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200 Ohms loading = lower volume

bloodlemons

bloodlemons

Member
I am using a DB Systems DBP-6MC Resistive Loading Kit for the first time today with my Audio Technica AT-ART9 cart using an AT SUT with 200 ohms load plugs from the kit into Parks Audio Budgie set to 47K ohms like a typical MM input.

The AT-ART9 has a recommended load impedance of "min. 100 ohms."

I tried 100 ohms and 200 ohms and 200 sounds quite a bit better. In fact, at 200 ohms it sounds pretty GREAT. [Currently spinning "The Blue Mask," by Lou Reed; soundstage, clarity and dynamics are really impressive at this load.]

The problem I'm having is that the volume is greatly reduced with the 200 ohms plugs in the chain. I have to dime the volume to fill the room. This, of course, raises the noise floor. My integrated is a mid-60s HK A300 tube amp, so there's definitely some low-level white noise at this volume level. It's not that bad, but I'd prefer to eliminate it and have more useable volume.

Has anyone else experienced this type of situation? Am I doing something wrong with the loading kit?
 
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Nevermind. I think I figured it out. I was running the load between the SUT and the preamp input; now I am running the load between the TT output and the SUT input. Volume is back. Running the load after the SUT was, of course, working against what a SUT does, which is to increase the gain. Makes sense, but I needed to think about it for a minute. The difference in effect of loading is more subtle now, but things are still sounding very nice at 200 ohms.
 
bloodlemons said:
Nevermind. I think I figured it out. I was running the load between the SUT and the preamp input...
Click to expand...
As I was reading your original post I was thinking that's most likely what you had done.
You don't say what AT SUT you have but I measured one of their popular ones and it had a turns ratio of 1:14 (if I remember correctly). That would mean the cartridge sees a load of 240 ohms even without any additional loading. I don't know the exact details of what you have done but if you have put a 200 ohm resistor in parallel with the input to the SUT you haven't created a 200 ohm load, you have created a 109 ohm load (240 ohms in parallel with 200 ohms).
Similarly, if you put a 100 ohm resistor in parallel with the input to the SUT you will create a 70 ohm load.

The ART9 has a coil resistance of 12 ohms with negligible inductance, so a load impedance of around 120 ohms seems sensible (10x the source impedance). That's just a rough guide though. The tonal balance of a LOMC cartridge shouldn't be particularly load-sensitive and I wouldn't be surprised if you heard no difference between a 100 ohm load and a 200 ohm load. Get down to about 3x the source impedance, so 36 ohms in this case, and you will start to notice a difference. There will be a drop in volume and maybe a change in tonal balance, though possibly the drop in volume will be perceived as a change in tonal balance when it's really just a drop in volume.
 
rothwellaudio said:
As I was reading your original post I was thinking that's most likely what you had done.
You don't say what AT SUT you have but I measured one of their popular ones and it had a turns ratio of 1:14 (if I remember correctly). That would mean the cartridge sees a load of 240 ohms even without any additional loading. I don't know the exact details of what you have done but if you have put a 200 ohm resistor in parallel with the input to the SUT you haven't created a 200 ohm load, you have created a 109 ohm load (240 ohms in parallel with 200 ohms).
Similarly, if you put a 100 ohm resistor in parallel with the input to the SUT you will create a 70 ohm load.

The ART9 has a coil resistance of 12 ohms with negligible inductance, so a load impedance of around 120 ohms seems sensible (10x the source impedance). That's just a rough guide though. The tonal balance of a LOMC cartridge shouldn't be particularly load-sensitive and I wouldn't be surprised if you heard no difference between a 100 ohm load and a 200 ohm load. Get down to about 3x the source impedance, so 36 ohms in this case, and you will start to notice a difference. There will be a drop in volume and maybe a change in tonal balance, though possibly the drop in volume will be perceived as a change in tonal balance when it's really just a drop in volume.
Click to expand...

Thank you! It is an AT-630, which I believe is 1:15. I was actually reading some of your forum posts and eventually found your website yesterday when I was trying to diagnose my problem. Small world!
 
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