A 56 direct coupled to 2A3 SET amplifier project

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A 56 direct coupled to 2A3 SET amplifier project

Postby arnoldc » Sun Oct 05, 2003 8:32 am

It's been quite a while since a new project is born :D

When I got hold of some pairs of 56 tubes, I thought of using them in my pre-amp project. However, since I like the sound of the JE Labs 300BDX with a 76-6SN7-300B topology, I thought of making a 56-2A3 direct-coupled.

I used my DC Designer spreadsheet, and if the calculations are correct, then this is the design :D

Image

There will be a 470K resistor from the driver grid to ground.

This is experimental and I hope I don't blow up the tubes, he he he :lol:

Any comments from anybody? jm? mickey?
Last edited by arnoldc on Sun Oct 05, 2003 9:47 pm, edited 1 time in total.
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Postby johnmarc0 » Sun Oct 05, 2003 11:33 am

alright!
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Postby vintage_dog » Sun Oct 05, 2003 3:04 pm

oh no...not another 2A3 amp!!

why not an amp optimized for 45?
:idea:
that way it can also take 2a3 tubes?!

!


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Postby arnoldc » Sun Oct 05, 2003 7:23 pm

vintage_dog, the 45 is coming soon :D
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Postby red76 » Sun Oct 05, 2003 8:05 pm

Hi Arnold,

Cool project... :) I hope I can attend one of your meetings onde day and hear 'em. Maybe you can even try grid chokes if you have enuff chassis space...

Sorry mods, OT:

Sir JM,

Did you get my PM reply the other day? There were 3 minor questions I needed to clarify about the final dimensions, DC resistance of my drivers, and offset postion on baffles (just your insight/opinion on driver offset actually.)

I hope you don't mind that I'll resend them in your Hotmail account just to be sure. It seems that the PM won't go to the Sentbox (2 days now :? ) Just reply through PM if you have the time (Yahoo sucks :roll: .) Thanks a bunch again! :)

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Postby audionote2003 » Mon Oct 06, 2003 1:05 am

Pre, ano naman eto?
Nalilito na kami!!!
Baka another giant killer in the making
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Postby johnmarc0 » Mon Oct 06, 2003 8:25 am

wala yan kaunting exprimento lang

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Postby arnoldc » Mon Oct 06, 2003 8:33 am

yeah, experiments could kill bwahahahahahaha :D see you next week when this baby comes alive :wink:
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37 to 6B4G - SET amplifier

Postby john » Fri Oct 10, 2003 1:22 pm

Hello Arnold,

The 56 Direct Coupled to 2A3/45 is also similar to the 37 to 6B4G SET amp I have built last month. My views if I may, It needs a good preamp to make it sing beautifully. I tried changing the 37 to 76 by just replacing the cathode resistors, well the sound is still good.

56 and 76 differs only in the filament voltage.

Good luck Arnold!

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Postby arnoldc » Fri Oct 10, 2003 3:33 pm

john, pwede na ba foreplay as preamp? or this would mean i need to get my 76-6SN7 (JE labs) preamp soon?
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Foreplay = Bottlehead ? or Foreplay = Bootlegged ?

Postby john » Sun Oct 12, 2003 6:38 am

Arnold,

Bootlegged Foreplay, Bawal na yan! yes it will drive to a good sonics your 56-2A3 amp.

Ask the master, SET-UP1 about his own preamp design if it will be able to handle your experimental SET amp. He is in a much better position to give insights on this matter.

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Postby arnoldc » Sun Oct 12, 2003 8:49 am

john, my foreplay is experimental too. just want to hear how it sounds. my pre-amp to keep will be setup1's 76-6SN7 :wink: but i have to complete it as well.
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Foreplay for personal

Postby john » Mon Oct 13, 2003 9:37 pm

Arnold,

That's well if you intend to build and or are using Foreplay as a reference design. No problem with that Sir.

I know someone who did commercialized Bootlegged Foreplay and that is unlawful!

Goodluck to your SET amp designs...You might need good parts for your projects, Maybe I have something here that might interest you.

John[/quote]
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Re: Foreplay = Bottlehead ? or Foreplay = Bootlegged ?

Postby setup1 » Thu Oct 16, 2003 11:13 am

*SET-UP1 about his own preamp design if it will be able to handle your experimental SET amp. He is in a much better position to give insights on this matter.

Hi Arnold,

My 76-6SN7 topology is essentially a single stage line amp w/ K'follower and no feedback, the last time I fooled around with a Loftin-White derivative, it was the morrison micro [6SL7 parallel-DC-2A3] and the preamp had enough gain for that amp driving Altec 755Cs.

Since the 56 has less gain than a 6SL7, you may have to crank out the volume control past 12 o'clock especially if your speakers are less than 95 dB/1W/1M efficient. The only way to know is try it and let us know the result.

Regards,


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Re: A 56 direct coupled to 2A3 SET amplifier project

Postby drlowmu » Wed Sep 19, 2018 1:07 pm

Hello,

Well, you can not build a good two stage DC amp, unless the mu of the Driver tube is 70 ( 6SL7 - the bare minimum mu ) to a mu of 100 , ( preferred mu ).

This excludes 56s, 76s, etc., they are incorrect, gainwise, from the get go, a wasted effort.

In practice, a mu of 100 tube sounds better to me than a mu of 70, more lively of a music presentation, is inherent in the mu of 100's play back. Fun to experience.

Simply look at the better known DC amps, 95% or more used high mu tubes, most at a mu of 100. Name the builders, you say? Sure, look here:


USA early : Jack Robin and Chester Lipman ( 1947, 6SF5 )

Japan prior : Isamu Asano, 1914-81 ( 2A6) and Nobukazu Shishido 1929-98 ( 12AX7 )

Italy 1980s : Marzio and Jelasi ( Sound Practices VOL. 2, Issue 5 )

USA , prior, NLA : Don Garber ( Fi , 6SF5 ) and Craig Uthus ( Moth, 6SL7 ),

USA , today : Dennis Fraker ( Serious Stereo, since 1989, 7B4 ).

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