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Vintage threads from the first ten years

OT for SE EL84 amp

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6/28/2000 1:55 AM
Josh	OT for SE EL84 amp can anyone reccomend an OT for a single ended EL84 amp? there doesn't seem to be many amps like this and I'm having trouble locating a OT that would work. Josh

6/28/2000 2:46 AM
Bruce	I still have a handfull of the small 270v@50ma PTs and 5 watt 5Kohm:8ohm OTs used for 5 watt SE amps like this. I was letting them go the AX84 guys... well any AMPAGE/AX84 homebrewer actually... for $20.00 a pair plus shipping if your interested. Bruce

7/4/2000 4:41 PM

Dean Hazelwanter

Bruce:

My co-worker (Clare) has been communicating with you about purchasing 2 sets of transformers, and one of these sets is for me. My question is, how would these transformers work with a 6V6?

I've already built a SE EL84 amp combo, from a console stereo power amp, a homemade (Vox) front end, and a gutted CarriVoice SS PA cabinet. It sounds *really* nice.

These are the options I'm kicking around:
1) Build an AX6V6 P1. The AX84 P1 project, but using a 6V6 instead of an EL84. What circuit modifications from the AX84 P1 (rev 11) would be required?
2) Build an AX84/6V6. Build with 2 power tube sockets, one for EL84 and one for 6V6, with power tube-specific components mounted on or near their respective socket. Populate either the EL84 or the 6V6, but not both at the same time. Alternatively, use an actual switch to switch between the 2 power tubes, depending on the similarity of the support circuitry for each tube type.
3) Build an AX84+6V6. Build a stereo head chassis with a complete AX84 amp and a complete AX6V6 amp.

7/4/2000 5:11 PM

They will work fine for both tubes, with the EL84 being a better tube because of it's full power at lower B+ rating.
Right, those OTs and PTs are not big enough to run both power tubes at the same time.
You can do what you wanted with the switchable dual power tubes, but keep in mind a 6V6 takes a much larger preamp drive signal to turn on full bore and an EL84 requires much less then that... in other words if you optimize the preamp for the EL84, the 6V6 will always sound a little wimpy and if you optimize for the 6V6 the EL84 will go into unuseable and unmusical nasty over drive distortion pretty quickly.
If you use the 6V6GT as the main tube, your
"tube switching" would also have to send a bunch of the preamp signal to ground, or limit the signal before the grid of the EL84 somehow.
Personally I like the SE 6V6GT sound better then the EL84 but I do both also.
Bruce

7/4/2000 5:53 PM

Dean Hazelwanter

Thanks for the *speedy* reply, Bruce!

Ok, the 6V6 requires a hotter signal, so messing with R6 and R10 (the post tonestack voltage divider on the Rev11 AX84 P1 schematic) should fix that, right? What (if any) other changes, especially in the cathode (bias) circuit and the screen circuit are necessary?

How would you characterize the difference in tone between the EL84 and the 6V6, and what is the difference between the 6V6 and 6V6GT?

Thanks for all your assistance!

6/28/2000 2:48 AM
Winnie Thomas	Josh, You can use a Hammond 125E. Also, Antique Electronic supply has some surplus 5000K into 8 Ohm OT's for less than $10. Winnie

6/28/2000 5:40 AM
Josh	would the 10watt fender champ OT work well for this? Josh

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