My speakers with tubes

hearingimpared · May 2010

mhardy6647 wrote: »

heh, newb...

;-)

edit: jes' kiddin'...

Actually when it comes to tubes I am as newbie as it gets even though I was raised on them. When I was in tech school back in the stone age, we built a point to point five tube superheterodyne receiver. Solid state was just making it big at the time. AND gates, NAND gates, NOR gates . . . hehehe!

mhardy6647 · May 2010

TTL, DTL... I hear you :-)

One of the things I like best about vacuum tube amplifiers (back, sort of, on topic) is the simplicity, (in most cases) the robustness of the components and the availability of parts even today. The downside is that pesky high voltage... but all in all the old vacuum tube gear is easy to troubleshoot/repair and restore. Most vintage solid state stuff is just too complicated and finicky for my rudimentary repair skills (and parts are often unobtanium). New tube amp components are fine too; DIY is readily achievable (and there are also many nice kits) for those of us too cheap to buy new/ready-made gear.

I guess that's my vacuum tube hardware manifesto :-)

And on top of everything there's the sound quality...

Pycroft wrote: »

I would categorize these as non-efficient:

86 db sensativity, 8ohm resistance, 40-200 watts. 55lbs each.

I really have no idea what you just said about anything. What is imp? Steady imp? Flat imp? etc. etc.

Thanks for the info, at least what I understood of it

James

"imp" means impedance. For amplifiers such as SETs (single-ended triode amps) with minimal or no negative feedback and relatively high output impedance, yes, it is true that speakers with broad/flat impedance characteristics will be easier loads to drive (at least in terms of frequency response accuracy of the amp/speaker combination)... BUT tube amplifiers tend to be extremely tolerant of complex, reactive loads (think of Polk Cobra Cables!) that would immolate many solid state amplifiers. The only thing you don't want to do with a vacuum tube amp is run it without a load (i.e., open circuited; with no speaker connected) - that runs a significant risk of destroying an output transformer :-(

hearingimpared · May 2010

mhardy6647 wrote: »

TTL, DTL... I hear you :-)

.

:eek::eek::eek::eek::eek: Memory cells just kicked in, wow that hurts!

mhardy6647 · May 2010

Mr. Pycroft, have you seen/read this vacuum tube hifi primer? It's pretty good.
http://archive.anthemav.com/OldSitev1//pdf/taste.pdf

Speaker impedance and the physics of loudspeaker design (not to mention interaction of reactive loads with amplifiers) is a little more complicated for one-stop shopping. I do like this treatment of Thiele-Small parameter estimation (although it refers to an individual driver rather than a loudspeaker system with crossover and contour networks, but the basic ideas are the same):
http://sound.westhost.com/tsp.htm

That "sound dot westhost dot com" site actually has quite a bit of good albeit somewhat technical information if you roam around there a bit.

hearingimpared · May 2010

Thanks for the link Mark, I didn't have that!

Pycroft · May 2010

I have not read it, but I will glance when I get a chance. To be honest, I'm not sure I care TOO much about understanding. I'm not sure understanding it perfectly will help me enjoy the sound better

I will take a look so I can engage in this discussion with a better background.

mhardy6647 · May 2010

The more you know, the less easily you'll be swayed by the vagaries of fashion and the more you'll trust your ears... plus, I can assure you that you'll be able to get more bang for your buck when you buy (or build)!

I am a fricking biochemist, not an EE :-) This is a fun hobby, but the software (music) is most important - I suspect we're in violent agreement on that subject!

mhardy6647 · May 2010

One final (?!) thought on the topic: this three-volume series may arguably be the best readily-available primer out there, and, thanks to pro designer/DIY supporter Pete Millett, you can download them gratis (they are in the public domain) from his website!

http://www.tubebooks.org/Books/crowhurst_basic_1.pdf
http://www.tubebooks.org/Books/crowhurst_basic_2.pdf
http://www.tubebooks.org/Books/crowhurst_basic_3.pdf

http://www.tubebooks.org/technical_books_online.htm

Pycroft · May 2010

I read the primer (Scanned really). I have come across two Dynaco ST-70's. The person is only selling as a pair. They are stereo - what is the point of getting two of them? If I use one per speaker, are they more powerful? I believe they are 35 wpc...that should be fine to run my 'not-so-efficient' speakers right? ANy comments on build/sound quality?

Thanks

James

organ · May 2010

Sorry I wasn't clear on my previous post. Mhardy cleared it up:) The man knows A LOT when it comes to tubes and have quite the collection of gear too lol.

ST-70's are excellent but you should really look into the pair being offered to you. Do you have a link to the seller's ad? Most of them are from the 60's and will have parts which have drifted out of spec and need to be replaced. If they've been restored to original specs, you're good. If not, you'll have to do some work on them.

The ST-70 was my very first tube gear and like you, I didn't know a thing about tubes when I first started. I had to do a lot of work on mine because it was from 1959 and all parts were stock. So some caps had to go, along with some resistors, tube sockets, etc. But I learned so much from working on the Dynaco and it pretty much got me into learning about tubes.

Your speakers are probably mid-efficiency so I'd recommend looking into push/pull designs. The ST-70 is push/pull @ 35w/ch.

Have you considered a tube pre amp with your SS amp? Much less hassle than tube amps or int's.

cnh · May 2010

I am a fricking biochemist, not an EE :-) This is a fun hobby, but the software (music) is most important - I suspect we're in violent agreement on that subject![/QUOTE]

That's interesting...but that also means you're a trained scientist who studied Calculus, Biology, Chemistry and Physics--at least at the undergrad level. And I would bet MONEY that you also had a hard course on computer languages--hence your interest in all things technical (nothing wrong with that) but it is also much easier for you to engage those things. If I'm not mistaken, James, Pycroft has more of a Fine Arts background.

The Principles of EE would be easily grasped and processed by someone in the hard sciences and he would actually find them interesting.

In any case...you're a valuable resource and we can all learn from that.

cnh

wayne3burk · May 2010

Pycroft wrote: »

I read the primer (Scanned really). I have come across two Dynaco ST-70's. The person is only selling as a pair. They are stereo - what is the point of getting two of them? If I use one per speaker, are they more powerful? I believe they are 35 wpc...that should be fine to run my 'not-so-efficient' speakers right? ANy comments on build/sound quality?

Thanks

James

James -- the ST70s have a monaural switch on them... if you run them in that mode you put only one input into the left channel rca jack ( i believe

check manual ) , then you're running 65WPC ( i have no idea where the other 5 watts went to ).

Depending if anyone has modded them or not... I've been watching ST70s on ebay for months now -- you should expect to pay between $400 and $600 apiece for them.

p.s. -- my dynaco A25s are 89db sensitivity and i'm driving them with my 13wpc magnavox chasis ($30 at my local thrift store) to very comfortable listening levels with my computer (itunes, winamp, last.fm, etc) using the volume controls for those programs in conjunction with the volume control panel.

but i'd definitely buy those ST70s or look for a pair of Dynaco MKIIIs (60 wpc mono amps)

happy shopping

-- wayne --

mhardy6647 · May 2010

I think that the auction link said, or at least implied, they were re-habbed. 800 smackers for a pair doesn't seem outrageous.

FWIW, I am not a huge fan of the stock ST-70 sound... but they've got great output transformers and they are certainly a sturdy, well-known, dependable and upgradeable platform.

zingo · May 2010

I would go with push-pull tube amp as they are more powerful, but still have the great sonic qualities of tubes.

Would you consider your Sony speakers bright? I sometimes don't like the combo of laid back speakers and tubes.

Pycroft · May 2010

The Sony's are very neutral and natural. I wouldn't classify them as bright or laid-back.

My quest continues. I already have a tube preamp, but it's a starter one. I'm looking for one with a phono section. Always on the prowl

James

ViperZ · May 2010

wayne3burk wrote: »

James -- the ST70s have a monaural switch on them... if you run them in that mode you put only one input into the left channel rca jack ( i believe check manual ) , then you're running 65WPC ( i have no idea where the other 5 watts went to ).

Depending if anyone has modded them or not... I've been watching ST70s on ebay for months now -- you should expect to pay between $400 and $600 apiece for them.

but i'd definitely buy those ST70s or look for a pair of Dynaco MKIIIs (60 wpc mono amps)

-- wayne --

Some people do not like ST-70s in "mono", and ST-70s cannot be switched to true mono amp with the switch. You have to put a jumper on the back between two outputs, and then use the switch. With the turn of magic, the amp will do current steering from 2 channels into 1. It will not give you anything close to 70 Watts (2x35), but more like 55 Watts in stock configuration.

I love my ST-70s, and as soon as the 2nd one is fully updated, I'll run them 1 per channel to see how they sound that way

.

Oh yeah, if you want a budget tube pre with a phono, try Dynaco PAS-3(x). If you can find a very quiet one, don't even bother modding it (the preamp mods are the most difficult, and if you screw up even a single ground connection or add a ground loop, you'll be looking for the fix for hours/days). My PAS-3 is silent, and I like its phono stage better than SS Carver C-1 and Cambridge 640A.

Pycroft · May 2010

Man,

I don't mod anything. I get a headache looking inside one of these things

James

mhardy6647 · May 2010

Mr. Pycroft...
here's why you want tubes...

I hear mariachi static on my radio,
and the tubes they glow in the dark...

Pycroft · May 2010

Would ONE dynaco ST-70 be able to compare to my current setup or would I need two of them - one for each speaker?

Imspun4u · May 2010

Some may laugh but I bought a Onix tube amp three year's ago from AV123 and it's going strong. Not a high end tube amp but it's not syrupy sweet like a lot of tube amps. Over the year's I have collected a lot of tube's for it that can change the sound quality. I just wish it would except EL34s. I think it would mate up well to a solid state for bi-wireing. Just another idea to throw in the hat.

organ · May 2010

Pycroft wrote: »

Would ONE dynaco ST-70 be able to compare to my current setup or would I need two of them - one for each speaker?

I don't see why not. One should be able to power your speakers just fine unless you like it really loud. Whatever amp you go for, don't forget to give the 4 ohm output taps a try.

organ · May 2010

mhardy6647 wrote: »

Mr. Pycroft...
here's why you want tubes...

I hear mariachi static on my radio,
and the tubes they glow in the dark...

The warm glow of tubes. BEAUTIFUL!

My speakers with tubes

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