Rothwell In-Line Attenuators?

I've used them with good results to lower gain.

I've used them, and they work as advertised, but I think they are no better than the less expensive FMOD attenuators, which come in a variety of attenuation levels (3,6,9,12 dB, I believe). You can get them from www.partsexpress.com.
Rich

Dare I put in a dissenting report? I tried a pair, and in my usage noted, as advertised, a reduction of gain. But I also noted a slight veiling of the sound, particualrly in the upper frequencies-- I was conscious of their presence in the system, and took them out. YMMV.

I'll have to agree with Swklein. Anything added to the signal path will degrade the sound

I agree that anything will affect the sound, but I can't go along with it will always be degraded. In this case we are talking about two high quality resistors, a few solder joints, and an extra connection. I can see where using these could change the load on the preamp and degrade the sound, but if the values of the resistors are properly chosen you could maintain the same load and attenuate the level. In that case, whatever slight change in the sound occured could easily be outweighed by the benefit of operating the preamp further away from the lower limit of the volume control.

According to what I see on Rothwell's website these come in only one configuration that they claim has been chosen to "work well" with just about any combination of input/output impedances you are likely to encounter. One has to wonder if Swklein's equipment wasn't a good match for them. I find it hard to believe that the values they settled on are the ideal for all applications.

If Swklein tried them on the AR amp he currently has listed with an input impedance of 100K ohms using an AR preamp that one would have to assume is optimized to work into that load, I can see where an attenuator with a different input impedance could adversely affect the sound.

That is why I would make my own, or better yet pad the input to the amp to reduce the gain and get rid of the extra connection. That way you could experiment with different values until you found a good match for the equipment. On the other hand, they are pretty cheap in the grand scheme of things so you don't have much to loose by trying them.