Ken Fox- tube question

Curt Langston · Posted 16 Dec 2005 5:40 am

Hi Ken. I have a Carvin X-60 amp that I would like to use as a steel amp. It stays really clean and clear at loud volumes, however it is about time to chang tubes. What tubes would you recommend, for the cleanest, warmest sound. A Groove Tube dealer/tech recommends this:

quote:
Curt, The EL34LS are pretty good (as far as EL34's go.... no where as clean as 6L6's IMHO) I stock #5 ratings becuse they seem to my ears to have the best overall performance... still warm (not harsh) and break up pretty late in the game... for preamp tubes, my manual states 3 tubes... i would put a 12AY7 in postion 1 to reduce first stage gain (cleaner), i'd put an ECC83 in postion 2 (very linear & bright) and a 12AT7-MPI in postion 3 (matched phase inverter). The 12AT7 handles more current and is cleaner than the 12AX7-MPI... that's my recipe.... (you can find all of them on my eBay store... if you do buy all 5 tubes, tke a $5 discount on the PayPal screen... i'll ship for free)
Regards,
Rick

Ken would you agree, or what would you do?
Thanks for your input. I appreciate it very much. Tubes are costly, and I want to make an informed decision!

[This message was edited by Curt Langston on 16 December 2005 at 05:41 AM.]

Ken Fox · From: Nashville GA USA

I do not know the amp at all! Sounds a sif he is very knowledgeable. I do prefer JJ tubes. If you want, you can get them at tubesandmore.com. I have never had an issue with Groove tubes, just never used them! JJ tubes are the most durable I have used in my repairs. I quit using NOS American tubes due to issues with microphonics. I have been very pleased with the consistency of JJ/Telsa products. Hands down they have the best 6V6 and 5AR4/GZ34 tubes I have seen. I prefer the preamp tubes for their darker tone, more like the old RCA I used to use (less the microphonics). The 6L6GC tubes will habdle even the most extreme plate voltages, such as Musicman and the Fender amps with the ultralinear output trnasformers(late 70's and early 80's)!

Curt Langston · Posted 16 Dec 2005 6:06 am

Ken,can the 6L6's be used in place of the EL34's....Thanks again.

Ken Fox · From: Nashville GA USA

I would not do it without checking the pinout and see if rewiring and rebiasing would be required. I would proceed cautiously as it is not a listed sub for the 6L6GC tube. Plate load impedance and more must also be considered.

6L6-GC Pinout

6L6-GC Substitutes
Close or identical STR387, STR415, SV6L6GC
Different rating or performance 6L6, 6L6G, 6L6GA, 6L6GB, 6L6GT, 6L6WGA, 6L6WGB, 6L6WGC, CV1286, CV1947, CV1948, CV586, EL37, VT115, VT115A
Different pinout 5B245M, 6BG6, 6BG6G, 6BG6GA, 807, 807W, ATS25, ATS25A, CV1060, CV124, CV1364, CV1374, CV1572, CV2796, CV2817, CV3618, CV3809, CV428, QV0525, VT100, VT100A, VT60(RAF), VT60A(RAF)
Different filament voltage 19BG6G, 19BG6GA

Warning: Substitutes are given as a guide only - please refer to original manufacturers data sheets to ensure that a substitute is safe and appropriate for your application.

Close or identical CV1741, EL34G, EL34WXT
Different rating or performance E34L, E34LS

http://tdsl.duncanamps.com/tubesearch.php

Ken Fox · From: Nashville GA USA

E34L-JJ Matched Pair JJ/Tesla

Plug-in compatible with any EL34, but has slightly different parameter. Top choice amongst guitar player including Yngwie Malmsteen for clean yet thick tone. Excellent in audiophile applications with smooth but strong low mids. Price is for a matched pair.

Ken Fox · From: Nashville GA USA

Some more good reading from the net:

EL34, 6550, KT88, KT66, 6L6GC and 6V6 are all the same pinout (called "octal base"). They're swappable to some extent, they have WILDLY differing performance characteristics and major internal adjustment (rebiasing) is needed. In some cases they're fully incompatible. All these tubes use the same socket.

Geek input:

"I just put 2 6CA7EH big bottles in my amp to replace Siemens EL34's and they sound great. They 6CA7EH is a direct replacement for EL34's (with a bias of course). The reason they are different than other EL34/6CA7 tubes is that they are a beam tetrode tube made with the same design as old Philips tubes. The beam tetrode 6CA7 is commonly called the American version of an EL34 due to having the same output, but the American made 6CA7 is tonally of the 6L6 family. It is basically a 6L6 with the high gain output of an EL34. Better Bottom end then regular EL34's, and more durable. I think they are pretty cool, and very cost friendly."

"If you want an alternate to EL34s, one user suggested 6550s. Zakk Wylde uses 6550s in his Marshalls, and with an input boost to push the amp to get a little extra gain, it should sound something like Zakk Wylde... pretty meaty! KT66s also maintain a full range of tones, but are quite expensive. I would go the KT66 route only if you plan on getting most of your gain from the power amp."

"kt-88's are replacements for el-34's, very similar to 6550's, if you have room for their huge bottle design. These suckers are expensive, but worth it if you can afford them. They have a huge bottom end that remains tight without losing any mids or highs. This is truly one the best all around tubes that can go to either end of the spectrum. Billy Corgan used these in his JCM800."

"Thanks for the info on the KT88's! Yeah, that's about what I've heard about them. I read somewhere that it has the low-mid warmth of an EL34 and the mid-high tone of a 6L6. Kinda the best of both worlds I guess."

WARNING: These tubes are not all created equal. Some combinations will explode or melt your amp. Do not swap powertube types without someone experienced in tube-based electronics involved!! This is not something for a novice or even an intermediate to be playing with. This is something for a serious electrical guy, not just a guitar player. Getting it wrong could melt your amp, or kill the guy touching the guitar, and that is absolutely no joke.

The EL84 is a physically smaller tube, the same socket size as 12xx but about twice as tall. They have much lower power (8.5w per tube vs. 30w per tube in an EL34). They are often described as "glassy", which I think of as a sort of sparkly quality to the clean which comes out as a brittle quality when driven. They are definitely not more midrangey than EL34s.

Groove Tubes sells a device called the 'Yellow Jacket' which lets you use EL84 tubes in an octal base amp. One geek had the following review of them: "They are nice. When I was contemplating downsizing my rig and looking at THD's Univalve and Flexi amps I had the chance to swap back and forth a slew of tubes in a Flexi-50, and used the Yellow Jackets for a set of EL84s. Other than the expected change in tone, there was no noticible difference/ noise/ buzz. I was very surprised. The idea that you can re-tube and have in essence a completely different amp is very, very cool."

[This message was edited by Ken Fox on 16 December 2005 at 06:59 AM.]

ajm · From: Los Angeles

Just to reiterate, these tubes are not created equal. Different plate specs, different bias voltages, different heater currents (especially the 6550)..........If I were you I'd just stick with the 6L6's unless you have a specific reason for wanting to change.

Biasing.....If you change power tubes I'd definitely have it rebiased. I have a Carvin XV112E from about 1984. Tolex covered, 4x6L6, graphic EQ. From what I have read coupled with my own experience, Carvin biases these amps so that they won't get many returns from customers, but in doing so the sound can suffer. They bias them so they draw relatively little plate current at idle; I seem to remember around 25 ma per tube. I have messed with mine a lot and it does make a difference in sound.

I have also changed a lot of stuff in the preamp and it sounds much better to my ears. I play mainly guitar and lately have been leaning towards a more blues/rock/heavy rock approach though and not a pedal steel application. However, there are some things that I have changed that would probably be of benefit to anyone with these amps. Nothing I have done has required any cutting or drilling or modiification to circuit traces; mostly just changing resistor and capacitor values. If you have a little electronic experience and are interested let me know.

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Artie McEwan

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