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PILOT SA 232 WITH 6L6 AS OUTPUTS

B

blabla_19_d

New Member
Hello everyone,

I'm pondering on building me push pull amp with 6l6gc as the outputs and using the pilot sa 232 topology as the gain and driver stage. Is this doable or just scratch it?

I've drawn up a mock up schematic and please feel free to correct and criticize. I would greatly appreciate all your inputs. Reason im leaning towards the pilot SA232 topology is that i have heard one recently am im amazed by it and i wish i could have one but i need a little more piwer to drive my speaker. And i have all the parts in my bin.

heres the schematic in pdf file

Regards to everyone
 

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Cool. I really can't comment, but ....... I too am starting a DIY power amp using Pilot 602 schematic and transformers.

:lurk:
 
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hi Jd,

Good luck with your build. Hoping to get more inputs before proceeding with the build. Looking to see if my operating points for the 12ax7 drivers are correct and will be able to drive the outputs properly.
 
EL84/6BQ5 are easy to drive tubes so your not likely to be able to get it to work however it may work fine with the 6V6 though they are harder to drive. Hey try it as maybe it will work well enough though likely have to be modded. Maybe look at circuits for Pilot's bigger PP amps that used the bigger tubes like the EL34 or 6550/KT-88. Of course there are lot's of aftermarket circuits to improve the big Dynaco amps which would surely work!

Another thought as yes, I agree the EL84/6BQ5 are a great sounding tube so if you need more power is to go PPP with those tubes to double your power. Maybe that circuit would still work as they are easy to drive , and you would have to 1/2 the primary impedance of your output transformers so around 4-5K would do.
 
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Personally I wouldn't. Its a paraphase inverter, which is kind of not amazing for various reasons. I also suspect it just will not have enough voltage swing to get the job done. If you really want to keep with this design, the Pilot SA-260 is the one you want to copy. Same basic design but it will get an EL34 to full power. It has the limitations of the inverter though, namely that its sensitive to tube parameters and they tend to shift the balance with frequency. Making it a floating paraphase would be an improvement, its not as sensitive to the particular tube in the phase inverter spot. I did actually attempt a floating paraphase conversion on my own SA-260 but it didn't come out right. Not sure what I did wrong but somehow it performed worse and I lost my patience with it so it went back to stock. The transformers are a limiting factor on the 260 and I think I was running into that.

Of course high frequency tuning and feedback depends on the transformers selected so figure on spending time making that work out properly.

Personally I'd be looking at a Mullard 5-20 if you're scratch building, subbing 6L6's for the EL34 might need changes to the bias resistor but thats nothing major.
 
Hello,

I wish everyone a joyous thanksgiving and would like to thank everyone as well.

I guess i have to junk this build and look for a suitable project. Besides the mullard 5-20 that gadget 73 had suggested can you guys please help me choose my next project build. I know there are lots of projects available on line but i need proven designs which someone had also built.
Here are my requirements
1. 20 to 30 watts per channel
2. Use 6l6gc tubes, have plenty of them
3. Has to be musical and engaging
4. I would like that 3d soundstage

Regards to everyone
 
How about an Eico ST70 type circuit? Voltage amp feeding a LTP inverter. Feedback as desired. A couple of years ago I did a scratch build for a friend using Eico ST-70 output transformers with 6L6GB's and built just the power amp section with the B+ adjusted for the 6L6's to have a fairly large class A range. Worked great and sounded very good.
 
Another thought is the Harman-Kardon A500. The 7355 is pretty much a 6L6GB or 5881 with a different base arrangement.

of course you'll have to fiddle with the feedback unless you are running the specific transformers any given schematic is drawn for.
 
Hello everyone,

I really do appreciate all the inputs. So far i have not decided yet on what to build. I will have to research some more on the circuits. Im leaning towars the eico st70 and the mullard 520.
Thank you all
 
The Eico is kind of a variant on the Mullard circuit, big difference is it uses a triode up front instead of a pentode. Not everyone digs the sound of small signal pentodes, they tend to be a little on the bright side compared to triodes.
 
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