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What's the current thinking on 7591's?

Naptown Rob

Naptown Rob

Ponographer
I've recently pressed my long dormant Fisher 500C back into service. I've rolled all the tubes I want into the phono, preamp & phase positions, but I'm wondering what the current landscape of output tubes looks like. I'm running Electro Harmonixes now & I'm thinking I could do better without mush of an investment.
What's your experience folks?
 
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To the thread title; "What's my quickest easiest way to earth?"

I'm not up on modern 7591s, but rather like EH7868s. I wonder if they use the same guts?
 
Rob,

You are good on play on words titles .. "Current" I get it :)

EH's all the way as IMHO everything else is playing with fire literally.

But if you can be patient you could get a quad of matched up NOS Westinghouse 7591's and be done with it for life for 100.00.

Frannie
 
Hiya,

The old stock tubes sound slightly better than EH but it aint worth the price
Click to expand...

I have to disagree on the following criteria.

The old ones do sound better and they are more durable to boot. The NOS ones are typically about 2 to 3 times as much to be sure and there is zero debate about that criteria.

But the NOS tubes will last much longer in typical use. Meaning 10 to 20 hours a week of usage.

I figure as much as eight to ten times more life.

So they are more economical over a lifetime.

That being said and I may have opened a can of worms the newer tubes are catching up albeit slowly.

Frannie
 
Yeah but the EHs glow blue at night.

If you change the grid bias resistors to 180k to 220k and bias the EHs around 34, they'll last a long time and they sound very good. They fit in the Fisher receivers. Jim McShane sells matched pairs or quads. He tests the heck out of them and his are well matched and behaved.

As far as getting NOS old stock, good luck with that and having them be under $200.
 
Don,

If you change the grid bias resistors to 180k to 220k and bias the EHs around 34, they'll last a long time and they sound very good. They fit in the Fisher receivers. Jim McShane sells matched pairs or quads. He tests the heck out of them and his are well matched and behaved.
Click to expand...

Yep hard to debate that.

Not like I have piles of NOS 7591's laying around.

But Rob has EH 7591's already.

He was wondering about others ..

Frannie
 
I've purchased 20 vintage 7591's over the last eight years. I was able. To get two matched quads out of the bunch. My McShane matched EH 7591's are going on four years of Fisher X 101 B abuse. I don't plan on buying any more vintage.
 
Thanks to all. I think I'll live with the EH's for now while keeping an eye out for older tubes at reasonable prices. Something about the bottom end just isn't clicking for me. Perhaps experimenting with the placement of some of the small signal tubes (currently a mixture of 12ax7, 7025 & 5751's) will..umm...rectify that situation...

I will say, I'm being picky. Currently listening to some Brubeck (went to see Silver Linings Playbook with the wife today & Unsquare Dance on the soundtrack perked my ears) and anybody who wasn't being hypercritical would say it sounds awesome.
 
Naptown Rob said:
Thanks to all. I think I'll live with the EH's for now while keeping an eye out for older tubes at reasonable prices. Something about the bottom end just isn't clicking for me. Perhaps experimenting with the placement of some of the small signal tubes (currently a mixture of 12ax7, 7025 & 5751's) will..umm...rectify that situation...

I will say, I'm being picky. Currently listening to some Brubeck (went to see Silver Linings Playbook with the wife today & Unsquare Dance on the soundtrack perked my ears) and anybody who wasn't being hypercritical would say it sounds awesome.
Click to expand...

Rolling preamp tubes is huge for performance. I transformed my very good sounding Fisher 400 into a great sounding Fisher 400. Tubes cost a lot though. :D
 
One thing of note, there are grid resistors on the output tubes that need changing to keep the EH tubes from self-destructing. When that happens, the coupling cap values also need to change to keep it from rolling the bottom end off too much. Possibly worth a look to see if that wasn't done with yours.
 
Rob,

I've been 'messing' with several different 7591 amps of late, and doing the same with a number of different sources of 7591 tubes. I began this process with a couple of sets of JJs 7591s.......and as far as use in the 500C, I received a number of posts from people advising against this.....due to perceived weakness in that tube. The EH tubes, on the other hand, got pretty high marks from most responses. It's been about 6 months of playing around now.......and amps included a pair of 500Cs, and 800, several Scott 299s and 233s, and a rather odd 'clone' of a 500C power amp section built on a Dynaco ST-70 chassis. After some very frustrating evenings.......and a few rather rewarding ones.......I will tell you that almost without exception, EVERY amp sounded better with some of the old OE tubes. I found that even some old US tubes that tested 'weak' on my Hickok 6000A STILL had some amazing sound! Pushing them to high volume levels revealed their weakness.....but at 'normal' listening levels....they were simply MUCH better to my ears. If you'd like, you're more than welcome to invite yourself over some evening and play 'swap-about' with some of these yourself. I currently have one of the 500Cs still in line with the Forte IIs. Bring some CDs of your choice and see what you think. BTW, if you can find a good quad of these for $100........you should buy them! That sounds like a 'friends n family' deal! I'm thinking more like $160 for 4 of them.....and that's not necessarily very well matched.......just 'good'. Does your 500C have the IBAM Mod? If not....you're buddy Larry can probably get that done for you. I don't know but what maybe Frannie also does that kind of thing for others in the area. But......this is just my 2 cents worth....... Tom D.
 
buglegirl said:
Hiya,



I have to disagree on the following criteria.

The old ones do sound better and they are more durable to boot. The NOS ones are typically about 2 to 3 times as much to be sure and there is zero debate about that criteria.

But the NOS tubes will last much longer in typical use. Meaning 10 to 20 hours a week of usage.

I figure as much as eight to ten times more life.

So they are more economical over a lifetime.

That being said and I may have opened a can of worms the newer tubes are catching up albeit slowly.

Frannie
Click to expand...
2 or 3x better? I don't think so but they are better thou. Your logic on buying the old stock and because they last longer overtime compared to the newer ones is a good one/true I didn't think about that one when I was compiling my data. Hopefully I come across some old stock during some tag sale thou :)

For everyones info I originally had JJ in my fisher 800c than switched to EH than to old stock.
 
I've been successful at using EH 7591s in receivers and not looking back.
I save the small bottle ones for integrated amps.
I'm picky about my sound too.
Preamp tube rolling and output coupling cap rolling makes far more difference than the output tube formulation in these Fishers.
 
Hiya,

2 or 3x better? I don't think so but they are better thou.
Click to expand...

No I meant 2 to 3 times as much as in cost .. I see where the sentence leads down the "Blond" path .. So sorry :)

What is better "Sounding" than another is too subjective for me to step into.

FYI I am not dissing new production tubes I hope people understand.

But if I am reading things correctly here you have to "Dial" back bias to make the EH tubes last longer right ???

Frannie
 
buglegirl said:
Hiya,



No I meant 2 to 3 times as much as in cost .. I see where the sentence leads down the "Blond" path .. So sorry :)

What is better "Sounding" than another is too subjective for me to step into.

FYI I am not dissing new production tubes I hope people understand.

But if I am reading things correctly here you have to "Dial" back bias to make the EH tubes last longer right ???

Frannie
Click to expand...

Sometimes I am blond when I wear my wig. But yes you need to dial back the bias on the newer tubes... I did on my older old stock thou because I heard it will make it last longer so might as well.
 
Don,

You know I have the greatest of respect for your opinions. So, for me to offer anything that may 'appear' as 'contrary' is almost painful for me. But, in the interest of 'discussion only'.....I've had almost the exact opposite experience with my 'testing' in my 2 Fisher 500Cs, the one 500B, and the 800. For me, it was the output tubes making almost all the difference, with the pre-amp tubes making little to no discernible difference. Because the units take so many 12AX7s to be functional......I ordered 30 of the Chinese 12AXs from CEDist. I then did a LOT of rolling between amps.....including the use of the old Teles, some British Mullard and Ampex tube.....and of course, some old US types. In the end, I was hearing a more 'brittle' or 'harsh' sound from use of JJ outputs, less so with the EH, and essentially NONE of that condition from old US 7591s. The 12AXs seemed to make little difference during my testing. HOWEVER, I will also note that ALL 12AXs used were either VG if old......or were NEW versions of the Cino tubes. Honestly.......I was not only surprised....but somewhat delighted. I then turned to putting some of these Chinese tubes into the integrated amps I had and I found similar results. To me, this may reflect a change for the good in the Chinese 12AX7s.......as a decade ago I would not have even attempted this test due to the poor quality of these tubes. Further, I'm a dyed-in-the-wool patriot......and use of NON-US stuff is REALLY difficult for me on general principle. But, sometimes 'economics' necessitates compromise......so I gave these things a try.....and with very satisfactory results. Now, one comment would be that of the 30 I've ordered, 3 have failed due to cracks in the glass by the pins. So, figure that into the mix. CE replaced these at NC to me......but still....that's a 10% failure ratio....which is HORRIBLE by most any production standard! But, still, figuring the cost/tube vs projected acquisition cost of 30 US or Euro tubes, and then consider the performance to be 'ok' at worst......and it becomes rather compelling. Anyway......if Rob decides to make it over here.....I'll let him do some rolling as well and see if he agrees. Tom D.
 
Well one thing is for sure: when you start messing around with rolling tubes in a 500C it's not long before you with your beautiful cabinet had a flip up top...
 
Hiya,

Well one thing is for sure: when you start messing around with rolling tubes in a 500C it's not long before you with your beautiful cabinet had a flip up top...
Click to expand...

I run mine without the Cabinet .. projects a light airy feel .. OK I am being silly ..

Sorta ..

Frannie
 
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