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Gain and Rothwell attenuators

I have a Rega planet 2000, Cary slp-50a, and linn LK-85 amp. When I first got the cary I couldn't turn the volume up past the 8 o'clock position! That was about as loud as I could stand. I put in some Rothwell attenuators (-10db) and now I'm at about 10 o'clock with the same result. Problem is is that the Rothwell attenuators dramatically alter the sound. Right now they are between the cd player and pre-amp. I tried them between the pre and power amp and the music sounded strangled. When I take them off completely things open up but seem uneven and I start getting different L/R signal strength through the speakers at lower volumes, with some cds becoming unplayable because of this. I haven't seen much written about attenuation or any other way to solve this problem. Are there other, more neutral ways to achieve this or has anyone come across another posting on this issue? Thanks and happy holidays.
stuartbranson
wywhcan
39 posts
 
Stuartbranson,

I retract my earlier assumption that the attenuator won't do much when placed between the CDP and pre. I was under the impression that there might be some AGC circuit preceding the PRE input stage (I suppose it is not necessary with 2V output of a CDP). So, I took out my attenuators (12db or .25Vin) and placed them after the CDP. Yes, there is a big drop in volume. And it does sound better than putting them after the pre. But, what happened to the Bass!! And all the low level details!! Looks like with a 0.5V CDP output now, a lot of low amplitude info is getting buried.

In any case, I prefer not to use the attenuators. I'm stuck between 7 & 8 o'clock just like you. I'm just glad I have dual volume control.
stuartbranson OP
183 posts
 
Yeah, it's kinda six of one, 1/2 dozen of the other. Some aspects sound better with the attenuators and without the sound is a little strained but bass is better. What to do. Still no word from Cary.
twl
3,251 posts
 
You've got impedance mismatch problems, when you are placing that resistive attennuator in the line. This is typical with passive preamps, and it is always a struggle to get them to be anywhere near acceptable. The way out of this, if you want to stay with a passive pre, is to use a transformer-based passive, that provides better impedance matching characteristics, because of the nature of it's design. Since a transformer has separate windings on input and output, the impedance can be better matched. All of these things that you are complaining about are typical of resistive-based passive preamps. Check out the Bent Audio website for further information on this subject. They sound cleaner, and work better. Much more beneficial all around. They can be gotten even as a kit, if you are working within a budget.
bob_bundus
1,834 posts
 
Parts quailty of the resistor attenuator elements may be compromised. If you know the required values then you might experience better sonic performance by replacing them with Holco, Caddock, or Vishay's avalable from Michael Percy Audio. Use a quality silver bearing solder such as WBT.

http://www.percyaudio.com
stuartbranson OP
183 posts
 
Cary suggests I send it to them for a "shunt volume modification." Anyone know what this is?

Bob_bundus. Sounds like fun but that's beyond my ability or daring.
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