829B as LTP?

DrewP · 15th June 2009, 02:47 AM

829 B is a dual tetrode with a shared cathode. I know that in the past people have parallelled the two halves and converted the whole thing into a triode for SE use.

Pondering... If you strapped it in triode on both sides, could it successfully work as a diff amp stage such as a common cathode phase splitter or an LTP?

Does it have any particular characterisitics that would make it unsiutable for this purpose?

Has anyone done this?

I have 4 NOS RCA 829B's sitting here under my desk and I'm wondering what use I could put them to...

aardvarkash10 · 15th June 2009, 03:33 AM

in the interests of Closer Economic Relations, and in defference to the ANZAC brotherhood, you should send them to your poor cousins in NZ. PM me for my delivery address...

aardvarkash10 · 15th June 2009, 03:39 AM

as I recall, they have a spectacularly low rating on the G2 which makes U/L problematic, but I always thought they would be a sitter for the "Compact" treatment. IIRC they have a reasonably easy drive requirement, so you could conceivably get a 10-12wpc pp stereo unit from three tubes - a dual triode voltage amp and two 829B outputs. Leaves you two spare 829B tubes for later when they start getting tired! Or you can send them to me...

DrewP · 15th June 2009, 05:35 AM

you're not set up for PM or email at present...

aardvarkash10 · 15th June 2009, 07:05 AM

no wonder I hadn't received any of the free-bees I've been soliciting!

Colt45 · 15th June 2009, 07:13 AM

The screen is common between sections, so you can't triode strap each section independently.

aardvarkash10 · 15th June 2009, 07:54 AM

to both sections, as is the cathode. Still, in pentode you can get PLENTY of watts out and still only need 36V pp to drive it. Triode is out though. here's a design - can't vouch for its quality however.

Bandersnatch · 15th June 2009, 01:00 PM

hey-Hey!!!,
There is also a g2-cathode internal capacitor. Rigging that one as triode requires a means to deal with substantial grid-plate capacitance. Now if you can do a LTP in pentode mode, that tube is a fine option. Type 832 as well...

cheers,
Douglas

Shoog · 15th June 2009, 06:22 PM

Since you are forced to use these in Pentode mode, then you should go look at Gary Pimms Tabor amp for inspiration. This design allows triode levels of output impedance with Pentode power, and all with local feedback. The sound is very neutral and has nothing of the pentode nastyness. Think of driving it with a pentode LTP for best results. The DC coupling is tricky to get right so I advise dropping it in favor of coupling caps.

Shoog

Merlinb · 17th June 2009, 11:26 AM

As Colt noted, the screens are shared. But you could still run it as a pentode LTP instead. Just for novelty?

15th June 2009, 02:47 AM	#1
DrewP diyAudio Member Join Date: Jan 2002 Location: Canberra, Australia	829B as LTP? 829 B is a dual tetrode with a shared cathode. I know that in the past people have parallelled the two halves and converted the whole thing into a triode for SE use. Pondering... If you strapped it in triode on both sides, could it successfully work as a diff amp stage such as a common cathode phase splitter or an LTP? Does it have any particular characterisitics that would make it unsiutable for this purpose? Has anyone done this? I have 4 NOS RCA 829B's sitting here under my desk and I'm wondering what use I could put them to...

15th June 2009, 03:33 AM	#2
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	...sigh... in the interests of Closer Economic Relations, and in defference to the ANZAC brotherhood, you should send them to your poor cousins in NZ. PM me for my delivery address... __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

15th June 2009, 03:39 AM	#3
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	alternatively as I recall, they have a spectacularly low rating on the G2 which makes U/L problematic, but I always thought they would be a sitter for the "Compact" treatment. IIRC they have a reasonably easy drive requirement, so you could conceivably get a 10-12wpc pp stereo unit from three tubes - a dual triode voltage amp and two 829B outputs. Leaves you two spare 829B tubes for later when they start getting tired! Or you can send them to me... __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

15th June 2009, 07:05 AM	#5
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	fixed! no wonder I hadn't received any of the free-bees I've been soliciting! __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

15th June 2009, 07:54 AM	#7
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	true, G2 and G3 are common to both sections, as is the cathode. Still, in pentode you can get PLENTY of watts out and still only need 36V pp to drive it. Triode is out though. here's a design - can't vouch for its quality however. __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

15th June 2009, 05:35 AM	#4
DrewP diyAudio Member Join Date: Jan 2002 Location: Canberra, Australia	you're not set up for PM or email at present...

15th June 2009, 07:13 AM	#6
Colt45 diyAudio Member Join Date: Feb 2002 Location: Canada	The screen is common between sections, so you can't triode strap each section independently.

15th June 2009, 01:00 PM	#8
Bandersnatch diyAudio Member Join Date: Jul 2003 Location: Ann Arbor, MI	hey-Hey!!!, There is also a g2-cathode internal capacitor. Rigging that one as triode requires a means to deal with substantial grid-plate capacitance. Now if you can do a LTP in pentode mode, that tube is a fine option. Type 832 as well... cheers, Douglas __________________ the Tnuctipun will return

15th June 2009, 06:22 PM	#9
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	Since you are forced to use these in Pentode mode, then you should go look at Gary Pimms Tabor amp for inspiration. This design allows triode levels of output impedance with Pentode power, and all with local feedback. The sound is very neutral and has nothing of the pentode nastyness. Think of driving it with a pentode LTP for best results. The DC coupling is tricky to get right so I advise dropping it in favor of coupling caps. Shoog

17th June 2009, 11:26 AM	#10
Merlinb diyAudio Member Join Date: May 2006 Location: York	Re: 829B as LTP? As Colt noted, the screens are shared. But you could still run it as a pentode LTP instead. Just for novelty?

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