Cathode Follower

[emollusc]

My existing pre-amp in basically a passive Pre2 with a DACT CT2 (50K) volume control and a DACT CT3 selector switch which works pretty well. I'm thinking of converting this to a Pre3 CF by inserting the relevant electronics.

Having no experience of a CF, I would be interested to understand what difference this change would make, if any?

Also, I'm assuming that I could keep the existing volume control and just plug in the electronics?


Brian

[John Caswell]

Hi Brian,
Last question first - You would require all the bits for a Pre3 CF plus a PSU of some sort and the necessary interconnecting cables.
Advantages - A relatively low impedance output enabling you to use longer leads, simplicity itself. Can keep existing Vol control/input selector
Disadvantages - loss of gain -0.9dB, Large capacitor to isolate output DC, power supply and all attendant bits, cables etc.
As to how it would sound, I will pass on that, suffice to say I work on the Dr Lanchester principle "if it sounds right it is right" He quoted the maxim "If it looks right it is right" which applied to aeronautics
I know that this is going to create howls of protest here, but the only real criteria are your ears, equipment and listening room, and even music. I have had people say "I don't like the sound" when they really didn't like the music being played

John

[Richard]

Hi Brian,

Completely agree with John and I/we have had the advantage of a direct comparison between a Passive pre as you have, a WD conversion CF pre, and a Transformer pre in one sitting in the same system a few years ago.

Short answer is the 3 of us all preferred our own, probably due to familiarity.

I had the passive on short i/cs near to the power amp. The power amp for all was 100K input and line sensitive. To my ears it simply offered attenuation and the sound was clear and open. (I should caution that I've tried the same passive pre with a 20K input ss power amp and it wasn't so good, so impedance matching, I think, is important with a passive.)

The CF was good but narrower sound stage and somewhat limited in open-ness and highs but the owner preferred the more focussed and tidier presentation.

The TX was super-sweet and creamy sounding I was amazed. It lacked dynamics and timing compared to the others but did sound special.

It was easy to hear the differences and we all agreed those but had our own preferences.

[bob orbell]

Reading Richards post I found the TX pre harsh sounding in my system, the passive was OK but weak, the CF did it for me, no gain is not a problem at all, I lived with this set up for a long time but changed to a kit from Glassware, the Aikido CF, this is basically a CF with active load but with significant improvements, and finally a separate power supply for each, pre and phono, with regulated HT, this now all sounds way above any active pre. Bob

[John Caswell]

Chacun à
son goût as they say.


John

[emollusc]

Originally Posted by bob orbell

Reading Richards post I found the TX pre harsh sounding in my system, the passive was OK but weak, the CF did it for me, no gain is not a problem at all, I lived with this set up for a long time but changed to a kit from Glassware, the Aikido CF, this is basically a CF with active load but with significant improvements, and finally a separate power supply for each, pre and phono, with regulated HT, this now all sounds way above any active pre. Bob

Thanks Bob,

are the power supply changes detailed on this forum anywhere?


Brian

[John Caswell]

To be perfectly honest I would doubt if you will hear/notice any difference. Before you commit hari kiri on a new set of expensive cables see if you can borrow some.
1 Metre is not too long a length to worry about.

John

[bob orbell]

Originally Posted by emollusc

Thanks Bob,

are the power supply changes detailed on this forum anywhere?


Brian

Not yet Brian, I have been trying for months to get one to work properly, now I have, all I will say at the moment is that it uses a LD1084 regulator chip and a IXCP 10M45S constant current source chip, I have one working at 200 volts DC and the other at 250 volts DC . Bob

[emollusc]

Originally Posted by Richard

Hi Brian,

Completely agree with John and I/we have had the advantage of a direct comparison between a Passive pre as you have, a WD conversion CF pre, and a Transformer pre in one sitting in the same system a few years ago.

Short answer is the 3 of us all preferred our own, probably due to familiarity.

I had the passive on short i/cs near to the power amp. The power amp for all was 100K input and line sensitive. To my ears it simply offered attenuation and the sound was clear and open. (I should caution that I've tried the same passive pre with a 20K input ss power amp and it wasn't so good, so impedance matching, I think, is important with a passive.)

The CF was good but narrower sound stage and somewhat limited in open-ness and highs but the owner preferred the more focussed and tidier presentation.

The TX was super-sweet and creamy sounding I was amazed. It lacked dynamics and timing compared to the others but did sound special.

It was easy to hear the differences and we all agreed those but had our own preferences.

Thanks Richard,

what a fantastic opportunity to test all three types of amplifiers. Sounds, like I would need to 'suck it and see' or 'hear' in this case to see if I liked the change.

What do you class as short interconnects? I have 1m pre to power connections but I'm considering replacing them with low capacitance 0.5m ones. This is mainly due to DACT recommending a 10K attenuator and low capacitance interconnects as this increases high-end bandwidth and I have no intention or replacing my 50K attenuator due to cost. DACT have provided a attenuation curve calculator which may be of interested.


Brian

[Richard]

Originally Posted by emollusc

Thanks Richard,

what a fantastic opportunity to test all three types of amplifiers. Sounds, like I would need to 'suck it and see' or 'hear' in this case to see if I liked the change.

What do you class as short interconnects? I have 1m pre to power connections but I'm considering replacing them with low capacitance 0.5m ones. This is mainly due to DACT recommending a 10K attenuator and low capacitance interconnects as this increases high-end bandwidth and I have no intention or replacing my 50K attenuator due to cost. DACT have provided a attenuation curve calculator which may be of interested.


Brian

Hi Brian,

I used 0.5M of low cap cable (100pf/M). I agree with John that 1M should be no problem but be aware some real cheapies can be several hundred pF/M.

The comparison day was very enjoyable, quite a while ago now 2006, and included a lot of what we are still discussing in your recent threads. Nice to re-visit those days.

I've dug out 2 threads, the first about the 300B stereo amps and clone versions made by Greg and friends, and the second about the meet up we had to listen to them, pre-amps, SB, dacs etc. Wordy but you might find parts of interest

Old 300bpp Ringing

300B PP NottFest Meetup