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Old 10th August 2006, 08:03 AM   #1
kegger is offline kegger  United States
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Default Tube LTP CCS?

This is a circuit I’m working on and wanted to implement a tube CCS as I have (2) 9 pin sockets
to where I was going to run a couple dual triodes for this setup of something like 6CG7’s, 12BH7’s
and or 12AU7’s depending on how things shake out, which for this driver and LTP leaves me one
triode open so I wanted to see how a tube CCS would work out and kinda like what I see here.

The resistors R,17 and R,14 are because I wanted a 190ohm resistor so I had to parallel the 510
and 300 to get basically 189. Don’t worry about the input as I have that toned down since there
is no feedback implemented here yet my gain is quite high so it looks better on the scope.

So I’m curious if my tube CCS is implemented correctly and if there is any glaringly obvious errors
in my concoction here. Or if it’s not the traditional way to do it but looks like it would work I’d like
to know that also, as I have no experience with a tube CCS but would like to try one.

I’m curious what the gurus or anyone else that would like to chime in have to say.
(If the circuit is to tough to follow with all my meters I can take them out and reprint)
This is done in the free 45day version of Multisim with my modded tube models.

Thanks.
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File Type: gif vta_6j5g_pi_6j5g_drv_410v_tube_ccs.gif (42.0 KB, 508 views)
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Old 10th August 2006, 08:42 AM   #2
EC8010 is offline EC8010  United Kingdom
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Default Re: Tube LTP CCS?

Quote:
Originally posted by kegger
(If the circuit is to tough to follow with all my meters I can take them out and reprint)
That's quite an achievement, you've managed to draw a valve circuit that I can't follow! Your second stage is a LTP, but for the life of me I can't work out how the other two valves are configured. A scanned back of an envelope sketch would make life much easier.

You seem to have a 410V positive HT and are using 6J5. 6J5 need plenty of HT, so although you have enough, you can't really afford to waste any by raising the cathodes of the LTP to 100V or so to allow a valve CCS in their tail. If you can provide a negative HT, then an EF184 pentode would make a nice CCS for the LTP. Otherwise, just make a semiconductor cascode CCS (search for DIYaudio CCS board).
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Old 10th August 2006, 09:08 AM   #3
kegger is offline kegger  United States
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Allright I'll work on getting the meters out of there and making it easier to follow, it can be a little daunting I'm sure.

But it's basically a 6J5 as a driver with a pair of 6J5's as the LTP with another 6J5 as the CCS for the LTP. (2 6SN7's really)

These are all single 6J5's to spread them out to work on it but it will be 2 twin triodes, a 12bh7 driver for one
of it's halves and the other halve as the CCS for a 6CG7 LTP splitter, at least that's what I'm thinking as of now.

I have (2) 9 pin sockets to work with so I wanted to stay to a pair of dual triodes as I have them and they seem
to fit the application, I wanted to try and do it all tubed with no solid state parts and I wanted to try a triode CCS.

I've never seen a setup like this so it made me even more intrigued to try it. (There probably is I just haven't seen it)

Usually you see as you say, a pentode or solid state CCS but I wanted it to be different and fit it in my 2 sockets.

I'm just not sure if I've got it all worked properly or if it will work right, but it sure seems to look right in the sim, I think.

Thanks for your reply and I'll try to get an easier to follow schem up shortly.
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Old 10th August 2006, 09:17 AM   #4
EC8010 is offline EC8010  United Kingdom
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Although you can make a CCS using a triode like a 6J5, it won't be a terribly good one. See if you can't find another 9 pin socket. Beware that it's only worth going to all this trouble if you can be sure that the load on the LTP will never stray out of Class A.
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Old 10th August 2006, 09:27 AM   #5
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Quote:
Although you can make a CCS using a triode like a 6J5, it won't be a terribly good one.
I agree, I wouldn't call it a CCS at all. You need a sharp cutoff pentode with high gm. A pentode makes an excellent CCS and won't blow up without warning, like some SS devices can do.

I'm sure you don't intend to go out of class A, so you're well advised to use a CCS in the tail. It should give almost perfect balance and will make a big difference.
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Old 10th August 2006, 09:57 AM   #6
kegger is offline kegger  United States
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Default Here it is cleaned up.

I took out the driver and just left the LTP and Tube CCS. With the tubes I'm thinking of using, or simular.

If the Sim is any indication I get perfect balance with equal plate resistors and nicely in the plate curves.
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File Type: gif ltp_12au7_tubeccs_12bh7.gif (14.8 KB, 429 views)
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Old 10th August 2006, 10:03 AM   #7
EC8010 is offline EC8010  United Kingdom
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What is that 27k resistor doing in the anode circuit? If it's needed to get the DC right, move it down into the cathode circuit where its value can be multiplied by the amplification factor of the CCS valve.
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Old 10th August 2006, 10:10 AM   #8
kegger is offline kegger  United States
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It's a variation of the LTP, a SCHMIDT.

I will see how it looks though with it like you say.
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Old 10th August 2006, 12:21 PM   #9
kegger is offline kegger  United States
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Default Traditional LTP

And here is your standard LTP with and without meters.
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File Type: gif vta_12au7_pi_12bh7ccs_410v_ccs_ltp.gif (39.7 KB, 331 views)
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Old 10th August 2006, 12:23 PM   #10
kegger is offline kegger  United States
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Default No meters

Easier to follow.
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File Type: gif vta_12au7_pi_12bh7ccs_410v_nm_ltp.gif (14.3 KB, 346 views)
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