News: Trouble logging in? Log in from the login page.
August 09, 2020, 06:33:48 AM

Author Topic: Something new - 2A3 monoblocks  (Read 1672 times)

0 Members and 1 Guest are viewing this topic.

Offline Doc B.

  • Administrator
  • Hero Member
  • *****
  • Posts: 8186
    • Bottlehead
Something new - 2A3 monoblocks
« on: November 01, 2019, 06:13:46 PM »
PB, PJ and I have been working on a new project for the past couple months. This is our new premium 2A3 monoblock amplifier. It is designed to run a broad range of 2A3 variants up to and including the JJ 2A3-40 by virtue of a two way switchable operating point. The current draw of the 2A3 in a given operating mode is indicated by the meter. It uses a parallel feed output stage and a cap coupled, shunt regulated driver stage. It uses the big OT-5 output transformer that we use in the Kaiju. I'm going to let PB weigh in on the performance specs of various 2A3 tube types, as he is the one who has been playing with them. Sonically it is a little more towards neutral than a Kaiju (a but less lower midrange/upper bass weight) and thus has a little bit more resolved sounding vocals and a wee bit more top end shimmer. That said, with similar circuits and iron both amps are definitely from the same sonic family. Universal power transformer, and a very low noise floor similar to the old Paramount monoblocks. Kit price is estimated at $2250 for the pair of monoblocks. Yes, those shrouds and the black finish are how the production kit will look.
« Last Edit: November 01, 2019, 06:28:38 PM by Doc B. »
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Doc B.

  • Administrator
  • Hero Member
  • *****
  • Posts: 8186
    • Bottlehead
Re: Something new - 2A3 monoblocks
« Reply #1 on: November 01, 2019, 06:16:17 PM »
If the image is way too big when you open it, right click on the image and click "open in new tab". Then open that tab.
« Last Edit: November 01, 2019, 06:30:17 PM by Doc B. »
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline oguinn

  • Sr. Member
  • ****
  • Posts: 645
    • DIY Audio Gallery
Re: Something new - 2A3 monoblocks
« Reply #2 on: November 01, 2019, 07:09:03 PM »
That’s really exciting! Congrats, guys. I’d love to grab a pair someday - but I probably ought to finish the Kaiju and the Bee Pre first. And get better speakers. And a better turntable. And a good bankruptcy attorney.
Jameson O’Guinn

-

Main System: Schiit Bifrost MB, Schiit Sol, Eros 2, BeePre, Kaiju/Stereomour II, Jägers, Mainline

Desktop System: Crack with Speedball

Offline Bonzo

  • Full Member
  • ***
  • Posts: 243
  • My name is Marco, best known as Bonzo
Re: Something new - 2A3 monoblocks
« Reply #3 on: November 01, 2019, 08:23:31 PM »
REALLY nice!
And really apartment-friendly!

These would be my dream now
Bisogna avere orecchio!

Offline triode

  • Jr. Member
  • **
  • Posts: 45
Re: Something new - 2A3 monoblocks
« Reply #4 on: November 01, 2019, 10:17:02 PM »
Very intriguing...
More info please : what is the driver tube? how much power with JJ2A3-40? DC filament option? looks like 8X10 base size like Paramount?

Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 13228
Re: Something new - 2A3 monoblocks
« Reply #5 on: November 02, 2019, 06:13:38 AM »
More info please : what is the driver tube?
The driver tube is the 5670.

how much power with JJ2A3-40?
7W @ 10% THD with the switch on the higher current operating point.  The Sovtek 2A3 that we will send with the kit will make 6.5W or 5W depending on the switch position.  I suspect the big EML 2A3 will also be around 6-7W, but we don't have a pair on hand to try out.  The fun thing about this amp is that you can go from the low current operating point with an RCA 2A3 to the high current operating point with the JJ 2A3-40 and go from listening to a 2A3 to 300B amp very easily. 

DC filament option? looks like 8X10 base size like Paramount?
The amp will come with DC filaments straight away.  The chassis is 10"x12".  The larger chassis helps fit the substantially larger iron, and it helps keep the amp running a bit cooler on the inside.  We are also providing the amp with film cathode bypass caps, and that requires a bit of extra space as well.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline kgoss

  • Sr. Member
  • ****
  • Posts: 270
Re: Something new - 2A3 monoblocks
« Reply #6 on: November 02, 2019, 07:26:16 AM »
Great looking amps guys. And since you designed them I know they will sound as good as they look. They will definitely go on my wish list. I don’t really need them, but I want them! 😃

I’ll go ahead and ask if these can be modified to run 45 tubes, since its a standard forum question for a 2A3 amp.
Ken Goss

Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 13228
Re: Something new - 2A3 monoblocks
« Reply #7 on: November 02, 2019, 07:34:36 AM »
Yes, you'd have to change 3 resistors to make it into a #45 amp. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Raymond P.

  • Full Member
  • ***
  • Posts: 125
Re: Something new - 2A3 monoblocks
« Reply #8 on: November 02, 2019, 07:49:02 AM »
What are you guys going to name this kit?
Raymond P.

Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 13228
Re: Something new - 2A3 monoblocks
« Reply #9 on: November 02, 2019, 07:52:29 AM »
We may be open to suggestions on naming.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline oguinn

  • Sr. Member
  • ****
  • Posts: 645
    • DIY Audio Gallery
Re: Something new - 2A3 monoblocks
« Reply #10 on: November 02, 2019, 09:07:34 AM »
Since there are two and it’s based on the Kaiju: Bi-ju or Kai-two. Or something better.
Jameson O’Guinn

-

Main System: Schiit Bifrost MB, Schiit Sol, Eros 2, BeePre, Kaiju/Stereomour II, Jägers, Mainline

Desktop System: Crack with Speedball

Offline Deke609

  • Hero Member
  • *****
  • Posts: 1126
Re: Something new - 2A3 monoblocks
« Reply #11 on: November 02, 2019, 09:43:46 AM »
Very cool. More questions:

(1) Choke? The Kaiju OT is mentioned, but not the plate choke. Is is it the Kaiju PC?

(2) OT impedance - wired for 3K, 6K, or some other primary impedance?

(3) Switching operating points - when switching between high and low current, does the amp also switch between choke inductances?

cheers and thanks, Derek
Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline kgoss

  • Sr. Member
  • ****
  • Posts: 270
Re: Something new - 2A3 monoblocks
« Reply #12 on: November 02, 2019, 10:30:35 AM »
Name suggestion.

If the circuit is a refinement of the Paramour, Stereomour amps how about MonoAmore ...
Ken Goss

Offline Raymond P.

  • Full Member
  • ***
  • Posts: 125
Re: Something new - 2A3 monoblocks
« Reply #13 on: November 02, 2019, 10:52:04 AM »
I was thinking along the same lines. Specifically, Monomour, a play on words on the French words "Mon Amour".
« Last Edit: November 02, 2019, 10:55:36 AM by Raymond P. »
Raymond P.

Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 13228
Re: Something new - 2A3 monoblocks
« Reply #14 on: November 02, 2019, 11:24:32 AM »
(1) Choke? The Kaiju OT is mentioned, but not the plate choke. Is is it the Kaiju PC?
Yes, but with the full winding, so a bit more inductance.
(2) OT impedance - wired for 3K, 6K, or some other primary impedance?
The Kaiju OT is 3K.  I wouldn't be surprised if the performance wan't optimal trying to reflect 6K.

(3) Switching operating points - when switching between high and low current, does the amp also switch between choke inductances?
No, these don't run as much HV current as a Kaiju does, so there's no need to go to the lower current tap on the plate choke.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man