DaveyW
Well-Known Member
Hi All,
I’ve responded to a few posts recently regarding the benefits of varying resistive loading in order to tune cartridge character.
There’s been quite a few responses stating that this feature is not available on the respective phono-stages and there appears to be varied awareness regarding how to apply a parallel resistance in order to achieve this.
Application of an incremental parallel resistance is a very simple and low cost method of delivering variable resistive loading.
I did a quick trawl using the search facility to see if I could find a thread to direct any enquiries to, but struggled to find one.
Apologies if this is old ground, but given the replies I’ve been getting, I thought it worth opening a thread just to run through the process.
First up what’s the effect?
Although most modern MM/MI/HOMC’s are supposedly designed around what’s become the standard 47k/50k ohm MM stage resistive load, this may not be the optimum setting for individuals personal taste or from a system matching perspective.
The application of an incremental parallel resistance will reduce the overall MM stage resistive loading.
This tends to dampen higher frequency response, but it’s not like a simple tone control that might affect a small range, it’s more of a total tonal change through lower mids all the way up. It can also tighten up a slightly woolly or loose lower end.
Some carts are affected more than others and only need a subtle reduction to make a significant effect. HOMC’s tend to require bigger swings in resistance before the audible differences can be heard.
Personally, I’ve found very few MM/MI/HOMC’s that deliver their optimum performance bang on 47k and tend to tweak most of them.
For example here are a few preferred loadings (to my ears and on my system) of some popular cartridges;
Audio Technica AT 440mla (MM) – 32k
Denon DL 160 (HOMC) – 1k
Dynavector 20XH (HOMC) – 1k
Grado Reference Sonata (MI) – 38k
Before we get into how, it needs to be stated that increasing the resistive load (to liven up the general character) requires phono stage surgery.
The MM stage load resistor has to be replaced with a higher value item.
I have done it, but IMHO it really is only for those who are totally comfortable with electronics and use of a soldering iron.
I am not intending to go into that here.
OK so how’s it done?
Well as I say it’s very simple, you need to apply a parallel load to the MM input stage to reduce the overall resistance.
Here’s the maths;
1/Rtotal=1/Rphono+1/Rplug
Where;
Rtotal is the modified delivered load
Rphono is the quoted resistive load of the phono stage
Rplug is the incremental plug resistance wired in parallel
So if you had a 50k ohm phono stage and applied a 200k ohm plug you’d get a total load of 40k ohms.
So how do we do it?
First thing you need is a pair of good quality RCA Y splitters (1 male to 2 female) such as pictured here;
The male plugs into one of the phonostage RCA connectors and the equivalent channel TT male connector goes into one of the females on the splitter.
You then need to add your parallel resistance.
The simple way is to buy some resistors and male RCA plugs and solder up like this;
Ultimately you can make up a little kit that looks like this;
Once the Y Splitters are in place it’s then a very simple process to replace the resistor plugs to vary the loading and understand it’s effect.
Don’t forget – no plug at all means you’re right back where you started with the standard Phono Stage resistive load when doing comparisons.
PLEASE ENUSRE THAT THE PHONO STAGE AND MAIN AMP ARE SWITCHED OFF WHEN SWAPPING THE RESISTORS
You can get some pretty harsh spikes if you leave the amplification on, risking circuit and speaker damage.
This is probably all you’ll need.
All of these items are readily available through electrical retailers and on the bay.
I personally have taken it one step further and built up this infinitely variable loading box;
It uses a pair of calibrated potentiometers in two ranges.
I use this to adjust resistance “on the fly” and it helps me home in on the optimal loading fairly quickly.
But this has its dangers. I did induce quite a bit of hum with this unit and had to spend a fair amount of time getting the earthing sorted.
There you go.
I hope this is of some help.
I certainly have not looked back since delving into this.
Cheers
Dave
I’ve responded to a few posts recently regarding the benefits of varying resistive loading in order to tune cartridge character.
There’s been quite a few responses stating that this feature is not available on the respective phono-stages and there appears to be varied awareness regarding how to apply a parallel resistance in order to achieve this.
Application of an incremental parallel resistance is a very simple and low cost method of delivering variable resistive loading.
I did a quick trawl using the search facility to see if I could find a thread to direct any enquiries to, but struggled to find one.
Apologies if this is old ground, but given the replies I’ve been getting, I thought it worth opening a thread just to run through the process.
First up what’s the effect?
Although most modern MM/MI/HOMC’s are supposedly designed around what’s become the standard 47k/50k ohm MM stage resistive load, this may not be the optimum setting for individuals personal taste or from a system matching perspective.
The application of an incremental parallel resistance will reduce the overall MM stage resistive loading.
This tends to dampen higher frequency response, but it’s not like a simple tone control that might affect a small range, it’s more of a total tonal change through lower mids all the way up. It can also tighten up a slightly woolly or loose lower end.
Some carts are affected more than others and only need a subtle reduction to make a significant effect. HOMC’s tend to require bigger swings in resistance before the audible differences can be heard.
Personally, I’ve found very few MM/MI/HOMC’s that deliver their optimum performance bang on 47k and tend to tweak most of them.
For example here are a few preferred loadings (to my ears and on my system) of some popular cartridges;
Audio Technica AT 440mla (MM) – 32k
Denon DL 160 (HOMC) – 1k
Dynavector 20XH (HOMC) – 1k
Grado Reference Sonata (MI) – 38k
Before we get into how, it needs to be stated that increasing the resistive load (to liven up the general character) requires phono stage surgery.
The MM stage load resistor has to be replaced with a higher value item.
I have done it, but IMHO it really is only for those who are totally comfortable with electronics and use of a soldering iron.
I am not intending to go into that here.
OK so how’s it done?
Well as I say it’s very simple, you need to apply a parallel load to the MM input stage to reduce the overall resistance.
Here’s the maths;
1/Rtotal=1/Rphono+1/Rplug
Where;
Rtotal is the modified delivered load
Rphono is the quoted resistive load of the phono stage
Rplug is the incremental plug resistance wired in parallel
So if you had a 50k ohm phono stage and applied a 200k ohm plug you’d get a total load of 40k ohms.
So how do we do it?
First thing you need is a pair of good quality RCA Y splitters (1 male to 2 female) such as pictured here;
The male plugs into one of the phonostage RCA connectors and the equivalent channel TT male connector goes into one of the females on the splitter.
You then need to add your parallel resistance.
The simple way is to buy some resistors and male RCA plugs and solder up like this;
Ultimately you can make up a little kit that looks like this;
Once the Y Splitters are in place it’s then a very simple process to replace the resistor plugs to vary the loading and understand it’s effect.
Don’t forget – no plug at all means you’re right back where you started with the standard Phono Stage resistive load when doing comparisons.
PLEASE ENUSRE THAT THE PHONO STAGE AND MAIN AMP ARE SWITCHED OFF WHEN SWAPPING THE RESISTORS
You can get some pretty harsh spikes if you leave the amplification on, risking circuit and speaker damage.
This is probably all you’ll need.
All of these items are readily available through electrical retailers and on the bay.
I personally have taken it one step further and built up this infinitely variable loading box;
It uses a pair of calibrated potentiometers in two ranges.
I use this to adjust resistance “on the fly” and it helps me home in on the optimal loading fairly quickly.
But this has its dangers. I did induce quite a bit of hum with this unit and had to spend a fair amount of time getting the earthing sorted.
There you go.
I hope this is of some help.
I certainly have not looked back since delving into this.
Cheers
Dave
