6V6 ->EL84 with 12AT7?

zxx123 · 2nd April 2006, 06:09 AM

I like EL84 . I can see some schematics
such as driving EL84 with EF86, 6SL7, 12AX7, etc.

However, EF86 and 6SL7 are not welcomed because my amp case is very small. 12AX7 has too much gain.

How about 12AT7 with EL84? Originally, this idea is from SE 6V6.
Absolutely, I need to adjust bias first of all. However, they use almost same current under plate voltage 250V with same load resistance(5K).

How about your idea?

rdf · 2nd April 2006, 06:32 AM

Hi zxx123. 12 volts across 130 ohms as shown to the right of the schematic implies 92ma through the EL84. It won't be close. Off the top of my head in the range of 6 volts is more likely. I recommend leaving the 250 in place to start, it's close to my favourite and trades off increased 2nd harmonic distortion (and in my tests reduced upper harmonics) for a little more power. Everyone has a preference, check ten schematics you'll find ten operating points. The 6V6 values are a safe place to start and sound pretty good.

zxx123 · 2nd April 2006, 06:50 AM

Quote:

Originally posted by rdf
Hi zxx123. 12 volts across 130 ohms as shown to the right of the schematic implies 92ma through the EL84. It won't be close. Off the top of my head in the range of 6 volts is more likely. I recommend leaving the 250 in place to start, it's close to my favourite and trades off increased 2nd harmonic distortion (and in my tests reduced upper harmonics) for a little more power. Everyone has a preference, check ten schematics you'll find ten operating points. The 6V6 values are a safe place to start and sound pretty good.

Thanks, you are right.
I post corrected one again. (It was my mistake!)
Can you recommend me any power transformer for this 6V6 and EL84 project? I think the 2ndary should be 220V or little bit more, but I cannot find proper one in tubesandmore.com

Eli Duttman · 2nd April 2006, 06:21 PM

Think about a doubler B+ supply as used in "El Cheapo". Smaller caps. in the doubler stack will lower the rail voltage. Follow the "extended" CLC filter with a RC section and you should be able dial the final B+ voltage value in exactly.

amperex · 5th April 2006, 01:15 AM

I am not a fan of 12AT7 sonics. How about Telefunken ECC85 (6AQ8). Lower gain than a 12AT7, but should have enough gain.

SY · 5th April 2006, 01:47 AM

Quote:

I am not a fan of 12AT7 sonics.

Used properly (not often done!), it is stunningly linear. The bad rep comes, I think, from all the poor circuits that chunk it in.

gabriel611 · 5th April 2006, 06:13 AM

SY,

just how exactly do you bias a paralled AT7 tube driving a 2a3 tube instead of 6v6 at 5k load?

gabriel

SY · 5th April 2006, 12:39 PM

If it were me, I'd run one section as a voltage amp (2mA current, 375V supply, 120k plate load), the second section as a cathode follower.

JimW · 5th April 2006, 07:12 PM

12at7 works well in srpp configuration as a 2a3 driver. Gordon Rankin's "baby ongaku" used this tube. I use it as a 2a3 driver in a much less ambitous (cheap) amp and it works very well.

2nd April 2006, 06:32 AM	#2
rdf diyAudio Member Join Date: Jun 2004 Location: the thermionic past	Hi zxx123. 12 volts across 130 ohms as shown to the right of the schematic implies 92ma through the EL84. It won't be close. Off the top of my head in the range of 6 volts is more likely. I recommend leaving the 250 in place to start, it's close to my favourite and trades off increased 2nd harmonic distortion (and in my tests reduced upper harmonics) for a little more power. Everyone has a preference, check ten schematics you'll find ten operating points. The 6V6 values are a safe place to start and sound pretty good. __________________ Blame the Manichaeists

2nd April 2006, 06:21 PM	#4
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Think about a doubler B+ supply as used in "El Cheapo". Smaller caps. in the doubler stack will lower the rail voltage. Follow the "extended" CLC filter with a RC section and you should be able dial the final B+ voltage value in exactly. __________________ Eli D.

5th April 2006, 12:39 PM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	If it were me, I'd run one section as a voltage amp (2mA current, 375V supply, 120k plate load), the second section as a cathode follower. __________________ "...we stumble and get up, we are sad, confident, insecure, feel loneliness and joy and love. There is nothing more; but I want nothing more.” - Christopher Hitchens 1949-2011

5th April 2006, 07:12 PM	#9
JimW diyAudio Member Join Date: Oct 2004	12at7 12at7 works well in srpp configuration as a 2a3 driver. Gordon Rankin's "baby ongaku" used this tube. I use it as a 2a3 driver in a much less ambitous (cheap) amp and it works very well.

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5th April 2006, 01:15 AM	#5
amperex diyAudio Member Join Date: Feb 2005 Location: MI	I am not a fan of 12AT7 sonics. How about Telefunken ECC85 (6AQ8). Lower gain than a 12AT7, but should have enough gain.

5th April 2006, 06:13 AM	#7
gabriel611 diyAudio Member Join Date: Feb 2006 Location: manila	SY, just how exactly do you bias a paralled AT7 tube driving a 2a3 tube instead of 6v6 at 5k load? gabriel

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