. If you don't like what wrenchone has done or is doing then don't comment. Lets see if we and work and play together today, ok?
My suggestion is this.....if you don't like the name of the thread then don't comment on it. If you don't like what wrenchone has done or is doing then don't comment. Lets see if we and work and play together today, ok?
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