valve rectifier replace

[sergio]

how do you know when is time to replace the valve rectifier? (GZ34)
Thanks

[FYL]

how do you know when is time to replace the valve rectifier? (GZ34)

You may measure the valve and see if emission is still within specs.

A real GZ34 lasts for decades if not abused, modern versions last a few years at best.

[Ken Moon]

I knew it was time to replace when the JJ GZ34 started making loud spitting and hissing sounds, and got really bright

The bad thing is, I had 4 or 5 new tubes, so I tried them one at a time, and found thet the overall noise floor of the amp changed with different GZ34s - not good at all, since I spent forever getting this design as quiet as possible for a wreck-style amp.

I bought a couple of 1200V/8A TO-220 package common-cathode rectifiers, and I'm going to try one in my next build - they're supposedly designed to eliminate switching noise, and the need for snubbers.

[FYL]

I knew it was time to replace when the JJ GZ34 started making loud spitting and hissing sounds, and got really bright

Defective valve.

[JD0x0]

I just use the SS tube recto replacements. They're easier on tired PT and they dont change tone whatsoever (unless you want to by changing the values) Since no guitar signal passes through the rectifier it wont effect tone as long as the voltages stay the same. I actually prefer the tone of SS rectifiers anyway. More headroom and tighter bass is a must for channel switching amps. (IMO)

[67plexi]

Last weekend a 66 pro reverb was delivered to me for repair, the first thing I test is the gz-34 it was a bad mullard replaced the gz-34 with a NOS mullard
pluged in my guitar sounded great funny thing is it was one of my old amps
that I traded in to the music store for a 1967 marshall 50 lead amp way back in 1986. The mullard gz-34 lasted 1966-2010 not bad. 44 years.

[FYL]

I just use the SS tube recto replacements. They're easier on tired PT and they dont change tone whatsoever

Easier, yes. No 5V/2 to 3A for heaters, 10 to 15W spared and a cooler/tighter running PT.

Tone ? Hmmm. All standard valve rectos show a relatively high source Z and induce some compression/sag/... Mo' current thru it => mo' voltage dropped per Ohm's law.

[JD0x0]

I just use the SS tube recto replacements. They're easier on tired PT and they dont change tone whatsoever

Easier, yes. No 5V/2 to 3A for heaters, 10 to 15W spared and a cooler/tighter running PT.

Tone ? Hmmm. All standard valve rectos show a relatively high source Z and induce some compression/sag/... Mo' current thru it => mo' voltage dropped per Ohm's law.

Yes but most of the SS rectifier replacements simulate the voltage drop of a tube rectififer. (I guess because tubes are "less predictable" youre going to get a slightly different result every day)

Point is you can get similar results, with higher reliabily with the SS. Also by adjusting the voltage drop you get more versatility since you can basicly control sag at this point. You cant really control a tube's specs, unless you do alot of testing.

[FYL]

Also by adjusting the voltage drop you get more versatility since you can basicly control sag at this point.

A dedicated KOC-style sag control is IMO a much better technical option than playing with dropping resistors.

[passfan]

I just use the SS tube recto replacements. They're easier on tired PT and they dont change tone whatsoever (unless you want to by changing the values) Since no guitar signal passes through the rectifier it wont effect tone as long as the voltages stay the same. I actually prefer the tone of SS rectifiers anyway. More headroom and tighter bass is a must for channel switching amps. (IMO)

I've read this about 4 times and I can't get my head around it. Isn't it a contradiction? How can you prefer the tone of a SS rectifier if there's no tonal difference?

[JD0x0]

I just use the SS tube recto replacements. They're easier on tired PT and they dont change tone whatsoever (unless you want to by changing the values) Since no guitar signal passes through the rectifier it wont effect tone as long as the voltages stay the same. I actually prefer the tone of SS rectifiers anyway. More headroom and tighter bass is a must for channel switching amps. (IMO)

I've read this about 4 times and I can't get my head around it. Isn't it a contradiction? How can you prefer the tone of a SS rectifier if there's no tonal difference?

'

Read what was in the parenthases

What im talking about is stiffer power rectification. You can buy weber copper caps (for example) that imitate the voltage drop of a tube rectifier (frees up heater power as well) which will sound like a tube rectifier. Or you can switch components (or buy a different copper cap) to make it similar to a "true" SS rectifier less voltage drop and sag, more headroom and bass response like i mentioned earlier (which i prefer)

My point was the SS is tunable in a way the tube is not. And since no guitar signal is passing through it the tone wont change (provided the voltage drop is simulated to mimic your tube of choice) Which means higher reliabilty, more versatility, More consistant tone, and no need to replace the rectifier tube anymore.

If you dont want to go through the trouble of tuning it weber has the "copper caps" as ive mentioned.