Phono stage loading

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Graeme
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#1 Phono stage loading

Post by Graeme »

Skip to the gap in text to avoid the drivel 😂
I eventually bought a new cart. I couldn't decide what to get so I did the least sensible thing and bought a used garrott microscanner decca london.
It's good.
However, it is very responsive to all changes. Vtf, vta, effective mass, damping, and loading!
I think its going to take some time to get this set up just right.
With this in mind I need to sort out some variable loading for the Phono stage. I've tried from 10k to 180k and it seems the sweet spot is probably going to be between 30k and 65k.
Where it ends up will depend on where I settle on vta etc.
At the moment, just for some quick trials, I hot glued a load of resistors to the outside wooden frame of my Phono and am swapping between them with clip leads. This arrangement has induced alot of hum though. Ok for a quick couple of hours getting an idea but I could do with sorting something better. I'd quite like to have switchable loading on the Phono permanently. Maybe focused around 2 ranges (8k to 15k for mc, and maybe 35k to 65k for anything else).

Is there any way of making loading variable, with as many options as possible, without making it sound bad? Ideal situation would be 2 pots maybe, switchable between. But I've read loading resistors can make quite a difference to sound so not sure pots are a good idea.
Any thoughts?
If I have to pick 2 settings, is a switch between them ok? Might still have some mercury wetted relays left.
izzy wizzy
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#2 Re: Phono stage loading

Post by izzy wizzy »

I don't fiddle with loading but have always thought a second phono socket in parallel would allow all kinds of loading to be applied via a resistor in a phono plug. Could even try an external pot for giggles. If that isn't possible, you can get a double phono socket to phono plug gizmo to start with. Think Vampire do one. I've got some but would have to dig them out.

Edit: https://richelectronics.co.uk/product/p ... ed-om0701a
Graeme
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#3 Re: Phono stage loading

Post by Graeme »

Using Phono plugs is an option, but I'm probably going to want to try alot of different values.
I'd like to be able to vary it during play too if possible, at least for a few weeks while I get this dialled in.
Every tweek I make a change to vta, arm effective mass or damping etc, it tends to go hand in hand with another tweak in loading.

I've been trying to perfect one change at a time, but it's not working out like that.
Graeme
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#4 Re: Phono stage loading

Post by Graeme »

I have a 50k alps blue. Wondering if I can use that, with 20k in series to give the range of variability I'd like to try with this decca.
I guess I could switch that 20k between being in series or in parallel to give me a suitable range for mc (I use step up transformers with mc)

I guess ultimately, I am wondering how much difference to the sound resistor type makes in loading resistors.
If its not as big a deal as folk say then I'll stick a pot in it.

Thing is, I only have this pot as I replaced it with a stepped attenuator which I prefer. Don't know if it will make much difference in this situation though.
Ant
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#5 Re: Phono stage loading

Post by Ant »

Graeme, i have a 250k stereo stepped attenuator here, a 23 step one that is a series type if you want to try that?
Hey, wait, I got a new complaint
Forever in debt to your priceless advice

www.bte-designs.weebly.com
simon
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#6 Re: Phono stage loading

Post by simon »

Years ago I built a phono and used 2 no. 12 way switches to wire in 12 different load resistors per channel. And yes it did make a surprising difference. If you know the recommended range I'd be inclined to choose a range of values from a bit below to a bit above and try. Going way off will sound way off. When you've found what works buy a nice one :-)
izzy wizzy
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#7 Re: Phono stage loading

Post by izzy wizzy »

Graeme
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#8 Re: Phono stage loading

Post by Graeme »

Ant wrote: Wed Feb 24, 2021 7:32 pm Graeme, i have a 250k stereo stepped attenuator here, a 23 step one that is a series type if you want to try that?
Thanks for the offer, but I think I'll use my pot temporarily.
Graeme
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#9 Re: Phono stage loading

Post by Graeme »

simon wrote: Wed Feb 24, 2021 7:47 pm Years ago I built a phono and used 2 no. 12 way switches to wire in 12 different load resistors per channel. And yes it did make a surprising difference. If you know the recommended range I'd be inclined to choose a range of values from a bit below to a bit above and try. Going way off will sound way off. When you've found what works buy a nice one :-)
In that case, I'll replace with a fixed value when I've worked out what I like.
Graeme
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#10 Re: Phono stage loading

Post by Graeme »

izzy wizzy wrote: Wed Feb 24, 2021 8:27 pm Potentiometer loading
http://hifiheroin.blogspot.com/2020/05/ ... hives.html
Remote too!
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