You could also look at SY’s Red Light District amp thread here for ideas, although that was a pentode design. You could do worse than emulating that since you’ve already got EL84s connected to UL OPTs. Many people like the sound of the Dyna ST-35 which used triodes only in the gain stages in the power amp (it used a 12DW7 which is like a half 12AX7 plus half a 12AU7 in one envelop). Canuck Audio Mart is FREE Forum Messages. Unless you really want a project, the first option is not a bad way to go. of 12AX7s is like the Heathkit SA-2 Ive done the obligatory newsgroup search for this topic. These transformers were used in the following Heathkit EL84/6BQ5 amps: UA-1 UA-2 SA-2 EA-2 EA-3 AA-13 AA-111 AA-151 AA-161 Thanks. You have several choices here, just clean up the existing design (new caps and tubes, etc.) and enjoy a classic tube sound, or you can go all the way to the other extreme and salvage only the iron for something different.

There was purported to be some advantage in sharing current through just one resistor from bias averaging, although as I recall Dyna suggested buying matched quads of EL84s anyway. There’s nothing criminal about combining the four cathode currents, but channel separation and sound quality depends on the quality of the 100uF (or 50uF) cap. Can anyone tell me what sound characteristics should I expect from this amp Also, any info regarding Heathkit is appreciated. Will hook a pair of PSB B-25 speakers to it. The shared output tube cathode resistor was also seen in Dyna's EL84 amps, the SCA-35 and ST-35, although in those cases the resistor was 95 ohms and the bypass cap was bigger at 100uF. Heathkit Integrated Amp SA-2 Hide sidebar Guangui G Guangui Full Audioholic 1 I just got a vintage Heathkit SA-2 as a gift. Replaced the 6AN8 tubes with identical 6AN8A tubes.As Robert says, this is a classic configuration: a basic pentode gain stage followed by triode splitter circuit, driving ultralinear PP EL84s, with global feedback. Measured voltages with tubes removed to make sure they look correct. Did resistance checks with tubes removed to make sure all resistors in the stage were within tolerance. Verified wiring (after all, it was a kit) Note: The filament voltages are correct on both tubes. Use Hifi Shark to monitor pricing and global availability. I have the voltages listed below with the values from the schematic in parenthesis. Used Heathkit SA-2 Integrated amplifiers for sale on 400+ second hand hifi sites & shops. All voltages check out except for the voltages on the 6AN8 tubes that make up the power amplifier section. I went one step further and checked all power supply and tube voltages against the schematic. The amp passes the rudimentary initial test in the back of the manual.

So far I have replaced all electrolytic capacitors and any tubes that are marginal or have failed. I am restoring my father's Heathkit SA-2 14Watt Amplifier.

Heathkit sa 2