5k pushpull output transformer =a-a is 5k......but a to+....(one tube)= 1.25k.......not 2.5k.
The PP is for boxed 414-8A 60-300Hz midbass. Saving my only pair of E280F’s for 6B4GSE to the 3-horn combo 300Hz-20kHz.
Visited my warehouse yesterday and found a box with ten 6E5P. A pair of those will make better drivers than an E88CC, whichever I choose from autoformer or concertina.
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Another option is to use the two LL1667 5mA 800H I also found yesterday as Iron concertina´s at 4.5mA. On the downside is that they are quite bulky, will measure the chassi I picked up, to see if they can be shoehorned in.
Having been away from audio for more than ten years, have made me forget all the good stuff laying around.
Having been away from audio for more than ten years, have made me forget all the good stuff laying around.
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Some of the transformers for these experiments are relatively exotic (pricey) to a DIYer. I read somewhere that the humble little transformers used in Philips radios with 800R loudspeakers make excellent interstage transformers. The article was using one for driving a 300B, but I cannot locate it. I think the OPTs are 4500:800, and I think there are sources that have stocks from scrapped radios (Ask Jan First springs to mind).
They do not have a centre tap, but could a pair in series be used?
They do not have a centre tap, but could a pair in series be used?
Have now discussed the matter with Mirza at Lundahl and his explanation to why the Lundahl chokes will not work, is that coupling between the coils is low, ie two separate transformers are ruled out.
This means that the autoformer issue is out of the question for me.
This is my solution, all iron-free, though an advice of a suitable 500V PMOS would be great😉.
This means that the autoformer issue is out of the question for me.
This is my solution, all iron-free, though an advice of a suitable 500V PMOS would be great😉.
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Hey Fossa, please note we are discussing theories by using Spice. About Mirza, he can not.
k, the coupling coefficient, can be measured by short-circuiting one of the ports while
measuring the inductance of the non-short-circuited port.
I don't have a meter that can measure inductance that high.
measuring the inductance of the non-short-circuited port.
I don't have a meter that can measure inductance that high.
"I don't have a meter that can measure inductance that high."
Several years ago I bought DER EE 5000.
Measuring up to 2000H is enough good.
Several years ago I bought DER EE 5000.
Measuring up to 2000H is enough good.
You can use like 4M7 resistors in DC voltage divider, the upper one shunted by a cap.
Sorry I'm late to the party. I built this some years ago and it sounded fantastic. Had to sell it, much to my regret as I needed the money at the time. It used the Magnequest EXO-173PPS, that were modified for phase splitting. Originally they were a grid choke used in the Altec 1570B but Mike LaFerve redesigned the winding for better symmetry.
