THD Yellowjackets 6V6

Simple features: converts Class AB to Class A, trade volume for tonal qualities.

I have played several guitars through these Yellow Jackets in several different amplifier configurations. Across the board, I'd have to say that they allow the sound to "breathe" quite well. I have used them in vintage Fenders primarily, but always go back to the original tubes for some reason, I think Leo Fender had it worked out. I have settled on my trusty old Princeton for most of the playing that i do, and I don't notice much drop in volume, but the tone is well-defined and open, less cramped than with the 6V6 tubes, but not as throaty.
The benefit is compromised somewhat by the sacrifice of the tremolo circuit. I like that old swamp sound that CCR and some of the Zydeco
artists know how to work into their tone....casting "the spell" requires a good vibrato.

These always worked, I have had them now for five years or longer.

Never dealt with the company, haven't had any problems.

I have been playing for over 35 years. The list of other gear is too long to get into, but I have tried many guitars and amps over the years, and now I keep things real simple. Gibson Guitars and vintage Fender amps seem to be what works for me. I would reccommend these to anyone who wishes to expand their sonic options. They are a great product. They do exactly what the manufacturer claims they will do.

Put the Yellojackets into a Fender '65 Deluxe Reverb Reissue.
22 Watts. Original tubes are 2 6V6's.
Use the amp for a quiet experimental folk band. Main guitar is a '72 Tele Custom Re-issue with a Lindy Fralin Blues Special pickup in the bridge, and the stock Fender Humbucker in the neck. Glendale compensated brass saddles and non-magnetic bridge plate.
Pedals used are an HBE PowerScreamer with Fat boost, MXR 10 band EQ, Ernie Ball Volume Pedal.
Installation is super easy. Pull the tubes out and insert the converters, then the EL 84's.

I purchased the Deluxe reverb recently upon starting a new project that required a cleaner sounding, quieter amp. I found the deluxe on craigslist for a good price, and though I'd spent a little time with one in the past and didn't care much for it, thought it might work out anyway. I was pretty disappointed when I finally plugged it in with all of my gear and spent some time with it.

My opinion of the Fender Deluxe Reverb Reissue before the Yellowjackets - anemic, flabby bass, ice picky treble, breaks up way too early (no headroom) , doesn't like ANY overdrive or distortion pedal in front it, too dark or too bright. weak mids, one dimensional, farty sounding when overdriven.

I was getting ready to get rid of it entirely but I thought I'd give the Yellowjackets a try and see if they couldn't help before plunking down some serious money on another amp.

I put the Yellowjackets in and I have a completely new amp and it rocks!

The bass and treble controls are so much more useful now. The bass is much tighter. The amp has some punch and girth to it with a nice sheen on top. It's more three dimensional sounding now. I was concerned about losing too much volume, but it hasn't dropped by much, and if anything, I now have more headroom before the amp breaks up. It's like the harmonic range of the amp has been shifted into a spot that's perfect.
My PowerScreamer sounds awesome now. I can now use all the pickup combinations on my guitar whereas before, I set up the amps eq for the middle position on my tele, which is what I use the most, and the bridge or neck positions were practically useless and/or required changing the settings on the amp. The bridge pickup pre-yellowjackets was too biting and shrill and the neck pickup too dark. Now everything sounds so nice and full regardless.

This is probably the best sounding and least expensive investment I've ever made.
I could have spent hours and tons of money on various pedals, cords, speakers, pickups, strings, amp mods, etc., to try and fix the sterile sounding stock Fender Deluxe Reverb reissue, but with the yellowjackets I didn't have to.

This is an awesome product and I'm sure it would work equally well in whatever amp you have if you want to try some tonal variation.

I might try and put them in a Sovtek Mig 60 that Jeff Snider of Snider Amps modified for my, though, the voltage to the powertube plates might be too high for the yellow jackets to handle...we'll see...

From what I know of have heard about THD, I'm sure the Yellowjackets will be reliable.

Haven't had to use them and probably won't, but I've heard good things..

Awesome investment.
Great tool to bring life to a dead sounding amp, or to add a little versatility to what you have.

This is something I just had to try: switching the output tubes in my amp from 6V6 to EL-84. The amp I modified is a Reverend Goblin 10" combo, switchable from 5 to 15 watts output. The amp is quite nice the way it is, but a little chilly for my tastes. It has 3 EQ/gain profiles: one Fender-ish, one Supro-ish, one Vox-ish. In the Fender setting, it was impossible to significantly overdrive the output tubes, and I don't like strong preamp overdrive.

Installing the YJC Yellow Jackets (a breeze) made a HUGE difference! Not much of a difference in terms of volume, even though this change is said to cut the power by around half. But the tone is very different (see below)...

Now, I can strongly overdrive the output tubes in any of the settings. The tone is smoother, warmer, and "chewy." Clean sounds are great too, as are pedal-driven overdrive sounds. It's pretty amazing: before, I was looking for a tone I really liked, but now, I seem to like 'em all. It doesn't get much better than that. Next, I'm going to try a different brand of EL-84 (the Yellow Jackets come with JJ/Tesla) to see if I can get an even better tone.

(By the way, I'm playing an electric mandolin with Kinman Woodstock Strat pickups, and various lap steels.)

Too soon to tell, but it's a pretty low-power amp. I imagine the tubes will last.

Before buying these, I emailed the company a couple of times with questions and used their phone support once (they make a number of different models, and I wanted to make sure I was getting the right one). They were extremely--even surprisingly--helpful.

I've been playing a long time, but I'm only now beginning to get serious about getting the gear 'just right.' This has been the single easiest and most satisfying upgrade I've made on a piece of equipment. I would absolutely buy these again if they were lost. Think of it: less money than the average decent pedal to get something that makes your sound much better 100% of the time!

I also own a THD Hot Plate attenuator, which I use and like. I'm very interested in 'dialing down' power to low volumes, so I'm still searching in that department. I'm going to check out the Power Scaling Box made by London Power, which attenuates between the output tubes and the transformer rather than between the transformer and the speakers. We'll see...if and when I get that, I'll certainly write a review.

My amp is a twin reverb 65 reisue (85 w) When I bought it i played rock with some extra pedals etc. added to my set up.
I changed to a blues band that plays trad 50s and 60s style electric blues. The set up needed a change a my dealer sugested the yellow jackets and EL84 solution. I changed the 4 6L6s for only two EL84s, converting the heavy Twin to only a 20W amp. But anyway the power of 20W versus 85 W is not to define, it plays loud enough for club gigs.

I mainly use a Les Paul or a ES 175 for that bands gigs and with the humbuckers straight into the converted twin you dont need anything else. The amp is still quiet, no noise but just a beatyful dynamic distortion. Played on the treble strings the guitar can scream as you want it to and the bass can blow the bass drum out.
If you want a clean sound, just turn the volume on the guitar down.
With a strat or tele the distortion gets more moderat and you can easyly use the converted amp for country. However with humbucker guitar like the my ES175, this is not a amp for jazzy chords or solos anymore. (If you like it totaly clean)
General I think the Twin still sounds like a Twin perhaps with a litle crunchy Wox AC30 added to the top.

We will see, 6L6s can last for years, the EL84s is on hard work.

Onle had contact with my local dealer

I have been playing for 25 years, I have a bassman 65 top / Tonemaster 2x12 / 63 reverb.
Greatest feature is the sound comming straight from the amp, no pedals or anything to disturb you setting up your gear.
I would buy it again

Pretty basic enough. These as most know are tube converters which allow the replacement of amps using 6V6 power tubes over to EL84 power tubes without the need to rebias the amplifiers. Very easy to install. Its like having a whole new amp in 5 minutes

I use these in my '74 Fender Deluxe Reverb. These things make this amp come alive. Creates a whole new vibe and feel of the amplifier much like a Vox AC-15. Killer, jangly top end, and a chewy almost caramel-like midrange and bottom end as one would expect from a good old Vox, with a very unique and organic overall tone. Works equally well with different types of guitars/pickup combinations. My evaluations included a Fender Powerhouse Strat, a 1990 PRS Custom 24, and a old Kramer Focus from the 80's. Each had their own individual nuances and unique voice. Totally changed the breakup/distortion character and overall tone of the amp doubling or more the versatility of this amp. I love it

Haven't had any problems as of yet and they have been in my amp for over a month now. THD has a reputation of over engineering their products just for this reason. They are made with high grade ceramic tube sockets. I expect they will last for quite a long time.

Have not had to deal with them, but others folks I know have, and they have said it was a helpful and professional experience

These things are the single best under $100 investment I have ever made made toward my tone. I would definately with out fail buy them agin if something happened to them. They rock. As I have said b4 . Its like spending $100 and getting a whole new amp. This is a must have for studio cats who want to change the vibe of their 6V6 rigs. As mentioned earlier, the yellowjackets are very versatile and offer a great variety of tones with different guitars. I REALLY LIKE THESE THINGS.

I have owned and played most every kind of amp available.I love the sound and responce of EL-84's.I have had this expensive Fender Twin sitting around un-used for years.Loud and clean.I deceided to try the Yellow Jackets in the Twin.This Twin is now a totally different amp.I can turn it up to about stage volume and it rocks.Nugent tones with a Les Paul and Twin? Yes sir.

Lets you get great sounds out of sterile amps.Add them to any 6L6 equiped Fender and you have natural class A distortion without blowing the roof off the house.Wish I had invented these.

I am not sure.Only time will tell.I am curious as to how long the EL-84's will last.

Do not know.

I have been addicted to guitars and amps for about 30yrs.Now I can continue my addiction with a new tone tool.You really should get at least a pair of these things.I could easily be a sales rep. for these things.I like them that much.I just hope they do not turn out to be harmful to my amps.Anyone with a long history with these things,give me a shout.

This is the easiest thing to install - even I could do it! There comes a little instuction guide with it-but it just confused me-so I called THD and spoke to someone there who told me how to hook them up-then I realised I was thinking too hard and they are totally easy to install

I got them to use with my Vibro King amp. But wound up putting them in my Hot Rod deluxe and turned it in to one of the BEST sounding amps I have ever heard-the Hot Rod (up until now) really has not impressed me that much - tone wise. But with the yellow jackets I swear the amp sounds like Dickey Betts when I use my Les Paul. You can switch back and forth-putting your old tubes back in so there is no modification or anything-but they are great!

They look reliable-they came with with a set of groove tube EL-84's. They look pretty simple so I wouls the reliability to be good.

I called the company and they were very helpful.

I play blues mainly- I used to use Strats and teles, but now I have one electrai guitar only-Gibson Les Paul-and it does everything! love it-the yellowjackets replace the 6L6 tubes in your amp and turn it in to a class A EL84 tubes amp and they are incredible-if you got an extra hunder bucks laying around, you MUST try them out-you will be glad you did-its like getting another amp.

Yellowjackets are only designed to do one thing, and they do it well.

I had read about Yellojackets with great interest. I had wondered what it would sound like to have EL84s in my 1967 blackface Deluxe Reverb. I play a black Les Paul Classic with reissue PAFs. So by the time they arrived I had, needless to say, great expectations. I was thoroughly delighted with the results: Clean: clear Fender twang with a touch of Vox caramel. Overdriven: sings/sizzles like a Deluxe Reverb, but with a Voxy nasal honk that really squeezes out harmonics. With the EL84s this amp just opens up and cries. Wow. And since my amp is already biased for matched pairs of 6V6s, I need only take the Yellowjackets out and put the 6V6s in to return the amp to its stock sound. Beautiful.

The amp isn't harmed in any way, and the adapters are made well. The tube sockets are ceramic. I keep a matched pair of 6V6s as a backup. Since the amp is already biased for the matched 6V6s, having the extra tubes is like having an extra amplifier. The EL84s run in Class A mode, and so don't require biasing.

NA

I've been playing for 25 years. I play a Les Paul Classic through a stock 1967 blackface Deluxe Reverb, run through a Bandmaster 2 x 12 cbinet loaded with Celestian Greenbacks. For $100 I get a whole new amplifier that sounds uniquely beautiful. I would replace lost/stolen Yellowjackets without hesitation.

If you have $100 to spend for a whole new dimension for your current amplifier(s), they're worth a look/listen. They work great for my sound.

As indicated earlier, Yellow Jackets are EL84 tubes in an extended socket adapter that allows you to substitute the EL34 running in Class A mode for the output tubes in typical Class AB amps running 6V6, 6L6 and EL34 output tubes. The beauty of this arrangement is that no modifications are required, no bias changes are required (self-biasing Class A), and you can always go back to the original tubes by simply plugging them back in!

Upon installing the Yellow Jackets the tonality changes (more mid and high frequencies), the gain (or sensitivity) is noticeably higher, the maximum output power is reduced by approximately 50%, and the amp's power supplies and transformers are run at reduced stress levels.

I have tried these in 2 different amplifiers with good success (but with some caveats). For my first test, I substituted these for the 6V6 output tubes found in my older model (#126, 1987) GT Electronics (Groove Tubes) STP-G (Studio Tube Preamp for Guitar) amplifier. In addition to being the circuit-equivalent of a Fender Deluxe amp, this unit also has a reactive load and speaker emulator in it to allow you to overdrive the output tubes for the most pleasing distortion. This can output directly to an 8-ohm speaker at standard amp volume levels or as a line-level signal for recording or playing back through another amp at any level desired.

When using the line-level load/emulator mode, the 6V6 tubes exhibit smooth and creamy overload, but sound a bit bassy with little apparent "detail". It sounds great clean and only gets "tubby" when pushed into full overload. With the Yellow Jackets in place the characteristics change most noticeably (in most ways for the better). High Frequency detail is boosted dramatically and it no longer sounds "tubby" when overloaded! Gain is also increased, so my Stratocaster single-coil pickups can push the amp into overdrive more easily (without using extra input gain), and the amount of overdrive available gives me a wider palette of sonic colorings to work with (using the volume control of the guitar). I was quite happy with their performance in the STP-G.

My second test substituted the Yellow Jackets for the EL34 output tubes in my Music Man 410-65 combo. This amp is a hybrid with a solid state preamp section that excels at playing clean and loud, but only *just* becomes "bluesy" when the output tubes are overdriven (Master volume up full). With the Yellow Jackets, the same increase in high-frequency and mid-range energy seen in the STP-G is apparent (it "sparkles" more), but the BIG change is that it overloads VERY NICELY with the Stratocaster single-coils, going past "bluesy" and well into "hard rock", but short of metal or shred. It really makes this amp sing like it never has before!

One BIG caution here, though. The Yellow Jackets theoretically don't want to see any more than about 525 volts on the plate connection of the host tube sockets. The Music Man amp is a low current/high voltage design which uses about 700+ volts DC on the plates of the output tubes (in High Power mode). I would assume that this might cause the Yellow Jackets/EL84s to fail or arc-over, a potentially dangerous and damaging situation! Since the Music Man amplifiers have a half-power switch position (LO or Low Power cuts the plate and grid voltages in half), you should be able to safely run the Yellow Jackets as long as you stay away from the amp's high-power operating mode.

I did not get any documentation with my used Yellow Jackets, I am only going by the information I have read from the THD web page and other Internet sources.

I have not lived with these units for more than a few months, but I have not experienced any problems. I got mine used, so the "new car smell" was already baked out of them. So far, so good!

I would re-iterate that you must be careful when attempting to use this in a high voltage amp (like the Music Man), run them only in the Low Power position to be safe.

Full product, company and contact information appears on their web page (http://www.thdelectronics.com). I have not had a need to contact them or to get these serviced. They worked when I got them and they continue to work.

I have been playing guitar for 30 years, both semi-professionally and simply for my own enjoyment. 99% of my playing has been and continues to be electric, so I have owned a fair variety of amplifiers, both tube and transistor. Outside of external overdrive pedals, I have never had an opportunity to experiment with EL84 tube substitution. While the Yellow Jackets gave me a viable alternative to the 6V6 tubes in the STP-G (with improved gain and sensitivity), they literally TRANSFORMED the Music Main amplifier. This amp could barely be coaxed into the start of output overload consitions stock, but can SING & WAIL with the Yellow Jackets... if you can use it at close to full drive level in the low-power mode (estimated about 18-20 watts)!

Another drawback I noticed is the height. Together, the EL84 and its adapter are 25% taller than an EL34 and a full 100% taller than a 6V6 tube. While this is not a particular problem in my Music Man (inverted tubes, standard guitar amp tube mount method), the extra length might expose the tubes to damage in some amplifiers.

Unfortunately, this height issue prevents me from using the Yellow Jackets full time in my STP-G unless I can come up with a right-angle adapter. I have my STP-G mounted in a GT Soul-O head cabinet and there simply isn't enough vertical space to use the Yellow Jackets vertically as intended. I have no idea what possible implications on tube life will become evident if I attempt to operate them mounted sideways! They lose a point for their size (height= 5" above or below chassis)and another for their high-voltage limitations.

I Installed a matched duet in a 1972 Fender Deleuxe reverb that had been blueprinted to Blackface specs. I bought this amp used with the original (RCA,GE) tubes. So I had a good benchmark for evaluating the yellowjackets.
Features are pretty straight-forward: Yellowjackets convert your Class AB power section to cathode-biased Class A using EL-84 tubes.
It works exactly as advertised.

Purists will hate me, but I really love the sound of this amp with the yellowjackets more than I did with the GE 6V6s. I like a detailed surgical tone. The 6V6s always seemed to splatter a bit. Yellowjackets have greatly tightened up the bass and yet the high end is not strident. I had feared that the brighter EL84s night sound harsh with the Fender front end.
The midrange signature is now MUCH more forgiving of my pedals (MESA V-Twin, TS-808 and DM-2 analog delays).
Purists will say that I don't really have a Deluxe any more and perhpas should not have bought one in the first place. However, I think the yellowjackets are an improvement over the somewhat trashy Fender output stage,

They smelled a little funny for the first 1/2 hour. Otherwise, they seem to be functioning perfectly.

I ordered these direct from THD. They answered several of my questions in great detail before I placed the order. Very good vibe!

I may buy these for other amps. Curious as to how one of these would sound with their Uni-Tube amp. 10 watt class A amp anyone?