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 NEW  Bruce Heran outlines the details and construction of his simple DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project.

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PostPosted: 15 Dec 2011, 08:40 
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Joined: 20 Sep 2008, 19:49
Posts: 168
Location: Montreal, Canada
Hi,

I have never built a PP amp (only about 5 x SE), the attached one attract me simply because it's simple and so far for me the simpler the better sounds wise.

A typical 6V6 or 6AQ5 PP based on their datasheet puts out 10W in a normal PP AB type configuration with phase inverter and the whole shabang. Now, how about this configuration where it is a pure Class A PP, will the output be greatly reduced...

The biggest SE I own is rated about 6W so I'm hopping to built my first PP which would be slightly more powerful, I guess 10W would sound right power wise.

Could someone please estimate the output power of my schematic. Can my B+ be slightly increase instead of 250Vdc..
Attachment:
Simple 6AQ5 PP.GIF

As always, thanks for your help.
Isophon

_________________
DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
DIY Tube Amp : RH84 SE | 6V6 SET | 13FD7 SET (Chinook) | 807 UL SE | 6BQ5 Class A PP UL | 6LR8 SE
DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
DIY Pre-Amp : MooseFET.
To come : MLTL (CSS enabled EL70) + more tube amp...


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PostPosted: 15 Dec 2011, 09:55 
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Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
All the datasheets suggest 250V as max plate to cathode voltage for the 6AQ5. You could probably go a little higher than 250 but not enough to make a difference. If you swapped to 6V6 you could go with about 300V in your current configuration or about 325V if you switch to Pentode or Triode output. Keep the screens at 315V or less in UL or Pentode. JJ makes a 6V6S that is rated for even more voltage, if you need for your design.

With that amp you'd be at about 6-7 watts out. It will have a different damping factor so will sound different than your SE amp, but you'd have to build it to see if it "sounds" more powerful.

If you want about 15W look here for a similar design.
http://www.diyaudioprojects.com/Tubes/K ... -Tube-Amp/


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PostPosted: 15 Dec 2011, 16:22 
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Joined: 20 Sep 2008, 19:49
Posts: 168
Location: Montreal, Canada
Hi,

I do not intend to swap to 6V6, I already have a bunch of GE 12AQ5 and I want to know how they sound like ;)
I just wrote the 6V6 in bracket for people who do not know that the 6AQ5 is actually a 7 pin 6V6.

I guess 6-7W in UL mode would be OK, this will be my X-Mas project.

BR,
Isophon.

_________________
DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
DIY Tube Amp : RH84 SE | 6V6 SET | 13FD7 SET (Chinook) | 807 UL SE | 6BQ5 Class A PP UL | 6LR8 SE
DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
DIY Pre-Amp : MooseFET.
To come : MLTL (CSS enabled EL70) + more tube amp...


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PostPosted: 16 Dec 2011, 21:11 
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Joined: 04 Jun 2008, 20:59
Posts: 2416
Location: Arizona, USA
Hi, Sorry to disappoint you :| , but I prototyped one like that with 6V6 and it is less powerful than the EL84 Poddwatt. All share the same sort of output stage. I measured 3.5-3.8 watts (RMS) per channel at 2% distortion with the 6V6s. Nice sound, just not a lot of it. If you need a bit more power build it with EL34s or KT77s and get about 10 watts at those B+. Or go to about 450 B+ and get about 18 watts. Class A push pull amps are really nice sounding, but not efficient. BTW this design goes back a long time and was in disfavor until it became possible to get linear (and cheap) constant current sources. I have used variations of the design to go from as small as the 6V6 version to a current one with KT120s that delivers 45+ watts RMS.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:


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PostPosted: 19 Dec 2011, 23:31 
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Joined: 20 Sep 2008, 19:49
Posts: 168
Location: Montreal, Canada
gofar99 wrote:
Hi, Sorry to disappoint you :| ,
Good listening
Bruce


Hi Bruce,

No problem, thanks for the warning. I just had a few 12AQ5 laying around.

I will instead maybe built a Poddwatt with the 6N1P driver, thanks a lot for your schematics.

I already have 2 x PP 8K OPT from a RCA unit but they are not UL so..time to pass an order with Edcor.

Rgds,
Isophon

_________________
DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
DIY Tube Amp : RH84 SE | 6V6 SET | 13FD7 SET (Chinook) | 807 UL SE | 6BQ5 Class A PP UL | 6LR8 SE
DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
DIY Pre-Amp : MooseFET.
To come : MLTL (CSS enabled EL70) + more tube amp...


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PostPosted: 20 Dec 2011, 11:00 
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Joined: 04 Jun 2008, 20:59
Posts: 2416
Location: Arizona, USA
Hi, I try to steer folks away from problems I know about. The 12AQ5s would sound nice, just have a rather limited output. The 6N1P is an OK drive for the Poddwatt. Circuit values will need slight adjustments and you need to be aware of the limitations on the B+ for that family of tubes (6DJ8, ECC88, 6N1P).

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:


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