Gain and Rothwell attenuators
Why not contact Cary and see if there is some way that they can lower the gain of your preamp ? This is a VERY common problem when folks try to run tubed preamps with SS power amps. Having Cary take care of the problem directly at the gain stage should preserve the sonics of the system a lot better than introducing a "band aid" into the system and give you a more usable range of the volume control. Sean > |
I'm not sure putting the attenuator between the CDP and pre will make much of a difference in terms of overall gain for an active pre. Also, when placed between the pre and power amp, you need to plug the male end of the attenuator to the power amp in order to get maximum voltage (i.e. gain) drop. If plugged the other way around, you'll see very little drop. As for sound quality of the Rothwell, I'm not surprised that you found the sound altered. I used a 12db attenuator from PartsExpress and found that it reduced the noise level which is a good thing. But, it also took a lot of air out and the overall sound approaches that of SS type. |
I have the same problem. I eventually switched to a Njoe Tjoeb cdp. Add a couple solder joints and you can change the output voltage down from ~2.5 volts to ~1.25 or~0.7 volts. Worked well. You could also find a cdp with an analog volume control like the new Cary 308T and just turn it down a bit. I experimented with a couple passive attenuators and I just didn't like their sound. Good luck. Let us know what Cary says about modifying the gain on your preamp. Loren. |
I've had the Rothwell's in for about 2 months and I listen to alot of music so I'm guessing they are burned in. They aren't horrible in their present position between cdp and pre and even do some good, sonically that is, but I do find they slightly "shroud the music in a light mist". Between the pre and pwr amps is another story. yuk. Still waiting to hear from Cary. |
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. |
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. |
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 |
their shunt volume attenuator involves less signal degradation than typical series attenuators due to reduced series resistance in the signal path. It is possibly a simple pi-ladder design with two low-level elements in series & the adjustable element in parallel to signal ground. I assume that this design also reduces stage-gain or they wouldn't have recommended it? Or if not then at least linearity is improved such that the aforementioned issues are resolved. |
