Miles's Taste Tests for 6BQ5 / EL84


I got five new EL84/6BQ5 (the EL84 was the European designation; the 6BQ5 was the USA designation) type tubes from Lord Valve, Ned at Triode Electronics and Jim McShane . for comparison purposes. I also had an old Raytheon that we still use in my son's Model 1 Kalamazoo, because it sounds so nice.

Tech Notes

According to the RCA tube manual, a single 6BQ5 can produce up to 5.7 watts, with 10% THD. The design center maximum ratings were 300 volts on the plate, 65mA cathode current, and 12 watts static plate dissipation. The Kalamazoo Model 2 runs about 270 volts on the plate, with around 45mA plate current, or roughly 50mA cathode current. The amp is cathode-biased, and all the tubes pulled between 47mA and 52mA at the cathode, so I didn't worry with rebiasing.



I compared these power tubes in a Kalamazoo Model 2, a point-to-point, single-ended (true Class A 8^) practice amp from the 60s. This amp has all new caps, a new 6X4WA rectifier (through a typical, multi-stage capacitance filter), and a Sovtek 12AX7LPS in the preamp section. It has a single volume and tone control, and a simple tremolo which was not used for this test. It has a beefier output transformer than stock, and was tested through an open cabinet with a single, 12" vintage speaker of uncertain origin.

The primary guitar was a Hagstrom 1 with two DiMarzio SDS-1s and completely flexible pickup selection. I also used a BC Rich ST Platinum (Strat clone) with a humbucker in the bridge slot.


The Kalamazoo Model 2 is fairly representative of the sort of single-ended practice amps these tubes are commonly used in, and in fact has recently become a mild collector's item because it can be made to sound so good. The results here may or may not apply to your specific amp, especially if it uses a push-pull output stage with two or four EL84s. I would love to compare these in a VOX, but don't have one available.

I played for 15 - 30 minutes, minimum, per tube. Most tubes got much more play time, in particular the Raytheon, Tesla, Sovtek 6BQ5 and EI.


There were some obvious leaders and an obvious trailer. There were no complete duds, but one of the tubes didn't impress me very much.

The Tests


The Raytheons are my favorites, with the Sovtek 6BQ5 and Tesla more or less tied in a reasonably close second. The Ei EL84 comes in a solid third and the Sovtek EL84M comes in last. The EL84M isn't horrid, but it's not real exciting, either (although I would consider it for a jazz sound). The Tesla wins out slightly in terms of dynamics and is the brightest, but the Sovtek 6BQ5 wins in most other areas I can think of. I'd suggest getting both if you can, and seeing which works for you. I was torn between leaving the Sovtek 6BQ5 in the Model 2, with the Tesla as a backup, and vice versa. Then Jim told me about his Raytheon stock, and the NOS Raytheon claimed the working spot in the amp. The old Raytheon went back into my son's Model 1.

These results were also posted in the alt.guitar.amps newsgroup.

Last updated: 09 January 2002
Taste Test copyrighted Y2K by Miles O'Neal, Austin, TX. Incidentals copyright Y2K Miles O'Neal, Austin, TX. All rights reserved.
Miles O'Neal <> [remove the "XYZZY." to make things work!] c/o RNN / 1705 Oak Forest Dr / Round Rock, TX / 78681-1514