is getting a tube pre a valid option with ss amp?


hello all, advice time again. I have decided to go ht in basement and as such, can go dedicated 2 channel in living room.. I am thinking of getting a tube pre as a 1st step, although my amp is a ss theta dread 2..which i am going to keep in my living room....is a tube pre a good move forward over ss pre?or..will there not be much sonic difference..i have dali hellicon speakers which it seems warm up very nice to tube sound..thanx, Dan
dan001

Showing 1 response by raquel

You need to be careful to ensure that the output impedance of the preamp is at least ten times less than the input impedance of the amp. The problem is that virtually all tube preamps except those that use output transformers have high-ish output impedances in the bass, which can cause bass roll off (i.e., weak bass) with many solid-state amps.

The other problem is that tube preamps except those that use output coupling transformers have difficulty driving long (> 2 meters) interconnects, the result again being rolled off bass.

These problems are present far less often when a tube preamp is paired with a tube amp, as tube amps tend to have much higher input impedances: many have an input impedance of 100,000 Ohms. In contrast, solid-state studio amps often have an input impedance as low as 600 ohms, and audiophile solid-state amps often come in around 20,000 Ohms. As for preamps, top-shelf solid-state preamps can have output impedances as low as 50 Ohms across the frequency spectrum (darTZeel, classic Rowland), while even top-shelf tube preamps can have output impedances as high as 4,500 Ohms in the bass (BAT VK-51SE).

The rub is that few solid-state preamps have the musicality and layer space like a tube preamp, so, unless you really know what you're doing, it's easy to make a mistake whether you go with a solid-state or tube preamp. Rowland's Synergy IIi solid-state preamp is very good and can be had for less than $3k used. VAC's Renaissance preamps use output transformers and the "cheap" one can be had used for $3k-$4k. I strongly prefer top-shelf solid-state preamps, as no tube pre I am aware of can compete when it comes to noise floor, which is crucial at the preamplification stage.