6v6 pp amplifier - Page 5

alexmoose · 18th June 2008, 02:15 AM

They are not Electrostatic, however they are Planar Magnetic (its a common misconception, I thought that for a while and I own a pair). However, they both suffer from the same shortcomings when it comes to driving them with a vacuum tube/

My first priority is getting the Fostex done right, the Maggies are just gravy, I'll keep it in Class A. Thanks for the explanation, and i'll keep it around 350-380 volts.

Poindexter · 18th June 2008, 03:25 AM

I learned to tie the supressor to the plate from an article in Glass Audio.  The guy was taste-testing tubes to build a PP amp with. He ended up with the 812, which is evidently a monster if you can implement it.  Down somewhere near the bottom of his list (but still above all the common outputs) was the EL34, with a notation in the comments column, 'sounds better with supressor tied to plate.'  I tried it, and I thought so too.  I took the screen to the plate with a fewHundredΩ resistor, and the supressor directly.  When I learned the diode wrinkle from Al Marcy (TubeGarden), I tried various ways of attaching the supressor into the plot, and this sounds the best to me.  My hearing is definitely fallible, so you are encouraged to do your own spearmintation about this; it's simple enough to screw, ah, develop with.

Aloha,

Poinz

Eli Duttman · 18th June 2008, 03:26 AM

Moose,

"Maggies" exhibit a tube friendly flat impedance curve. 4 Ohm speaker taps are fine. The problem with "Maggies" is their INTENSE hunger for power. A H/K Cit. 2 in good repair is what you need in the way of tubed power amplification in combination with MagnePlanar speakers. One of the big, honking, Class "A" PP designs Doug P. (Bandersnatch) is fond of would be OK too. PP triode wired 6V6s and "Maggies"? No way, Jose!!!

Bandersnatch · 18th June 2008, 10:44 AM

Quote:

Originally posted by jazzbo

Bandersnatch: 6600/3 = 2200 * 0.063 = 139V

yeah...the divide by 3 is a typo. I described dividing by two, and should have wrote it that way. Sorry about the mistake. The rest of the numbers reflect using the 2.
cheers,
Douglas

DigitalJunkie · 18th June 2008, 10:28 PM

Quote:

Originally posted by Eli Duttman
Moose,

"Maggies" exhibit a tube friendly flat impedance curve. 4 Ohm speaker taps are fine. The problem with "Maggies" is their INTENSE hunger for power. A H/K Cit. 2 in good repair is what you need in the way of tubed power amplification in combination with MagnePlanar speakers. One of the big, honking, Class "A" PP designs Doug P. (Bandersnatch) is fond of would be OK too. PP triode wired 6V6s and "Maggies"? No way, Jose!!!

I've run Maggies off of my PP 6V6 amp (Tetrode wired) and it was okay. It wouldn't get up to concert-levels,but it was fine for casual listening,and some 'background' music at parties.
It really wasn't too bad,it worked out better than I had expected.

alexmoose · 19th June 2008, 01:43 PM

Okay, I love the EL34 design, and I can already feel my paychecks slipping away, could I use an LM337 to get the -22volts? it would be easier to regulate it it that way, then Bias voltage could be tweaked if necessary.

I would be afraid to use a regulated voltage on the -66 though, it seems like the regulator might get in a fight with the 10M45 chip, right?

jazzbo · 19th June 2008, 02:09 PM

Well first of all you will need more than -22V (this was the bias voltage for 6V6s) for the EL34 bias supply, and it needs to be adjustable. I don't see much advantage to regulating the bias supply if your plate supply isn't regulated as well. I made monos and can adjust each EL34 individually. Poinz' design feeds the same bias voltage to each pair, requiring closely matched pairs of tubes. I'd have to think about whether it would be better to regulate the tail supply. The CCS is set for a given current and will sink that current over a wide voltage range. I do recommend cascoding the 10M45s though. Hope this helps.

alexmoose · 23rd June 2008, 12:48 PM

Lets say for a moment that I will get carried away, and once the thing works well in Triode, I go for UL or Pentode mode. Are there any major changes that need to be made?

By the way, I'd love to see the EL84 version (assuming you have one built)

-Moose

jazzbo · 23rd June 2008, 01:35 PM

Well generally a ~3.5K load is recommended for pentode EL34s, ~5K for triode and ~6-7K for UL (depending on the UL tap)...

No, I haven't built an EL84 version yet. It's 2 or 3 projects down the line.

alexmoose · 23rd June 2008, 02:26 PM

I just placed the order for all of the Hardware, and most of the passive components, I am going to be gone for three weeks, so It has plenty of time to get here

18th June 2008, 03:26 AM	#43
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Moose, "Maggies" exhibit a tube friendly flat impedance curve. 4 Ohm speaker taps are fine. The problem with "Maggies" is their INTENSE hunger for power. A H/K Cit. 2 in good repair is what you need in the way of tubed power amplification in combination with MagnePlanar speakers. One of the big, honking, Class "A" PP designs Doug P. (Bandersnatch) is fond of would be OK too. PP triode wired 6V6s and "Maggies"? No way, Jose!!! __________________ Eli D.

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18th June 2008, 02:15 AM	#41
alexmoose diyAudio Member Join Date: Mar 2006 Location: Michigan	They are not Electrostatic, however they are Planar Magnetic (its a common misconception, I thought that for a while and I own a pair). However, they both suffer from the same shortcomings when it comes to driving them with a vacuum tube/ My first priority is getting the Fostex done right, the Maggies are just gravy, I'll keep it in Class A. Thanks for the explanation, and i'll keep it around 350-380 volts.

18th June 2008, 03:25 AM	#42
Poindexter diyAudio Member Join Date: Oct 2004 Location: Maui, Hawai'i, USA	I learned to tie the supressor to the plate from an article in Glass Audio.  The guy was taste-testing tubes to build a PP amp with. He ended up with the 812, which is evidently a monster if you can implement it.  Down somewhere near the bottom of his list (but still above all the common outputs) was the EL34, with a notation in the comments column, 'sounds better with supressor tied to plate.'  I tried it, and I thought so too.  I took the screen to the plate with a fewHundredΩ resistor, and the supressor directly.  When I learned the diode wrinkle from Al Marcy (TubeGarden), I tried various ways of attaching the supressor into the plot, and this sounds the best to me.  My hearing is definitely fallible, so you are encouraged to do your own spearmintation about this; it's simple enough to screw, ah, develop with. Aloha, Poinz

19th June 2008, 01:43 PM	#46
alexmoose diyAudio Member Join Date: Mar 2006 Location: Michigan	Okay, I love the EL34 design, and I can already feel my paychecks slipping away, could I use an LM337 to get the -22volts? it would be easier to regulate it it that way, then Bias voltage could be tweaked if necessary. I would be afraid to use a regulated voltage on the -66 though, it seems like the regulator might get in a fight with the 10M45 chip, right?

19th June 2008, 02:09 PM	#47
jazzbo diyAudio Member Join Date: May 2007	Well first of all you will need more than -22V (this was the bias voltage for 6V6s) for the EL34 bias supply, and it needs to be adjustable. I don't see much advantage to regulating the bias supply if your plate supply isn't regulated as well. I made monos and can adjust each EL34 individually. Poinz' design feeds the same bias voltage to each pair, requiring closely matched pairs of tubes. I'd have to think about whether it would be better to regulate the tail supply. The CCS is set for a given current and will sink that current over a wide voltage range. I do recommend cascoding the 10M45s though. Hope this helps.

23rd June 2008, 12:48 PM	#48
alexmoose diyAudio Member Join Date: Mar 2006 Location: Michigan	Lets say for a moment that I will get carried away, and once the thing works well in Triode, I go for UL or Pentode mode. Are there any major changes that need to be made? By the way, I'd love to see the EL84 version (assuming you have one built) -Moose

23rd June 2008, 01:35 PM	#49
jazzbo diyAudio Member Join Date: May 2007	Well generally a ~3.5K load is recommended for pentode EL34s, ~5K for triode and ~6-7K for UL (depending on the UL tap)... No, I haven't built an EL84 version yet. It's 2 or 3 projects down the line.

23rd June 2008, 02:26 PM	#50
alexmoose diyAudio Member Join Date: Mar 2006 Location: Michigan	I just placed the order for all of the Hardware, and most of the passive components, I am going to be gone for three weeks, so It has plenty of time to get here

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