Tube vs. Solid State Rectifier

If you end up preferring tube rectification over SS, the next question might be: then how much of a difference do different rectifier tubes make?

I have a Cary SLA-70 I bought here on Audiogon a couple of weeks ago that uses 5AR4 rectifiers. I have been listening to it almost non-stop since I got it. It came with some Chinese 5AR4's, and I did a little poking around on the net looking for opinions on how much of a difference rectifier tubes could make in the overall sound of an amp. From what I gleaned, I thought it might be worth a tube-roll on the 5AR4's to hear for myself, so I now have a pair of Amperex-branded Mullard 5AR4's on the way, and will report back to you on what kind of differences I hear - at least with these particular tubes in this particular amp.

Tube rectification is nice if you can do it! Newer tube amps have bigger power supplies and so can easily damage a tube rectifier during warm-up. So a tube rectifier usually means that the capacitance in the power supply is limited to a small value that might have been considered adequate about 40 years ago, but likely not in a lot of modern designs, especially higher-powered amps.

Tube rectifiers are nice due to their inherent low noise while converting AC to DC. Silicon rectifiers have a commutation (switching) noise that can contribute to the background noise of the amplifier. Commutation noise can be substantially reduced by small networks bypassing the rectifier's junctions, but usually this is not 100% removal. But generally semiconductor rectifiers can survive the large current inrush that is common in a lot of high end amplifiers. That extra capacitance of bigger supplies translates almost directly to better sound, so you can see that there **can** be tradeoffs.

In an SET I think tube rectifiers would be nice- this is an application where they can work quite well.

In amps that have too much capacitance for a tube rectifier to survive, you can often get a lot of the 'tube rectifier sound' by using superior semiconductors. HEXFRED rectifiers are a good example- the ultra fast/ultra soft recovery characteristics of HEXFRED rectifiers approaches that of the tube rectifiers, although they do not have the variable voltage sag with current that is also part of that sound. You really don't want the voltage to sag as you draw more current from the power supply!

In a class A amplifier, the voltage sag issue is not a concern as the draw on the device is constant. In a class AB amp a good semiconductor can actually sound better!

My general preference from DIYing a few preamplifier and amplifier combinations has been to use a tube rectifier in the pre and ss in the amp. This has struck a nice balance between the warmth of tubes and the perceived speed and "snap" of ss.

Of course, the best alternative would be to have the opportunity for you to compare both in your system as there may be other attributes to each amplifier that would better suit your system.

I wouldn't buy amp or preamp with solid state rectification.

Be careful trying out of those SS adapters. It will give a higher B+ voltage on the tubes,transformers,and caps/etc. These parts can be damaged.Those adapters don't have any voltage correction for different rectifier tube types.It can be risky.