TomSix
ALO Audio Studio Six deisgner
Has anyone tried to use the GZ37 CV378 Philips/Mullard as replacement for the current GZ34 / 5AR4? Are the G37 and GZ 34 compatible? I am looking at one NOS Mullard GZ37 from the 1960 as replacement of my current stock JJ. I am currently running two Marconi 6V6 and a GE-Ken Rad 6SN7GT Black Plates 1949, the latest has brought back balance tot he SS after the Marconi introduced a little narrow soundstage but amazing smooth, "tuby" sound. Any feedback from the forum and its amazing and knowledgeable members is highly appreciated.
MelaVerde,
I would hesitate to recommend using a GZ37 type rectifier in place of the specified GZ34 type rectifier used in the Studio-Six.
Yes, both tubes have identical base/pin connections, so that's not a problem. The GZ37 requires 2.8 amps of filament current, and that's no problem either, because the ST-6 power transformer is rated at 3 amps max 5V filament voltage.
A caveat, however, is that the GZ37 specifications are for a maximum of 4uF capacitance in a capacitive input filtering connection, and the ST-6 has 24uF input filter capacitance, and so exceeds the specified limit for the GZ37. This may or may not cause a failure of the tube in actual practice, but I would caution against taking the chance.
Also: the GZ37 has over three times the voltage drop of a GZ34/5AR4 type rectifier, and so you would get a reduced B+ voltage to the Studio-Six as a result. This could particularly be an issue if/when using the Studio-Six phono stage.
A likely result with the GZ37 would be a softer, less dynamic sound with decreased bass performance as compared to the specified GZ34/5AR4.
So yes, I do suggest staying within the GZ34/5AR4 family of rectifier tubes for the Studio-Six.
I believe you will likely find that trying various varieties of 6V6 type output tubes is the most effective route towards finding a sonic presentation from the ST-6 which most suits your personal tastes.
I hope that helps
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