Tube vs Solid State Rectifier for VTA ST-120

audiomaniac wrote:Hi All,

I'm new to the forum and need some advice. I'm looking at getting one of Bob's amps, the ST-120, and I'm getting hung up on the decision of going with tube or SS rectification. At first, I was all set on tube but since my speakers right now are pretty inefficient at 84db (Ascend Acoustics Sierra 2), I read somewhere on the forum that SS might be preferable. I know that if I did go SS, I would want to get the TDR mod. But as I understand it, this isn't recommended for tube rectification in case I want to try the tube rectification at a later date.

My question is, how many of you prefer one over the other and why. Would I be giving up the classic tube amp sound going SS? Would I be sacrificing some tube reliability or have more maintenance going with tube rectification?

Thanks for the help!

cci1492 wrote:SS rectifiers provide more current, therefore more bottom end (slam). I cannot hear a difference anywhere else other than more punch and only when playing the music loud. There are many high end tube amplifier manufacturers that use diodes for rectification, so it's a perfectly legitimate way to go. I use a gz33 because I like how it looks and its able to get very close to SS levels of bottom end punch (also, money to burn on nonsense). I used the Weber for over a year and loved it. If the gz33s became completely unavailable for purchase, my amps will continue to sound great, would only miss the look of the tube.  

Bob Latino wrote:

audiomaniac wrote:Hi All,

I'm new to the forum and need some advice. I'm looking at getting one of Bob's amps, the ST-120, and I'm getting hung up on the decision of going with tube or SS rectification. At first, I was all set on tube but since my speakers right now are pretty inefficient at 84db (Ascend Acoustics Sierra 2), I read somewhere on the forum that SS might be preferable. I know that if I did go SS, I would want to get the TDR mod. But as I understand it, this isn't recommended for tube rectification in case I want to try the tube rectification at a later date.

My question is, how many of you prefer one over the other and why. Would I be giving up the classic tube amp sound going SS? Would I be sacrificing some tube reliability or have more maintenance going with tube rectification?

Thanks for the help!

A solid state rectifier is probably a better choice IF ..
1. Your speakers are relatively inefficient (88 dB or below)
2. Your listening room is large (over maybe 400 square feet)
3. You play music at high volume levels much of the time

The nice thing about the VTA ST-120 is that you can use either rectifier in the amp. The solid state rectifiers are plug compatible with a 5AR4 tube rectifier. Just pull out the tube rectifier and install the solid state rectifier and rebias the amp (Note > If you have the AutoBias board, you need not rebias the amp as the AutoBias board will make the necessary adjustments for you.) That said, there are many ST-120 users who use a tube rectifier with success. If your speakers are above 88 dB efficient and your room is of modest size, a tube rectifier will work fine with the ST-120. I have had a Tung-Sol 5AR4 tube rectifier in my own ST-120 for about 2 years now .. Works great ..

Bob

LeGrace wrote:What is issue with GZ37?

deepee99 wrote:

LeGrace wrote:What is issue with GZ37?

The GZ-37 can't handle the voltage swings. (Well, they can: I was using a pair of GZ-37s in one of Bob's amps and they survived all those successive loads over two years unscathed.) I'll leave the technical explaining to Bob L.

audiomaniac wrote:Thanks everyone for your replies. I called Bob and had a nice conversation with him about my options. With my current speakers, I would have to go with the SS rectifier, which isn't a bad thing. As for the TDR mod, I know that it can be easily disconnected, even with my bad eyes. Which by the way is why I will probably get it wired. So much fun on this board and I'm glad to be here.

deepee99 wrote:"GZ33s can handle a much larger first input cap (200uF vs 16uF) thus much higher peak current handling" from Tube Asylum . Unless things have changed, the rectifier greets a 40-uF cap on VTA amps. That's a reach for the 16uF GZ-37,but no issues with the GZ-33's 200uF capacity. At 40 uF it's loafing.

Bob Latino wrote:

deepee99 wrote:

LeGrace wrote:What is issue with GZ37?

The GZ-37 can't handle the voltage swings. (Well, they can: I was using a pair of GZ-37s in one of Bob's amps and they survived all those successive loads over two years unscathed.) I'll leave the technical explaining to Bob L.

I have a number of customers using BOTH the Mullard GZ33 and GZ37 rectifiers with no problems whatsoever. The "problem" with both of those is that they are not made anymore and pricing on these has risen over the past few years to about $100 USD a copy.

Bob

rjpjnk wrote:According to the Weber website the WZ68 is not for use in HiFi. They suggest the WS1 instead. From reading the description of the two it appears the difference is that the WZ68 has a dropping resistor as  mentioned above. The WS1 is nothing but diodes and for 2.50 more you can add a thermistor. If you go with the WS1 your B+ voltage may be a bit high and there won't be any sag, i.e., voltage variation as a function of current draw. Guitar players like sag as it's part of the compressive tube amp sound. Not good for HiFi though.

https://www.tedweber.com/wz68

"FOR USE IN GUITAR AMPS. Not designed for use with HIFI tube amps, tube radios, etc. - Try the WS1 instead. Equivalent of 2x GZ34/5AR4 (dual rectifier). Voltage drop: 17V at Maximum Current: 450ma."

https://www.tedweber.com/ws1

Dogstar wrote:

I bought two WZ68’s before the WS1 was available. I’m still using the first one. What are the problems with using the wz68?

Bob Latino wrote:

Dogstar wrote:

I bought two WZ68’s before the WS1 was available. I’m still using the first one. What are the problems with using the wz68?

There are no problems with using the Weber WZ68 in any of the VTA amps BUT > For some reason the Weber web site gives some warning about using the WZ68 in "audio" amps ? I honestly do not know why they have that little blurb about not using the WZ68 in audio amps ?

Bob