Recommend Modern New Production 6550 for Mark III

BNR_1 wrote:Hello Everyone:

So searching the subject matter did not reveal anything recent like in the past 12 months.  So I would like to get your opinion and recommendation on modern new production 6550 tubes for a older generation Mark III amp.  My cousin is persuading his co-worker to sell to him his dad's amp.  His father passed away some time but his co-worker never tested it.  He did indicate there were no tubes except the small one (6AN8).  So my cousin will do the typical maintenance but eventually will need to get new power and rectifier tubes.  I have a couple spares of JJ 5AR4 to give him, but I have no idea which of the newer made 6550 is recommended for both sound quality and durability.  Before anyone post to go with NOS or tested OS from a reliable vendor my cousin is on a tight budget so neither of those options will work at the moment.  Besides, I recommended to him for testing he shouldn't use NOS or OS tubes.  But he did make a point that he didn't want to go with the cheapest for testing and use better modern tubes when the amp is proven reliable.  He wants one purchase to work for him under all situations.

Thank you

BNR_1 wrote:I recall the higher quality of the Winged =C= tubes so I will add it to the list.  But for some reason i thought they stop making tubes.

JJ and Gold Lions are duly noted.

Any others opinions and recommendations?

While it is some what related can the KT88 new production tubes be a simple drop in to the older version of the Mark III amps?  I realize biasing is a must.  I read in other forums that the KT88 can be used but it appeared that the Mark IIIs in the posting were the newer kits so I assume the PT is rated for such use.  But for the older Mark IIIs can I use KT88s?

Thank you

BNR_1 wrote:Thank you everyone.

Stew thanks for the link.  I need to verify which amp my cousin has.

If the power tubes are KT88s but biased for 6550s do you think it would last longer?  Sound quality maybe an issue, however.  Don't know.

BNR_1 wrote:The filament tranny I plan on using is rated for 10A.  I believe those are more then suitable for my purpose.  I don't own any Mark IIIs, but that will be my goal someday.  Hopefully the bucking tranny will be capable of handling the 2 amps and then some.

I have no idea if the fatboy KT88s will be too close.  I have seen images of EH KT88s on the Mark IIIs, and I just learned on my posting that the later Mark IIIs were designed around these tubes, but if the fatboys are much bigger than the average KT88s then someone will chime in.