Phono 3 Cartridge Loading

[Cycleallday]

I have a phono3 with step up transformers that have never been wired in. Using a Kontrapunkt b and the Pre3 I never needed any more gain when driving a Meridian power amp.

Now I have bought a Quad Integrated which has an internal (solid state phono) and I would like to see if the Phono3 makes any improvement. So my problem is how do I wire in the transformers as the Pre3 will no longer be used. I have got totally confused by what settings to apply.

The Kontra has an Output voltage of 470 µV and Recommended load impedance of 50-200 Ohm. The blurb states "variations of the resistive load can influence sound image to some extend, where higher values around 100-200 Ohm will open details further. But no less than 10 Ohm will tighten the sound image".

How do I work out whether I need to use the 10:1 or 20:1 ratio and what resister value should I use for the Load impedance?

Mel

[MrKettle]

Having a Kontrapunkt B, a Phono 3 and some Sowter 10:1 stepups I would say use the 10:1 settings and see how it works before fiddling with the load resistor (which would be 10k for a 100Ohm resistance). It probably depends on the sound you like but I haven't felt any need to fiddle.

[bob orbell]

Hi all, I think we need to know whether you have a phono 3 with phono 2 PCB or a phono 3s with relay input board, if you have no input board, the transformers are connected direct to the phono inputs, for low output MC cartidges connect pink & yellow to the centre pin and blue & orange to the outer tag. (left and rigt chanel respectively)
For high output MC cartidges connect pink to centre pin and orange to the outer tag, link blue & yellow and insulate. Change R13 &14 for 10K, if you have the 3s, it will be better to send you a copy of the manual. BOB

[John Caswell]

Hi all,
It doesn't really matter whether you have the input switching or not, for a 470µV output cart a 10:1 step-up will give a nominal 400mV output from the PhonoII/III which is about right.
As the impedance ratio = turns ratio squared with a 10: stepup you therefore have an impedance ratio of 100:1 so for a reflected load of 100R you will need a load on the secondary of 10K.
As the input impedance of phone II/III is already set by the 47K in the grid of V1 (assuming it is still in circuit and personally I would leave it in) you will need to fit a 13K in parallel with this 47K resistor to give you 10K (two resistors in parallel = product/sum).
I have used Ortofons for years and find a 100R load to be just about right.
Currently running a Jubilee/SME309 into a phono III. Any further queries just ask here

John

[Cycleallday]

Many thanks for the replies. I do have the full build documentation and the query was more related to a lack of understanding of the settings and their impact.

I will go with the suggested 10:1 and 100R load.

p.s. the Quad is an incredible amp in my view and seems happy with any genre of music - it partners the WD25T's very well.

Mel

[Greg.]

Originally Posted by John Caswell

Hi all,
It doesn't really matter whether you have the input switching or not, for a 470µV output cart a 10:1 step-up will give a nominal 400mV output from the PhonoII/III which is about right.
As the impedance ratio = turns ratio squared with a 10: stepup you therefore have an impedance ratio of 100:1 so for a reflected load of 100R you will need a load on the secondary of 10K.
As the input impedance of phone II/III is already set by the 47K in the grid of V1 (assuming it is still in circuit and personally I would leave it in) you will need to fit a 13K in parallel with this 47K resistor to give you 10K (two resistors in parallel = product/sum).
I have used Ortofons for years and find a 100R load to be just about right.
Currently running a Jubilee/SME309 into a phono III. Any further queries just ask here, John

I hopefully think John's post is also helpful to me at the moment. I've been banging my head against the wall trying to understand cartridge load calculations.

My situation is I'm using original Phono II. My current cartridge is an Ortofon (very early) very low output MC30. So, step up Tx is set at 1:20 and cartridge load resistor (R13/14) is 24K with the original input resistor (R15/16) remaining at 1K.

I now want to introduce my Ortofon Kontrapunkt b. Given the much increased output from the KB and considering what John has written above, is it simply a matter of changing my step up Tx's down to 1:10 ratio and changing R13/14 to 10K?

[John Caswell]

Hi Greg et al,
As the Kontra B output is about 470µV then 10:1 will be fine.
If you still have the original 47K grid leak in Phono II then you will need to have another 13K in parallel with it to give you 10K which with a 10:1 ratio (100:1 impedance) will give you a reflected load of 100R, this is what I use with my Jubilee. Don't worry if you do not have a 13K - 12K (9K55 = 95.5R) or 15K (11.37K = 113R) will be fine.
If you can tell the difference between those three loads then I am afraid it's the Loony bin for you

John