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Author Topic: Tube Rolling w/Crack  (Read 567094 times)

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Offline Jim R.

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Re: Tube Rolling w/Crack
« Reply #30 on: May 23, 2010, 11:56:31 AM »
Steve, thanks very much for that information -- that helps a lot, but also tells me that a dpdt won't exactly work to switch between 12au7 and 5670 configurations.  Oh well, at least now I have the info for future reference.

-- 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 Jim R.

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Re: Tube Rolling w/Crack
« Reply #31 on: May 23, 2010, 12:02:57 PM »
Hi Paul,

Now, that sounds tempting.  I still plan to try the stock config first, but I'm thinking the additional current drive would be nice with the 650s for a bit more detail...  perhaps.

Thanks again,

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)

Online Paul Birkeland

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Re: Tube Rolling w/Crack
« Reply #32 on: May 23, 2010, 12:26:19 PM »
Yeah, I think it really comes down to taste.  Doc loves his 12AU7's, and I totally understand that when we cue up tape and listen.  PJ is pretty into 6SN7's (as is Ed Fallon), and in PJ's case I think it's reflective of his preference for musicality.  In my case, I might go for a 6414 or something like that, except that gain is an issue, so wiring for 5687's or ECC99's seems like a good choice. 

Putting in a switch for the filaments seems easy enough and like a good plan.  With  the Speedball installed, you should be able to switch between 6CG7/6FQ7, 12AU7, and 12BH7 without tremendous voltage mismatch between the driver tube and the output tube.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jim R.

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Re: Tube Rolling w/Crack
« Reply #33 on: May 23, 2010, 12:39:51 PM »
Yes, it really does all come down to personal taste, and that's why I at least originally wanted to have the ability to use the 6cg7 (and because I have a few very nice examples of those on hand), but also because I too really like the musicality of the 6sn7 even though I do find that the ability to render dynamic contrasts to be high on my preferences list and the 6sn7 is really not the ideal tube for this.  On the other hand, (and I see you anticipated my next questions) is that with the direct coupling and no cap between driver and output, dynamic contrasts are much better than in cap coupled amps anyway.

So, all these unknowns and experiments to be done, but at least with my original plan to have a switchable filament arrangement, I can play with enough variations to keep me happy for a while and not worry about putting undue stress on the amp.

This is the kind of thing that makes BH kits so much fun!

-- 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 Dyna Saur

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Re: Tube Rolling w/Crack
« Reply #34 on: May 24, 2010, 11:25:15 AM »
Quote
Hey Jim,
The pin assignments for the 5670 are;

1-heater
2-cathode (2)
3-grid (2)
4-plate (2)
5-shield
6-plate (1)
7-grid (1)
8-cathode (1)
9-heater

Heater-6.3V, 350mA

Class A
plate voltage 150V
cathode bias resistor 240 ohm
amplification factor 35
plate resistance 6400 ohm
transconductance 5500 micromho
plate current 8.2 milliamperes
grid current -8V (Ib=10 milliamperes)

If you are re-wiring the driver 9 pin socket for 5670, then it will also be compatible with 2C51 and the ever popular and lovely WE 396A.

If 12BH7s are to your liking, then the 6GU7 is the 6V filament near equivalent, just wire the filament power to pins 4 and 5 and leave 9 open. Same pinout as 6CG7 / 6FQ7.
ed brown

Offline levlhed

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Re: Tube Rolling w/Crack
« Reply #35 on: June 03, 2010, 10:36:07 AM »
With  the Speedball installed, you should be able to switch between 6CG7/6FQ7, 12AU7, and 12BH7 without tremendous voltage mismatch between the driver tube and the output tube.

12BH7's come highly recommended to me as suitable 12AU7 subs.  With Speedball you're saying there'll be no concerns?  Would a particular model of output tube be better suited for use w/ a 12BH7?
Technics SL-1200 "MKE" ~> DL103r w/Ruby Cantilever & Contact Line Stylus ~> Audioquest PT-9 ~> Bobs Devices Cinemag SUT ~> Vista Audio PHOHO-1+ ACLE ~> Bottlehead Crack w. Speedball ~> Beyerdynamic T1

Online Paul Birkeland

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Re: Tube Rolling w/Crack
« Reply #36 on: June 03, 2010, 10:50:53 AM »
With the Speedball a 5-10v difference in driver plate voltage won't really affect the output tube.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Natural Sound

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Re: Tube Rolling w/Crack
« Reply #37 on: June 03, 2010, 12:15:29 PM »
Yeah, I think it really comes down to taste.  Doc loves his 12AU7's, and I totally understand that when we cue up tape and listen.  PJ is pretty into 6SN7's (as is Ed Fallon), and in PJ's case I think it's reflective of his preference for musicality.  In my case, I might go for a 6414 or something like that, except that gain is an issue, so wiring for 5687's or ECC99's seems like a good choice. 

Putting in a switch for the filaments seems easy enough and like a good plan.  With  the Speedball installed, you should be able to switch between 6CG7/6FQ7, 12AU7, and 12BH7 without tremendous voltage mismatch between the driver tube and the output tube.

Sorry if this has been asked before. Isn't the 12SN7 the same as a 6SN7 with different heater voltages (12V vs 6V)? Wouldn't this make a more suitable replacement for the 12AU7 since the filament voltage is the same? 12SN7's tend to be a lot cheaper too.

Offline Jim R.

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Re: Tube Rolling w/Crack
« Reply #38 on: June 03, 2010, 12:27:04 PM »
The actual filament voltage in the Crack, as in the s.e.x. amp (same power transformer) is 6.3v and you can run some of the 12v tubes on this by running the heaters in a parallel, rather than serial configuration.

Hope this helps,

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 Dyna Saur

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Re: Tube Rolling w/Crack
« Reply #39 on: June 04, 2010, 06:21:39 AM »
12SN7 has a 12.6 volt (only) filament, it is not tapped like the 12AU7 or 12BH7 which allows those tubes to run on either 6.3 or 12.6V.      Crack would need a 6SN7 (and an enlarged chassis hole to accomodate the octal socket.  "Hole Shrinkers" in reverse, anybody ?  ;^)   Yah, they're called Greenlee Punches ;-)

FWIW, though it doesn't really mean anything useful  for "The Crack", there is also an 8SN7.    Like my erstwhile experiment with the 8CG7, it will work, but gain will be low, and sound "subdued" as the operating voltages will be skewed from the 8CG7's reduced emission.

/ed B
« Last Edit: June 24, 2010, 10:41:11 AM by Dyna Saur »
ed brown

Offline Grainger49

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Re: Tube Rolling w/Crack
« Reply #40 on: June 04, 2010, 06:30:33 AM »
   .  .  .    Crack would need a 6SN7 (and an enlarged chassis hole to accomodate the octal socket.  "Hole Shrinkers" in reerse, anybody ?  ;^)

/ed B

Knockout, see this link:

Project Tools

See the first post under More Advanced Tools, and the second post for a link to Harbor Freight where you can buy a set cheap!  I have used my set often.

Offline Natural Sound

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Re: Tube Rolling w/Crack
« Reply #41 on: June 04, 2010, 02:25:12 PM »
Hmmm... now you got me thinking. I still haven't started building my kit yet. Maybe I'll punch the hole out and call up BH for some hole shrinkers. That way I can build the amp stock, get familiar with the way it sounds and then maybe drop in an octal socket and try the 6SN7 later. Are there any other component changes if I go this route?

Online Paul Birkeland

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Re: Tube Rolling w/Crack
« Reply #42 on: June 04, 2010, 02:32:14 PM »
Go with the octal socket right off the bat and buy some 6SN7 to 12AU7 adapters online.  Getting in there to enlarge the hole later will be pretty hard.  When you enlarge the 9 pin hole, be sure the socket mounting hole closest to the cooling vents is still a socket mounting hole (so position your punch appropriately), otherwise the speedball upgrade will give you problems.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Natural Sound

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Re: Tube Rolling w/Crack
« Reply #43 on: June 07, 2010, 05:52:31 PM »
Go with the octal socket right off the bat and buy some 6SN7 to 12AU7 adapters online.  Getting in there to enlarge the hole later will be pretty hard.  When you enlarge the 9 pin hole, be sure the socket mounting hole closest to the cooling vents is still a socket mounting hole (so position your punch appropriately), otherwise the speedball upgrade will give you problems.

Thanks! Are there any other component changes when going from the 12AU7 to the 6SN7?

Online Paul Birkeland

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Re: Tube Rolling w/Crack
« Reply #44 on: June 07, 2010, 06:14:31 PM »
Nope, no component changes, just the pinout/socket change.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man