News:
November 30, 2021, 01:25:45 PM

Author Topic: Something new is coming  (Read 22892 times)

0 Members and 1 Guest are viewing this topic.

Offline Grainger49

  • Hero Member
  • *****
  • Posts: 7175
Re: Something new is coming
« Reply #60 on: March 10, 2010, 10:15:37 AM »
Alder is a hardwood, unlike pine, fir, spruce, etc.

PJ, I just meant that there was a lot of Alder in the Pacific NW.  Like pines in the South.  Alder is the best wood for smoking salmon.

Offline Todd R

  • Full Member
  • ***
  • Posts: 135
Re: Something new is coming
« Reply #61 on: March 10, 2010, 11:20:46 AM »
Quote
What would you recommend as the minimum impedance for a set of headphones to use with the kit?

The output impedance of the 6080 cathode follower is around 100 ohms. So in theory the most ideal load will be 300 and 600 ohm headphones. You could push this down to 100 ohms and just expect somewhat increased distortion - in fact we tried it with 32 ohm phones and it sounded pretty darn good, but that is not the intended usage. The current wisdom seems to be that a S.E.X. amp with the 120 ohm resistors removed from the jack works best with low ( like 32 ohm)  impedance headphones. The curves of some 6080 relatives might give a little lower output impedance in the given circuit, but I have not pursued that yet. Remember, this kit is only about 10 days old.

Doc,
I have a Wheatfield HA-2 which also uses a 6080 tube. They suggest using a 6528A for low impedance phones, would that work with this kit?

BTW, how does it compare to the SEX amp when driving high impedance phones like Sennheisers?

Online Doc B.

  • Administrator
  • Hero Member
  • *****
  • Posts: 8769
    • Bottlehead
Re: Something new is coming
« Reply #62 on: March 10, 2010, 11:53:47 AM »
Hi Todd,

I mistakenly said that the amp might work with a 6528A, but the 6528A heater draws twice as much current as the 6080, so it is not a possibility. So far I like Crack better with high impedance cans, and S.E.X. better with low impedance cans.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Dr. Toobz

  • Sr. Member
  • ****
  • Posts: 431
Re: Something new is coming
« Reply #63 on: March 10, 2010, 12:41:14 PM »
Wouldn't a 5998 tube work here? I think the current draw is a little less than the 6AS7/6080 and the plate impedance is supposedly lower, too. I've seen it recommended in 6AS7 OTL circuits where a little lower Z-out is needed for 32-ohm phones.
A Bottlehead since 2009: S.E.X. 2.0, Stereomour (2A3), Eros & Seduction Phono, Crack, Quickie 1.0 (sold), Klipsch Heresy III speakers, Grado SR-325e headphones

Offline Todd R

  • Full Member
  • ***
  • Posts: 135
Re: Something new is coming
« Reply #64 on: March 10, 2010, 04:01:56 PM »
Hi Todd,

I mistakenly said that the amp might work with a 6528A, but the 6528A heater draws twice as much current as the 6080, so it is not a possibility. So far I like Crack better with high impedance cans, and S.E.X. better with low impedance cans.

OK, good to know.
Guess I'll go buy some, I mean a Crack

Offline Todd R

  • Full Member
  • ***
  • Posts: 135
Re: Something new is coming
« Reply #65 on: March 10, 2010, 04:25:11 PM »
Hey Doc,
Just paid for a Crack.
Couldn't see where I could order the official Bottlehead badge, do you still offer them?

Online Doc B.

  • Administrator
  • Hero Member
  • *****
  • Posts: 8769
    • Bottlehead
Re: Something new is coming
« Reply #66 on: March 10, 2010, 06:01:32 PM »
Yes, we do have badges. My bad, I will get an order button up tomorrow.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline corndog71

  • Sr. Member
  • ****
  • Posts: 590
Re: Something new is coming
« Reply #67 on: March 10, 2010, 06:49:39 PM »
Hey Doc,
Have you thought of producing a nice heavy foil type sticker as a cheaper alternative to the badges?
The world was made for those not cursed with self-awareness.

Rob

Offline vanofmonks

  • Jr. Member
  • **
  • Posts: 23
Re: Something new is coming
« Reply #68 on: March 11, 2010, 02:16:10 PM »
Is there enough overhead in the heater circuit to use a 7n7 instead of the 12au7?  Curious because they are cheap and I have some nice teflon sockets.

Offline Paully

  • Sr. Member
  • ****
  • Posts: 516
Re: Something new is coming
« Reply #69 on: March 11, 2010, 02:28:35 PM »
I would be curious to know that too, I have collected a bit of a stash of those.

Online Doc B.

  • Administrator
  • Hero Member
  • *****
  • Posts: 8769
    • Bottlehead
Re: Something new is coming
« Reply #70 on: March 11, 2010, 03:33:41 PM »
I had my transformer current capability figures confused and you should be able to use a few more different tubes than I originally said. I'm not going to figure every tube out that you guys ask for, but here's the general scoop:

The power trans can deliver 3.8A AC to the 6.3V heaters. Right now the 6080 draws 2.5A and the 12AU7 draws 0.3A. So right now the total draw is 2.8A. One could change to a 6SN7 (0.6A heater) by punching out the socket mounting hole and wiring in an octal socket. Or just do it the easy way and use a 6CG7 in the existing socket with the heater pins rewired from 9 and 4/5 tied to 4 and 5. 12BH7 should be pretty easy to do as well.

The 12AU7 is running at 75V and about 3.8mA - the FPIII operating point. You could also rewire the heater to 4 and 5 and use a 6922 without any other changes - essentially the Seduction operating point. Gain will be higher, which I don't necessarily consider an improvement.

One could also bump up the current through the 6080. However we are designing a C4S load for the 6080 that will work great at the present operating point, but will be running very hot if we increase it. So we will stick with the current point we have chosen (150V plate, 100V cathode, 30mA) and let builders play with hotter points if they want to.



Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Jim R.

  • Hero Member
  • *****
  • Posts: 2194
  • Blind Bottlehead
Re: Something new is coming
« Reply #71 on: March 14, 2010, 03:16:26 PM »
Is the input stage directly coupled to the output, and if not, what's the value of the coupling caps?

Thanks,

Jim
Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 15824
Re: Something new is coming
« Reply #72 on: March 14, 2010, 07:34:13 PM »
The two stages are directly coupled, there are just 100uf caps at the output.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Todd R

  • Full Member
  • ***
  • Posts: 135
Re: Something new is coming
« Reply #73 on: March 15, 2010, 12:25:56 AM »
Yes, we do have badges. My bad, I will get an order button up tomorrow.

Don't see the link yet. Is it under parts?

Offline Jim R.

  • Hero Member
  • *****
  • Posts: 2194
  • Blind Bottlehead
Re: Something new is coming
« Reply #74 on: March 15, 2010, 03:23:39 AM »
PB,

Thanks.  No interstage coupling caps -- have to love that too.  This is sounding like a really sweet design... congratulations.

-- Jim
Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)