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August 21, 2009 - 5:04pm
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Fun with vintage "grunge" hifi
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Word to the wise -- Sanus mdf stands are crap. Not even worth the cheap price.
Well..an SCA-35 is an awesome little amp. El-84 is an awesome tube and those particular transformers are very, very good. With a good refreshing and a fix up, the SCA-35 is a true world beater.
Have you ever run into or heard the Dynaco Stereo 70 (tube)? It's has a good midrange sound, not so hot in the bass, but pretty good overall. I heard about the modified one (van Alstine?) that resembles the Audio Research circuit is great.
Mine is the Stereo-35, not the SCA-35. That's a power amp, not an integrated. Bascom King used to list a modified Stereo-35 in his reference equipment list in his reviews in Audio Magazine. The front-end and driver circuit in the Stereo-35 is identical to the original Quicksilver amplifier.
I've got a few Stereo-70s, but only one of them is actually assembled and working at present. The Van Alstine Stereo-70 mod is nothing like an Audio Research, he just filters the input, increases the value of the coupling caps, and stiffens the power supply, while retaining a mostly stock Dynaco circuit.
There was an Audio Research modification to the Stereo-70, which replaced everything in the amp except the transformers and the chassis. It was available in kit form from Old Colony Sound Co. I built one of the kits for a friend once, and quite frankly I was not impressed with the result.
I'm still surprised by how well these Rogers speakers respond to a wimpy little 17.5W/channel tube amp.
Yes, maybe that was what I was remembering, because I saw the circuit schematic.
It wasn't much different from the original D-50.
Many moons ago, when I was considering purchase of my first "real" stereo system (as opposed to a record player), I had a friend whose system included an SCA-35. I thought his system sounded great, but I was determined to have a system that sounded even better. I went to a hi-fi store, where they persuaded me that tubes were old hat; the new equipment that used transistors was the way to go. I bought an Eico Cortina 3070 solid-state integrated amplifier, AR turntable, Pickering cartridge, and KLH 17 speakers.
The sound was impressive in some ways, but I kept thinking that my friend's system with the SCA-35 sounded more natural, not as edgy. His speakers were Celestion Ditton 10s, and I was pretty sure that the KLH 17s were superior, and yet...
The solution presented itself when I saw an ad for a used Dynaco PAS-2x, a pair of Stereo 70s, and an FM3 tuner. I bought these for...I think...$150, about what I had paid for the Eico Cortina--this was a long time ago!--and the sound was SO much better.
Bob
Without mentioning names, some of the early transistor power amps were "interesting". One of the hints is when distortion is spec'ed at 1kHz but not at any other frequency.
Not just Slew Rate distortion (something documented in tube op amps for analog computers in the 1940's, btw), but reduction in loop gain, gain modulation with current (that was not addressed locally) and rather some other stuff.
Experience in building amps with transistors was, of course, lacking.
And for euphonic misbehavior under stress, it's hard to beat a 6L6GC
One of the worst purchases I ever made was a Dynaco Stereo 120. I kept it about a month. That's because it took me three weeks to unload it.
Early-generation SS gear is pretty scary. Remember the SWTP Tiger .01 and Universal Tiger amps? Lots of power for the time, but they tended to oscillate and/or blow up. But the circuit design was one of the first essentially "modern" SS amps.
I don't get how Naim Audio manages to get (arguably) modern performance out of circa-1968 SS circuit designs.
BTW has anyone else here heard these Rogers LS7t speakers? I wonder if they're generally well-regarded, my early impressions of them are quite positive, they seem almost too good to be true. I'm sure I'll find a reason to get frustrated with them at some point, but for now I quite like them. They seem like cheerful little boxes.
The UT and Plastic Tiger were ok, actually, in my experience, in terms of stability. The "all balanced" design of the .01 and its followers-on, err, um, well, AM transmission anyone?
Of course, please do not ask about the slew rate of the Plastic Tiger ... Just don't. Or ask about storage time...
The KLH 17 were the first audiophile speakers I heard at a friends house. It id sound pretty good, much better than my Sears monophonic record player with a 2-tube amp.
I bought a FM3 (tube) from a friend who tweaked it with the cap mods and the teflon wiring mod. It sounds smooth in the midrange. Comparing to a FM5 (solid state) I built from a kit and later added the cap/wiring mod, I find the FM5 crisper sounding but the FM3 easier to listen to (not by much). I prefer the FM5 because of the muting circuit that's not available on the FM3.
j-j, are you saying that the 6L6GC sounds bad when pushed hard? I really didn't notice that, perhaps because it was used in music production, not reproduction, in Fender guitar amps.
JoeE,
I also built a Stereo 120 and bought a modded one also. The modded one sounds a little better from a comparison by memory of using one and then using another, but I can't swear by it. I still use my Dynaco PAT-4 and Stereo 120 as a caual-listening sound amplifier fed from the LCD TV (which has a joke of a built-in loudspeaker).
Ahhh, the lack of money student days of kit-building...
The 6L6 and EL84 are my favorite power tubes. It's uncommon for some of the least expensive valves to be so universally loved and widely available. I have an old, original Jolida SJ 101 that I could happily live with for the rest of my audio days. It's the only audio component that I've ever owned that doesn't provoke that audio nervosa disease in me.
Last I heard, "euphonic" meant "sounds good", eh?
At that time I also had a Stereo 70, 2 MK-III's, a PAS-3 and a PAT-4. Comparing the Stereo 120 to any of the tube gear was a very revealing comparison. The PAS was audibly superior to the PAT-4 although not nearly as quiet. The Dynaco factory was 3 blocks from my house. It was a very convenient location.
I still have and use what's left of the MK-III's. The power and output transformers and output tube type are the only things left from the originals. They are mounted on new Hammond chassis' with new input driver boards and fully regulated power supplies. They sound quite nice driving my ESL's
I like vintage 'grunge.'
Point to point wiring,baby!
Question: With modern IC's, at what point of miniaturization do the circuits start affecting themselves?
If you think of the tiny little traces all set microns apart, are they now shielded from each other?
Is this even an issue?
Getting back to the topic. Big Mike and I have played frequently with vintage 1980/81 receivers from Technics, Sansui, and Yamaha - and used them at shows with many positive comments. Even the phono stages seem to be holding up well!
j_j,
Sorry, I misunderstood. Maybe that's why those amps remained popular with musicians over the later solid-state versions.
Buddha,
As you already know, conductors near each other induce fields into each other when carrying current like music signals. When the conductors get very close, then several things change. There is increased capacitance. Inductance also is affected. But with circuit design, those can be accounted for. Even the small patch of PC traces that cross perpendicular to each other on two sides of a thin epoxy board has a small capacitance between the two rectangles at the crossing area. The effect I was told is frequency dependent, and more problematic at higher frequencies (GHz). Maybe at audio frequencies it does not matter. (?)
Modeling circuits can be simple of complex. You can start with a simple ideal-parts model connected with zero resistance wiring, or you can include every little piece of wire as an LCR circuit between non-ideal parts. The design decision is to make the model simple as possible without compromising the accuracy of the model too much - a sufficiently accurate model for the purpose.
Three blocks from the Dynaco factory? Did you ever get to meet the crew there, perhaps the late David Hafler?
Believe it or not, I still have a Dynaco QD-1 sitting around and not doing anything.
Fair enough, and I think your speculation is in fact quite right for a variety of reasons, one of which is the saturation behavior of the typical tube amp.
I'm not sure who I met. I could walk right into the service department and talk to the tech's and engineers. It began when I was building a PAT-4 and melted one of the poly caps. I called the service department and while on the phone I mentioned I was calling from a couple of blocks away. The tech told me to come over and he would give me the part. I used to go there once or twice a month after that. Sometimes I went just to talk about electronics and their gear. I was in college working on my BS EE. Visiting those guys was really interesting and a lot of fun. I learned a lot from them.
I guess that's what layman call 'graceful clipping'. Also, solid state amps then were not so great. Perhaps later ones better. I still have those amps with the four 6L6GC's in parallel/push-pull output stage.
Man, if I had that opportunity, I would practically live there and learn more too. Glad you had that experience.
Not to misdirect this thread, but I'm curious as to what you think about your EE knowledge and its relation to the High-End experiences you read about here, especially regarding the tweaks that's been reported.
I learned I didn't know as much as I thought. Seriously, I've been involved in this hobby for almost 42 years. During that time I went through SS is better than tubes, the Hirsch Houk theory that all amps sound the same and the all wire and cables sound the same school. Needless to say they were/are wrong. The wire and cable thing was the hardest thing to believe. As a fresh EE I truly believed that wire is wire. My books training and formula's said so.
My first wife clued me in to IC's sounding different. She had extraordinarily good hearing. She coached me in what and how to listen for the differences she heard. She could come in the front door and tell when I had changed anything in my man cave system. She would do it without coming downstairs. Although she was not an audiophile she was a music lover. She blew the 5 amp rail fuses on a Hafler DH-200 through playing music (rather loudly of course).
I must admit I'm still quite skeptical of some of the Belt theories. However, I keep an open mind about anything to do with audio thanks to my first wife.
PS: She was very unhappy when I traded a pair of Magnaplanar MG-3's for a pair of Acoustat Model 3's. She said the "stats" didn't sound warm like the Maggy's
Well, I found out early that I had a pretty good musical ear and ability. I didn't get into audio until college. That's when the music and sound reproduction experiences I had met with the science and engineering I was learning. Although the technical stuff was good and made sense, it never quite covered what I was interested in, the how and why something sounds the way it does. School teaches the fundamentals and one has to get that right or one will mislead oneself quite badly and not know it.
I can relate with your experience that your first wife was able to tell subtleties in the system changes. I suspect it is analogous to what I experienced with different capacitor types (attributed to or identified by dielectric). I didn't learn that in school, but I don't fault the school for not including all the details in a basic course (different dielectric, material, geometry, resistivity, etc.); it may be covered in more advanced courses.
Because of this, an electrolytic cap cannot act *exactly* the same as a equal-valued mylar cap. It may be true for the capacitance parameter (a capacitor is a capacitor), but the other parameters will change the behavior.
Thanks for sharing your EE vs. sound experiences. I believe we all can relate to this.
Back to the thread:
Ever have any personal experience with the Eico stuff or Heathkits? any vintage Fishers, if these have not already been discussed?
I built a couple of Heathkits. Mostly for friends and neighbors. The AR-15 and the guitar amp were the most difficult. The neighbor I built the AR-15 for still uses it along with a pair of AR4X's. I do a lot of scratch building and modifying now. My Hafler DH-200's have fully regulated power supplies and extra output transistors. They also have toroidal transformers, doubled power supply capacitance, audio grade caps, Vishay resistors, WBT connectors and an IEC jack. I think they sound quite good. My Dyna MK-III's have only the transformers in common with their beginnings. They are on new Hammond chassis' with new input driver boards, SS power supplies with soft start and other tweaks. They do a nice job driving my ESL's.