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A 56 direct coupled to 2A3 SET amplifier project

PostPosted: Sun Oct 05, 2003 8:32 am
by arnoldc
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?

PostPosted: Sun Oct 05, 2003 11:33 am
by johnmarc0
alright!

PostPosted: Sun Oct 05, 2003 3:04 pm
by vintage_dog
oh no...not another 2A3 amp!!

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

!


Image

PostPosted: Sun Oct 05, 2003 7:23 pm
by arnoldc
vintage_dog, the 45 is coming soon :D

PostPosted: Sun Oct 05, 2003 8:05 pm
by red76
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! :)

red76

PostPosted: Mon Oct 06, 2003 1:05 am
by audionote2003
Pre, ano naman eto?
Nalilito na kami!!!
Baka another giant killer in the making

PostPosted: Mon Oct 06, 2003 8:25 am
by johnmarc0
wala yan kaunting exprimento lang

JM

PostPosted: Mon Oct 06, 2003 8:33 am
by arnoldc
yeah, experiments could kill bwahahahahahaha :D see you next week when this baby comes alive :wink:

37 to 6B4G - SET amplifier

PostPosted: Fri Oct 10, 2003 1:22 pm
by john
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!

John

PostPosted: Fri Oct 10, 2003 3:33 pm
by arnoldc
john, pwede na ba foreplay as preamp? or this would mean i need to get my 76-6SN7 (JE labs) preamp soon?

Foreplay = Bottlehead ? or Foreplay = Bootlegged ?

PostPosted: Sun Oct 12, 2003 6:38 am
by john
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.

John

PostPosted: Sun Oct 12, 2003 8:49 am
by arnoldc
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.

Foreplay for personal

PostPosted: Mon Oct 13, 2003 9:37 pm
by john
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]

Re: Foreplay = Bottlehead ? or Foreplay = Bootlegged ?

PostPosted: Thu Oct 16, 2003 11:13 am
by setup1
*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,


Joseph

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

PostPosted: Wed Sep 19, 2018 1:07 pm
by drlowmu
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 ).

Drlowmu