I have made a mistake, I feed the Recitifing tube 6.3V instead of 5V for the glow. Of course did the tube end in an instant and painles death. It was more painful for me...
I rumbled around in my box with good tho have stuff and found an salvaged used 5Y3 and stuffed it to my SSE.
To my joy did the 5Y3 work. However are the voltage drop according to datasheets 60V and the GZ34 has only 10V.
What does a dropp of 50V or 20% of the B+ actually do?
I have not changed anything else, the anod resistor are the same. With the GZ34 was the cathod curret 56mA and dissipating power was about 20W. With lower B+ voltage do I assume that cathod current and dissapating power also will drop?
The 5Y3 has according to datasheet half the current capacity (125mA), as I'm in terory close to 125mA with 2x56mA do I assume it will not live for ever and eventually do I in the near future need to buy a GZ34 or do to solid state.
I rumbled around in my box with good tho have stuff and found an salvaged used 5Y3 and stuffed it to my SSE.
To my joy did the 5Y3 work. However are the voltage drop according to datasheets 60V and the GZ34 has only 10V.
What does a dropp of 50V or 20% of the B+ actually do?
I have not changed anything else, the anod resistor are the same. With the GZ34 was the cathod curret 56mA and dissipating power was about 20W. With lower B+ voltage do I assume that cathod current and dissapating power also will drop?
The 5Y3 has according to datasheet half the current capacity (125mA), as I'm in terory close to 125mA with 2x56mA do I assume it will not live for ever and eventually do I in the near future need to buy a GZ34 or do to solid state.
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It would change the operating point of the output tube. You'd get lower output power and probably also higher distortion. It would also reduce the headroom across the CCS on the input tube, but I think that's less consequential.
You could replace the rectifier with a pair of 1N4007 and get the full B+ voltage back. Or get another 5AR4/GZ34. There's no shortage of those as far as I know.
I don't see any harm in running the amp at a lower B+, though.
Tom
You could replace the rectifier with a pair of 1N4007 and get the full B+ voltage back. Or get another 5AR4/GZ34. There's no shortage of those as far as I know.
I don't see any harm in running the amp at a lower B+, though.
Tom
NOS or even old used GZ34 can be ridiculously expensive these days and the modern russian ones are known for having problems with arcovers. A couple of high voltage silicone diodes in series with the anodes can help against the arcing.
If you want to get close to the B+ provided by a GZ34's, you can use diodes like @tomchr already said, plus a couple of resistors wired in series with the diodes (or a single resistor after the pair of diodes) to simulate the voltage drop of the tube.
That's what I'm doing with a guitar amp that uses a GZ34. That particular amp already uses a pair of diodes in series with the GZ34 anodes, like @Fuling described. So I can simply wire up a pair of resistors on an octal plug, salvaged from a bad tube, and then can switch between solid state (with emulated sag) and an actual GZ34.
That's what I'm doing with a guitar amp that uses a GZ34. That particular amp already uses a pair of diodes in series with the GZ34 anodes, like @Fuling described. So I can simply wire up a pair of resistors on an octal plug, salvaged from a bad tube, and then can switch between solid state (with emulated sag) and an actual GZ34.
JJ GZ34 can be sourced for about €25, however do I also need to replace 4x E88CC in the Preamp and also change input selector switch. I have to wait untill next month for futher inestments.
Right now would the SS recifier option be the easiest temporary solution.
Right now would the SS recifier option be the easiest temporary solution.
Are sag a relevant topic for class A SE-Amps?
The current drain through the rectifier are constant, regardless of the output.
But why use NOS or old used when you can buy new? $22 from AES: https://www.tubesandmore.com/search/node/5ar4/
Tom
Sag is of course not relevant with your setup (or with my own SE amp, that uses a 5Y3 and which will be replaced with a pair of diodes and a resistor or two someday). The resistors will lower B+ to what it would originally be, and that will stay put due to the constant current draw.
As I mentioned, the ones manufactured today have bit of a reputation. Can't say if it's true for every brand but it's a known problem. I've personally had bad experiences with Sovtek GZ34s and changed to TV damper diodes instead, never had a single incident since then.
I had a Sovtek 5AR4 that died after a few years of use. They're cheap enough. Just pop in a new one. Or buy one from JJ. I've only had good experiences with their tubes.
Tom
Tom
JJs are probably better. My Sovteks didn't last long even when used far below their max ratings.
I seem to remember it had something to to with uneven oxide coatings on the cathodes, creating hot spots during startup.
I seem to remember it had something to to with uneven oxide coatings on the cathodes, creating hot spots during startup.
Yeah, I'm guessing here too, but I would imagine wrt Sovtek there are good years and not so good years, in terms of overall quality. All I know is I'm keeping one slightly used Mullard handy while I mess with diodes and resistors.
Pulling this from another thread on another board, but 50-60 ohms per anode is a ballpark resistor value. That's what I'll use in my application. I measured voltage drop with a GZ34 in place; it was a little less than 10vdc, but that will be current dependent.
That's imho the safest and cheapest route. ECC88s are not cheap nowadays!
Pulling this from another thread on another board, but 50-60 ohms per anode is a ballpark resistor value. That's what I'll use in my application. I measured voltage drop with a GZ34 in place; it was a little less than 10vdc, but that will be current dependent.
That's imho the safest and cheapest route. ECC88s are not cheap nowadays!
The original post is remarkably free of relevant facts.
The 5Y3 will have a larger voltage drop, so to maintain the same cathode current, you will likely need to slightly decrease the value of the cathode resistors. Generally speaking, more current slightly reduces distortion. Whether you can hear any difference is a different issue.
What was your original B+ voltage and cathode voltage? What type of power tubes are you using? The 12AT7 will draw about 10 ma / section, so that leaves 40-45 ma per power tube.
Old U. S. made rectifiers are tough as nails, still, you should probably look at the chart and try not to bust it too much. The 5Y3 is specified for only a 20 uF capacitor with capacitor input filters, however, I routinely use them with 47 uF capacitors and have gone as high as 100 uF and never had a problem, so whatever is in your SSE right now will probably be fine.
Win W5JAG
The 5Y3 will have a larger voltage drop, so to maintain the same cathode current, you will likely need to slightly decrease the value of the cathode resistors. Generally speaking, more current slightly reduces distortion. Whether you can hear any difference is a different issue.
What was your original B+ voltage and cathode voltage? What type of power tubes are you using? The 12AT7 will draw about 10 ma / section, so that leaves 40-45 ma per power tube.
Old U. S. made rectifiers are tough as nails, still, you should probably look at the chart and try not to bust it too much. The 5Y3 is specified for only a 20 uF capacitor with capacitor input filters, however, I routinely use them with 47 uF capacitors and have gone as high as 100 uF and never had a problem, so whatever is in your SSE right now will probably be fine.
Win W5JAG
So higher B+ means that I can pusch higher without clipping.
I have an offer for a Svetlana 5c3s. According to datasheets would this be a good replacement. Stronger specs than GZ34. I can not see any specs about voltage dropp, it should be lower as I utilise 50% of max current.
Any opinions about 5c3s before I order?
I have an offer for a Svetlana 5c3s. According to datasheets would this be a good replacement. Stronger specs than GZ34. I can not see any specs about voltage dropp, it should be lower as I utilise 50% of max current.
Any opinions about 5c3s before I order?
If it is similar to an American 5U4, it is good for about 250 ma, and the voltage drop is 50 ish. The 5U4 has a 3 amp heater - that is about an amp more than a 5AR4. Make sure your transformer can handle that.
The Sovtek 5AR4 tube is okay. All of the other Russian rectifier tubes I've used were junk. I've killed every one I've had - without trying.
Win W5JAG
The Sovtek 5AR4 tube is okay. All of the other Russian rectifier tubes I've used were junk. I've killed every one I've had - without trying.
Win W5JAG
According to google should the first capacitor be 4uF, this are a small cap compared to C1=47 uF on my.
I do have the inrush current limiter CL60 on the PCB and one CL90 on the mains on the transformer.
Will I kill the 5c3s with a C1 of 47uF?
I do have the inrush current limiter CL60 on the PCB and one CL90 on the mains on the transformer.
Will I kill the 5c3s with a C1 of 47uF?
I think 4uF is quite a bit different to 47uF, so likely to be detrimental for the rectifier.
Lots of sites say 'X is equivalent to Y', but GZ34 is hard to substitute.
What is the equipment you are talking about? If it is old, does it have alternate taps for different mains voltages? What prevents solid state as an option?
Lots of sites say 'X is equivalent to Y', but GZ34 is hard to substitute.
What is the equipment you are talking about? If it is old, does it have alternate taps for different mains voltages? What prevents solid state as an option?
I have an tubelab SSE, main trafo are Hammond 374Bx. I have considered to rewire it with 230V or 220V on the primary side to compensate the voltage dropp. However will this push up the 5V glow with +0.22V or +0.44V.
Solid state are an Option, last Option when everything else fails.
Solid state are an Option, last Option when everything else fails.
If the rectifier tube has a 2A filament, and with a 5% voltage increase, then add a resistor with R = 0.25/2, 0R1, about 2W (0.5W dissipated) and you have nothing to worry about.
I was considering a diod i serie for a voltage dropp. Realized that it would be a bad idea as the glow are 5VAC.
The resistor solution are better 🙂
The preamp has voltage regulators and are therfore less sensitive for variations on the primary side. Unfortunately do I not have enough margin in power to feed both amps with that powersupply.
The resistor solution are better 🙂
The preamp has voltage regulators and are therfore less sensitive for variations on the primary side. Unfortunately do I not have enough margin in power to feed both amps with that powersupply.