sweep tubes and audio application?

Mcintosh Mc-3500 & mi-350 use the 6lq6 6mj6 sweep tube. Kirkus is correct about the transformer winding ratio's as the Mc-3500's have three separate transformers one of them being a very complicated winding configuration with only one company capable of winding this transformer.

Also 6lq6 tubes are costing around 40.00 a pop and you will need 16 for a pair of these 350 watt amps.

On the positive side these amps are one of the best sounding amps ever and will take on any S/S amp with comparable output

Milbert and Berning amps use the 6JN6 tube. NOS are still $4-5 each, often a buck a piece at ham shows. After many years of use, I've never had one go bad.

John C.

The Berning 2100 and the Counterpoint SA4 both used the now ridiculously expensive 6LF6 (though it is a very nice output tube). Expect $80-$100 per tube for NOS; you have ham operators to thank for the price.

-Richard

i thank u all...

The 6LF6 was used by Futterman in some of his OTLs. They have high-current low-voltage capability. They have become rather expensive as they are no longer made.

These days the EL509 is the tube that replaces the 6LF6 although not directly. It is a powerful sweep tube and is also used in OTLs. There is a non-plate cap variant that could be used, but FWIW the KT90 was developed from this tube, so if you really want something like that the KT90 is probably the place to look, as the design of the amp is made simpler by having no plate caps and the use of octal sockets.