Tube Amp CCS?

JojoD818 · 8th June 2006, 08:17 PM

Hi Guys,

I would like to use a CCS for the attached circuit. SY's evolved Morgan Jones CCS with leds is what I had in mind, I had great success with it in preamps.

The first thing I want to do is to remove the 470 ohms and two 220 ohms in the driver tubes and replace that with a CCS. This should work right?

Now for the input triode, which should I replace? the 47K on the anode and use a current source or the 470 ohms on the cathode and use a current sink?

Any comments or suggestion would be a great help.

Thanks!

SY · 8th June 2006, 08:43 PM

Nope. If you change the cathode resistor to a CCS, you'll kill the gain of that stage. This particular circuit is not terribly amenable to CCS use.

Now, if you wanted to go open loop, you could replace the cathode resistor with an LED or LEDs, then put a CCS in the plate circuit...

JojoD818 · 8th June 2006, 08:47 PM

Hi SY,

Which are you talking about, the input tube or the driver tube? It's 5AM here and coffee is nowhere in sight...

anatech · 8th June 2006, 08:48 PM

Hi SY,
Your feedback would be "shorted" by the LED. Differential front end then?

-Chris

SY · 8th June 2006, 08:50 PM

Chris, that's why I said "open loop."

I was talking about the input stage. The driver stage could be set up as a CCS-long tail, but since it receives a balanced signal from the split-load phase splitter, that's not really necessary.

JojoD818 · 8th June 2006, 08:59 PM

Hi Chris, SY

so installing a CCS in the driver tubes (cathode) won't make much of a difference then?

what if I leave the 470 ohms cathode resistor of the input tube and then use a CCS for it's plate circuit?

SY · 8th June 2006, 09:03 PM

CCS plate loads hate cathode resistors.

Nope, this is a design (Williamson) which hangs together as a piece. Incorporating CCS will take some significant redesign. And if it were me doing the redesigning, <broken record>I'd use something like a 6SL7 diff amp input direct coupled to a 6SN7 differential driver</broken record>.

JojoD818 · 8th June 2006, 09:09 PM

just as I thought, so it's a hopeless case then until I break it apart...

anatech · 8th June 2006, 09:12 PM

Hi SY,

Quote:

Chris, that's why I said "open loop."

Gee, I didn't know where were being completely literal! I thought you were just indicating the higher gain from a CCS load. Can't get anything past you these days!

Quote:

<broken record>I'd use something like a 6SL7 diff amp input direct coupled to a 6SN7 differential driver</broken record>.

That broken record is playing a nice tune.

It would be interesting to see a complete design.

-Chris

SY · 8th June 2006, 09:21 PM

I'm tempted to do one in my HF87 re-rebuild. On va voire.

8th June 2006, 08:17 PM	#1
JojoD818 diyAudio Moderator Join Date: Mar 2003 Location: diyAudio Special Operations Center	Tube Amp CCS? Hi Guys, I would like to use a CCS for the attached circuit. SY's evolved Morgan Jones CCS with leds is what I had in mind, I had great success with it in preamps. The first thing I want to do is to remove the 470 ohms and two 220 ohms in the driver tubes and replace that with a CCS. This should work right? Now for the input triode, which should I replace? the 47K on the anode and use a current source or the 470 ohms on the cathode and use a current sink? Any comments or suggestion would be a great help. Thanks!

8th June 2006, 08:43 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Nope. If you change the cathode resistor to a CCS, you'll kill the gain of that stage. This particular circuit is not terribly amenable to CCS use. Now, if you wanted to go open loop, you could replace the cathode resistor with an LED or LEDs, then put a CCS in the plate circuit... __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

8th June 2006, 08:50 PM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Chris, that's why I said "open loop." I was talking about the input stage. The driver stage could be set up as a CCS-long tail, but since it receives a balanced signal from the split-load phase splitter, that's not really necessary. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

8th June 2006, 09:03 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	CCS plate loads hate cathode resistors. Nope, this is a design (Williamson) which hangs together as a piece. Incorporating CCS will take some significant redesign. And if it were me doing the redesigning, <broken record>I'd use something like a 6SL7 diff amp input direct coupled to a 6SN7 differential driver</broken record>. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

8th June 2006, 09:21 PM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I'm tempted to do one in my HF87 re-rebuild. On va voire. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

8th June 2006, 08:47 PM	#3
JojoD818 diyAudio Moderator Join Date: Mar 2003 Location: diyAudio Special Operations Center	Hi SY, Which are you talking about, the input tube or the driver tube? It's 5AM here and coffee is nowhere in sight...

8th June 2006, 08:48 PM	#4
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi SY, Your feedback would be "shorted" by the LED. Differential front end then? -Chris

8th June 2006, 08:59 PM	#6
JojoD818 diyAudio Moderator Join Date: Mar 2003 Location: diyAudio Special Operations Center	Hi Chris, SY so installing a CCS in the driver tubes (cathode) won't make much of a difference then? what if I leave the 470 ohms cathode resistor of the input tube and then use a CCS for it's plate circuit?

8th June 2006, 09:09 PM	#8
JojoD818 diyAudio Moderator Join Date: Mar 2003 Location: diyAudio Special Operations Center	just as I thought, so it's a hopeless case then until I break it apart...

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