simplicity itself - a line stage

Andrew · Post by **Andrew** » Sat Jan 05, 2008 12:06 pm

Paul, CCS, 300B? Am I imagining things?

Cressy Snr · Post by **Cressy Snr** » Sat Jan 05, 2008 12:19 pm

It's that Ivimey!

He started it with that EL84 amp!

Before that it was only you and Nick into that sort of stuff. Now we're all at it!

Steve

Post by **Nick** » Sat Jan 05, 2008 12:51 pm

Sorry, paul was trying CCS way before that, in fact he was the one who suggested I use them in the phono stage. In fact, if I remember, the 212 amp that tried to set fire to MarkJ's carpet started life with a CCS.

Once the 212 socket died, the next morning Paul and I tried comparing using interstages as chokes compaired as CCS's and that when we started to worry about the sound of CCS.

Paul, if I remember, the 112a amp you brought to mine, turned up with PX (4 or 25 can't remember, but with the SB no caps power supply), but I remember it sounded bloody great, then we tried it driving my 211 output stage.

Andrew · Post by **Andrew** » Sat Jan 05, 2008 1:33 pm

Nick wrote:Sorry, paul was trying CCS way before that, in fact he was the one who suggested I use them in the phono stage. In fact, if I remember, the 212 amp that tried to set fire to MarkJ's carpet started life with a CCS.

No, it was more that I know Paul had been there but I thought he didn't like the sound of either a CCS or a 300B so it was more a matter of surprise that he was re-visiting this, tho' the extra choke is an interesting twist.

-- Andrew

Andrew · Post by **Andrew** » Sat Jan 05, 2008 1:37 pm

In fact, Paul's been most places, I suspect

Seriously, if you think what was in that 212 amp for the first EF..............apart from Nick we're all playing catch up.

Paul Barker · Post by **Paul Barker** » Sat Jan 05, 2008 2:25 pm

Yes thats right Nick and I evaluated choke versus ccs at darrens carpet all those years ago and ccs was found lacking.

But in those days I was using discreat transistors.

I'm not saying ccs is better than a choke but ccs with a choke is better than a choke.

Suddenly now the 300b also has more apeal.

AS for the rest of what I had that day we tried grid chokes out that day Nick it probably did have the resistorless capacitorless power supply as used in eggfest one.

I am presently using that same supply but inserted Black gates because although r less c less is clearly the best sound it comes at a cost (in the form of effort and monitoring). I have had one shunt valve expire and when that happens your output stage is subject to whatever the power transformer can achieve, in my case that is considerably more than I want my px25's exposed to.

So the ultimate stuff is great but it's a good idea to find ground which is one step back down, more reliable and less effort.

Hence the 300b. We all know it's a substandard valve, but it's only one step down from no. 39. The oxide 211 is at the summit, a decent 300b is shortly behind.

Post by **Nick** » Sun Jan 06, 2008 2:30 pm

Well, I have tried to build a model. A couple of problems.

I cant find a model for the exact CCS, so I have used a 10M90S and I don't have a 112a model so I have used a 76 at 5ma. I have also guessed at about 150pf capacitance across the choke.

But given those, what in particular are you interested in?

Darren · Post by **Darren** » Sun Jan 06, 2008 3:03 pm

Paul Barker wrote:Yes thats right Nick and I evaluated choke versus ccs at darrens carpet all those years ago and ccs was found lacking.

And it was because of that day that I have never tried it myself. I wasn't impressed with the CCS.

I have watched someone else try them a few times (well it saved me doing it) Can't say it improved matters then either.

But some say it's a good investment, so they must be getting it right.
For me, I'll stick to the simple stuff. These chips have a habit of cooking when I poke them with a few electrons

Paul Barker · Post by **Paul Barker** » Sun Jan 06, 2008 3:13 pm

what am I interested in?

Goodness knows, does anything nasty appear?

I don't even have a scope these days.

Post by **Nick** » Sun Jan 06, 2008 3:49 pm

Nothing too obvious, one thing I noticed, looking at the voltage on the anode when sweeping from 1hZ to 100kHz, the plane choke has the excted falling response as the parallel capacitance comes into play. But the CCS case, the response actually rises from the same point.

These two responses are the same valve, and op and choke, and the CCS has no cathode bipass. It should be remembered the scale is only a tenth of a dB though.

http://home.lurcher.org/nick/images/choke_ccs.jpg

Andrew · Post by **Andrew** » Sun Jan 06, 2008 5:01 pm

What does it do with the CCS on its own?

And, I wonder what a fourier would tell us, depends upon the quality of the models, I suppose...

cheers,

-- Andrew

Post by **Nick** » Sun Jan 06, 2008 6:43 pm

I will see what just the CCS does. I am a little wary of taking the model too far, as I have made some assumption on the choke. I can post the CCS model I used so you can have a play.

.MODEL IXC_10M90S NMOS
+ LEVEL=3
+ L=2.0000E-6
+ W=19.000E-3
+ KP=1.0547E-6
+ RS=10.000E-3
+ RD=69.978
+ VTO=-4.4878
+ RDS=1.0000E9
+ TOX=2.0000E-6
+ CGSO=526.32E-15
+ CGDO=5.2870E-9
+ CBD=85.184E-10
+ MJ=1.5000
+ PB=2.6056
+ RG=10.000E-3
+ GAMMA=0
+ KAPPA=0

It started life as a pspice model so there may be problems, seems to work as expected from the spec sheet though.

Edit:

This is just the CCS http://home.lurcher.org/nick/images/ccs_only.jpg

So I think spice is not showing what Paul is hearing the choke is adding. I have every reason to believe that the improvement Paul is hearing is real, but shows why spice won't let you make decisions without listening in there as well. (IMHO).

Andrew · Post by **Andrew** » Sun Jan 06, 2008 7:15 pm

Yep, think your right, I reckon the choke is adding some 'lurve' whilst the CCS is keeping the DC conditions close to 'ideal'. Could it also be possible that the CCS is doing something close to what an active PSU might do? Isolate any PSU oddities?

-- Andrew

Post by **Nick** » Sun Jan 06, 2008 7:35 pm

Could it also be possible that the CCS is doing something close to what an active PSU might do? Isolate any PSU oddities?

That was my thought, which my simple sim isn't showing

Paul Barker · Post by **Paul Barker** » Sun Jan 06, 2008 7:49 pm

well you've got to consider it in context the area of change is only changing by 0.1 of a db whereas other parts of the amp the source the speakers and the room, not to mention my hearing will have differences of 3db al over the place.

Now I discover the baffles are imperfect for instance, so thes big flat boxes I have made are yet another batch of wood (£20 worth fortunately) for the scrap, so I can make so pyramid front ed u shaped baffles..

Conbined with which I next have to experiment with woofer position, having placed it as close to the floor as possible now I learn this cancels lower mid bass, I might prefer that portion to be uncancelled to the support the floor offers the lower bass, so now I have to try out different positions.

For one thing I can flip the cases up the other way and see where that leaves me.

audio-talk

simplicity itself - a line stage

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