Harman Kardon A-10 Reboot to Stout TMB or Superlite II

[Eulipian]

Just acquired a Harman-Kardon A-10 from flea-bay. Schematic attached. Two EC83 Two EL34 EZ80 rectifier. My intention is to reformat it as an 18-Watt and wonder what the pros who have built one would suggest to a noob who has not regarding: (1)  whether it would serve as a good donor candidate for 18W Stout TMB; (2) same for SuperLite TMB conversion; (3) problems with Stout or SuperLite TMB conversion; (4) any other ideas about whether or not to try this at home?

Thanks for any thoughts.

[sluckey]

Looks like a good candidate for a conversion or donor to me. Should be good for any of the EL84 P/P guitar amps.

[Eulipian]

Looks like a good candidate for a conversion or donor to me. Should be good for any of the EL84 P/P guitar amps.

Thanks Steve.  I notice the Stout uses a filter choke.  I don't think the Superlite TMB does.  Are there any implications for the redo to adding one to the circuit, other than space?


Thanks,
Carl

[Scsoul]

The HK would make a great doner for a 18watter you could use the choke if you want though there not commenly used, biggest challenge is the output transformer,  marshall used a oversized 8k Ryuot in there 18watters about the size of a 30 or 40watt fender ot. it gives the amp a huge sound and feel these amps are loud.   voltages on the HK schematic look great for the marshall conversion thougj you may want to invest into true 18watt marshall OT,  doug has them for about 50$,  being your first build you might try the lite vesion of the stout with just volume and tone, ive built 18watters with TMB and the supetlite and there not all that versatile  the liteIIb is the version i like too build myself, or you could try the classic 1974 tremlo version which is a killer amp.  What ever you decide to build you wont be disappointed   good luck.  Mark

[Eulipian]

The HK would make a great doner for a 18watter you could use the choke if you want though there not commenly used, biggest challenge is the output transformer,  marshall used a oversized 8k Ryuot in there 18watters about the size of a 30 or 40watt fender ot. it gives the amp a huge sound and feel these amps are loud.   voltages on the HK schematic look great for the marshall conversion thougj you may want to invest into true 18watt marshall OT,  doug has them for about 50$,  being your first build you might try the lite vesion of the stout with just volume and tone, ive built 18watters with TMB and the supetlite and there not all that versatile  the liteIIb is the version i like too build myself, or you could try the classic 1974 tremlo version which is a killer amp.  What ever you decide to build you wont be disappointed   good luck.  Mark

Thanks Mark. I appreciate the input.


Carl

[Eulipian]

Looks like a good candidate for a conversion or donor to me. Should be good for any of the EL84 P/P guitar amps.

Looking at the specs on the EZ80 vs. the EZ81 there seems to be a significant difference.  Valve Museum says: The EZ81 was the big brother to the EZ80 full wave rectifier, giving 150 mA against the 90 mA for the EZ80.  If I substituted an EZ81 are there any implications re the PT? I assume that the increased amperage to the plates could be addressed in the circuit if it's too high and that won't be an issue, but you know what they say about assumptions...


Thanks,
Carl

[sluckey]

If I substituted an EZ81 are there any implications re the PT? I assume that the increased amperage to the plates could be addressed in the circuit if it's too high and that won't be an issue, but you know what they say about assumptions...

The only issue is... can the PT supply the additional .4A filament current. I would certainly try it.

There will not be any increased plate current. The amp circuit determines how much plate current will be required

[Eulipian]

If I substituted an EZ81 are there any implications re the PT? I assume that the increased amperage to the plates could be addressed in the circuit if it's too high and that won't be an issue, but you know what they say about assumptions...

The only issue is... can the PT supply the additional .4A filament current. I would certainly try it.

There will not be any increased plate current. The amp circuit determines how much plate current will be required

Thank you Steve. 


Carl