View Full Version : Choices of 7591 tubes


DENNYDOG
01-21-2008, 08:31 PM
I am trying to make a decision on whether to put new 7591's in my Fisher 500c or try to find a nice quad of NOS tubes.

I've heard the new JJ's have been prone to failure so I don't like the idea of using them.

I've heard the EH's are too tall to fit inside the cabinet so they will not work.

I talked with Mark Wilson of Absolute Sound Labs when I dropped it off for him to do the restoration. He recomended that I try some Svetlana's. I guess this is what MacIntosh puts in some of their new amps so they must be pretty good. He didn't know how tall they are so he couldn't say for sure whether they were going to fit either. Has anyone else used the Svetlana 7591's?

Here is an article on the new Svetlana EL34's. It sounds like they are a much better tube than the Sovtek's.

http://www.tnt-audio.com/clinica/ta/svetlana_e.html

Or would it be better to try and find a quad set of NOS tubes?

Any opinions and recomendations are welcome.

Thanks,
Dennis

Sonytubes
01-21-2008, 08:40 PM
Ask Doug's tubes.com

I have bought tubes from him and he tests each one personally. Burns them in when called for.

NOS tubes are expensive and you are lucky if you find a true matched quad.
ebay used tubes are a crap shoot.
What is wrong with your current tubes? They ought to last fairly long (NOS).

I use the EH but ones from about 3-4 yrs ago. Good sound, good bass, taller than the NOS.
Some people claim they drift from spec with time. I also have NOS on other amps.

ask Doug for the dope on the latest production qualities.

Fred Longworth
01-21-2008, 08:41 PM
About four years ago, Antique Electronics sent me a memo indicating that rights to use the name Svetlana had been "removed" from the St. Petersburg factory and "reassigned" to Sovtek, thus making Svetlana simply another marketing name for Sovtek tubes. The St. Petersburg factory would continue to market their high-quality tubes under the named Winged-C.

I'm sure there's a great deal of back-story that the memo didn't touch on, but I immediately began ordering Winged-C tubes instead of Svetlana.

However -- and this is a big however -- that was four years ago, and the Russian industrial sector is highly volatile. It may be that things are entirely different in 2008 than they were in 2003-4.

As for the JJ's, I have stopped ordering JJ tubes totally, due to consistently low quality. I wish that Groove Tubes made 7591's, because Groove Tubes along with Winged-C are fine things.

Best,

Fred Longworth

jaymanaa
01-21-2008, 09:04 PM
All I know about 7591s is that Sylvania and Westinghouse sound very good in my Fisher KX200, and NOS RCAs didn't sound good at all.:thumbsdn: I'm a big RCA fan too, and got a beautiful quad, but they just didn't sound good at all.:dunno: I just used some 7868 EHs in a Sherwood and was VERY pleased with them. I think overall, I would choose EH over JJ about 90% of the time.:thmbsp:

Cut-Throat
01-21-2008, 09:04 PM
I am trying to make a decision on whether to put new 7591's in my Fisher 500c or try to find a nice quad of NOS tubes.

I've heard the new JJ's have been prone to failure so I don't like the idea of using them.

I've heard the EH's are too tall to fit inside the cabinet so they will not work.

I talked with Mark Wilson of Absolute Sound Labs when I dropped it off for him to do the restoration. He recomended that I try some Svetlana's. I guess this is what MacIntosh puts in some of their new amps so they must be pretty good. He didn't know how tall they are so he couldn't say for sure whether they were going to fit either. Has anyone else used the Svetlana 7591's?

Here is an article on the new Svetlana EL34's. It sounds like they are a much better tube than the Sovtek's.

http://www.tnt-audio.com/clinica/ta/svetlana_e.html

Or would it be better to try and find a quad set of NOS tubes?

Any opinions and recomendations are welcome.

Thanks,
Dennis

I don't think there is such a thing as a Svetlana 7591:no:

Sonytubes
01-21-2008, 09:10 PM
Fred is correct about the Rusian volatile market, that is why you ought to ask Doug for the dope on current stuff.
My EH 7591 quad is from about 4 yrs ago and are very good.
My last purchase about a year ago was winged C 6L6GC matched quad.
Did not need them but foresaw a possible change in venue so I grabbed while I could.

DENNYDOG
01-21-2008, 09:25 PM
I don't think there is such a thing as a Svetlana 7591:no:

I haven't been able to find any information on any. Mark said MacIntosh puts rebadged Svetlana's in their amps.

I'm not sure if Mac even makes any new amps that run a 7591 though.

jaymanaa
01-21-2008, 10:00 PM
Here's what Mr. McShane says


Genuine 7591A Electro-Harmonix tubes are in stock! $21.00 each single, $42.50/matched pair, and $79.50/quad.
Here's a typical customer comment... "I put the EH 7591's in my Pilot SA-264 power amp. Set the bias and let
'em cook a while. Then I listened. I was really surprised. They sound like the real thing. What a sweet sounding
amp that is."

Important note! There have been some cases where the new production 7591A tubes (EH and JJ) have had trouble
in circuits using a very high value grid resistor - as vintage Scotts, Fishers, and others do. The best solution is to change
all the grid resistors to 180K-200K (from the old value over 300K - sometimes they even exceed the old RCA tube manual
recommendation!), and change the coupling caps to .1 uf or .22 uf. I stock all the parts you need, the parts cost is only
$10.00 to $15.00 per amp, depending on the coupling cap value and voltage.

Click here for a look at a typical 7591 output circuit. Resistors R129 & R130 and caps C87 & C88 in the outlined
boxes are what may need replacement.

smollett5
01-21-2008, 10:07 PM
I've tried the ElectroHarmonix version of the 7591A and I had extremely poor results with them. Consequently, I only use NOS 7591As, most often Sylvanias, but also occasionally GEs, Westinghouses, and other branded tubes, in my McIntosh MC225, Fisher 500-B & C, and KX-200.

With a 500-C, why skimp if you can afford to buy the real thing?

DENNYDOG
01-21-2008, 11:01 PM
I've tried the ElectroHarmonix version of the 7591A and I had extremely poor results with them. Consequently, I only use NOS 7591As, most often Sylvanias, but also occasionally GEs, Westinghouses, and other branded tubes, in my McIntosh MC225, Fisher 500-B & C, and KX-200.

With a 500-C, why skimp if you can afford to buy the real thing?

Agreed. I would say that to be true of any amp though.

Thanks to everyone for the help,

Dennis

drewbolce
01-22-2008, 10:22 AM
There is no doubt the JJ's have quality problems. I have had them fail in circuits with 200k resistors and individual bias controls. No doubt it was the tube. They also are consistently weaker than the EH's or NOS.

The EH's compare in power with the NOS I have seen, however, I have not had a real "New" NOS. Let me know when someone gets a quad of real NOS. I haven't seen one yet.

I believe the reason Fisher put in the 330k over spec resistors was to use a cheaper coupling cap. It stands to reason that if they were so cheap that they would put in a 600v and a 400v on a PP pair then they would cook the output tubes so they could downsize from a 0.1uf to a 0.047uf coupling cap.

I always use 600+v 0.1 uf coupling caps with 200k resistors.

If you do the resistor mod, add individual bias controls and have a 5-7pf cap on pins 2 and 7 of the phase splitter, you should not have any problems with the EH's.

They do fit in the stock cabinet. However, you must remove them, put the chassis in cabinet and then reinstall them (in the correct order). No big deal in my book.

Cut-Throat
01-22-2008, 10:26 AM
There is no doubt the JJ's have quality problems. I have had them fail in circuits with 220k resistors and individual bias controls. No doubt it was the tube. They also are consistently weaker than the EH's or NOS.

The EH's compare in power with the NOS I have seen, however, I have not had a real "New" NOS. Let me know when someone gets a quad of real NOS. I haven't seen one yet.



I'd say this auction (http://cgi.ebay.com/Sleeve-of-5-Sylvania-7591a-7591-A-Tubes-NIB-NOS-Tested_W0QQitemZ230212272119QQihZ013QQcategoryZ678 16QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) that just ended, the buyer truly got some NOS 7591s.

http://i24.ebayimg.com/02/i/000/d1/f3/2387_1.JPG

drewbolce
01-22-2008, 10:35 AM
I'd say this auction (http://cgi.ebay.com/Sleeve-of-5-Sylvania-7591a-7591-A-Tubes-NIB-NOS-Tested_W0QQitemZ230212272119QQihZ013QQcategoryZ678 16QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) that just ended, the buyer truly got some NOS 7591s.



I am not so sure. There isn't a picture of the tops of the tubes. On Ebay I look for what isn't there.

ehoove
01-22-2008, 11:16 AM
:lurk:

bricktop
01-22-2008, 11:35 AM
One would think that a company could simply break open one of those and copy it piece by piece. I have a hard time believing there are still patents on these... I'm sure it is a little more involved, but to a major company, what of it?

I'm fixing up an LK-72, and bought an EH quad, I hope they sound ok...:worried:

FalconEddy
01-22-2008, 11:35 AM
I've been the route of new production 7591's (JJ). Never again.

Those of you that have had a good track record with them, I'm happy for you.

However, I'm back using 1962 NOS Westinghouse 7591's, 1965 Sylvania 7591A's, and 1966 GE 7591A's. Even used 7591's that are older production (pre 1970's) appear to have better performance and longevity than the new production power tubes.

YMMV.

. . Falcon

drewbolce
01-22-2008, 12:25 PM
One would think that a company could simply break open one of those and copy it piece by piece. I have a hard time believing there are still patents on these... I'm sure it is a little more involved, but to a major company, what of it?

I'm fixing up an LK-72, and bought an EH quad, I hope they sound ok...:worried:

There's a lot more to it. Materials, coatings, manufacturing tooling and techniques, etc. I agree all of the patents are long expired. But so have the people with the knowhow.

I did a little research into EH when the Russian mob was trying grab the factory (talk about a real hostile takeover). Definitely not a major company. Just a guy who made some money in the music business and now is following his passions.

bricktop
01-22-2008, 12:53 PM
I wish China would make 7591s so we hifi-ers had another option, then maybe JJ would pick up the QC. China seems to make form-fit-function tubes that work OK. KT66 and 12AX7 are a few examples, I know they do not have the longevity of the NOS types, but they are reliable and sound decent (at least to me, ymmv). Maybe since the 7591 was a tube exclusively made in the US (is this right? i can't find any foreign types minus current productions), the tube construction data never clearly made it to the current companies, and they simply made something up to mock the curves.:dunno: At any rate, the current situation on these tubes sucks, I wish there were JJ/EH business-reply-mail comment cards in every tube box:scratch2:

jaymanaa
01-22-2008, 06:58 PM
Who's making the new GEC KT88 (they're supposed to be better than the real thing)? I want to say new sensor but I'm not sure. Point is that there are some damn good tubes being made today and it's a shame that one of the good companies isn't making 7591s. RCA basically listed it as an audiophile tube back when, which I always thougth was pretty impressive. What is the story on new sensor? Are they making tubes? I think they are making the new TungSol 12AX7 that I'm converting to. I was looking for a good AX7 for folks that want all new stuff in their amps so I tried one and wow, what a tube. Big fat plates that make killer bass, smooth mids, and shimmering highs. I like it.:yes:

fsjonsey
01-22-2008, 07:41 PM
I can attest to the poor quality of the JJ 7591. I've had to return multiple quads over the last two years, being used in two different amps. Most failed within hours of their first use. I started using the EH '91a and havent looked back. The JJ's are just shoddy all around. Loose bases, crooked bottles that look ridiculous , and very shoddy internal construction. These tubes make Shuguang look like Mullard in terms of build quality.

Cut-Throat
01-22-2008, 07:43 PM
These tubes make Shuguang look like Mullard in terms of build quality.


I have had very good luck with Shuguang.

DENNYDOG
01-22-2008, 11:45 PM
Well I bought the quad of Eico/Westinghouse that just ended on ebay. The horror stories with some of the new tubes scared me off from that idea.

I'll let everyone know how these work out for me once I get my Fisher back from the restoration.

Thanks again for everyones input.

Dennis

jaymanaa
01-23-2008, 05:24 AM
I think you made a good choice Denny. With all the trouble we go through to get these old amps up and running, a couple hundred for trouble free tubes that sound good, is really pretty cheap.:thmbsp:

FalconEddy
01-23-2008, 09:50 AM
Well I bought the quad of Eico/Westinghouse that just ended on ebay. The horror stories with some of the new tubes scared me off from that idea.

I'll let everyone know how these work out for me once I get my Fisher back from the restoration.

Thanks again for everyones input.

Dennis

I just checked out that quad of Westinghouse 7591's. I was surprised to see both the date (end Feb-beginning Mar '67) as well as double getters on a Westinghouse produced 7591, at such a late date in the 60's. I've only seen this a few other times, with dates between '65 and '68, and they were only single tubes; not a complete quad. Great find!

The vast majority of 7591's being produced by that point in time (by Sylvania and GE) were the 7591A's who's new design had rotated the plates to basically reduce noise between pairs that were mounted in very close proximity.

. . Falcon

fsjonsey
01-23-2008, 10:40 AM
Who's making the new GEC KT88 (they're supposed to be better than the real thing)? I want to say new sensor but I'm not sure. Point is that there are some damn good tubes being made today and it's a shame that one of the good companies isn't making 7591s. RCA basically listed it as an audiophile tube back when, which I always thougth was pretty impressive. What is the story on new sensor? Are they making tubes? I think they are making the new TungSol 12AX7 that I'm converting to. I was looking for a good AX7 for folks that want all new stuff in their amps so I tried one and wow, what a tube. Big fat plates that make killer bass, smooth mids, and shimmering highs. I like it.:yes:

New Sensor is producing the GEC KT88's at the reflektor plant in Russia.

ccheath
01-23-2008, 10:57 AM
I wonder if JJ is the reason why my Fisher 400 with 4 old tubes measured "BAD" has alot of bass than my 500c with 4 JJ tubes. My 500c sounds good but gutless compared to 400. Right now 500c has 1 shorted tube.

smollett5
01-23-2008, 09:06 PM
For all the reasons I do not use newly manufactured "7591As", I also only use NOS or good used, USA-made 7868s in my two Fisher 400s. They both sound great.

I believe that original 7591A tubes were only manufactured in the US. I have a NOS quad of Philips-branded, coin-based 7591As bearing the USA legend.

MrZero63
02-04-2008, 08:38 PM
The JJs sound great to me - for about 12 hours, then they either go bad or get noisy. Not good. :thumbsdn:

fsjonsey
02-04-2008, 08:47 PM
I think that the reason so many fisher amps are turning up with fried output transformers is due to people trying to use weak 7591's that have long outlived their service lifespan. I'd rather use the EH tubes than take a chance on questionable "NOS" 7591's from ebay.

sleddogman
02-04-2008, 09:59 PM
That 5 pak of Sylvannias at $25 a piece was a GOOD deal. I've run across a few folks who have put up the old bulk paks like that and have picked up a 5 pak of new GE labeled xf2 Mullard EL34s and 5 pak of new GE 6L6CGs. So far they've all been as healthy as horses.

John L
03-19-2008, 09:32 AM
I'm getting my Sansui 1000A back in a few days, and the tech says I need to perhaps replace the 7591s, because one channel is louder than the other. It's nothing serious, but I am beginning to worry about replacements.

I also checked out the Chinese tube maker, and they don't produce 7591 series trubes, from what I can see.

But let's recap. Are we all agreed that the Electo-Harmonix beats the JJs? If so, I will consider them first for new stock.

I have gone to Parts Express catalogue and they do not sell JJs 7591 tubes. Perhaps there is a reason for this? But they do sell Sovtek and Electro-Harmonix.

The Sovtek is a 7591XYZ tube. Does anyone know what the XYZ stands for?

If you purchase them in a matched quartet (http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=072-354&FTR=072-354&CFID=6765563&CFTOKEN=76816040), they are only $41.14. If you purchase them as a single tube (http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=072-350&FTR=072-350&CFID=6765563&CFTOKEN=76816040), they are only $8 each.

E-H sells the 7591A EH tube. Does anyone know what the EH stands for?

The E-H tubes are more expensive. If you purchase them as a matched quartet, (http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=072-854&FTR=072-854&CFID=6765563&CFTOKEN=76816040) they are $93.60. If you purchase them as a single tube, (http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=072-850&FTR=072-850&CFID=6765563&CFTOKEN=76816040) they are $21.00 apiece.

Damn!, quite a difference in price. The Sovtek tubes have dropped in price from the present catalog, and the E-H have gone up quite a bit. I was totally surprised with this. I wonder why this has happened?

Let's say you purchase tubes from PE, and they don't pan out, you can always return them for an exchange, right? Wouldn't it be better to buy from a souce that will refund/exchange any bad tubes? I would think so.

Comments?

bricktop
03-19-2008, 09:37 AM
Might want to check all the important resistors in the amp to see if any have drifted before buying tubes. If some plate, cathode, or feedback resistors have went out of spec, that can cause channel imbalance as well.:thmbsp:

Just reread and see the tech has it. Hopefully he has already done this:D

John L
03-19-2008, 10:54 AM
Might want to check all the important resistors in the amp to see if any have drifted before buying tubes. If some plate, cathode, or feedback resistors have went out of spec, that can cause channel imbalance as well.:thmbsp:

Just reread and see the tech has it. Hopefully he has already done this:D

He has.

Do you have any idea as to why the Sovtek tubes, at PE, are so inexpensive? for $8 each, that is worth trying out just to see if they work well, I would think.

Also, what does the "XYZ" and the "EH" stand for? Are they new series tubes?

I'm just full of all sorts of questions here.:D Soooo, here is another one: does anyone here have a tube tester, and how well do they work in measuring the tubes?

andy
03-19-2008, 11:39 AM
He has.

Do you have any idea as to why the Sovtek tubes, at PE, are so inexpensive? for $8 each, that is worth trying out just to see if they work well, I would think.

Also, what does the "XYZ" and the "EH" stand for? Are they new series tubes?

I'm just full of all sorts of questions here.:D Soooo, here is another one: does anyone here have a tube tester, and how well do they work in measuring the tubes?

I believe the 7591XYZ is really just a 6L6 with a 7591 pinout. It requires significantly more negative bias than the real 7591. These were made several years ago, before real 7591s became available. They're cheap because they're old stock that they want to get rid of.

I doubt bad output tubes could cause one channel to be quieter than the other. Less power, and more distortion, sure, but not lower volume unless they were almost dead.

Steve O
03-19-2008, 11:49 AM
He has.

Do you have any idea as to why the Sovtek tubes, at PE, are so inexpensive? for $8 each, that is worth trying out just to see if they work well, I would think.

Also, what does the "XYZ" and the "EH" stand for? Are they new series tubes?
I'm just full of all sorts of questions here.:D Soooo, here is another one: does anyone here have a tube tester, and how well do they work in measuring the tubes?

The 7591XYZ is really just a Sovtek 5881/6L6WGC with revised pinout to fit a 7591 position. Bias and drive reqmts are quite a bit higher for the XYZ compared to real 7591. The XYZs were a New Sensor stopgap measure from years ago until "real" 7591 types were back in production. There is little demand for them now, thus the low price. Personally, I wouldn't bother with them. If new mfg is what you want, the 7591EH is probably the best choice although the envelope is much larger than old 7591 and barely fits into many Fisher apps. You probably should also reduce grid resistor value as described on Jim McShane's site. The "EH" stands for Electro Harmonix, a brand name.

All things considered, my first inclination would be to obtain NOS 7591s or, if you trust the seller, good/used.