Why not try a pair of Endler or EVS attenuators. These are stepped attenuators that include custom RCA jacks. One end is male and plugs into the RCA inputs on your amp. The other end is female and is where you will connect the output cables of your source. This should give you a good idea of how a resistor based passive device will sound and they are relatively inexpensive to try. I believe one or both brands may come with a trial period, so you can return them if you don't like them.
I personally prefer transformer volume controls as for the most part they avoid the impedance matching issues of resistor based passives. I've been using a custom built unit using S&B transformers for a while now with excellent results.
I personally prefer transformer volume controls as for the most part they avoid the impedance matching issues of resistor based passives. I've been using a custom built unit using S&B transformers for a while now with excellent results.