Vintage HiFi Audio Forum
Audio Discussion => General Discussion => Topic started by: RnR on November 18, 2014, 09:49:16 AM
-
Hey guys,
Been using tube music equipment for quite some time now, and am strongly considering going the tube route in my home audio system too. I need so much stuff for my current system its insane... but iv got DYNACO FEVER! There is a Dynaco ST-70 for sale that I am interested in, and am hoping to get any info I can about them. I listened to one the other day for a few hours and was really impressed, of course I understand it will sound different depending on speakers and other factors. I plan to drive a pair of Klipsch forte II's and use a Carver C-1 as the Pre. I tend to listen at higher volumes, but others have said in the past I would more than likely feel no limitations with it, would you say that is pretty accurate? 35 watts into klipsch forte IIs? Its hard for me to gauge the power difference between 30 tube watts and 30 SS watts because 30 SS watts seems a bit to light to me. I wouldn't want to buy too small of an amp and be driving it hard constantly.
Have you had one or listened to one extensively?
How would you describe the sound signature?
What kind of equip does it like to be paired with?
How much is too much to pay for it?
How long do tubes typically last in home audio stuff?
Do they tend to be reliable or unreliable?
What are it's strengths?
what are its drawbacks?
Any experience or knowledge of the Dynacos would be appreciated
-
The reliability issue is totally dependent on whether the amp has been restored or not. I have one that has been totally restored and it has never given me a minutes trouble.
The only comment I can make on sound signature (it was driving Klipsch KLF-20s) was the bass sounded flabby to me until new issue Genalex KT-77s were installed as the power tubes.
Mine has an after market driver board too, so that probably invalidates any sound signature observations I made.
-
1: Its hard for me to gauge the power difference between 30 tube watts and 30 SS watts because 30 SS watts seems a bit to light to me.
2: I wouldn't want to buy too small of an amp and be driving it hard constantly.
3: Have you had one or listened to one extensively?
4: How would you describe the sound signature?
5: What kind of equip does it like to be paired with?
6: How much is too much to pay for it?
7: How long do tubes typically last in home audio stuff?
8: Do they tend to be reliable or unreliable?
9: What are it's strengths?
10: What are its drawbacks?
1: 1 watt is 1 watt is 1 watt. There's no asterisk next to the forumlae for calculating power that requires a parameter declaring whether or not you are calculating a solid state watt or a tube watt. The real difference here is clipping. Clip a SS amp with compression drivers and you are asking for a Klipsch repair bill. Clip that Dynaco and, well, nothing happens.
2: Given that the power supply caps, rectifier, and transformers are behaving properly and the bias is reasonably close to spec, driving it too hard won't be an issue. My Heresy I's are 96 dB efficient and are 8 ohm nominal. I drive them with a 6V6 amplifier that is rated at 8 watts of power while driving an 4 ohm load. With an 8 ohm load such as the Heresys, that amplifier makes about 4 watts. I never have the volume up above the 1:00 point as it gets painfully loud.
3: Fairly so. The old old shop had one up and running with KT88's for quite a while when I hung out there regularly. Ian (vstarkwell) also has a very nice ST70 in his collection.
4: Assuming the topology of the original circuitry has not been modified, it'll vary based on your tube complement, tube condition, and the condition of the resistors and capacitors in various circuits.
5: Loudspeakers that have both high efficiency and drivers that possess a high electromechanical damping factor are always a plus for any tube amp that makes low to moderate power.
6: It depends how badly you want the amp.
7: Assuming that the amplifier is operating properly, quality manufactured tubes will last an awful long time. My Magnavox 8800 has original power tubes from 1960. I know nothing about how often the unit was used before I acquired it. All tubes tested very strong. I've run the amp at least 1-2 hours a day for the past year or so and everything is just fine.
8: As bmwr75 said, if the components on the amplifier are all operating properly and routine maintenance is not ignored, they are extremely reliable.
9: You'll fall in love with your music collection all over again.
10: You'll have a bit of parting anxiety when you sell your solid state amp.
-
BMWR75, thanks for the response. Sounds like you have an awesome amp on your hands! Glad you mentioned your experience with changing tubes and how it effected the sound. Tight bass is important to me because of the style of music I am into. Also heard some people online complaining about lack of bass, ext. Could also be due to the age of the equip and 1000 other factors..
8 watts, ur insane! thank you for taking the time to give me such a detailed response. I am really interested in hearing your Klipsch setup, I always see you posting about it and it seems to be a beefed up version of what i'm going for right now.
Any other low/medium tube power amps under 500 I am over looking? I guess I am into the dynaco because its so classic, and I heard one last week for a few hours and was really really impressed. This one was paired with the PAS3 preamp, it was a great sounding little setup, paired with some small bookshelf speakers that were detailed as hell.
I am hopefully going to go look at it tomorrow, strangely the pic he has is different than most i'v seen. No tube sockets on the front?
-
I also have a Dynaco PAS2 preamp and it sounded bad to my ears until I by-passed the tone controls. Before that the selenium rectifier was replaced and it was completely recapped. There are a lot better preamps out there than a Dynaco PAS2 IMHO.
-
Clip that Dynaco and, well, nothing happens.
Assuming that the amplifier is operating properly, quality manufactured tubes will last an awful long time. My Magnavox 8800 has original power tubes from 1960. I know nothing about how often the unit was used before I acquired it. All tubes tested very strong. I've run the amp at least 1-2 hours a day for the past year or so and everything is just fine.
Nothing bad will happen anyway. Many people will argue that tube amps sound best when subtly pushed to clipping.
My Leak Stereo 20 has all original tubes from (best estimate) 1964.
-
Any other low/medium tube power amps under 500 I am over looking?
This one was paired with the PAS3 preamp, it was a great sounding little setup, paired with some small bookshelf speakers that were detailed as hell.
I am hopefully going to go look at it tomorrow, strangely the pic he has is different than most i'v seen. No tube sockets on the front?
Depending on your levels of skill and ambition, you can find a console pull amp on ePay or CL relatively cheaply and modify it for stand alone use. Both of my Magnavox amps are console pulls. I've got under $200 into the pair (not including a matched quad of NOS Siemens EL84s).
As bmwr75 said, Dynaco tone controls are notoriously bad. I have a Dynaco PAT-4 and it has the same issue (among others). There's a popular mod out there that covers building a regulated power supply for the Dynaco preamps as well.
Unless someone modified the Dynaco amp, those are not tube sockets. Those are proprietary control connections.
-
The tube sockets on the front of an original ST-70 are used for power tube bias measurement. Never did anything else with them.
-
The tube sockets on the front of an original ST-70 are used for power tube bias measurement. Never did anything else with them.
I knew they involved controlling the bias. I didn't know they were actual tube sockets. Whoops!
-
I had the st70 many years ago. I bought it 2nd hand. Had a Curcio Audio driver board to replace the original driver board.
You may wanna check it out. http://www.curcioaudio.com/dynadr_3.htm. (http://www.curcioaudio.com/dynadr_3.htm.) Not totally sure but 7199's may be harder to come by now a days.
I really enjoyed that amp. It was musical driving the original meadowlark kestrals I had back then. As Scott said it may not have the ultimate woofer control but its not flabby, one note bass by any means. I would by a clean one again with no reservations. Its solid tube fun at an affordable price. There are many mods out there. Some swear by the cloth lead transformers vs the plastic covered leads etc but don't get too hung up on that. Again...I would by another one. But. If you are looking for ultimate bass control this my not be it.
-
Bad link. Curcioaudio.com. left side has links for mods etc
-
I got my mitts on a Dynaco PAS-4 Preamp, I love the thing. All the tubey pre-amp goodness I needed in my life. It has no tone controls on it at all, guess they figured best to get rid of it then have a weak link. There is an external loop for a processor on the unit which is selectable.
-
7: Assuming that the amplifier is operating properly, quality manufactured tubes will last an awful long time. My Magnavox 8800 has original power tubes from 1960.
I've pondered this a time or 2...do power tubes degenerate at an excelerated rate compared to say the tubes in a pre amp? I've still got original tubes in a 490t cd player and it sounds OK to me?
-
Thanks for all the great advice.
The Dynaco I was interested in sold this morning, I was supposed to go look at it tonight after work... Pretty bummed. I am going to keep researching and try to get more educated on the Dynacos. If you see one for sale please let me know. Thanks a lot.
-
Too bad. But if you run into a Jolida 302 they are very nice amps for the money. No rebuild to worry about. They're still young and shouldn't need any recapping. I've long sold mine so Im not that current on the newer Jolida amps.
-
7: Assuming that the amplifier is operating properly, quality manufactured tubes will last an awful long time. My Magnavox 8800 has original power tubes from 1960.
I've pondered this a time or 2...do power tubes degenerate at an excelerated rate compared to say the tubes in a pre amp? I've still got original tubes in a 490t cd player and it sounds OK to me?
I've always read that quality power tubes will last 1/2 as long as small signal tubes, all other things being equal. ???
-
You can think of them somewhat like (DC) lightbulbs, in that the higher the voltage running through them the brighter they'll burn, but the shorter they'll live. Bigger power tubes, especially if you've got the bias cranked on them beyond MFR specs, will almost definitely have a shorter life than small-signal tubes. It's just a lot more work to do!
-
Speaking of Dynaco fever, I have a SCA-35 on the way. It should be here around Christmas. I am very anxious to hear the mystical 'warm tube sound."
-
I've always read that quality power tubes will last 1/2 as long as small signal tubes, all other things being equal. ???
[/quote]
If that long. The high output AC voltage tubes generate a lot of heat. The tube life is a of the function of the heat generation by the tube. Heat kills tube life. Signal tubes operate at a much lower temperature compared to power tubes. I always enjoyed the EL84 (6BQ5) more than the 7591, GZ34 or the KT tubes. The EL84 playing with an efficient or small speaker sound very nice. Smooth, buttery or just more involving are words that come to mind. I have not owned a set of Klipsch speakers so you will need to judge that for yourself. Also cheaper tubes will have shorter life.
I have heard many nice sounding ST-70 Dynacos with mid size speakers playing at reasonable sound levels. If you are not interested in a nice three dimensional stereo image, and just want to play music at high volume levels to shake the walls, I recommend a solid state amp. tubes don't add SQ when listening to music at 90 dB or higher. Your just making noise
If you want a lot of power and the smooth sound of tubes, use a tube preamplifier and a solid state amp. High ouput tube amplifiers will never match the dynamics of a good solid state amps.
-
High ouput tube amplifiers will never match the dynamics of a good solid state amps.
I don't agree with that. :D
-
If you want a lot of power and the smooth sound of tubes, use a tube preamplifier and a solid state amp. High ouput tube amplifiers will never match the dynamics of a good solid state amps.
Well said Carl I fully agree.
>:D
-
I don't know if 'never match the dynamics of a good solid state amp' is fully true, but cost-effectively it is I feel. I love my tube-pre w/ solid state power combo. Some people say tube pre + tube amp is too 'tubey', it's all very setup dependent. I think I'm going to stick with this setup as my main for now though.
-
I think it is a dangerous assumption that if you run a tube preamp and a solid state amp you will get that perfect dynamic sound with the added smoothness. I think it is more about matching individual sound signatures and hoping the equipment plays nice. Sound signature of both the preamps and amplifiers can easily be changed with tubes (assuming you aren't trying to replace 16 300B tubes). My recommendation is if you can buy the piece of equipment and sell it to make a profit or at the very least break even, it doesn't hurt to try it in your system. If you can't resell it and at least break even then there is always another deal (possibly a type of equipment you didn't know existed).
-
If you want a lot of power and the smooth sound of tubes, use a tube preamplifier and a solid state amp. High ouput tube amplifiers will never match the dynamics of a good solid state amps.
Well said Carl I fully agree.
>:D
I think he meant a good quality SS amp. Not a HT amp. :-X
-
Some small signal tubes (preamp tubes) will last 10,000 hours. Power tube typically last 1/5th as long if biased as they should be.
-
If you want a lot of power and the smooth sound of tubes, use a tube preamplifier and a solid state amp. High ouput tube amplifiers will never match the dynamics of a good solid state amps.
Well said Carl I fully agree.
>:D
When you increase the number of turns in an OT, you increase the capacitance and primary leakage inductance, both of which may compromise dynamics, especially at higher frequencies. Keep increasing turns and you lose HF extension.
You can roughly calculate the high frequency cut off as:
FrequencyCutoff = PrimaryImpedance / (2 x 3.14 x LeakageInductance)
Less turns in an OT means reduced low frequency output. It's all a balancing act.
-
High ouput tube amplifiers will never match the dynamics of a good solid state amps.
I don't agree with that. :D
I sort of agree. The way I understand it is that at low output, tubes and solid state will have roughly equal dynamic range. But as you get close to max output, tubes have the effect of compressing the signal while SS clips it. To my ears, the compressed tube sound is "better" than the clipped SS sound, but the SS does technically have more dynamic range at that point.
-
I think it is a dangerous assumption that if you run a tube preamp and a solid state amp you will get that perfect dynamic sound with the added smoothness. I think it is more about matching individual sound signatures and hoping the equipment plays nice. Sound signature of both the preamps and amplifiers can easily be changed with tubes (assuming you aren't trying to replace 16 300B tubes). My recommendation is if you can buy the piece of equipment and sell it to make a profit or at the very least break even, it doesn't hurt to try it in your system. If you can't resell it and at least break even then there is always another deal (possibly a type of equipment you didn't know existed).
I absolutely agree with this.
-
I think it is a dangerous assumption that if you run a tube preamp and a solid state amp you will get that perfect dynamic sound with the added smoothness. I think it is more about matching individual sound signatures and hoping the equipment plays nice. Sound signature of both the preamps and amplifiers can easily be changed with tubes (assuming you aren't trying to replace 16 300B tubes). My recommendation is if you can buy the piece of equipment and sell it to make a profit or at the very least break even, it doesn't hurt to try it in your system. If you can't resell it and at least break even then there is always another deal (possibly a type of equipment you didn't know existed).
Nothing is perfect, and everything is subjective. Let your ear be the judge.