CCS rules supreme!

andrew Ivimey · Post by **andrew Ivimey** » Thu Nov 22, 2007 8:29 pm

I got the idea of the 'lazyman's CCS' from Diyparadise.com. Aimed at a very unusual el84PP amp (it's alongtailed pair dummy) I found it was a way to match up totally unmatched putput pairs of el84s .... nice; big improvement.

Then, thinks I, where can I use this CCS, elsewhere? so I drag out the very odd 6DN7 derivative push pull amp that came to Witham. Its a nice amp but how many can a boy have? nice ain't enough ... it was aiming for the chop.

Spare that amp, axeman!

I thought, try CCS on the output cathodes. It will at least balance the output pairs and I could reap sonic rewards, so I did. And I did - much more interesting.

Louder, clearer and yes a stay of execution.

I worked on the basis of 60ma but how do you work out the current that is 'right' for a valve??? beginner's luck - I've got loads.

I promise I won't start building mosfet amps, but you know, I feel I am cheating, using SS devices!

Post by **Nick** » Thu Nov 22, 2007 8:40 pm

Sounds very like Allen Wrights diffential amps

http://www.vacuumstate.com/various/dpa3 ... lo-rez.pdf

pre65 · Post by **pre65** » Thu Nov 22, 2007 8:51 pm

Hi Andrew-do you recon this is worth a go on the 832 ?

Give me a clue what is needed !

Andrew · Post by **Andrew** » Thu Nov 22, 2007 9:00 pm

I've been using CCS in my phono's for a while, C4S specifically, and I like them.

Seems they are gaining favour. I even heard Nick was using them in a D3A driven 2A3.

I was going to suggest it as a mod to the one Shane and Colin are talking about building, but thought we should get a tried and tested design going first.

Keep it up t' Andrew, whatever next, solid state regulated PSU?

cheers,

-- Andrew

andrew Ivimey · Post by **andrew Ivimey** » Thu Nov 22, 2007 9:08 pm

I suspect the theory is the same Nick. Those amps are a bit posh looking though.

Philip, it would be easy to implement on the 832 ... up to a point. First measure the voltage cathode to earth of the output valves. The LM317 will have a breakdown if the difference is more than 40 volts across the input /output. It should be safe but I haven't measured it. Then you have to decide on how much current makes these valves sing, I don't know. Then, there is 1.25volts difference between pin 3 and output, so 1.25 over R1 (what you have to decide on) equals the current in milliamps. So e.g if you want 80ma the resistor you need is 15ohms. I used 18ohms in the el84 amp you heard for 69ma - which I am told is nice and safe for el84s.The CCS replaces anything you have on the cathode to earth (cap and resistor) The cathodes are effectively tied together and go down to earth through the CCS. Now... thinks are there two separate cathodes? If not, they are already tied together, just do the same and listen to teh result. I would guess that by varying the current, using differnt resistors, you will vary the output some and tone, quite a bit.

-worth a try! I'll get round to it but I am rather busy at the mo'.

pre65 · Post by **pre65** » Thu Nov 22, 2007 9:18 pm

Hi-on the link that Nick provided it says that with a push pull amp and the CCS if one valve draws say .001ma more the other valve will automatically draw .001ma less,keeping the total current the same.

But,as the 832 has a common cathode for both halves would putting in a CCS have the same effect ?

Cressy Snr · Post by **Cressy Snr** » Thu Nov 22, 2007 9:32 pm

Now then lads

All I need to find is a regulator that is happy to drop 70V at 100mA to balance up my 6AS7 output valves.

I recently put those "lazyman" CCSs in both my voltage amp and driver stages and got a very useful improvement in bass definition and clarity.

Just the output stage to do now.
Personally I can't see anything wrong in using SS technology in valve gear where it would be a PITA to get the same effect with valves.

Andrew · Post by **Andrew** » Thu Nov 22, 2007 9:37 pm

SteveTheShadow wrote:Now then lads

All I need to find is a regulator that is happy to drop 70V at 100mA to balance up my 6AS7 output valves.

The IXCP 10M45S might get you there with a thumping great hintsink! Its rated for 450v @ 100mA.

I bought some for a power amp project I'm working on.

cheers,

-- Andrew

Cressy Snr · Post by **Cressy Snr** » Thu Nov 22, 2007 10:23 pm

Thanks Andrew,

After a bit of searching I managed to find a nice regulator that could also be used.

The Texas Instruments TL783 high voltage regulator is rated at 125V and 700mA; available from Farnell.

This is ideal for low voltage/high current regulator triodes being used as output devices. Great as a CCS in my situation. No good for HT regulation of the more "normal" valves though.

Steve

andrew Ivimey · Post by **andrew Ivimey** » Thu Nov 22, 2007 10:29 pm

very promising, Steve!

Andrew, your CCS, is it a mosfet based one?

Post by **Nick** » Thu Nov 22, 2007 10:51 pm

Just be aware that not all CCS's are equal, and the simple high current ones, may not be that perfect in terms of frequency and phase response.

The LM types are adding a lot of additional circuitry that a c4s doesn't have.

Steve: At 70v I would have thought you were in the range of a pentode CCS?

pre65 · Post by **pre65** » Thu Nov 22, 2007 10:57 pm

Hi-i might try a few things on 832 PP

Perhaps triode mode to start and then a CCS, and possibly both !

I do have a couple of LM317 to play with but not sure how to connect them up.

Can anyone point me to a diagram ?

andrew Ivimey · Post by **andrew Ivimey** » Fri Nov 23, 2007 7:48 am

I thought I already had!

any way .... diyparadise.com/yhlmccs.html

This lazy man's ccs does away with the cathode cap and resistor and is one lm317 and one tiny resistor. Expect huge difference Philip. We've already talked about how difference does not = better.

worse is easy!

(It was Mr Rankin's use of a pentode under the 45 in his DC CC that got me started thinking about this. Valves are more elegant.)

pre65 · Post by **pre65** » Fri Nov 23, 2007 8:21 am

andrew Ivimey wrote:I thought I already had!
any way .... diyparadise.com/yhlmccs.html

Hi Andrew-i'm confusing you !

I have a copy of the article but i'm not sure how the LM317 is actually wired to suit this application with regard to its 3 legs and where the resistor is positioned.

I get the bit about measuring the cathode voltage and working out the resistor size to get the required current.

I told you i was a bit "lacking" in the "knowing what i'm doing" department !!

andrew Ivimey · Post by **andrew Ivimey** » Fri Nov 23, 2007 8:28 am

LM317 has three wires - that gives you nine possibilities .... or ...

google LM317 and get the spec sheet. That will tell you which wire is input, output and Adj. Then .... well if you are using 832, I see no reason why not to start with what the artickle tells you to do to el84s. 'In' goes to cathode and 'Out' goes to ground.

If you get it wrong, no damage will occur, within reason, the vaves won't conduct and the ic is internally protected from silly bastards; I connected mine the wrong way round first time. The spec. sheet shows the i.c. from the back not the face (where the writing is) larffs eh!.

One thing you may try is to do one channel first, listen and compare and then hurry onto the second channel - should be good. My 6DN7PP is playing downstairs as I type (should be driving to work!)

tata4now

audio-talk

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