"Blues" Tubes, specifically EL37.

Over at another forum that I frequent, there's a question posed: "What's the best tube for Blues ?"

Now, given that you might be a fan of SRV / Strat type blues; Peter Green / LP type blues; or a myriad other "styles", that seems to me like a pretty far-ranging question.

However, the majority had it, that the KT66 is king. Personally, I like the warmth of the 6V6.

I once, stupidly, bought and sold a quartet of GEC KT66's, and rurned a nice profit. The last ones that have come up for auction on our Ebay equivalent sold for moon-money !

I have access to a couple of reasonably priced NOS Mullard EL37's, which are of course 6L6 / KT66 "family".

Do any of you have any experience with the EL37, and/or any comment to offer regarding similarity/difference vs. KT66 please ?

Since you asked for opinions....

If you prefer 6v6's use them. Must blues guys were gigging musicians who used whatever they could afford and I suspect 6v6's were a main dish, so to speak. Back in the day, you could get tubes in the corner drugstore and I suspect they used whatever was cheapest.

Default said:

Since you asked for opinions....

If you prefer 6v6's use them. Must blues guys were gigging musicians who used whatever they could afford and I suspect 6v6's were a main dish, so to speak. Back in the day, you could get tubes in the corner drugstore and I suspect they used whatever was cheapest.

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That little Silvertone 1482 with 6V6's sure does sound nice.

I'm curious to know about the EL37, cos my THD Univalve (single-ended) affords me the facility to try out a fairly wide range of power valves.

Hi Coastie; didn't find as much on the KT66 as the others. Pic below shows the pinouts for this family; all the same. As indicated here 6L6 v. 8417, provided the screen voltage is adjusted and except as discussed below, these tubes are - downwardly - interchangeable; tubes with higher plate ratings; KT66(EL37) and KT88 can go in lower powered 6L6 amps. As a point of reference, 6V6s typically operate at about 300v on the plates while the 6L6 / KT88s can handle 460-500v.



Based on a quick suvey of schematics at Free Info Society; Fender, Ampeg, Marshall, Hiwatt, Matchless and others; the KT66 is used much less frequently that the 6L6 / KT88 where the latter is strongly favored by the Audio types; Audio Reseach VT100, Conrad Johnson MV75, Dynaco Mark III although almost always with an expensive output transformer with an extra set of B+ taps for the screen supply; that is, the screen power is not taken directly from the power supply but instead from the OT.

A very rare Guild amp w/ 6550s belonging to BBer megadan embedded in the link - matsickma also has one of these infrequently seen animals; Megadan's 6550 amp, page 2

I'm a fan of the 6V6 because volume isn't an issue; I think that one of the reasons for the rise and reign of the 6L6 atop the commercial amp food chain is that it can be driven way up in power and volume before it breaks into distortion. Yes, you can get a 6V6 amp loud but, at some point, it's output gets raggedy. It's one thing for you and I to stand there, toe-tapping (with Heinies correctly positioned) and sounding pretty good but if Kurt or 'Frono came over and brought their pal the drummer along, they had a few Heinies too, the issue of volume is a little different.

One of the reasons for the 'Master' volume control on many amps is to allow the preamp/power amp to operate at saturation/distortion levels - levels reached by the 6V6 at '4' - and then turn the volume down so that the output is at a more listenable level or leave all the way up for large venues or overcoming raucous crowd noise, something that without a PA, the 6V6 can't do.

Like preferences in cheese, I like the warm, crunchy sound of 6V6s at '4' and because, to my ear, they sound better at '4' than they do at '8' while posing less risk of failure and domestic discord. But if you and I go on the NZ pub tour w/ 'Frono, we'd probably need 6L6 power:

Coastie to audience: "Ya know, if you chaps could keep it down a little, you'd be able to hear how cool my pair of 6V6s sounds"
Audience: "Cool this willya; just turn it up"

Volume: It's at least an explanation for how come so many biggies use other than 6V6s for live performances.

capnjuan said:

Hi Coastie; didn't find as much on the KT66 as the others. Pic below shows the pinouts for this family; all the same. As indicated here 6L6 v. 8417, provided the screen voltage is adjusted and except as discussed below, these tubes are - downwardly - interchangeable; tubes with higher plate ratings; KT66(EL37) and KT88 can go in lower powered 6L6 amps. As a point of reference, 6V6s typically operate at about 300v on the plates while the 6L6 / KT88s can handle 460-500v.

Based on a quick suvey of schematics at Free Info Society; Fender, Ampeg, Marshall, Hiwatt, Matchless and others; the KT66 is used much less frequently that the 6L6 / KT88 where the latter is strongly favored by the Audio types; Audio Reseach VT100, Conrad Johnson MV75, Dynaco Mark III although almost always with an expensive output transformer with an extra set of B+ taps for the screen supply; that is, the screen power is not taken directly from the power supply but instead from the OT.

A very rare Guild amp w/ 6550s belonging to BBer megadan embedded in the link - matsickma also has one of these infrequently seen animals; Megadan's 6550 amp, page 2

I'm a fan of the 6V6 because volume isn't an issue; I think that one of the reasons for the rise and reign of the 6L6 atop the commercial amp food chain is that it can be driven way up in power and volume before it breaks into distortion. Yes, you can get a 6V6 amp loud but, at some point, it's output gets raggedy. It's one thing for you and I to stand there, toe-tapping (with Heinies correctly positioned) and sounding pretty good but if Kurt or 'Frono came over and brought their pal the drummer along, they had a few Heinies too, the issue of volume is a little different.

One of the reasons for the 'Master' volume control on many amps is to allow the preamp/power amp to operate at saturation/distortion levels - levels reached by the 6V6 at '4' - and then turn the volume down so that the output is at a more listenable level or leave all the way up for large venues or overcoming raucous crowd noise, something that without a PA, the 6V6 can't do.

Like preferences in cheese, I like the warm, crunchy sound of 6V6s at '4' and because, to my ear, they sound better at '4' than they do at '8' while posing less risk of failure and domestic discord. But if you and I go on the NZ pub tour w/ 'Frono, we'd probably need 6L6 power:

Coastie to audience: "Ya know, if you chaps could keep it down a little, you'd be able to hear how cool my pair of 6V6s sounds"
Audience: "Cool this willya; just turn it up"

Volume: It's at least an explanation for how come so many biggies use other than 6V6s for live performances.

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Miami,

I agree with you entirely re. 6V6's. Less than half volume's about right, both with the Silvertone and Univalve. The Univalve, by the way, has a Hi V / Low V switch to accommodate the use of 6V6's and EL84's. And an adaptor of course to accommodate the EL84 pin-configuration. (Yellow Jacket)

Volume isn't an issue; I only noodle at home.

I guess I'm going to have to invest in those EL37's and try them out. After all, EC didn't get a bad tone out of his Marshalls with KT66's !

My god !

Imagine the hilarity of the Guild band on tour down under ! We could call ourselves "The G-Spots".
Not hard to imagine a Bob's Country Bunker scenario, wherein the band hoovers up all the beer and goes home broke !!

As a point of note. kt88/8550's are more akin to el34's the 6L6's. 8550's have a TON of clean headroom, think distortion @9 instead of 6 or 7. They aren't drop-in replacements for 6L6s. They were used in American market Marshalls for a while, because the failure rate on el34's were extremely high at the time.

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As a point of note. kt88/8550's are more akin to el34's the 6L6's. 8550's have a TON of clean headroom, think distortion @9 instead of 6 or 7. They aren't drop-in replacements for 6L6s. They were used in American market Marshalls for a while, because the failure rate on el34's were extremely high at the time.

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I have a couple of GEC KT88's, and TungSol 6550's which can be used in the Univalve, and they certainly do have a ton of clean headroom.
A VERY loud 15 Watts !

I'd love to swap the Celestion Blue that I have in the Silvertone, into the cabinet that I use with the Uni ( it has a Greenback in it ), but that seems to me a little risky.

For playing "da blues" around the house without shakin the pictures off the walls with a Twin, I have found that a modded Blues Junior is an excellent option. Most of the mods I have done can be found here:

http://home.comcast.net./~machrone/bluesjunior.htm

As stated in the site, if you never removed the circuit board from a BJ before, exercise care & patience or it gets expensive. Plastic tabs on fat switch also break VERY easily.

BD

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As a point of note. kt88/8550's are more akin to el34's the 6L6's. 8550's have a TON of clean headroom, think distortion @9 instead of 6 or 7. They aren't drop-in replacements for 6L6s. They were used in American market Marshalls for a while, because the failure rate on el34's were extremely high at the time.

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Yup; drop-in only in the physical, not electronic, sense and usually depend on 'ultra-linear' screen taps on the OT.

As far as I know SRV never used amps with KT66 nor EL37. In fact I cannot think of any blues players that are known to have used amps with EL37s. The EL37 is a true pentode and stays cleaner than a KT66; they can sound real nice, but are more associated with hi fi amps than guitar amps. They were only made in European plants operated by Phillips and haven't been made in a long time.
The only production guitar amps I know of that came with EL37s were made by Ampeg for a while in the late 50s/very early 60s; the EL37 was their higher powered tube instead of 6L6GC, etc, before they went to 7027 and 7591s.

teleharmonium said:

As far as I know SRV never used amps with KT66 nor EL37. In fact I cannot think of any blues players that are known to have used amps with EL37s. The EL37 is a true pentode and stays cleaner than a KT66; they can sound real nice, but are more associated with hi fi amps than guitar amps. They were only made in European plants operated by Phillips and haven't been made in a long time.
The only production guitar amps I know of that came with EL37s were made by Ampeg for a while in the late 50s/very early 60s; the EL37 was their higher powered tube instead of 6L6GC, etc, before they went to 7027 and 7591s.

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Thanks TH; that's very useful information.

Doesn't sound to me like I need any EL37's !
I could kick myself for selling the KT66's that I had. Early, grey glass GEC's !

You're very welcome Coastie.

Old KT66 are nice tubes indeed. I run a pair of those in an old Grampian PA head which has been revoiced a little for guitar and puts out only about 12 watts due to cathode bias, a simple low gain preamp, and an EZ81 rectifier giving lower voltage than you would need to get the most power out of those tubes. I would like to get some other amp in that configuration but without the noise issue, since I really like the sound and the compression.

I also run EL37s in a Grampian Vibromajor head, which is interesting, but noisy, and can't really be fixed without basically redoing the whole grounding scheme (which is more of a modification than I care to have done to a scarce old amp). I've tried EL37s in a couple other amps as well, and have consistently found them to have very nice clean sounds but not my favorite kind of distortion. They sounded kind of wrong in my Selmer Zodiac, in a way which is hard to describe; for some reason that amp only sounds right to me with RFT/Siemens EL34s and a Mullard GZ34, which is a somewhat dangerous combination in that amp with the stepup transformer I must use.

teleharmonium said:

You're very welcome Coastie.

Old KT66 are nice tubes indeed. I run a pair of those in an old Grampian PA head which has been revoiced a little for guitar and puts out only about 12 watts due to cathode bias, a simple low gain preamp, and an EZ81 rectifier giving lower voltage than you would need to get the most power out of those tubes. I would like to get some other amp in that configuration but without the noise issue, since I really like the sound and the compression.

I also run EL37s in a Grampian Vibromajor head, which is interesting, but noisy, and can't really be fixed without basically redoing the whole grounding scheme (which is more of a modification than I care to have done to a scarce old amp). I've tried EL37s in a couple other amps as well, and have consistently found them to have very nice clean sounds but not my favorite kind of distortion. They sounded kind of wrong in my Selmer Zodiac, in a way which is hard to describe; for some reason that amp only sounds right to me with RFT/Siemens EL34s and a Mullard GZ34, which is a somewhat dangerous combination in that amp with the stepup transformer I must use.

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The Trademe (NZ Ebay equivalent) price of KT66's has rocketed recently. Most recently a quad of NOS GEC's sold for US $695 and change, probably not a bad price by US standards.
Coincidentally lately, there have been several sales of old Quad hi-fi amps.
Seems reasonable to assume that the two events are linked.

A few years ago, I befriended an old fella (since died) who had a huge stash of NOS and used valves. He'd already been visited by some bludgers who had helped themselves to some of his stuff, but there was still some treasure left. He offered me the lot for NZ $100, but I wanted him to benefit from their sale. There was lottsa common, low-value stuff, but amongst the stash were 5 NOS Mullard EL37's. We agreed that I'd take any used, or un-boxed stuff that I fancied. I got US $1700 for him, and I ended up with a heap of unboxed RCA 6G6G's and Mullard and Telefunken ECC 83's, among other guitar-relevant bits and pieces almost all of which tested "new".
Everybody was happy; US $1700 was then worth about NZ $2300, and I got myself a nice stash. Pity that I didn't keep one of those EL37's though !