2 channel 4 el84 amp, useing both ots

[menger]

iv got a rca power amp 2 channels 2 ots cathiod biased, can i use both ots for a 36watt build, i remember there was a guy awhile back that was gonna use 2 se ots combined for a 18 watt amp, iv no idea of specks of these ots although i dont think there 8k, most likely closer to delux iron 6.6K, i do have iron that is for 36 watters, but would like to save them, for a little nicer build than a conversion, is using both original ot a good idea, is it do-able? they are a tad smaller than true 18 watt iron, i was thinking something like a light basic pre amp cascade with just 1 input just a screamer, how would i hook up the ots? both primarys to pin 7 of the inner powertubes then run jumper wires out to outers? mark

[krx]

Never heard of doing that. I don't know if that makes sense since you'd have two secondaries (two primaries I'm okay with).

[rock_mumbles]

I've heard of connecting two identical output transformers in parallel, all primaries and secondaries are paralleled to double the power capacity ... with all primaries and secondaries paralleled the reflected impedance is the same ...

[Cathode_Ray]

Had a Silvertone amp years ago that did this. I think it was a "Twin 12". Actually single 4 6L6 amp using 2 output trannys. Got it in pieces so don't recall if series or parallel though.
In mid 70's tubes were scarce and $$$ so I lost a lot of what would be valuable hardware.

[p_christov]

The JTM45/100 has 2 OT's. I have seen the schematic with the OT's connected in parallel as rock_mumbles says.

Peter

[dotfret]

I saw something like that silvertone described a while back, running a centre tap from the join on the o/p side. Looked like an ingenious solution to using up an old stock of transformers.

[katopan]

As stated already if you parallel all the wires of the two transformers you'll still get an 8k primary and would have to mismatch the speaker load to get the 4k a quad of EL84s want to see.

I'd like someone to confirm what I'm saying, but I'm pretty sure if you parallel the primaries but series the secondaries then you'll have 4k. Depends on what taps you have on these OTs and what you need for the speakers you've got.

[p_christov]

Katopan,
It seems to me that it's the same case as in transformers with two secondaries that can be connected either in parallel or in series.
So if when connected in parallel you have 8K primary load, in series it must be 2K with the same speaker load.
But you can get 4K if you double the speaker impedance and connect the secondaries in series.

[katopan]

Thanks p_christov. Where's that head slap smiley? Of course connecting in series would give 1/4 the impedance rather than 1/2 for the same tap connection. So either way (secondary in parallel or series) you would need to mismatch the speaker load to the tap being used. You don't really gain anything by going series.