Resistor value for Phono III with Pre III CF.

[bob orbell]

Originally Posted by Richard

Hi Colin, Bob,

I may be reading it wrongly but I took Bob to be wanting the value to fit inside Phono3.

This is R41 in Phono3 or R35 in Phono3S.

It is changed depending on the load of the Preamp (i.e. if Pre3 is used or not, or in Bob's case for use with the lighter load of Pre3CF)

Yes, you are spot on Richard.

[bob orbell]

Thanks all, Richard is on the ball, I have sold Phono to a member with a PSU and a Pre III CF and want him to simply plug in and play, so I am asking for the correct resistor value so as I can change it, at present it is 1K. Bob

[bikerhifinut]

OK Bob,
Understood.
For what its worth, maybe my observations might help Colin or any other experimenter who may be attempting a slightly different combination of amps and PSU versions.
I'm sure Colin is conversant with the principles and use of Ohms and power laws when fine tuning an HT rail.

The idea still is valid if using a regulated PSU to supply 2 different loads, but the maths is easier cos you know the starting voltage so calculating values for a given voltage drop is more rellable.

Andy.

[colin.hepburn]

Originally Posted by bikerhifinut

OK Bob,
Understood.
For what its worth, maybe my observations might help Colin or any other experimenter who may be attempting a slightly different combination of amps and PSU versions.
I'm sure Colin is conversant with the principles and use of Ohms and power laws when fine tuning an HT rail.

The idea still is valid if using a regulated PSU to supply 2 different loads, but the maths is easier cos you know the starting voltage so calculating values for a given voltage drop is more rellable.

Andy.

Hi Andy/All
Yep I take on what you say regarding the ohms law and stuff which I am not too good at but I manage with it and use resistor calc as well but here I only posted what it stated on the bloody schematic trying to help I am now done
Colin

[bob orbell]

OK, lets not get tachy, I now know that R9 in Pre III and Pre IV is 1K, Pre III CF and Pre IV CF is 20K as stated by Colin, but what is the value of R35 in Phono 3S when used with Pre IV CF ? of course, if I had all three units here, I could find out, but, I don't, I am going to take an educated guess that it is 10K as both Pre III CF and Phono 3S connected to PSU will draw very little current, may be less than 8mA. Thank you to all, I hope someone can confirm. Bob

[Richard]

Guys, this can be very confusing as there are now at least 4 preamps, a PSU, and Phono3 versions with different resistor numbers.

I built the 3 series 15 years ago and had to read Bob’s question a couple of times and dig out the build sheets. Even then it was only when I saw the picture in the review of Pre4 (there isn’t a Pre4CF review) sitting alongside PSU that I twigged what might have happened with the 20k value Col posted. I feel sure Col's value will be correct for CF run off PSU but Bob needs the value for Phono.

http://www.world-designs.co.uk/v11%2..._HFW_May19.pdf

Col, I would be very grateful if you have a pdf of any CF build sheets you can send me as I don’t have any of them so couldn’t work out the CF current draw accurately.

Pic attached of R41/35 inside Phono3/S. It can be snipped close to the body to leave legs in place to solder a new value to. Or if 10k is in place it could be piggy-backed by a common value parallel resistor. Sleeve the legs with teflon tube to save melting PVC sleeving if you will be dabbing on a different value.

10k (for stand-alone)
10k//1k = 910R (for use with Pre3 or Pre4)
10k//20k = 6k8 (for use with Pre3CF or Pre4CF)

[colin.hepburn]

Originally Posted by bob orbell

OK, lets not get tachy,

Hi/All
Sorry I had no intention of offending anyone and I miss read Bob’s post as wanting the resistor value for the pre-3 CF and PSU3 I had an irritating day and wasn’t paying attention it happens to us all sometimes again my apologies to all
Colin

[colin.hepburn]

Richard
You have PM
colin
here's a short review of the Pre3 CF
http://www.world-designs.co.uk/v11%2..._HFW_Aug19.pdf

[Richard]

Ah, excellent, many thanks Colin

[colin.hepburn]

Richard
You have PM again file size issues