GZ37 Rectifier

Just thought I would pass on this experience. The other day when I powered up my ST120 their were 'fireworks' happening inside the Mullard GZ37 followed by a blown main fuse in the amp. The GZ37 was installed about 9 months ago. Bought it on that big auction site as 'used but tests strong'. We all know that could mean anything...

Anyway, not knowing what caused the rectifier to fail, I didn't want to risk blowing my backup GZ37 or GZ33 tubes so I plugged in the original Weber WZ68, replaced the fuse, crossed my fingers and powered up the amp. All is fine. Back to normal.

Here's the interesting part: I swear the amp now has more balls in the low end! The bass sounds deeper and tighter. Furthermore, I have not noticed any change or sacrifice in mid or high frequencies. I'm going to run the amp with the Weber for a few weeks and then try another GZ37 to see if I can hear a difference and confirm what I think i heard.

I don't want to start a solid state vs tube rectification argument, just figured many of you would be interested in the experience.

Wayne

Oddly, I just had a revealing experience with a GZ-37 Mullard which is similar. In my case, I switched from a Weber WS-1 to the GZ-37 and it remained cold and dead even after all the cleaning and retensioning I could perform. So I went back to the original Latino-supplied Ruby GZ-34 and re-biased. Wouldn't you know it - I actually find it gives me the best overall sound of any rectifier. The Webers were almost too ballsy (and the bias pot positions had to be lowered). The Mullard gave a lovely smooth sound, but the bias pot positions were quite a bit higher. With the good ol' GZ-34, the sound is right in the middle, as are the bias pot positions.
My guess is that differing B+ voltages from different rectifiers give differing results. I'm gonna stick with the GZ-34 which the VTA ST-120 was designed for. Probably order a Genalex GL or two, as these seem to be the most solid of the new-production types.
The more things change, the more they stay the same.

{This thread is apparently a "Massachusetts-only" thread! }

Let's make this a thread from states that begin with M thread ...

Still like my GZ37 ... maybe a bit more bass with the Weber WZ68, but overall cleaner power all the way up the scale with the big bottle. Possibly a result of running the KT120's, as those also bump the bottom some over most KT88's ... but ... I can just bump up the bass synth a bit with the TAD KT88STR's and get the same results. I can also roll tubes in the TubeMagic DAC, using that as a pre-buffer to tailor what the Latino sees ...

Interestingly enough, my setup is a bit different with the CL90 thermistor. Those never open up completely and tend to choke the B+ down a bit more than without. With the GZ37 and my lower efficiency speakers (90db), I still prefer the sound of tube rectifier.

Proof positive, it's all in the ear of the beholder. Ancillary equipment in the system can also make a BIG difference in what you hear.

*Oh ... and that big bottle just looks so much better than having that copper cap squatting on the chassis plate ...

sKiZo wrote:Let's make this a thread from states that begin with M thread ...

Proof positive, it's all in the ear of the beholder. Ancillary equipment in the system can also make a BIG difference in what you hear.

*Oh ... and that big bottle just looks so much better than having that copper cap squatting on the chassis plate ...

Funny how there doesn't seem to be any consistency or pattern with regards to rectifier behavior Some added info:

The first thing I checked after the GZ37 died was the voltage coming out of my variac. It was 117vac as usual.
Bias was set at 0.56vdc for the KT120/GZ37 combo.
Bias was re-set at 0.56vdc for the KT120/WZ68 combo.
Followed Bob's instructions to start with the adjustment pots turned all the way down before powering up the amp.
Speaker efficiency is 91db.

Kentley, keep us posted on how the GZ34 works out for you.
sKiZo, I agree that the 'big bottle just looks so much better...'
BoB, Thanks for the technical details. I don't play too loud nowadays. Just enough to fill the room. About the same level you had your amp playing when I came over for an audition. Maybe a smidgen more

I usually lurk in the shadows reading and learning from the others in the know on this forum.  Regarding the GZ34 saga, when I purchased my VTA ST-120 7&1/2 years ago I went through several in the first year and a half, however over the last 4 years, the stamina of the Russian and Chinese tubes seem to have improved somewhat.  I have had to replace the GZ34 only twice for an average of one every two years.  Granted that still does not equal the longevity of originals from yesteryear, but it is an improvement.  My VTA ST120 is one of the first off Bob's assembly line, constructed with all first generation design parts with no upgrades, and love it.  I used a Weber WZ68 for a short while but went back to GZ34 and have not looked back.  I don't run the amp hard because I listen almost exclusively to classical music at what would be considered concert hall level.  Once in a while I will dig out DSOTM, FWMack, etc. just to knock the dust off the speakers and give them a little workout, then back to classical again and thus I will stay with GZ34's because some old dogs just don't like new tricks.

ArlanB

ArlanB wrote:I usually lurk in the shadows reading and learning from the others in the know on this forum.  Regarding the GZ34 saga, when I purchased my VTA ST-120 7&1/2 years ago I went through several in the first year and a half, however over the last 4 years, the stamina of the Russian and Chinese tubes seem to have improved somewhat.  I have had to replace the GZ34 only twice for an average of one every two years.  Granted that still does not equal the longevity of originals from yesteryear, but it is an improvement.  My VTA ST120 is one of the first off Bob's assembly line, constructed with all first generation design parts with no upgrades, and love it.  I used a Weber WZ68 for a short while but went back to GZ34 and have not looked back.  I don't run the amp hard because I listen almost exclusively to classical music at what would be considered concert hall level.  Once in a while I will dig out DSOTM, FWMack, etc. just to knock the dust off the speakers and give them a little workout, then back to classical again and thus I will stay with GZ34's because some old dogs just don't like new tricks.

ArlanB

Exactly my tune. Cheers.