Thanks, I've heard the "too complicated" comment before.
I built the SP-8 preamp with phono and line stages on the same board,
and it burns me that the phono tubes are burning
while I'm listening to the line stage.

Haha!

Tom wrote:Thanks, I've heard the "too complicated" comment before.
I built the SP-8 preamp with phono and line stages on the same board,
and it burns me that the phono tubes are burning
while I'm listening to the line stage.

Haha!

As far as I know, no commercially produced (single chassis) tube preamplifiers have ever offered a provision for separately powering up the line and phono stages. Yes, it increases the complexity which also increases the cost. The difference probably being enough to purchase a spare set (or two) of replacement tubes.

Best Regards,
Charlie

Ah! That rings of challenge.

If cost, complexity or even rationality
had anything to do with,
we'd still be listing to our first Close-n-Play.
(albeit with a cartridge upgrade)

It could be done but requires some thought, You could have a 3PDT switch which 2P switch the signals while a 3P actuates a bunch of relays which remove the cathode grounds on the phono pre stages. that would be costly in terms of space and complexity but doable if you really wanted it

dunwichamps wrote:It could be done but requires some thought, You could have a 3PDT switch which 2P switch the signals while a 3P actuates a bunch of relays which remove the cathode grounds on the phono pre stages. that would be costly in terms of space and complexity but doable if you really wanted it

And do you really WANT relay or switch contacts on the cathode grounds? Everything that flows in the plate circuit...and that is
what constitutes the sound that the tube stage "makes"...flows through the cathode, too. Whatever you do at the cathode, affects the sound.
Last time I looked, a straight soldered connection is still better than the BEST contact.

I say, "not worth the effort."

GP49 wrote:

dunwichamps wrote:It could be done but requires some thought, You could have a 3PDT switch which 2P switch the signals while a 3P actuates a bunch of relays which remove the cathode grounds on the phono pre stages. that would be costly in terms of space and complexity but doable if you really wanted it

And do you really WANT relay or switch contacts on the cathode grounds? Everything that flows in the plate circuit...and that is
what constitutes the sound that the tube stage "makes"...flows through the cathode, too. Whatever you do at the cathode, affects the sound.
Last time I looked, a straight soldered connection is still better than the BEST contact.

I say, "not worth the effort."

well i merely suggested how it could be done not that I would do it. I dont see much harm just letting the tubes idle all day which is why I just had switched inputs.

dunwichamps wrote:
well i merely suggested how it could be done not that I would do it. I don't see much harm just letting the tubes idle all day which is why I just had switched inputs.

Agree with you, there! Typically tubes in low level stages have a very long life anyway, so the gain isn't worth the effort.

GP49 wrote:

dunwichamps wrote:
well i merely suggested how it could be done not that I would do it. I don't see much harm just letting the tubes idle all day which is why I just had switched inputs.

Agree with you, there! Typically tubes in low level stages have a very long life anyway, so the gain isn't worth the effort.

i dont do much hifi stuff so I am typically ignoring hifi concerns in the design, that headphone amp was a special gift for my grandfather's 50 wedding anniversary and my 1st foray into building a stereo amp. Most of the time I am thinking about how I can absolutely make people deaf with huge guitar rigs.

build is just about to get rolling

here are the turret boards I fabricated for the build



the choke, power cord, and that small enclosure is for a footswitch



some other random items, tubes, a small hammond PT for the bias supply

main circuit board and main power board are coming along

chassis is in, dry fitting stuff to it

You would be good at Tron.

davidness wrote:You would be good at Tron.

ive never played it but possibly if my wiring style translates well.