6as7 p-p with transformer phase-splitter

hummel · 15th July 2011, 11:07 PM

Hello,
I have been looking around for a tube-amp project. I build a van Waarde headphone amp and was very impressed by the sound. My current wish is a small parts count, low wattage amp to use as the high-frequency driver in a bi-amp system. So, 5-10W will be fine. I ran across this, 6AS7 PP1, and it looks very nice. I have a few 6as7's and 6080's would probably work as well. Lundahl has an interstage xformer, LL1660, that appears to be for exactly for this sort of amp.
So, has anyone experience with this amp topology? For a treble driver it seems it would work well.
Thanks for your views.
- Hummel (aka Michael)

tinitus · 15th July 2011, 11:21 PM

Quote:

Originally Posted by hummel

For a treble driver it seems it would work well.

then I would consider small SE

hummel · 15th July 2011, 11:29 PM

Quote:

Originally Posted by tinitus

then I would consider small SE

Regarding SE, I am also considered this, Lundahl Transformers - 8W SE amplifier designed by Claus Byrith. It appears to be a very fine amp. Has anyone made this?
- h

tinitus · 16th July 2011, 04:15 AM

with a 2.5-3kohm SE trafo I think you would be able to use for severral different designs(tube)
I'm no expert
but that's what I would do if I could 'rethink' my own project

tinitus · 16th July 2011, 05:28 AM

or just because it looks like a fun build A Proposed Push-Pull 6C45 Spud Amp

oh, and I just now noticed who(member)
http://ekingsbu.users4.50megs.com/index.html

polyphaze · 04:09 PM

The 6AS7 is somewhat non-linear, and as such is not a great choice for SE topologies IMO.
However, in pp it sings! I recently built class A monoblocks that each use a pair of 6AS7s with triodes paralleled, and I am delighted with their performance.
With the Lundahl IT you mentioned, I believe you could get away with one gain stage. Also the Lundahl could serve as the driver plate load instead of cap coupling as in the 'PP1' you referenced.

hummel · 16th July 2011, 06:14 PM

@tinitus
That 'spud' amp looks really cool, and the parts count is definately low, but I am not up to reworking the topology for a bit more powerful tube. (Maybe 6AS7s? Hmmm.)

@polyphaze
I am pretty sure I will try this amp. Am glad to 'hear' of your positive impression of the 6AS7 in P-P mode. And thanks for the hint about removing the cap.

- hummel

Shoog · 16th July 2011, 06:47 PM

Built just such a beast using a power toroidal as the interstage and as outputs. The interstage was the weak link - but still the amp sounded excellent, if slightly rolled off at the top. With the Lundahl you will have a fantastic sounding amp.
My current amp used the 6AS7 schaded with an input transformer - again a hard to beat excellent sounding amp for very small money.

I agree that PP works excellently but SE will not match it at all.

Shoog

hummel · 16th July 2011, 08:13 PM

Shoog,
That's really good news! I have a few Svetlana 6H13C tubes that I bought for a headphone amp I built (I got a batch of NOS at a very good price) and a couple of RCA JAN 6AS7Gs (also NOS but more expensive). FWIW, I find the 6H13s have a bit more open, brighter sound that I like better than the RCAs which sound also very good but a bit more 'intimate' like the room is smaller or something (this is with headphones and string quartet, e.g.)
I think the tubes might sound nice as treble drivers for my hi-fi. So...
But I wanted something relatively simple that I can understand the circuit of. The xformer splitter seemed a good idea to me. Passive instead of active=simpler.
- hummel

tinitus · 17th July 2011, 12:57 PM

6as7g - Google Search

15th July 2011, 11:07 PM	#1
hummel diyAudio Member Join Date: Jun 2011 Location: Hamburg	6as7 p-p with transformer phase-splitter Hello, I have been looking around for a tube-amp project. I build a van Waarde headphone amp and was very impressed by the sound. My current wish is a small parts count, low wattage amp to use as the high-frequency driver in a bi-amp system. So, 5-10W will be fine. I ran across this, 6AS7 PP1, and it looks very nice. I have a few 6as7's and 6080's would probably work as well. Lundahl has an interstage xformer, LL1660, that appears to be for exactly for this sort of amp. So, has anyone experience with this amp topology? For a treble driver it seems it would work well. Thanks for your views. - Hummel (aka Michael)

16th July 2011, 03:47 PM	#6
polyphaze diyAudio Member Join Date: Apr 2011 Location: New York	The 6AS7 is somewhat non-linear, and as such is not a great choice for SE topologies IMO. However, in pp it sings! I recently built class A monoblocks that each use a pair of 6AS7s with triodes paralleled, and I am delighted with their performance. With the Lundahl IT you mentioned, I believe you could get away with one gain stage. Also the Lundahl could serve as the driver plate load instead of cap coupling as in the 'PP1' you referenced. Last edited by polyphaze; 16th July 2011 at 04:09 PM.

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16th July 2011, 04:15 AM	#4
tinitus diyAudio Moderator Join Date: Nov 2005	with a 2.5-3kohm SE trafo I think you would be able to use for severral different designs(tube) I'm no expert but that's what I would do if I could 'rethink' my own project

16th July 2011, 05:28 AM	#5
tinitus diyAudio Moderator Join Date: Nov 2005	or just because it looks like a fun build A Proposed Push-Pull 6C45 Spud Amp oh, and I just now noticed who(member) http://ekingsbu.users4.50megs.com/index.html

16th July 2011, 06:14 PM	#7
hummel diyAudio Member Join Date: Jun 2011 Location: Hamburg	@tinitus That 'spud' amp looks really cool, and the parts count is definately low, but I am not up to reworking the topology for a bit more powerful tube. (Maybe 6AS7s? Hmmm.) @polyphaze I am pretty sure I will try this amp. Am glad to 'hear' of your positive impression of the 6AS7 in P-P mode. And thanks for the hint about removing the cap. - hummel

16th July 2011, 06:47 PM	#8
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	Built just such a beast using a power toroidal as the interstage and as outputs. The interstage was the weak link - but still the amp sounded excellent, if slightly rolled off at the top. With the Lundahl you will have a fantastic sounding amp. My current amp used the 6AS7 schaded with an input transformer - again a hard to beat excellent sounding amp for very small money. I agree that PP works excellently but SE will not match it at all. Shoog

16th July 2011, 08:13 PM	#9
hummel diyAudio Member Join Date: Jun 2011 Location: Hamburg	Shoog, That's really good news! I have a few Svetlana 6H13C tubes that I bought for a headphone amp I built (I got a batch of NOS at a very good price) and a couple of RCA JAN 6AS7Gs (also NOS but more expensive). FWIW, I find the 6H13s have a bit more open, brighter sound that I like better than the RCAs which sound also very good but a bit more 'intimate' like the room is smaller or something (this is with headphones and string quartet, e.g.) I think the tubes might sound nice as treble drivers for my hi-fi. So... But I wanted something relatively simple that I can understand the circuit of. The xformer splitter seemed a good idea to me. Passive instead of active=simpler. - hummel

17th July 2011, 12:57 PM	#10
tinitus diyAudio Moderator Join Date: Nov 2005	6as7g - Google Search

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