How does Komet do that?!
Moderators: pompeiisneaks, Colossal
How does Komet do that?!
Now that I've seen the pictures and thought about it, a question has popped into my head. How do they use a tube rectifier (GZ34) and have what looks to be 160uF of capacitance for the first stage? I have read that the highest any rectifier tube can handle is 50uF. I assumed the caps were in parallel, but it is hard to tell from the pictures. If they are in series than it is 40uF and I have no argument. Does anyone know?
-erigm
Re: How does Komet do that?!
Yes, the input cap is 80uF, and that is theoretically too high for a GZ34, which (according to all the old data) has a 60uF max. I guess the rectifiers in a Komet don't last a long time?
--mark
--mark
Re: How does Komet do that?!
series, I believe...
Re: How does Komet do that?!
Aha, so you think it might be series?! That is what I am thinking also, but I couldn't quite tell from the pictures. I have read in KOC's books about putting a rectifier tube in series with silicon diodes, or using the tube in one half of a bridge rectifier and silicon diodes in the other half. Does anyone know if these techniques allow you to have a higher capacitance in the first stage?
-erigm
Re: How does Komet do that?!
There are two more 80uF caps under the power supply board(that's why it's up so high) that are in series with the two above the board.erigm wrote:Now that I've seen the pictures and thought about it, a question has popped into my head. How do they use a tube rectifier (GZ34) and have what looks to be 160uF of capacitance for the first stage? I have read that the highest any rectifier tube can handle is 50uF. I assumed the caps were in parallel, but it is hard to tell from the pictures. If they are in series than it is 40uF and I have no argument. Does anyone know?
Re: How does Komet do that?!
Yeah, I saw there were caps under the board too ... I just couldn't tell their orientation. Thanks for the responses.
-erigm
Re: How does Komet do that?!
Odd that they would be 450v caps then. Evan at silly high voltages 350 each would be more then enough.markd wrote: There are two more 80uF caps under the power supply board(that's why it's up so high) that are in series with the two above the board.
--mark h
Re: How does Komet do that?!
It's the surge current that a big cap creates that is "bad" for tube rectifiers. So, if your application does NOT drain the caps, then there is no surge, or at least less of a surge. One can check this with a oscilloscope, monitoring a known resistance. The current spikes could still be in the spec of the tube.... but don't assume this if you cant check this.
For my latest beast, it has exactly 32uF on the tube rect.'s output. BUT, then after 200 ohms resistane, another 32uF, then 10k resistance, a whopping 164uF, 10k then finally 220uF. This whole chain has a lot of parallel capacitance, but it does not over do it on the rectrifier tube. Those resistors slow down the rate that the caps charge, keeping the surges down.
I am next planning on trying multiple tube rectifiers, like Mesa/Boogie uses, and YES I am really putting some caps in there, big ones....
I have a scope and I'm not afraid to use it.
For my latest beast, it has exactly 32uF on the tube rect.'s output. BUT, then after 200 ohms resistane, another 32uF, then 10k resistance, a whopping 164uF, 10k then finally 220uF. This whole chain has a lot of parallel capacitance, but it does not over do it on the rectrifier tube. Those resistors slow down the rate that the caps charge, keeping the surges down.
I am next planning on trying multiple tube rectifiers, like Mesa/Boogie uses, and YES I am really putting some caps in there, big ones....
I have a scope and I'm not afraid to use it.
Re: How does Komet do that?!
Spincycl,
That is cool, thanks for the info. Sounds like a neat amp you're building. So, if you have two tube rectifiers you can have a 100Watt amp. Does this also mean you can double the first stage of capacitance? Seems to me like it would, but I may be missing something.
That is cool, thanks for the info. Sounds like a neat amp you're building. So, if you have two tube rectifiers you can have a 100Watt amp. Does this also mean you can double the first stage of capacitance? Seems to me like it would, but I may be missing something.
-erigm
Re: How does Komet do that?!
To be honest, I dont' know what to expect with alternate rectifiers and caps. I have not seen schematics for any multi-rectifier amps, unfortunately. I have seen some setups where the "beefy" rectifier is on the OT/ power tubes. Then, the other rectifier is mainly running the first stages.
If I were to just make a wild guess, I would think that perhaps a smoother DC source on the first stages COULD provide some benefit... At the very least, this setup would keep the preamp supply smooth even if the power amp is really driving to the max on the output.
As for the THIRD rectifier, like on the Mesa Triple.....hmm....
I suppose splitting the power amp's DC with two rectifiers could have some benefit, and perhaps could improve sound (or degrade, depending on your tastes).
I can say this, though. Since they include such nice rectifier tubes, I can say that it does look quite impressive. All three of them are the ones with a bulge at the center of the envelope, kinda like a reversed hourglass.
If I were to just make a wild guess, I would think that perhaps a smoother DC source on the first stages COULD provide some benefit... At the very least, this setup would keep the preamp supply smooth even if the power amp is really driving to the max on the output.
As for the THIRD rectifier, like on the Mesa Triple.....hmm....
I suppose splitting the power amp's DC with two rectifiers could have some benefit, and perhaps could improve sound (or degrade, depending on your tastes).
I can say this, though. Since they include such nice rectifier tubes, I can say that it does look quite impressive. All three of them are the ones with a bulge at the center of the envelope, kinda like a reversed hourglass.