October 16th, 2018, 7:43 pm
Roscoe Primrose wrote:Grover Gardner wrote:About twenty years ago, I attended a listening session that featured Lowther speakers in fancy plywood boxes driven by single-ended 300B monoblocks built entirely with vintage Western Electric iron. About $12,000 there. Acoustic guitar sounded wonderful, Mahler not so much. The wine was flowing and in the middle of the session, our host for some reason plucked a $2000 1950's WE 300B out of one of the amps--he was going to make some point about the construction, I believe--and bobbled it. The rest of us watched it fly into the air...and drop on the hardwood floor. And I thought, that's not's going to be me.
I watched Vu's (ex I believe) wife pick up a boxed NOS 50 once and the bottom of the box came open.....
Roscoe
October 16th, 2018, 8:28 pm
Stuart Polansky wrote:Hey Grover,
I'm putting together a set of Class A amps that can use any of the common octal output tubes: KT100, KT90, KT88, KT77, KT66, EL34, 6L6, etc., just so long as the pinout is the same.
My application will have two channels used from ~100Hz to 3.5kHz, the other from 3.5kHz up.
I can use different tubes in each of the four "channels". With the larger set of tubes, ~ 25WPC, the smaller ones ~15 WPC. I think even the 15WPC will be more than adequate.
Given your expertise, and what Charlie tells me are a great set of ears, what would your tube recommendation be? Price is an issue!
Thanks,
Stuart
October 17th, 2018, 7:17 am
October 17th, 2018, 4:46 pm
Roscoe Primrose wrote:Grover Gardner wrote:About twenty years ago, I attended a listening session that featured Lowther speakers in fancy plywood boxes driven by single-ended 300B monoblocks built entirely with vintage Western Electric iron. About $12,000 there. Acoustic guitar sounded wonderful, Mahler not so much. The wine was flowing and in the middle of the session, our host for some reason plucked a $2000 1950's WE 300B out of one of the amps--he was going to make some point about the construction, I believe--and bobbled it. The rest of us watched it fly into the air...and drop on the hardwood floor. And I thought, that's not's going to be me.
I watched Vu's (ex I believe) wife pick up a boxed NOS 50 once and the bottom of the box came open.....
Roscoe
October 17th, 2018, 8:45 pm
Stuart Polansky wrote:Thank you for the recommendations.
Stuart
October 17th, 2018, 10:25 pm
Grover Gardner wrote:Stuart Polansky wrote:Thank you for the recommendations.
Stuart
You're welcome, hope it helps. I tried to build a simple, cheap no-feedback PP triode amp with beam tubes/pentodes. Never sounded good to me. These little Williamsons are another matter.
In 1952 the Navy tested a bunch of commonly available Williamson amps. The low-frequency capabilities were of interest to them in their sonar research. They were consistently blown away by the Peerless S-265-Q. With no alterations to the stock circuit, bandwidth and squarewave response were almost flawless. The Partidge WWFB got good marks, but the Patridge CFB, something of a holy grail for Williamson devotees, was disastrous. They tried two samples and a number of tweaks, and nothing helped. Poor bass response and above 10K it looked like a roller coaster. Interestingly, a low-cost Stancor did extremely well with the addition of a tuning cap across the feedback resistor. Another loser was the Acro TO-300. It rang like a bell above 10K and absolutely nothing they tried could get rid of it.
I guess I'll ask Mike LaFevre if he'll still make some S-265-Q's on special order. Probably cost an arm and a leg. But it appears to be the hands-down OPT of choice for a triode Williamson design.
October 17th, 2018, 11:06 pm
October 17th, 2018, 11:16 pm
Roscoe Primrose wrote:Grover Gardner wrote:About twenty years ago, I attended a listening session that featured Lowther speakers in fancy plywood boxes driven by single-ended 300B monoblocks built entirely with vintage Western Electric iron. About $12,000 there. Acoustic guitar sounded wonderful, Mahler not so much. The wine was flowing and in the middle of the session, our host for some reason plucked a $2000 1950's WE 300B out of one of the amps--he was going to make some point about the construction, I believe--and bobbled it. The rest of us watched it fly into the air...and drop on the hardwood floor. And I thought, that's not's going to be me.
I watched Vu's (ex I believe) wife pick up a boxed NOS 50 once and the bottom of the box came open.....
Roscoe
October 18th, 2018, 3:45 pm
Grover Gardner wrote:TubeDriver wrote:Do you know how the TO-330 faired?[/quote+"TubeDriver"]
It was not among those tested. The candidates were McIntosh 20, 50 and 100 wpc, a Scott 221 (which they found irredeemably poor), a handful of Williamson triode circuits including the Stancor kit, a Craftsman and some long-gone brands, and a few ultra-linear Williamsons. You can google "navy williamson test" and see the results. It's very interesting.
I've read elsewhere that the Acros are not all they're cracked up to be and very circuit-specific. I have a pair of the TO-330s myself. The Acro catalogue features a PPP 807/KT66 schematic that's rather tempting.
October 18th, 2018, 8:54 pm