Dynaco ST-70

organ

Are you referring to the front-left output tube or the one closest to the power supply. Kinda hard to tell with the output tube because it could be the camera's flash. But the tube closest to the power tranny is suppose to be different because it's the rectifier tube.

Mismatched power tubes shouldn't harm the amp unless their specs are way off. Matching is more for optimum performance.

Maurice

dcarlson

Front left in the corner.

Over-analysing maybe?

Tour2ma

Agree maurice, something to look at in person.

dc, a rebuilt OT is not necesarily a bad thing, if the one who rebuilt them knows what they are doing. If the plate holes are misaligned, just a sign of carelessness that may or may not reflect the rest of the effort.

If more than the end caps on the OT's are painted, that would be sign #2 of carelessness.

Don't sweat the tubes, you'll likely end up buying more anyway. Not that expensive.

Again, if he's quoting that price for both the 70 and the PAS 3, it'd take a fair amount more than a humming phono input and a suspect OT to put me off the deal...

dcarlson

He's selling them separately. He's asking $275CDN for the PAS-3.

organ

Originally posted by Tour2ma
Don't sweat the tubes, you'll likely end up buying more anyway. Not that expensive[/B]

Depends if Derick goes tube crazy like I did:D. I don't even want to know how much I spent on tubes LOL

Maurice

dcarlson

Hehe. Well, I guess you may have done the leg work for me. The Svetlanas eh?

I've emailed the guy to see what he says about the misaligned cap.

organ

LOL The Svets kick ****. Are you still using the 12AX7 on your CD player?

Did you ask him about the transformer too?

Maurice

dcarlson

I think you're mistaking me for someone else. I've got a Rotel RCD-1070 as a CD player.

Did you ask him about the transformer too?

That's what I meant.

organ

Oops. Sorry man, I think it's Paul who got the modded CD player.

Maurice

dcarlson

He responded about the misaligned OT.

Left and right are the same,are stock and original....I am assuming U mean the alignment holes at the top of the trannies.Not that I ever looked at any other Dynacos that closely before...I guess i don't have an answer for U as to why this is.

Do you think offering the guy $350CDN is lowballing a little too much? I'd like to get it for $400 and he is asking $450.

faster100

so offer him $400, just a thought

I buy and sell stuff/junk/treasures all the time, some times people "change" their mind about selling when you lowball to much, But im all for a deal.. so i always ask.. figure what you wanna spend max... and offer it up, he passes.. pass yourself. Sometimes they will pursue you after that.. then your in charge.

good luck

dcarlson

I offered him $400, we'll see what happens.

Maurice,

Do you have any favorite websites regarding the ST-70 you'd like to share?

Tour2ma

Audio Asylums vintage section has many threads on the 70. A couple other sites I've bookmarked:

Rebuilds
http://www.avahifi.com/root/equipment/amplifier/70_rebuild_plans.htm

General
http://home.indy.net/~gregdunn/dynaco/components/ST70/

Hope the fellow takes the $400 CA... I think it's fair given the output tube questions...

dcarlson

It looks like it's a done deal.

He wants extra for the JJs because of the $400. Should I just order some new tubes and not bother with the JJs?

organ

Congrats Derick. I'm sure you'll love the wonderful world of tubes.

What kind of music do you listen to most? The ST-70 really stands out on classical, opera, vocals, etc. It still does a damn good job on rock, metal and other heavy stuff.

Tour gave some great sites there. I love audioasylum because there's a LOT of info on ST-70 if you use the search function. Another great site I'd like to add is www.dynaco-doctor.com You can download restoration guides, original instruction book, mods, etc. They also have a forum there.

IMO, the JJ tubes are crap. A lot of people seem to like them on ST-70's but to my ears, it has no personality. Go for the Svets, they're much warmer, richer and have stronger bass.

A few things to keep in mind...Don't turn on the amp with no speakers connected. Lower the bias pots to min when replacing tubes and increase slowly to 1.56V over a period of 15-30mins. Keep checking throughout the day and night just to make sure it's not drifting.

What speakers will the amp be powering?

Keep us posted. I'd like to see what you think of the sound and maybe some pics:).

Maurice

organ

Since you're in Ontario, your closest online tube dealer should be www.thetubestore.com I purchased most of my tubes from there. Express shipping takes less than 48 hours. www.triodeelectronics is another great place for tubes and Dynaco stuff.

Maurice

dcarlson

I usually listen to Rock like the Stones, Pearl Jam and range over to Radiohead, Pink Floyd and Neil Young. I imagine tubes would do a great job on live albums? If that's the case, Crosby Stills Nash and Young's 4 way street on vinyl should be a treat.

The tubestore's in Hamilton.

How difficult is it to bias? I have a voltmeter, would that do the trick?

organ

Live music sounds great on the Dyna especially when the recording is really good. I remember listening to Radiohead's OK computer and my ST-70 and thought it sounded awesome. Track 4 was very cool with the echoes and stuff.

Biasing is very easy. You can see the two adjustment knobs for the pots in front of the power transformer. Use a screw driver (make sure you only touch the insulated part with your hands incase the amp decides to bite). Turn clockwise to increase bias and counter-clockwise to decrease. Your voltmeter will work. Set it to read DC Voltage, insert the positive lead on the front tube socket labeled "Bias 1.56V" and touch the chassis with the negative lead.

Maurice

dcarlson

Any ideas on having it shipped? Or should I play it safe and pick it up? It's a 2 hour drive away.

organ

I don't think it can get damagaed easily. The only part that could suffer damage during shipping is probably the cage (if not boxed properly). That amp is built like a tank. But if it's boxed very well, I'd be more worried about getting the tubes damaged instead of the amp. It's also VERY heavy. If you don't mind driving, go for it. At least you'll know it's going to arrive safely and it's faster than shipping.

Next time you go out, stop by Canadian Tire and pick up an Autosol Metal Polish. It wil make the nickel chassis sparkle. The rag I used turned black after cleaning my ST-70 with it. Becareful with other brands. Some are very abrasive and will take out the lettering on the front.

Maurice

Tour2ma

Yup, if having it shipped, the tubes should be pulled and wrapped/ boxed separately.

If you price shipping, I think you'll end up making the drive.

I've purchased tubes from the tube store. Good folks to deal with.

dcarlson

I was going to make the trip, I just wanted to confirm it wasn't a waste time vs. shipping.

Thanks for all the help. I'll need quite a bit more help once I get her home.

dcarlson

OK, so I want to buy some tubes.... Should I replace all of the tubes or can I get by with simply replacing the output tubes?

organ

You should try to replace all the tubes just to be safe. The 7199 are becoming rare and expensive and current production 7199 from Sovtek is crap. I hear it's not even a real 7199. It's another tube where the internal is modded to work in a 7199 circuit. The 5AR4/GZ34 is really up to you. Mine worked nicely with a Sovtek. The NOS Mullard made a big difference though. DON'T buy the Shuguang 5AR4. They have problems in ST-70's.

This is the 7199 I'm using. http://www.thetubestore.com/janphilips7199.html They're expensive, but they sound great. Anyway, it's better to buy it and keep the two that came with the amp as extras because NOS is getting expensive. I paid $30 each back in Septemeber and now the price have gone up $7.

Maurice

*edit* I just took a look at their Mullard 5AR4. If you want to get it, you should do it ASAP. The price just went up $10. I paid $89.99. It's now $99.99 The Mullard rectifier tube is something you won't need to replace for a long long time. Some people have been using them for 30+ years and they still test good.

Tour2ma

Good edit, maurice. I was just going to add the NOS Mullard note. I bought two when they went up to $90 a while back. Looks like on of the better investments I've made lately...

organ

Now I feel like buying more:D. Did you get to try them out on your ST-70 yet?

Maurice

dcarlson

I was looking at the pics a little more carefully, specifically the tubes. Is it possible that they're the original tubes as well?

Or at least the same as in the pic from Tour's link.
http://home.indy.net/~gregdunn/dynaco/components/ST70/

I wanted to order the tubes today but considering the price of replacing all of the tubes, I'll have to wait until I have the amp to make sure it's in good working order. $360CDN is quite a bit.

dcarlson

I picked it up.

There's 3 matching Dynaco by Mullard output tubes and the oddball is a Sovtek. The 2 driver tubes are Sovtek and the rectifier tube is a Realistic.

When attempting to bias, what am I supposed to get as a result on the multimeter? I'm getting half the reading of a AA battery while biasing. Does that mean I need new tubes or something else?

As the seller indicated, everything does seem to be stock except for the binding posts.

The one thing I notice is the size of the soundstage. It's not as detailed as the Musical Fidelity but I do like the sound and I'm very encouraged at the potential this thing could have once I start swapping some parts. It needs a good polishing, there's some minor pitting. I have some Eagle One rim cleaner that did a good job on the platter of my TT.

dcarlson

Oh... the left Bias Potentiometer is cranked to max and the right is at about half to match the left.

Tour2ma

Bias to 1.56 V as should be indicated on the stenciling.

Having to bias to the max indicates a component is weak. One of the tubes is the most likely possiblility, but possible it's another component.