pre-CF4 ccs circuit change over switching

[bob orbell]

I have spent a lot of time ( 20 years ) with different configurations of cathode followers, from cathode bias, valve CCS as in active load, White CF and ACF ( aikido cathode follower ) the latter I use today and has the best sound and an excellent PSRR, the White was also very good but requires a very well sorted PSU, I could have lived with any one of these, but the ACF wins for me. I will be interested in Colin's thoughts on his build. Bob

[Richard]

So... has anyone here compared CCS to cathode resistor on this Pre3/4CF and what switching if any did you use or was it connected on tags/pins? Was the sound difference noticeable?

What's the consensus on shorting vs non shorting switches - would either allow hot switching to compare or is it always safer to power off first etc?

[bob orbell]

It would be interesting to know how many Pre III / IV CF units Matthew has sold, I only know of two. Bob

[vinylspinner]

Well, I’ve had two and sold one to Geoff (pager8) recently.
Mine works exceptionally well with the WAD 300B clone and 2a3 push pull amps that I own.

[Fred Shaw]

I’ve bought a Pre3 CF from Matthew. Currently doing a fine job driving my WAD (clone) 300B.

[vinylspinner]

Originally Posted by Fred Shaw

I’ve bought a Pre3 CF from Matthew. Currently doing a fine job driving my WAD (clone) 300B.

Hello Fred, is that the copper chassis amp that John sold recently? Very nice amp, had a look inside when John was working on it.

Nigel

[Fred Shaw]

Hi Nigel,

Yes, it is the copper chassis one that John was selling and very nice it sounds too. It is certainly a step up from the WAD KIT88 I used previously. It’s a pity the 300Bs are now so expensive 😢

[Richard]

Yes I believe sales of the new CF models are going well and quite a proportion of them are going out as ready built. Matthew's build quality is very high. Have a look at the pics and review with test figures from Noel in HFW for the Pre3CF (Pre4CF uses the same pcb),

http://www.world-designs.co.uk/v11%2..._HFW_Aug19.pdf

For anyone following the switch query, one pic in the review shows the pcb and the links in question top and bottom of the left hand side of the pcb. You'll see LK1 just needs a change-over switch and LK2 an on/off. (ctrl scroll on the pdf)

[bob orbell]

Nigel / Fred, do you run yours with or without the CCS ? have you compared both options ? I should imagine that you both have opted for the transistor CCS, let us know please. Bob

[Fred Shaw]

Yes Bob, I run mine with CCS. I haven’t tried it without so I don’t know which is “best”. Anyway, I’m happy with the way it sounds so don’t intend changing it at the moment.
Fred.