Migrating to triode amps and more sensitive loudspeakers.
These are two monoblock Ultralinear amps, built on the Hafler/Keroes schematic.
They have the following iron under the hood:
T1 Triad Ultra R-5A outputs 600 VAC at 65mA (primary) and 6.3 VAC at 2.7A
T2 C354 Dynaco filter choke
T3 Freed FT3273670A
T4 Stancor P-8357-B (secondary in series with T3 section 1 as voltage doubler
T5 Freed output transformer FT3273671A The 16 ohm tap is used for negative feedback.
Each amp was serviced in 2013 by Jason Kritz of Sugar Grove, NC.
He meticulously wired each lead for the next service tech.
There are three modifications to the original schematic:
The input jacks are two different colors, white and red.
There is a triode "lift" switch.
The bias resistors were replaced with precision 1 ohm values, so when reading the bias meter 1 mW equals 1 mA bias current.
Wired for 110 VAC 60 hz
When tested with KT88s (Jason likes that tube best) with conservative bias the amps output just over 130 watts at 1kHZ in ultralinear, 65 watts in 'triode' mode.
I use KT90, and keep the bias low - around 35 mA. More power could be gained, running the output tubes hotter, but that's not for me.
The tubes included are Marked KT91 Audio Research and have lots of little welds all over the main plates - I think these are Type II.
There's about 500 hours on these, at my operating bias only.
Sold as pictured, with the tube complement as shown (I will label them so that getting bias again will be simpler.)
THEY"RE HEAVY - shipping won't come cheap. Figure $50 for each chassis in the US.
They were used to drive Quad ESL63, crossed over at 100 hz. In my opinion, that sounded best in Ultralinear.
$2250 including all tubes shown, for both amplifiers - shipping paid by buyer.
PayPal preferred, I absorb the fees.
