help me designing parallel SE guitar amp with 12at7 as power tube

jule · 16th August 2011, 07:01 PM

My schematic came so far by now(lower it is)

I am aiming to get that early blues sound.

I got 24k/8ohm/2W output transformer which is almost like the one Fender used in reverb units (23k/8ohm/3.5W).

They used parallel SE design:

So there is loadline for each half:

I am probably going to use 200V B+, so my calculatoins got like this:

From graph I get 6.5mA per stage, so togheter 13mA and -2V on grid. So I would need 154 ohm resistor(not marked value on schematic I suppose it would get 0,3W output power.(Ia*Ua/8) and 0.8W of dissipation.

But how could I get a little more power out of it? Can it be done? I would like at least 0.5W if possible.

I am going to use 8' ,8 ohm, 15W speaker.

Also check component values on the schematic, suggestions are welcome. This is my first design of an amp. (But I already built one 5W SE with el84)

firechief · 16th August 2011, 07:51 PM

Should word as drawn, and might be fun.

jule · 17th August 2011, 10:40 AM

what about bias of power tubes?

dcgillespie · 17th August 2011, 11:35 AM

More power? Try operating the 12AT7 in push-pull. Yeah, it would need a PI stage, but it would make the whole thing even more unique!

Dave

Printer2 · 18th August 2011, 01:59 AM

Quote:

Originally Posted by dcgillespie

More power? Try operating the 12AT7 in push-pull. Yeah, it would need a PI stage, but it would make the whole thing even more unique!

Dave

Check out the The Hundred-Buck Amp Challenge

The Hundred-Buck Amp Challenge

You could run in push-pull in a self-split arrangement. I did one version of my amp with it but with 6AQ5's. Another amp used 6AU5's I think, about the same power level as yours. I used a 70V audio matching transformer, think his was a 100V. You could add a PI stage. Come visit, looks like your amp would fit right in.

bendix6384 · 18th August 2011, 08:27 AM

for an early 'blues' sound use the pre circuit fron princeton 5F2A -- simpler and will give you more fat crunch

bendix6384 · 18th August 2011, 08:29 AM

more power ? use a voltage doubler on PS ? fender ran 400V on 12AT7..

jule · 18th August 2011, 11:03 AM

Now I decided to dump at7 as power tube and run ecc99 in push pull mode. For better performance

Alastair E · 18th August 2011, 04:04 PM

Quote:

Originally Posted by jule

Now I decided to dump at7 as power tube and run ecc99 in push pull mode. For better performance

A wise choice I think....

There's a few double-triodes like the 7119, 5687 and my personal favorate, the 7044 that should do well for your amp as well...

Fenris · 18th August 2011, 04:31 PM

Mine is using 6N1P tubes in P-P with the triodes in each tube paralleled. Should be about 3 watts of power.

16th August 2011, 07:01 PM	#1
jule diyAudio Member Join Date: Jul 2010	help me designing parallel SE guitar amp with 12at7 as power tube My schematic came so far by now(lower it is) I am aiming to get that early blues sound. I got 24k/8ohm/2W output transformer which is almost like the one Fender used in reverb units (23k/8ohm/3.5W). They used parallel SE design: So there is loadline for each half: I am probably going to use 200V B+, so my calculatoins got like this: From graph I get 6.5mA per stage, so togheter 13mA and -2V on grid. So I would need 154 ohm resistor(not marked value on schematic I suppose it would get 0,3W output power.(Ia*Ua/8) and 0.8W of dissipation. But how could I get a little more power out of it? Can it be done? I would like at least 0.5W if possible. I am going to use 8' ,8 ohm, 15W speaker. Also check component values on the schematic, suggestions are welcome. This is my first design of an amp. (But I already built one 5W SE with el84)

16th August 2011, 07:51 PM	#2
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	Should word as drawn, and might be fun. __________________ "You can keep your insurance baby nothing is guaranteed" -Tom Petty

18th August 2011, 04:31 PM	#10
Fenris diyAudio Member Join Date: Jun 2004 Location: The last frontier	Mine is using 6N1P tubes in P-P with the triodes in each tube paralleled. Should be about 3 watts of power. __________________ Listen to the music through the stereo, not the stereo through the music.

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17th August 2011, 10:40 AM	#3
jule diyAudio Member Join Date: Jul 2010	what about bias of power tubes?

17th August 2011, 11:35 AM	#4
dcgillespie diyAudio Member Join Date: May 2010 Location: Ball Ground, GA	More power? Try operating the 12AT7 in push-pull. Yeah, it would need a PI stage, but it would make the whole thing even more unique! Dave

18th August 2011, 08:27 AM	#6
bendix6384 diyAudio Member Join Date: Aug 2011	for an early 'blues' sound use the pre circuit fron princeton 5F2A -- simpler and will give you more fat crunch

18th August 2011, 08:29 AM	#7
bendix6384 diyAudio Member Join Date: Aug 2011	more power ? use a voltage doubler on PS ? fender ran 400V on 12AT7..

18th August 2011, 11:03 AM	#8
jule diyAudio Member Join Date: Jul 2010	Now I decided to dump at7 as power tube and run ecc99 in push pull mode. For better performance

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