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In Reply to: RE: Eico HF-14 build from scratch posted by banpuku on March 25, 2015 at 06:11:13
An exact clone is not possible without the Eico audio transformers.
The EZ81 is an excellent rectifier tube for lower wattage output amplifiers. I prefer the higher current capacity Mullard GZ34, but is expensive.
I replaced rectifier tubes in DIY amplifier designs and find better performance using low noise SS rectifiers with a low DCR design power supply.
I believe a modern 'clean sheet' design would perform best. I recommend the readily available Dynaco clone audio transformers from Triode Electronics.
Follow Ups:
Newbie question: If I use the Mullard GZ34 in lieu of the EZ81, would I need to modify any other parts or circuitry?
The two tubes have different heater voltages thus the power transformer must support the rectifier tube being the GZ34 requires a separate & dedicated 5 volt winding. The EZ81 is fine for a 14 watt amp.
...you'll need at least a different PT with a 5V-2A rectifier winding. DC output might be a bit higher but probably within an acceptable range.
I am in touch with the manufacturer of the original Eico HF-14 transformers. They can build me original spec'd PT and OPT.
I also have the option of going with a new PT and OPT brand like Hashimoto, Lundahl, Tamura, etc.
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