Re-tubing stock ST70

[indianajo]

I have a totally stock 1961 dynakit ST70. I put it away 10 years ago because it was getting weak and the guitar shop was charging $25 for imported tubes. Now there is the internet! cool. I am going to buy some 6CA7's probably from tubesandmore because they are the only source of something else I need, and I only want to pay one shipping charge.
So which ones, JJ's ($57) (hungary?), stocker electroharmonics($57) russian, or winged C electroharmonics.($144) . They don't mention country of origin on ruby, groove tube, or Valve art, so I guess they are Chinese, whatever their features. I'm sure not buying any milk from China soon.
A guitar amp builder on chopship's thread said JJ's fail a lot. Agree? disagree?
My 25 year old GE's have the big bottle like the winged C, but I don't know if that means anything. Nobody cares what my amp looks like.
I precharged the caps, ran it at 70 VAC for a minute, then heated it up to night. I had put a test point out on point "C" the first B+ cap after the choke. I'm getting 410V idle and 400V with signal so I guess my 5AR4 is okay. The B+ can was installed in 1983, a cardboard tube from cornell-dublier, oddly enough, 20-15-15-15@525. I can't get more than 1 v bias current on either output pair, with new electrolytic caps on bias I installed this week. Putting 1/2 V pp in on both channels at about 800 hz quasi sine, I get about .5 v pp out on 8 ohm 225 W resistors, a little less on one channel. So I'm pretty sure it is output tube time. That is why I put it away.
Is the $144 tube set really better? This is not a guitar amp, no overdrive.
I was only getting .6V pp at the end of the .1 caps to the grids on the 6CA7's, with 330 V on the preamp B+ socket on the front, so I think the 7199's are probably weak, too. No recourse on that, except I'm getting ready to transistorize a Hammond H and it has 3 7199's in it. A little more signal in might have helped, but .5 v out is so much lower than the stocker 16.6 v pp that the scope confirms my ear, the tubes are tired. The 0.1 output grid coupler caps are film type installed in the seventies. The bias rectifier is selenium stack, installed in the seventies.

 

[6L6]

I have a Alan Kimmel driver board on my ST70

I have used JJ, Sovtek and (St.Petersberg) Svetlana (now Winged C). I have had no problem with any of them. I would seriously look at the EH and the new 'Mullard'.

My only experience with Chinese tubes in this amp is the 5AR4, which I believe I had 3 failures before I totally and completely swore off Chinese tubes for the rest of my life.

As for 7199, I can't comment, my amp uses a completely different circuit.

 

[Eli Duttman]

IJ,

Good current production tubes for the amp include the SED (=C=) EL34, the EH 6CA7, and the "reissue" GEC KT77. Of late, JJ's Octal production has been garbage, so stay clear.

Like it or not, the 7199 is fast going the way of the Dodo. I strongly suggest you think about Triode Electronics' replacement driver board populated with 2X EF86 and an ECC99. You retain the OEM topology but employ available types that are, in fact, superior to the 7199.

What is it that only AES has? Check in with Jim McShane. Jim's prices are fair and his service is 2nd to none. The man burns tubes in and matches them under real world conditions. All too often, factory "matching" is a bad joke.

 

[DigitalJunkie]

I'd suggest replacing that selenium bias rectifier with a modern silicon part. Bad things happen when those go south.

 

[Burnedfingers]

I would recommend replacing the stock driver board with something more current that would allow you to source the tubes easily. I have used the SDS Labs 6AU6/12Au7 driver board and found it sound quite well. I am also very fond of the Mapletree Driver board that uses a 6sj7 6sl7 combination. I would also suggest modifying the bias circuit to allow for individual tube bias adjustment in addition to the other mods already covered.

Output tube replacement is a difficult choice. My personal favorites are the
6bg6ga's and I also like the Russian 6n3cE tube. The 6n3cE is a more hefty version of the 6n3c. The 6n3cE is a very balanced sounding tube and it is cost effective.

 

[kstagger]

if the amp is totally stock and original, I would also be worrying about the electrolytics. SDS (via Triode Electronics) has a nice board that slips under the chassis. It will effectively replace the can-cap which you can keep in place for visual purposes.

My old Dynaco 70 had the SDS driver board (EF86/12AU7) and the power supply board. The sound afterwards was much more punchy and less soggy than the original. The end effect was a better amplifier, but (not to be a spoil-sport) still not a 'top leaguer".

 

[indianajo]

IJ,
Good current production tubes for the amp include the SED (=C=) EL34, the EH 6CA7, and the "reissue" GEC KT77. Of late, JJ's Octal production has been garbage, so stay clear.
What is it that only AES has? Check in with Jim McShane. Jim's prices are fair and his service is 2nd to none. The man burns tubes in and matches them under real world conditions. All too often, factory "matching" is a bad joke.

Thanks for all responses.
Mr McShane doesn't say where Genelex (not GEC) tubes are manufactured. "Doesn't say" means china to me until proved otherwise by your experience. Electroharmonix (russia) has a winged C 6CA7 at tubes&more, don't know who is selling "SED" or where they come from.
I've been busy coping with the trash tube era by putting 100 ohm resistor between the rectifier cathode and the first capacitor, and 30 gauge wire between the transformer and plate on the ST70 and the organs. This consumes phenolic headers, as does replacing the selenium rectifier with a 1N4002. Headers are also useful for putting Metal Oxide Varistors on the main voltage coming in to transistor devices to snub lightning strikes, which we have a lot of here. Mouser, Newark, triodeelectronics don't have them, only tubesandmore has them and they call them "terminal strips" which is what everybody else calls screw barrier strips. My caps are fine, and are available new from FP at T&M & triode. I bought an "EF86" from triode, it came in as a "6*32n" also CT21 and =C= and since I can't yet manufacture a tube grounding ring where the ittermittant socket has been removed where it goes, I haven't tried it out. Are these "6*32n" things as good as Mullard & GEC EF86's which if genuine, are very expensive? Who is =C=? I thought winged C refered to the plate on the 6CA7, which looks like a black gutter with wings standing up in my GE (US) 6CA7's.
I've just bought the best speakers I've ever owned, and am wanting to try the up to stock ST70 versus the DJoffe bias mod ST120 and the stock Peavey CS800S to see what they all sound like. As I said, I've got a whole organ full of 7199's to loan if it is a problem, and the loan woud be temporary since the ST70 consumes so much power silent. The ST70 was my main music box for 30 years, but time marches on.

 

[Eli Duttman]

The "reissue" Genelex tubes are made at New Sensor's Saratov, Russia, plant. New Sensor has acquired the rights to many famous brands and they have been doing a good job of making the tubes so labeled.

The "Flying C" (=C=) logo is used by the Svetlana plant in St. Petersburg, Russia. New Sensor owns the Svetlana brand in the U.S. So, SED is how =C= tubes are marketed here.

The "6*32n" things are older Russian EF86s, which (IIRC) were made at St. Petersburg. They are not good. OTOH, New Sensor currently makes the EH EF86 and the TungSol EF806, both of which are good. The TS is better and, at 2X the price of the EH, should be.

Stop fussing over MOV mounting. Buy a high quality computer surge suppressor power strip and kill 2 birds with 1 stone. You get the power outlets and the MOV Lightning protection.

 

[kstagger]

Just a quick word on the EF86 - I used to be an EF86 "fanatic", using the darn thing just about everywhere - driver tube for SE amps and triode connected in a preamp.

The Russian EF86 was just plain nasty triode connected. Very harsh! The EH was much better! The still common Phillips/Mullard/etc is worth the hunt while the GEC CV4085 was the top of the bunch.

In amplifiers with loop feedback, differences started to shrink into near insignificance.

 

[indianajo]

Thanks for the clear responses. There is no point in buying a 7199 replacement PCB for the ST70 if it uses EF86 and the only decent EF86's are NOS and priced for rich people. With the importers buying up trademarks like Sovtek and EH and muddying up the works by sourcing them from somewhere else leaves a bad taste in my mouth. I can get a whole Hammond organ for $100 with 3 Hammond brand 7199 and an EF86 in it. The "EF86" I got from Triode was inferior you say, not even marked that way, so what is the point. Lots of scams going in tubes.
As far as power strips go, the only "surge suppressor" ones available in my county are from R**** S*****. I don't think I have ever bought anything from R**** S***** that wasn't junk in some way. The strips are made in China anyway, the MOV's I use are from blown up motor drives and are US origin. Cutting up used old junk doesn't hurt the balance of payments. I didn't buy the Russian 6CA7s in 1983 because I had just come off a term of defending the Fulda Gap and the Berlin wall wasn't down yet. Russia hasn't shot any missiles over the seventh fleet lately, I may go with them.

 

[Jim McShane]

Thanks for all responses.
Mr McShane doesn't say where Genelex (not GEC) tubes are manufactured. "Doesn't say" means china to me until proved otherwise by your experience.

Excuse me, but Genalex (not Genelex) tubes are made in Russia. It is printed right on the tube base. It is widely known to be Russian made - do a Google search and see. If you didn't want to do that you'd have been welcome to email me and ask. I take some offense at the tone you took - as if I was hiding something in an effort to deceive my customers. Never!!

Electroharmonix (russia) has a winged C 6CA7 at tubes&more, don't know who is selling "SED" or where they come from.

Again, Google is your friend...

Electro-Harmonix is a long standing trademark of New Sensor Corp from New York. They used it on guitar effects pedals and similar items long before it was applied to any tubes. Electro-Harmonix (EH) tubes are made in the Xpo-Pul/Reflektor production plant in Saratov, Russia.

SED is the US trademark for tubes produced in the St. Petersburg, Russia plant owned and operated by the parent company - Svetlana Electronic Devices. Outside the US these tubes are called Svetlana, but because the rights to the Svetlana name is owned by another company (New Sensor) it can't be used in the USA. So in the US these tubes are referred to as "SED" or "Winged C".

The 6CA7 is not a "winged C" tube. It is made in the Saratov plant, not St. Petersburg.

BTW, New Sensor OWNS the plant in Saratov, as well as many widely known brand names such as:

Sovtek
Electro-Harmonix (EH)
Svetlana (for tubes distributed in the US only; these tubes are Saratov made, not St. Petersburg made.)
Mullard
Tung-Sol, and
Genalex Gold Lion

I think the implication in your post was uncalled for. People who know me can tell you that I am 100% above board in everything I do. Your post was inappropriate IMHO.

 

[indianajo]

I apologize. I didn't know you were in business. I wanted specific information, thank you, now I have it. Google searching doesn't help me much on where things come from, the level of expertise on this board is much higher than other places I have been. Wrong information is completely free. Triode & T&M are not entirely clear on the Sovtek/EH/winged C phenomenon and apparently the importer has changed the meaning of the names recently according to a deep page on T&M. I'd never heard of SED, GEC and Genelec mean to me GE of UK that quit making tubes in the seventies, I wanted some clarification of your abbreviations. If you had a FAQ on your website, a link would have been fine. Actually your post above should be a FAQ, it is extremely clear. 99.99 % of everything manufactured sold in the US comes from *****, I was looking for specific responses. I am too green purchasing tubes to match the abbreviated company names and the text on the website. If that was your website I looked at, do please have someone clean up & organize as time allows, I don't intend to wade through a lot of used tubes and outdated special offers to buy new ones.

 

[Jim McShane]

I apologize. I didn't know you were in business. I wanted specific information, thank you, now I have it. Google searching doesn't help me much on where things come from, the level of expertise on this board is much higher than other places I have been. Wrong information is completely free. Triode & T&M are not entirely clear on the Sovtek/EH/winged C phenomenon and apparently the importer has changed the meaning of the names recently according to a deep page on T&M. I'd never heard of SED, GEC and Genelec mean to me GE of UK that quit making tubes in the seventies, I wanted some clarification of your abbreviations. If you had a FAQ on your website, a link would have been fine. 99.99 % of everything manufactured sold in the US comes from *****, I was looking for specific responses. I am too green purchasing tubes to match the abbreviated company names and the text on the website. If that was your website I looked at, do please have someone clean up & organize as time allows, I don't intend to wade through a lot of used tubes and outdated special offers to buy new ones.

I'm sorry you find my site lacking. So I suggest you not bother with looking at it. FYI I've just started work with a great web designer to update and streamline my site. But I would suggest that even when it's done you don't bother looking at it.

I did a Google search for "Genalex Gold Lion made" - The 4th entry on the 1st page answered the question. Searching "Genalex Gold Lion tubes" gave the answer on virtually every page 1 entry.

BTW, I sell a LOT of used tubes, some go to some of the people here. Used tubes are great values in many cases. Who are you to say that because you don't want them that others shouldn't either??

Just a tip - if you need help, ask for help - don't come in here with guns blazing and expect a warm, friendly reception.