Good evening.
As we all must have noticed, tubes are getting more and more expensive. Instead of stockpiling spares for every new project, how about building one amp with two or more different sockets in every position, wired in parallel to allow different tubes to be used (only one at the time for each position, of course)?
This idea struck me a couple of years ago when I couldn´t decide whether to use 6L6s or 807s in a project, I had both types on the shelf but only in small numbers.
I´ve mostly been building guitar amps during the pandemic and lately I´ve been thinking about an amp with one row of 7 pin miniature sockets (6AU6 input stage, 6J6 phase splitter and 2x 6AQ5 outputs for example) and one row of novals (EF86, 12AT7 and 2x6BQ5). Grid and plate connectors would be common for both rows but at tleast the output tubes would require separate cathode bias resistors.
Any thoughts on this?
As we all must have noticed, tubes are getting more and more expensive. Instead of stockpiling spares for every new project, how about building one amp with two or more different sockets in every position, wired in parallel to allow different tubes to be used (only one at the time for each position, of course)?
This idea struck me a couple of years ago when I couldn´t decide whether to use 6L6s or 807s in a project, I had both types on the shelf but only in small numbers.
I´ve mostly been building guitar amps during the pandemic and lately I´ve been thinking about an amp with one row of 7 pin miniature sockets (6AU6 input stage, 6J6 phase splitter and 2x 6AQ5 outputs for example) and one row of novals (EF86, 12AT7 and 2x6BQ5). Grid and plate connectors would be common for both rows but at tleast the output tubes would require separate cathode bias resistors.
Any thoughts on this?
Blackie Pagano built such amp for NY Noise. He had many tubes already pre-heated for easy no delay rolling.
You might have problems with noise and hum due to the non tubed socket being an antenna due to the non connected wires. I’m playing with the idea of doing it anyway just for testing. I’m going to wire up parallel 8 and 9 pin sockets so I can use either a 6sl7 or a 6cg7 to see if there is any difference. I’m going to use individual grid stoppers on each socket but other than that they will be jumpered pin to like pin. Hey, Columbus took a chance! Look what happened to him! E died broke with VD! I’m hoping for better results.
That's an interesting idea, although propably more so for hifi than for instrument amps. I mentioned tube rolling which sure can be interesting, especially since this would allow comparing tubes that are only vaguely equivalent, the other purpose would be to have an amp that can be populated with a broader range of tubes, like cooking something edible out out leftovers.
This sure is a concern, though I think it should be managable with close proximity between the sockets, separate grid stoppers and by avoiding high gm tubes?
He probably played guitar, too...😀
You don't really need multiple sockets for each position, just make an adapter to fit the standard socket in use. Use a pin aligner tool to hold the pins in position in an adapter PCB for soldering. Using 2 stacked adapter PCBs allows changing pin configuration with short wires.
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