my third RH84

mctavish · 9th September 2009, 10:02 PM

Hey everyone! Im just starting my third RH84 on an ''existing chassis'' and i've got three 9 pin sockets and one octal on a very small chassis. My power transformer has two 6.3v secondaries and no 5v, so ive been trying to think of a tube solution.

Does anyone know of a 6.3v octal FW rectifier capable of 150 or so m.a.d.c.? I have a few 6X5's but there not capable of that kinda current...

Thanks!

vinylkid58 · 9th September 2009, 10:15 PM

How about a 6BY5G, good for 175ma. It does drop a bit of voltage thou.

Jeff

mctavish · 9th September 2009, 10:25 PM

PERFECT!!! I could stand to lose that kind of voltage too. Thanks for the help! And cheers! to mr. Kitic for the design and for sharing it. Previously I used some japanese output transformers from a nice reel-to-reel and that amp is simply amazing!

vinylkid58 · 9th September 2009, 10:46 PM

Glad to help where I can.

Quote:

Originally Posted by mctavish

Previously I used some japanese output transformers from a nice reel-to-reel and that amp is simply amazing!

Akai perhaps?

Jeff

mctavish · 10th September 2009, 12:01 AM

Hmmm... yes Akai. What a hidden gem. I've picked up many over the years just to butcher them. There dipped in wax (so no corrosion

) and each have their own power tranny and cute little choke. Its a recipe for nice S.E. amps, and if your lucky they come with some good Matsushita EL84 's!

dsndblm · 10th September 2009, 03:18 AM

I used the 6BY5 on my lastest amp build. They are nice tubes. In directly heated cathode, nice sound and have a really nice glow at night!

Shoog · 10th September 2009, 07:53 AM

Since your've built two successful RH84 amps, why not try a bit of variety. The partial feedback approach works best with a high output impedance driver - so a pentode is just the job. I have had great success using a 6AU6 in similar circuits. I would be more than interested to find out if there was a noticable difference in sound quality doing it the right way.

Shoog

mctavish · 10th September 2009, 11:26 AM

I've tried A triode-strapped EF86 in some experiments which sounded very nice, Plenty of gain. I've also built an amp with trioded EF804 driving 6v6's with some p2p feedback for my father-in-law with a pod dock and he seems quite pleased.

Were you using the 6au6 as a pentode? I vaguely remember a push-pull thread with some plate to plate feedback going on, was that you Shoog?

bigwill · 11:56 AM

Wiring pentodes as triodes in this position defeats the point, you need a high dynamic impedance so that the feedback signal isn't eaten by the tube's anode

Shoog · 10th September 2009, 01:59 PM

Yes I did use the 6AU6 as a pentode in two partial feedback PP amps now. As Bigwill says doing anything else defeats the object of the exercise.
The EF86 doesn't make the best candidate - you need something which will carry a standing current of at least 5mA at about 150V on the plate - this makes the 6AU6 an excellent candidate - and its dirt cheap.

Shoog

9th September 2009, 10:02 PM	#1
mctavish diyAudio Member Join Date: Feb 2008 Location: Niederösterreich	my third RH84 Hey everyone! Im just starting my third RH84 on an ''existing chassis'' and i've got three 9 pin sockets and one octal on a very small chassis. My power transformer has two 6.3v secondaries and no 5v, so ive been trying to think of a tube solution. Does anyone know of a 6.3v octal FW rectifier capable of 150 or so m.a.d.c.? I have a few 6X5's but there not capable of that kinda current... Thanks!

10th September 2009, 12:01 AM	#5
mctavish diyAudio Member Join Date: Feb 2008 Location: Niederösterreich	Hmmm... yes Akai. What a hidden gem. I've picked up many over the years just to butcher them. There dipped in wax (so no corrosion) and each have their own power tranny and cute little choke. Its a recipe for nice S.E. amps, and if your lucky they come with some good Matsushita EL84 's!

10th September 2009, 11:54 AM	#9
bigwill General Nuisance diyAudio Member Join Date: Dec 2004 Location: UK	Wiring pentodes as triodes in this position defeats the point, you need a high dynamic impedance so that the feedback signal isn't eaten by the tube's anode Last edited by bigwill; 10th September 2009 at 11:56 AM.

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9th September 2009, 10:15 PM	#2
vinylkid58 diyAudio Member Join Date: May 2005 Location: Victoria, B.C.	How about a 6BY5G, good for 175ma. It does drop a bit of voltage thou. Jeff

9th September 2009, 10:25 PM	#3
mctavish diyAudio Member Join Date: Feb 2008 Location: Niederösterreich	PERFECT!!! I could stand to lose that kind of voltage too. Thanks for the help! And cheers! to mr. Kitic for the design and for sharing it. Previously I used some japanese output transformers from a nice reel-to-reel and that amp is simply amazing!

10th September 2009, 03:18 AM	#6
dsndblm diyAudio Member Join Date: Aug 2009	I used the 6BY5 on my lastest amp build. They are nice tubes. In directly heated cathode, nice sound and have a really nice glow at night!

10th September 2009, 07:53 AM	#7
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	Since your've built two successful RH84 amps, why not try a bit of variety. The partial feedback approach works best with a high output impedance driver - so a pentode is just the job. I have had great success using a 6AU6 in similar circuits. I would be more than interested to find out if there was a noticable difference in sound quality doing it the right way. Shoog

10th September 2009, 11:26 AM	#8
mctavish diyAudio Member Join Date: Feb 2008 Location: Niederösterreich	I've tried A triode-strapped EF86 in some experiments which sounded very nice, Plenty of gain. I've also built an amp with trioded EF804 driving 6v6's with some p2p feedback for my father-in-law with a pod dock and he seems quite pleased. Were you using the 6au6 as a pentode? I vaguely remember a push-pull thread with some plate to plate feedback going on, was that you Shoog?

10th September 2009, 01:59 PM	#10
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	Yes I did use the 6AU6 as a pentode in two partial feedback PP amps now. As Bigwill says doing anything else defeats the object of the exercise. The EF86 doesn't make the best candidate - you need something which will carry a standing current of at least 5mA at about 150V on the plate - this makes the 6AU6 an excellent candidate - and its dirt cheap. Shoog

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