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4 ELl84’s convert to 2 EL34’s
Posted: Mon 02/09/15 2:37 pm
by glhein
A couple questions…I own a 36 watt amp running 4 el84s. (VHT Standard 36)
If I was considering converting the amp to use 2 el34’s, should the stock transformers work?
This amp has a cathode cap and resistor for each pair of tubes…pulling the outer 2 or inner 2 to reduce power and headroom should not be a problem right?
Thanks in advance
Re: 4 ELl84’s convert to 2 EL34’s
Posted: Mon 02/09/15 7:38 pm
by dotfret
It would help if you actually quoted the transformer type/model, but one would imagine that the transformer would also be suitable for using a pair of EL34.
If you pull one valve of each pair, it might be expected that the amp would run that way under reduced power, but the output load the remaining pair sees has to be considered. As a rule of thumb, doubling the set output impedance is a way forward - so if you take out one from each pair, and the amp is set for 4 ohm output, use an 8 ohm speaker load to avoid creaming something.
Re: 4 ELl84’s convert to 2 EL34’s
Posted: Mon 02/09/15 10:06 pm
by glhein
I run an 8 ohm load now...so I take it I need to run a 16 ohm speaker load but use the 8 ohm speaker jack to avoid mismatch.
Re: 4 ELl84’s convert to 2 EL34’s
Posted: Tue 02/10/15 2:16 pm
by dotfret
Yes, but it is only a rule of thumb - you really should calculate the effect - but that is how most of the amps that are designed to work on 2 or 4 output valves work.
Re: 4 ELl84’s convert to 2 EL34’s
Posted: Thu 02/12/15 1:30 am
by CurtissRobin
glhein wrote:A couple questions…I own a 36 watt amp running 4 el84s. (VHT Standard 36)
If I was considering converting the amp to use 2 el34’s, should the stock transformers work?
I wouldn't go there. The operating characteristics of the EL84 and EL34 are utterly different and even if the PT and OT would handle the EL34 I'd expect the vibe would disappoint you.
This amp has a cathode cap and resistor for each pair of tubes…pulling the outer 2 or inner 2 to reduce power and headroom should not be a problem right?
It may work fine or it may not. I suggest that you carefully evaluate the circuit before doing that.
KennyO
Re: 4 ELl84’s convert to 2 EL34’s
Posted: Thu 02/12/15 6:55 pm
by glhein
Thanks for the replies.
Re: 4 ELl84’s convert to 2 EL34’s
Posted: Thu 02/12/15 7:17 pm
by JMPGuitars
Don't worry too much about "the vibe" - that's a personal taste thing, and can be tweaked if necessary. I also love EL34 tubes and will be doing a similar amp soon. I started drawing it up, but I've been too busy to finish. Hopefully by the summer I'll have time to get it going.
EL34 and EL84 tubes are very different, and I definitely want at least one of each in my arsenal.