Will MV Twin PT handle 4 EL34

[Stanz]

I have searched through and seen several responses to this question, but they usually refer to a replacement PT. I get that replacement PTs, when compared to a 60's Twin PT, will have a higher than stated current capacity for the heaters. Still looking to see if anyone knows if a MV 70's Twin PT will handle 4 EL34 as well as all 6 12ax.. tubes.

[tubedogsmith]

Probably not the answer you're looking for but, some of the will and some of them won't. Go ahead and try it. Play the amp for a while and then lay your hand on the outside bell of the PT. If it's not too hot to touch you're probably OK.

[Bob-I]

I don't agree that temperature is the way to test this. I'd measure the heaters watching for voltage drop. If the heaters drop more than a few 1/10's of a volt with EL34's, add on a filament xformers.

[tubedogsmith]

Bob, I don't disagree with you, the voltage will usually drop some but the trannie may very well still be able to take it, most were over rated. With the wall voltages to day there is most likely still plenty of juice as well even with the drop.

[Firestorm]

I sure wouldn't count on that PT to handle 4 EL34s. Sure, it MIGHT, but it's potentially a pretty expensive experiment. The tranny is likely rated for 5.5 amps, and you'll be asking if to deliver nearly 2.5 amps more.

At the very least, I'd get a 2 amp 6.3 volt auxilliary transformer and pulll the preamp tubes off the main PT. That will free up almost 2 amps of current for the EL34s and I'm sure the original tranny can handle the difference between 5.5A and 6A.

[Stanz]

Thanks for the ideas. I would imagine running it once for a short enough time to measure voltages shouldn't get it hot enough to do damage. I also have considered just running it with two EL34s. It is not like dropping a few db would hurt anything, but I always wondered if the speakers remaining at 4 ohms would affect the sound, since the OT only has the one secondary.

[Firestorm]

If you pull two output tubes, you'll be better off running an 8-ohm speaker cabinet. I had a Twin once that had been equipped with 2 16-ohm speakers for just the reason. Optimal impedances for EL34s are already a bit different than for 6L6s, so running to a half-size load will only make things worse. It shouldn't be dangerous, but it won't sound the same.

[Stanz]

I have set up my speakers with a switch so I can go either 4 or 8 ohms so I can use the speakers for amps that are set up for 8 ohms. Using Emi RWB and they are rated at 125W. I am not gigging with this amp, just recording, so not a problem. I still am not clear on the whole OT / speaker load thing. 4 EL34s is really what I want, but that seems like a whole new project and I got it running pretty nice with 4 6L6s, I just want EL34s as an option.

Thanks

[Firestorm]

You've got it pretty simple then; rewire the sockets for EL34s, stick two in and run an 8-ohm speaker load. If you like what you hear, add a filament transformer and go with 4 EL34s into 4-ohms. But I can't imagine why you'd want 4 EL 34s for recording. Most guys can't stand the volume playing live!

[Stanz]

I am living on an old military base and the interior walls are made of masonry. I have a separate room just for amps and vocals. Pretty stout building. But you are right, the 100W 6L6 HRM is a beast (built from an MV Quad), as is my Twin. I am loving my 5E3 deluxe and AC15. That is about the right size in my book. My main reason has to do with my inclination that four output tubes has a different feel and sound. I think it has to do with four different sound sources all being slightly "off" coming together to make a harmonically rich tone, as opposed to two. Thanks for all the input. Going with two tubes sounds like the easiest route, and with all the projects I got going, this HRM is a wrap.

[heisthl]

I have set up my speakers with a switch so I can go either 4 or 8 ohms so I can use the speakers for amps that are set up for 8 ohms. Using Emi RWB and they are rated at 125W. I am not gigging with this amp, just recording, so not a problem. I still am not clear on the whole OT / speaker load thing. 4 EL34s is really what I want, but that seems like a whole new project and I got it running pretty nice with 4 6L6s, I just want EL34s as an option.

Thanks

You mean you have 2 speakers and a switch that disables one of them?
Otherwise I'd like to know how 2 speakers can change from 4 to 8 Ohms on a switch.

[Stanz]

You mean you have 2 speakers and a switch that disables one of them?
Otherwise I'd like to know how 2 speakers can change from 4 to 8 Ohms on a switch.

Yep, wired two 8 ohm speakers in parallel with a heavy duty carling switch to switch out one of the speakers. This allows me to use the RWB for a head needing 8 ohms. At 125 watts each, more than enough to handle anything I will throw at it. Although, I am really liking my Avatar 1x12 open back with a 50W Emi Red Fang. mmmmmm