Tube Amps

Terrax

What would be a good low cost tube amp to try and buy? Be it new or used. That would run any number types of speaker over time.

dcarlson

There's a few of us who have a Dynaco ST-70.

organ

I'm with Derick on this. Look for a Dynaco ST-70.
The only problem with them is their age. Some parts may need replacement. So if you can use a solder iron, it's a great amp. You'll learn a lot about tube amps just by working on it. The ST-70 will give you a lot of that tube sound especially if you get the ones with tube rectification. Another plus is that the amp can easily be modded. The circuit is simple because many were sold as a kit. This is one amp that I'm not afraid to play around with.

If you decide on the ST-70, make sure you let us know about it because there are many versions out there. The one you wanna look for should be a 'Dynakit' with the larger hand wound power and output transformers.

If you want something easy and not expensive, check out the low powered mono blocks from Antique Sound Lab. www.divertech.com

You could go for a tube pre amp and use a SS amp.

Which speakers will you be powering?

Maurice

Terrax

As far a speakers, I'm currently looking at a pair of Triangle Zerius, which I'm being told will mate better with tubes than with SS. Also, I'm still running my Klipsch CF-1's some, which could benefit from tubes.

What about Jolida tube amps? Thoughts on these? Also, I've never owned or for that matter heard many tube amps, but I keep seeing consistant low wattage in tube amps, is this the norm, wattage wise, how do they compare to SS?

Thanks guys,
Terry

organ

Those speakers are very efficient and would be a great match for a tube amp.

I also considered Jolida at one time when my Dyna broke down. But It's been fixed and I enjoy it very much.

If you're looking for a 'romantic' sound, you should look at amps with EL34 output tubes.

For more power and slam, look for amps running KT88 output tubes. I hear they have SS characteristics though. Jolida makes both KT88 and EL34 based amps.

Tubes are low powered. They can power many speakers but will sound their best on high eff speakers. When transistor amps clip, they clip the waveforms and produce an audible distrtion. Tubes compress the signal and it will remain clean. My amp powered the LSi9 and it sounded great. But I noticed the dynamics and tube sound comes out more with efficient speakers. Tube rectification will 'sag' while diodes distort the sound. There's a lot of juice in a tube amp. If you turn off the amp with a source playing, it takes a while before the tubes run out of power and you can hear the music slowly fading out. Some people run 2W/ch tube amps using 100+db/w/m speakers.

Have you thought about an integraed unit?

Maurice

Terrax

Thanks Maurice, for the information, it helps alot. Yeah, I have been thinking about integrated, still trying to figure out the best approach to take. Money is a big factor, and well...... just wanna get a nice bang for the buck.

dcarlson

The guy I bought my Dynaco off of had a pair of Triangle speakers. I'm not sure what model but they sounded very good.

I had a quick listen to this integrated and it seems to be getting some good reviews. It sounded pretty nice for the very brief period I listened.

http://cls.audiogon.com/cgi-bin/cls.pl?ampstube&1093232814

TroyD

Terrax,

When you come to the Polkfest, I *should* have a couple of tube amps to try out, a Jolida and a CJ MV60....

BDT

Terrax

Sounds good, I look forward to it.

Ballylongford

Hi:

Any interest in a Harmon Kardon A300 integrated amp with a Bogen Tube tuner?

BOTH w/ beautiful wood cabinets

I have a friend selling a pair in the SF Bay area; $250 + shipping

If you are local you can audition them

Email if interested

Thanks

PolkWannabie

Try the flea market ...

faster100

I'm also thinking of tubes as i get more and more into this 2 channel rig.... Ive been looking at vintage heathkit mono's and dynakits and dynaco's stereo and mono amps.... Nice looking gear... wonder how they would do with this SS pre and my lsi7's??

madmax

The LSi7's need much more power than the tubes will supply. It should sound good a low volume though.
madmax

faster100

ah, maybe a set of Rti38's or my 25i's would mate better.... Thanks

organ

Faster,
SS pre will work nicely with a tube amp but eventually you'll want a tube pre in the future:).

I agree with Madmax about the LSi. I had the LSi9 hooked up to my Dyna and the RT series sounds better with it. You want to go as high up in efficiency as possible to get the best result.

You might want to look at the Dynakit models. They were sold as kits and are much easier to work with. You'd also want one with the 'good' transformers. PA 060 power tranny and A470 output trannies if you're thinking about the ST-70.

Maurice

dcarlson

I'm curious to hear a Tube Pre and SS amp combo. Speaker options would be limitless.

faster100

Originally posted by organ
You might want to look at the Dynakit models. They were sold as kits and are much easier to work with. You'd also want one with the 'good' transformers. PA 060 power tranny and A470 output trannies if you're thinking about the ST-70.

Maurice

what would a st70 run? i found one possible needing tubes locally for $275.00 that to much in working condition with no tubes
factory wired dynakit

dcarlson

I paid $400CDN for mine with tubes that I replaced anyway. If it's in good working order it may be worth it. I'm thinking factory wired is a good thing. Like Maurice said, which transformers it has is the more important question. Look for cloth leads from the trannies and the part numbers he quoted are printed on the top of them.

You may need to do some work to it as well, if you're up for that.

Try here.
http://www.audioasylum.com/forums/dynaco/bbs.html

organ

That's a great price. Is it possible for you to visit the seller and check out the amp in person? You should ask him if he made any changes or mods to the amp.

I agree with Derick. You'll probably have to do some work to it due to it's age. Do you know how to solder? It's very simple. I learned after getting my Dyna because I knew I'd have to work on it. rat shack have good silver solder.

Find out when was the last time he powered up the amp. If it's been over a year, you're going to have to bring it up slowly on a variac so you don't damage the caps. All technicians at repair shops should have a variac.

Maurice

faster100

Its stock, i possible could look at it, havent called and asked... i was told it was ran for a week on a good set of tubes and it worked fine... don't know when it was ran before that week.. no tweaks done... and i can solder... ive been tinkering with electronics crap for years... just not amps and audio specifically.. Thanks for the info


edit: just called the guy and he's real educated it seems with tube and vintage audio gear, we just spoke for 25 minutes... He said it was brought up on a variac, ran for 2 days.. then another weeks worth with no problems... would guarantee for a week or so... after that its fate. says no hums.... has bottom cover. might be cloth leads but he will look. now where to find the cash for it? LOL.... Thanks for the help

faster100

let me bump this back up so someone can chime in, Not to derail the thread.. seems like a more general type thread

organ

Sounds good. Trust me, the price of the amp is nothing compared to the amount of money you'll be spending on tubes;). It's so much fun, each brand of tubes have their own unique sound.

Since you like to play around with electronics, this is a great amp. I've done a lot of work on mine and enjoy the improvement each upgrade makes. Derick have done quite a bit of work on his too.

For tubes, check out www.thetubestore.com I've purchased A LOT of tubes from them and have had no problems at all. The ST-70 uses four EL34 output tubes, a single 5AR4/GZ34 and two 7199 signal tubes. Stay away from the Sovtek 7199. They're not real 7199. It's a different tube, re-wired internally to work in a 7199 circuit.

Do you have a Volt meter(multimeter)? You're going to need one to bias the amp.

Maurice

dcarlson

If you don't like it. (I know you will ) You could easily make your money back.

faster100

I'm thinking hard on this one.... I dont have a volt meter as of yet... But will get one if i get the amp.. problem is i gotta sell to buy... so its either the rotel amp or a pair of lsi's gotta go for me to afford this...

dcarlson

Which Rotel and what are you using it for?

faster100

Rb980bx(120x2 @8) and im useing it on my 2 channel with the lsi7's...