Parallel el34 OT question

[rkscott7]

Hey I have two 12 watt SE OT at 5K if I ran two el34 in parallel that would half the impedance?Could I run the OTs in parallel (correctly phased)?I got three of these smaller OTs would hate to have to buy a big ass $$$ OT

[rkscott7]

Well one thing i was looking at is SE in triode not pentode the z is a lot lower like 2K in pentode my mistake I need to recalculate.
Has anybody ever run a speaker secondary in a delta config? I was just wondering if this made sense to anybody sometimes some great designs were made just by the engineers having to work with the parts they hahttps://ampgarage.com/forum/download/file.php?mode=view&id=64852&sid=d6d1841a07366e9af5c3ccdfd578723dd.

parallel el34 wdelta.pdf

[pdf64]

What’s the benefit of the delta connection of the secondaries?

[rkscott7]

To tell you the truth PDF I don't know if there is an advantage to running Delta Im a DDC and chiller tech I know delta is an ultra effiecient way of running electric motors a speaker coil really is a type of motor I was hoping some brainiac engineer type might have some input on this idea without tearing me to shreds.LOL
The only thing that I can see different would be the OTs would be firing simultaneously so there would not be a true three phase but for speaker sound that would be what you wanted anyway in most cases.I have heard about old ampeg bass cabs with opposing fired speakers but I don't know if the efficiency is lost if there is not a true three phase.

[pdf64]

With motors, delta wiring is great as it works with the 3 phase supply to spin the rotor.
But however you arrange them, you’ve only got a single phase available from the OT secondaries. The only variable is the relative polarities of the various windings and voicecoils; get that stuff wrong here and efficiency will take a dive, and may stress the output stages.

[rkscott7]

A PSC single phase uses a capacitor to generate a pseudo third phase but then a gain that is really 2phase they just don't call it that.Which comes back to the question of why would you want speakers firing out of phase anyway? I guess the only thing you could do is wire one speaker to fire back ward and the other two forward giving the cabinet a push pull effect but speakers are not designed to run backward and if you wanted one to you could just reverse the polarity. yup I'm about done with this I guess its handy for coupling a trio of under powered ots to give you a larger out put but very complicated wiring.

[pdf64]

Try to avoid getting phase and polarity mixed up.
Working with a fixed mains frequency, it's possible to use a cap or inductor to get a fixed phase shift.
That's not going to be the case when dealing with the audio, or even just the guitar, bandwidth, phase shift will change with frequency.
If conducting a single frequency circuit analysis, a polarity flip looks the same as a 180 degree phase shift, however a polarity flip affects all frequencies equally.
A phase shift contains a time shift component, whereas a polarity flip doesn’t.

[statorvane]

For my parallel SE amplifier, I wired the OT primaries in parallel, the secondaries in series. The OTs are Hammond 125ESE. This is essentially two AX84 P1Extreme poweramps running EH 6CA7s (close enough to your EL34s) into a 4 x 10" Marshallesque open back cab w/4 Emi Ramrod speakers @ 8 Ohms impedance. I did not have to resort to delta thingy phasing or three OTs, etc. I tried to keep it simple.

Let me know if you want the schematic.

[rkscott7]

That sounds pretty damn cool.Do you have a sound bite? PDF I see what your saying since we are dealing with varying frequency the phase is not a constant either.
I would like to see the schematic .I also have a question if either of you can answer it. I need 4 amps of filament current for a build but the only transformers I have put out three.Is there any way to wire them together that wont burn them out on each other?

[sluckey]

I need 4 amps of filament current for a build but the only transformers I have put out three.Is there any way to wire them together that wont burn them out on each other?

Yes. Just connect the secondaries in parallel, but you must get the phasing correct.

[rkscott7]

Okay I have done this with Power transformers on an oil furnace a long time ago I'd forgotten that you could do this. The way I made sure they were phased correctly striking them very quickly together if I saw a big blue spark wrong phase thanks slucky. Hey I've tried to register at Hoffman amps go there for years it's like I've been blocked or something maybe too many attempts to register you know people over there right? Also I've been looking at your AO 35 rework that's some pretty nice stuff. I have an AO 39 that's been sitting around that's the one I believe it was a Reverb amp on an A100 it does not have a preamp and the power trannie looks smaller I was going to try and find another and make a hi fi mono block amp but I could not find any

[sluckey]

you know people over there right?

Yes. A lot of them hang out over here too.

Also I've been looking at your AO 35 rework that's some pretty nice stuff.

I've never messed with an AO-35.

[bepone]

Hey I have two 12 watt SE OT at 5K if I ran two el34 in parallel that would half the impedance?Could I run the OTs in parallel (correctly phased)?I got three of these smaller OTs would hate to have to buy a big ass $$$ OT

instead of paraleling the transformers why not to connect each transformer to each EL34? EL34 circuits cathode, grid leak, grid stopper etc build separately for each EL34. inputs g1 over separated coupling capactors connected to the same point .secondaries in series.

this configuration can be very interesting, variety of bias possible, EL34 can be biased differently one hot, one cold, both the same, different cathode capacitors etc etc etc

[rkscott7]

Very cool Idea

[rkscott7]

If I wire the secondary in series isnt that going to change the impedance on the primary's?