Yellow Jacket Converters?

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J

jcb

Well-known member
Joined
Apr 9, 2005
Messages
64
Has anyone ever used these?

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ADAPTER, YELLOW JACKET, CONVERTS 6L6, EL34 TO EL84/6BQ5

This Yellow Jacket converter is a specialized adapter which permits the use of EL84/6BQ5 power tubes in place of 6L6 or EL34 type tubes. Yellow Jacket converters not only re-arrange the pin locations of the tubes but also provide the necessary current limiting on the screens and cathode. Yellow Jackets' block the amplifier's grid bias voltage, which configures the EL84/6BQ5 into a class A self adjusting bias circuit. Tubes are not included. Manufacturer recommends the JJ EL84/6BQ5.

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ADAPTER, YELLOW JACKET, CONVERTS 6V6 TO EL84/6BQ5

This Yellow Jacket converter is a specialized adapter which permits the use of EL84/6BQ5 power tubes in place of 6V6 type tubes. Yellow Jacket converters not only re-arrange the pin locations of the tubes but also provide the necessary current limiting on the screens and cathode. Yellow Jackets' block the amplifier's grid bias voltage, which configures the EL84/6BQ5 into a class A self adjusting bias circuit. Tubes are not included. Manufacturer recommends the JJ EL84/6BQ5.

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ADAPTER, YELLOW JACKET, CONVERTS 7591 TO EL84/6BQ5

This Yellow Jacket converter is a specialized adapter which permits the use of EL84/6BQ5 power tubes in place of 7591A type tubes. Yellow Jacket converters not only re-arrange the pin locations of the tubes but also provide the necessary current limiting on the screens and cathode. Yellow Jackets' block the amplifier's grid bias voltage, which configures the EL84/6BQ5 into a class A self adjusting bias circuit. Tubes are not included. Manufacturer recommends the JJ EL84/6BQ5.

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Please discuss, thanks.
 
I don't know what the point of this device is. The reason different tubes were originally developed was to fulfill specific requirements. That is why a 6CA7 and a 6L6 have the same base pinouts, but they are meant to drive different load impedances at different voltages at different power levels. I think it's ludicrous to plug a 6BQ5 into a 6L6 circuit and expect it to do the work of a 6L6. Why not just use the appropriate tube for the application?
 
> expect it to do the work of a 6L6.

I don't think it is supposed to do heavy work. This seems to be the claim:

"...used in a Marshall 50 watt or similar amplifier, the overall power drops to about 20 watts and takes on more of the character of an old Vox AC30. The distortion is smoother and more even and the output is both substantially reduced and more compressed due to the Class-A nature of the Yellow Jackets." "...a whole new warmth and richness."
http://www.thdelectronics.com/products/yellow_jacket.htm

If you have an OK amp, but a little too loud and brash, putting in the modest little 6BQ5 working in a tolerant Class-A mode will CUT the power and change the flavor. The 6BQ5 is a flavorful little bottle, even though we mostly know it from super-cheap amps. I shudder to think of putting 6BQ5 in my Ampeg VT40: the 590V B+ is about twice the 6BQ5's rating. But I know we abused the 6BQ5 back in the day, they rarely gave trouble, and I bet new-production 6BQ5 are built with the same plate-stuff as the 6L6GC/EL34 replacements, which I would expect to work in the VT40.

It is of course a big waste of power-iron and chassis space, but the world is full of Big Hammers and there is sometimes a need for a lighter (in sound if not in weight!) weapon. This is a mod that electro-idiots can handle, un-do in a jiffy if they need the Big Sound for a gig, offers nearly zero danger to the amp, won't hurt the amp's Vintage Value.

Like Getting A Whole New Amplifier quote-unquote.

There was a special need for the 7591 converter: 7591 was out-of-production for nearly 30 years, and what few were around were bid-up by Macintosh and Scott hi-fi lovers. The 6BQ5 is not such a tough tube, but close enough to make you happy, and has generally been available. In the last couple years ElectroHarmonix has released a medium size high-gain tube they call 7591, but for many years 7591 amps were white elephants. (Ask the man who owned one: a lovely Mac MC-230 in excellent shape, but I let it go for $100 because I "knew" it could never be re-tubed.... :cry: )

To the point: no, I never used the Yellow Jackets.
 
I bought a reissue JCM 900 some time ago, and thought the tone was bit harsh and brittle. The power tubes were 6L6. I did a mod and changed them over the EL34, and the tone, IMO, improved dramatically. Still wasn't as good as the original JCM 900, but the midrange quality of the guitar tone was so much softer and lush. I don't know enough about tubes to comment on those exact conversions, just thought this would be slightly revelant to the topic.
 
[quote author="Greg"]I bought a reissue JCM 900 some time ago, and thought the tone was bit harsh and brittle. The power tubes were 6L6. I did a mod and changed them over the EL34, and the tone, IMO, improved dramatically. Still wasn't as good as the original JCM 900, but the midrange quality of the guitar tone was so much softer and lush. I don't know enough about tubes to comment on those exact conversions, just thought this would be slightly revelant to the topic.[/quote]
Are we talking about the same amp?
I have an "original" 1995-ish JCM900 50watt head - in custom ordered Purple (I was bored and in those days and custom colours were FOC).
Didn;t relaise they had been reissued
I bought them when they were 6L6s - they had just moved over from the EL34.. then after I bought them they moved back again..
(fired it up on Sunday after 2 years of not touching it - I think all my power amp valves have gone - .. oh dear)
 
http://www.drtube.com/marshall.htm#JCM900

I'm talking about the 4100. Here's an excerp from that site:

"The 4100's were introduced in 1990 and discontinued in 1999. The 4100 was reissued in 2003."
 
[quote author="Greg"]http://www.drtube.com/marshall.htm#JCM900

I'm talking about the 4100. Here's an excerp from that site:

"The 4100's were introduced in 1990 and discontinued in 1999. The 4100 was reissued in 2003."[/quote]
Blimey....
Thanks - never thought it was that impressive enough to bring back
 
I don't care for the 900's either, but I noticed that my tastes in Marshalls seem to be following about 25 yrs behind current production. I started out with a plexi in 1992 and sold it for a 1973 Lead 100 which I liked much better. Now that amp sits around gathering dust and all I play is my 1976 50W master vol. I used to hate JCM800's and now they aren't sounding so bad to me anymore. I figure by 2020 I'll be drooling over a JCM900 :wink:
 
[quote author="Emperor-TK"] I figure by 2020 I'll be drooling over a JCM900 :wink:[/quote]
I'll stick the purple one in storage
Worst mistake I ever made - in 1995 flogged a 1960s JTM45 head for £100 (it had a master volume mod on it) - bought it for £60 from a music shop!
Almost as bad as me giving away a 1960s Selmer amp - with attached speaker cabinet - maybe a 1 x 15inch? (on a sort of hinge-ey attachment).
Got pissed off with it sitting there so I gave it away to my local guitar tech, if he would pick it up from my house
20 minutes later he's at the door, two rectifier valves he had lying around in his hand, to sweeten me up just in case I had changed my mind
And then he ran out of the door (probably laughing his tits off)
 
Yes, I have since sold my JCM 900. I'm actually a bass player, not a guitar player. I was in a band at the time and our guitarist quit. We knew of a great bassist, so I switched over to guitar. After many months of writing and playing, I realized that it'd be better to stick to my guns as a bassist.

I'm actually a JCM 800 fan :roll: . I also like the Vox and the clean tone on a Mesa Dual makes me jizz in my pants for alot of the rock I record.
 
Anybody try these Yellow Jackets in a Fender Bassman Head...say, to make it more like a Marshall sound?
 
[quote author="jcb"]Anybody try these Yellow Jackets in a Fender Bassman Head...say, to make it more like a Marshall sound?[/quote]
Interesting
Weren't the original Marshalls just rejigged Bassmans anyway?
 
[quote author="jcb"]Anybody try these Yellow Jackets in a Fender Bassman Head...say, to make it more like a Marshall sound?[/quote]

I think it will head more towards the tonal properties of a Vox than a marshall...
 
As this is a DIY forum and surly everybody wants to know what is inside these, i'll quote a post by the man himself from another forum:

From:

Andy Marshall ([email protected])

Date:
1/5/2002 10:06 PM

Subject:
Re: Yellowjackets--2203

All Yellow Jackets come with EL84 tubes. We used to use Sovtek non-military El84s, but a few years ago switched mostly to JJ/Tesla EL84s. We have had good luck with them both sonically and in terms of reliability.

What in them? Different models of Yellow Jackets have different components, but basically they have a cathode circuit (parallel power resistor and capacitor), a capacitor to block the grid bias from them amplifier, a grid reference resistor, a supplemental current limiting power resistor on the screens and, in most models, a set of Zener diodes to give a constant voltage reduction on the plate and another set of Zeners on the screens. Most Yellow Jackets, you see, have around 9 discreet components in the circuit, excluding the socket and base. Building them is more like jewelry making than like electronics.

Furthermore, there are a few different sleeves of Teflon and/or fiberglass to add insulation to the certain internal components so that they cannot short to one another.

Another consideration, in addition to the component values and ratings, is the manufacturer of the component. The Zeners that we use do, under certain circumstances, get hot enough to melt solder joints, so these components are connected using a special high-heat crimp connection that is tested repeatedly before final assembly.

You may ask how a Zener could possibly survive getting hot enough to melt solder. Good question. Most brands cannot survive this. We have found one brand of military-grade Zeners that can take this heat all day long with no ill effects. Are they expensive? Yes. Are they time-tested? Well, we have about 7000 Yellow Jackets in the field, some of them almost 10 years old, and the field failure rate is well under 1%.

Could you possibly build your own? Sure, but there are a bunch of things to keep your eyes open about. Build it sturdy, insulate the heck out of everything; don’t forget to study the temperature de-rating curves of your components.

Also, for safety’s sake, don’t even consider using metal tubing for the body of the adaptor. (We use fiberglass tubing.) If something were to go wrong, it is way too easy to get plate voltage on the body, and touching that could be very unpleasant. While I have never heard of anyone being killed by this, a few people I have heard from have gotten NASTY shocks from metal-bodied copies of the Yellow Jacket.

Be careful and have fun experimenting!

- Andy Marshall, THD Electronics, Ltd.
Click to expand...
 
[quote author="Sammas"][quote author="jcb"]Anybody try these Yellow Jackets in a Fender Bassman Head...say, to make it more like a Marshall sound?[/quote]

I think it will head more towards the tonal properties of a Vox than a Marshall...[/quote]

I thought one of the big things about a VoxAc30 had to do with the top-end boost...I'm not sure if you would get that by using Yellow Jackets in a Fender Bassman Head...

But if it did sound like a Vox instead of a Marshall...that would be OK with me...

The Fender Bassman head I'm thinking of trying the Yellow Jackets on was modified by Dan Torres Engineering to have Marshall circuits and sound...but it currently still has 6L6's in there IIRC...so it's not quite a Marshall...maybe with a Yellow Jacket tube swap it might have more of a Marshall flavor...

Anyone know how much these Yellow Jackets cost? I have yet to see a price for them...
 
[quote author="jcb"][quote author="Sammas"][quote author="jcb"]Anybody try these Yellow Jackets in a Fender Bassman Head...say, to make it more like a Marshall sound?[/quote]

I think it will head more towards the tonal properties of a Vox than a Marshall...[/quote]

I thought one of the big things about a VoxAc30 had to do with the top-end boost...I'm not sure if you would get that by using Yellow Jackets in a Fender Bassman Head...

But if it did sound like a Vox instead of a Marshall...that would be OK with me...

The Fender Bassman head I'm thinking of trying the Yellow Jackets on was modified by Dan Torres Engineering to have Marshall circuits and sound...but it currently still has 6L6's in there IIRC...so it's not quite a Marshall...maybe with a Yellow Jacket tube swap it might have more of a Marshall flavor...

Anyone know how much these Yellow Jackets cost? I have yet to see a price for them...[/quote]

If its been modded perhaps it will sound similar to a marshall. The only marshall that used EL84's was the 18 & 20 watters IIRC. I put a pair of YJ's in my Egnater TOL-50 and it gave it a lot of chime and jangle.

They cost just under $100 a pair... It might almost be worth it to mod the amp for EL34's...
 
Can we define the characteristic sound of the following amps by specifying the pre and power tubes?


Fender: pre-tubes(_______) power tubes(________)


Vox: pre-tubes(_______) power tubes(________)


Marshall: pre-tubes(_______) power tubes(________)


I bring this up since I forget the differences, it may help in selecting a Yellow Jacket Converter.

PS,

I do not see Yellow Jackets that allow you to swap out the pre tubes, just the power tubes...

Will changing only the power tubes be sufficient to change the amp so that it is "close enough" to the target amp for gov't work?
 
FWIW, I have a vintage Ampeg Reverberocket 2 which used 7591a's. The original tubes were not bad, but I re-capped it and tried the EH 7591a's. I was not happy with the sound of these tubes, so I bought a couple of Yellow Jackets and JJ EL84's. The amp sounds much better now. I always liked the EL84's sound better than the 6L6's or the 7591A's anyway. When I got the Yellowjackets, one was defective, causing the tube to glow very brightly. I exchanged it and have been using this amp pretty regularly and have no problems with them.
 
I think generally speaking that the 18-20 watt el 84 combo is a nice
place to stop power wise .
When i tried my yellow jackets in friends jcm 800 they helped it get that loud pushed sound without killing me , seemed a little bass shy but it
wasn't a problem . they helped a boogie combo i have out enough that
that is the only way i'll use it , the YJ did seem to get screechy when
used under heavy attenuation however .

regards Greg
 

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