Dynaco ST-70 Series 3 Tube Amplifier Review

[EJ3]

I agree; Mcculloch motors had no business being on a saw. In my case I bought a brand new (3.7 ci) Mcculloch saw in 1989. One woodcutting bud had a Husky 266 and the other had a Stihl 056. Both their saws would throw rooster tails of sawdust while my Mcculloch would barely keep the sawdust out of the cut. After 40 hours of use the chain groove on the bar of my saw was so worn it would barely cut and would not cut straight. To the junkpile went the Mcculloch to be replaced with a Jonsered 625II which I still use to this day.

By 1989 McCulloch was no longer worth a damn.
That changed just about the day after Robert McCulloch died (February 25, 1977).
It became just a marketing name, like most things once the originator has either sold the corp. or passed on.
The newer stuff generally being junk is why I still have m Shindawa T230 and my RedMax 8200 (both 3 & $400 items in 1996) that blow the new Stihl & Husky stuff away.
Also, my 2007 Cub Cadet (designed and built by International Harvester). Cub Cadet was sold off & promptly became junk the second half of 2007.

 

[motorstereo]

My father had a big Mcculloch in the late 60's which he thought was the bee's knee's. It replaced his beastly Lombard which seemed to have constant issues. The little that I can remember of the old big Mac was when it ran it was a great woodcutter.
Now that you mention it yes there was quite the decline in wood cutting ability between those 2 saws. In those 20 years Mcculloch went backwards instead of forward and now I understand why.

 

[OldManMatt]

I still enjoy tube equipment. Aesthetics & sound can be very beautiful to me if the circuit & chassis fits my taste.

ST-70 was the first amp I ever layed a soldering iron to. I have never listened to the Series 2 or 3 ST-70. My favorite ST-70 circuit is the Ultimate 70 by Frank Van Alstine. A very quiet tube amp. It's a good design in my opinion.

I'm actually building a 2nd one right now. This one is literally from scratch or all new parts... new transformers & chassis. All the parts & chassis are easy to find online. Without having to buy tubes I'm probably around $900 all in. Using quality parts, sockets, etc. $2k cheaper than buying something like the one in the review. One can build a new ST-70 for a cheaper price than a lot of the used ones I see for sale with their old humming transformers & out of spec passive parts.
Van Alstine provides excellent build notes if anyone is considering doing a build. There are good build instructions for the Original & a few different ST-70 types out there. Tubes4Hifi sells a full kit for under $1k. Beefier power transformer.

There is some quality tube equipment out there. I also use well engineered solid state equipment like RME dacs & a Hypex Nilai.

Here are some specs provided to me of the last 2 tube preamps I built this year.

 

[375HP2482]

This is what has typically led to distinguishing tube from SS amps IME, along with tube amps often having higher noise floor (more hiss).

I once had both the Dynaco PAS-3X (tube) and PAT-4 (SS) preamplifiers. I stopped using the PAT-4 due to its much more noticeable hiss. Which Dynaco must have been aware of since they included a switchable LPF to knock down the hiss.

Back then I'm not sure if the preamp designers were aware of base-spreading resistance.

 

[DonH56]

I once had both the Dynaco PAS-3X (tube) and PAT-4 (SS) preamplifiers. I stopped using the PAT-4 due to its much more noticeable hiss. Which Dynaco must have been aware of since they included a switchable LPF to knock down the hiss.

Back then I'm not sure if the preamp designers were aware of base-spreading resistance.

I do not remember the PAT-4 devices after all this time. A lot of early SS designs suffered from hiss due to "noisy" transistors; high levels of impurities and such in the semiconductors caused high noise levels.

 

[Doodski]

I do not remember the PAT-4 devices after all this time. A lot of early SS designs suffered from hiss due to "noisy" transistors; high levels of impurities and such in the semiconductors caused high noise levels.

So.. That's what was it was. I suspected all along it was those germanium transistors specifically.

 

[SIY]

So.. That's what was it was. I suspected all along it was those germanium transistors specifically.

PAT-4 schematics. Silicon, of course, and modern versions of those same transistors could be dropped in and possibly yield lower noise.

 

[Doodski]

PAT-4 schematics. Silicon, of course, and modern versions of those same transistors could be dropped in and possibly yield lower noise.

Wow. That speaks to the integrity of the germanium transistors for sure. Those things are abouttt 50 years old?

 

[DonH56]

So.. That's what was it was. I suspected all along it was those germanium transistors specifically.

I don't think the PAT-4 used Ge; it was in the Si transistor days.

 

[anmpr1]

Because good amplifiers reached a point of diminishing returns 70 years ago, in terms of transparency. And there has always been a market for nostalgia and antiques.

I think that, plus more. It always brings (or should bring) a personal sense of satisfaction whenever you build something that you can use in your daily life. Of course back in the nascent days of hi-fi, if you wanted something you most likely had to build it yourself. Ready-made gear was always expensive. Heath, Dyna, Scott et al provided not only the 'fun' of DIY, but the added value of a discount.

Today it is cheaper and easier just to buy something ready-made, usually SS, and then hope it lasts before you throw it out. Specs will always be better with SS, so that should not even be an issue for anyone. With all that in mind, this Dyna 'Series II' was not intended as DIY in the sense of 'real' Dynaco; Radial was just using the historic name and a 'general but loose' design language. [FWIW, the company for a time also sold some phono gear under the Hafler name.] I guess that's the 'nostalgic' part of the equation.

Dyna and the rest from that era (along with what is now offered new in kits today, either stock or modded) represents the niche hobbyist more than the typical 'music' lover, the latter who can just flip a switch on a black box and have streamed an entire music library at his ear tips, on demand.

I'm personally glad the kits are still around, but would never jump into the discussion about measurements, or overall sonic quality (much of that is always imaginary, anyhow).

My suggestion FWIW is that if ASR is going to fool with tube gear, that gear should have its own seperate category. Superimposing the distortion graph of an ST-70 with an AHB-2 is pretty ridiculous, if you ask me (who asked me?). On the other hand, a comparison with other tube gear might make some sense, if not add interest.

 

[Petrushka]

I think that, plus more. It always brings (or should bring) a personal sense of satisfaction whenever you build something that you can use in your daily life. Of course back in the nascent days of hi-fi, if you wanted something you most likely had to build it yourself. Ready-made gear was always expensive. Heath, Dyna, Scott et al provided not only the 'fun' of DIY, but the added value of a discount.

Today it is cheaper and easier just to buy something ready-made, usually SS, and then hope it lasts before you throw it out. Specs will always be better with SS, so that should not even be an issue for anyone. With all that in mind, this Dyna 'Series II' was not intended as DIY in the sense of 'real' Dynaco; Radial was just using the historic name and a 'general but loose' design language. [FWIW, the company for a time also sold some phono gear under the Hafler name.] I guess that's the 'nostalgic' part of the equation.

Dyna and the rest from that era (along with what is now offered new in kits today, either stock or modded) represents the niche hobbyist more than the typical 'music' lover, the latter who can just flip a switch on a black box and have streamed an entire music library at his ear tips, on demand.

I'm personally glad the kits are still around, but would never jump into the discussion about measurements, or overall sonic quality (much of that is always imaginary, anyhow).

My suggestion FWIW is that if ASR is going to fool with tube gear, that gear should have its own seperate category. Superimposing the distortion graph of an ST-70 with an AHB-2 is pretty ridiculous, if you ask me (who asked me?). On the other hand, a comparison with other tube gear might make some sense, if not add interest.

I’ve observed people and their audio equipment for 60 years, and I’ve never met any living breathing audiophiles, in person.

I know they exist, because I’ve seen stuff at estate sales. I just don’t know anybody who sits down and listens critically.

So the current influx of competent gear at reasonable prices will, I think, take the place of the Fisher consoles of the 50s. State of the consumer art. And not bad at all.

"It appears to me, Miss Leete," I said, "that if we could have devised an arrangement for providing everybody with music in their homes, perfect in quality, unlimited in quantity, suited to every mood, and beginning and ceasing at will, we should have considered the limit of human felicity already attained, and ceased to strive for further improvements."

Edward Bellamy, 1887.

 

[Petrushka]

I don't think the PAT-4 used Ge; it was in the Si transistor days.

My first stereo was a Pat-4 and Stereo 120, from kits. My older brother built Heathkits.

They were definitely silicon. Noisy controls.

 

[ElJaimito]

I’ve observed people and their audio equipment for 60 years, and I’ve never met any living breathing audiophiles, in person.

I know they exist, because I’ve seen stuff at estate sales. I just don’t know anybody who sits down and listens critically.

So the current influx of competent gear at reasonable prices will, I think, take the place of the Fisher consoles of the 50s. State of the consumer art. And not bad at all.



Edward Bellamy, 1887.

I've met quite a few, and not all were idiots. The ones who weren't did however rather tend to focus in on just one aspect of the reproduction, at the cost of the overall fidelity. That's the opposite of my own goals, as I try to create music to sound good on as many playback systems as feasible.

 

[ElJaimito]

I think that, plus more. It always brings (or should bring) a personal sense of satisfaction whenever you build something that you can use in your daily life. Of course back in the nascent days of hi-fi, if you wanted something you most likely had to build it yourself. Ready-made gear was always expensive. Heath, Dyna, Scott et al provided not only the 'fun' of DIY, but the added value of a discount.

Today it is cheaper and easier just to buy something ready-made, usually SS, and then hope it lasts before you throw it out. Specs will always be better with SS, so that should not even be an issue for anyone. With all that in mind, this Dyna 'Series II' was not intended as DIY in the sense of 'real' Dynaco; Radial was just using the historic name and a 'general but loose' design language. [FWIW, the company for a time also sold some phono gear under the Hafler name.] I guess that's the 'nostalgic' part of the equation.

Dyna and the rest from that era (along with what is now offered new in kits today, either stock or modded) represents the niche hobbyist more than the typical 'music' lover, the latter who can just flip a switch on a black box and have streamed an entire music library at his ear tips, on demand.

I'm personally glad the kits are still around, but would never jump into the discussion about measurements, or overall sonic quality (much of that is always imaginary, anyhow).

My suggestion FWIW is that if ASR is going to fool with tube gear, that gear should have its own seperate category. Superimposing the distortion graph of an ST-70 with an AHB-2 is pretty ridiculous, if you ask me (who asked me?). On the other hand, a comparison with other tube gear might make some sense, if not add interest.

I have now zero interest myself in valve gear for high quality reproduction, AFAIAC it's a contradiction in terms. IMHO valves/tubes belong in guitar amps, if anywhere. That said I did just buy two new Pultec-style valve-based equalisers, but not for the accuracy of their reproduction; quite the converse!

 

[Petrushka]

I've met quite a few, and not all were idiots. The ones who weren't did however rather tend to focus in on just one aspect of the reproduction, at the cost of the overall fidelity. That's the opposite of my own goals, as I try to create music to sound good on as many playback systems as feasible.

I’m sure there are a few people out there who can hear the difference between Spotify and lossless streaming. There are people who have four color vision receptors rather than three. I just don’t personally know anyone who cares.

 

[DonH56]

I’ve observed people and their audio equipment for 60 years, and I’ve never met any living breathing audiophiles, in person.

I know they exist, because I’ve seen stuff at estate sales. I just don’t know anybody who sits down and listens critically.

We need to meet. I have spent many hours listening critically to music, and a fair amount listening to the gear to see what is lacking and/or can be improved. I do tend to spend more time just listening (or watching) now than listening for flaws in the gear (or processing). Maybe it is more the older generation, but of my two boys (both with nice systems courtesy of dad ) one listens critically all the time, and the other is more interested in games sounding good.

 

[Petrushka]

We need to meet. I have spent many hours listening critically to music, and a fair amount listening to the gear to see what is lacking and/or can be improved. I do tend to spend more time just listening (or watching) now than listening for flaws in the gear (or processing). Maybe it is more the older generation, but of my two boys (both with nice systems courtesy of dad ) one listens critically all the time, and the other is more interested in games sounding good.

I no longer hear well enough to listen critically. I listen to music.

Just a subjective observation, but despite losing high frequencies, I can still judge speakers. There is a part of the brain that discriminates one human voice from another, and that also allows me to tell live from memorex.

For people interested in objective testing, the key frequency range is roughly between 60 and 4000 Hz. That is where the brain is most fussy. Nail that, and you have a semblance of reality. The rest is acoustics. Room effects.

It’s sad to lose the overtones, but you can still hear the music.

 

[ElJaimito]

I’m sure there are a few people out there who can hear the difference between Spotify and lossless streaming. There are people who have four color vision receptors rather than three. I just don’t personally know anyone who cares.

Yes, my wife for example. Was a top fashion designer, sees colour differences that I miss... not sure they matter though.

 

[Sal1950]

I’ve observed people and their audio equipment for 60 years, and I’ve never met any living breathing audiophiles, in person.

What on earth led you to make a statement like that?.
I'd say about 50% of our members are true audiophiles. 40% are slowly coming out of their audiophool media induced
comas, and 10% have closed minds and here to simply troll.

 

[Petrushka]

What on earth led you to make a statement like that?.
I'd say about 50% of our members are true audiophiles. 40% are slowly coming out of their audiophool media induced
comas, and 10% have closed minds and here to simply troll.

What part of participating here involves meeting people in person?