Hi everyone-
I have my new Tubelab SSE playing right now and *love* it (running the big Edcors, EH KT88s, GE 5 Star 6201 for the 12AT7, Sovtek rectifier, and Auricaps). Will have the chassis done soon, but for the time being I couldn't resist giving it a listen. (Thanks George!!)
I have a question re the inrush limiters - is there any advantage to keeping the CL-90 per the manual in line with the mains if I have the CL-140 on the board?
After reading the manual and this (link) thread, I put a CL-90 in line after the fuse on the mains, as well as one in line with the CT high voltage lead.
When the amp didn't work at first, after some searching, finally realized we had updated boards, learned about the diodes and CL-140 to help protect the rectifier tube and jumpered those connections just to get it going and give it a listen.
Is it belt-and-suspenders to have two inrush limiters with the new boards? Should I get rid of the first CL-90 if I have the CL-140 and just use that?
Many thanks for any info-
Pete
I have my new Tubelab SSE playing right now and *love* it (running the big Edcors, EH KT88s, GE 5 Star 6201 for the 12AT7, Sovtek rectifier, and Auricaps). Will have the chassis done soon, but for the time being I couldn't resist giving it a listen. (Thanks George!!)
I have a question re the inrush limiters - is there any advantage to keeping the CL-90 per the manual in line with the mains if I have the CL-140 on the board?
After reading the manual and this (link) thread, I put a CL-90 in line after the fuse on the mains, as well as one in line with the CT high voltage lead.
When the amp didn't work at first, after some searching, finally realized we had updated boards, learned about the diodes and CL-140 to help protect the rectifier tube and jumpered those connections just to get it going and give it a listen.
Is it belt-and-suspenders to have two inrush limiters with the new boards? Should I get rid of the first CL-90 if I have the CL-140 and just use that?
Many thanks for any info-
Pete
A quick follow up - reading here (link) that tube rectification can serve as a sort of "soft start" for your power tubes as the rectifier warms up. If I were to do the solid state option, would keeping the additional CL-90 in line with the mains provide some of that "soft-start" benefit?
Many thanks-
Pete
Many thanks-
Pete
Excellent choice.
When using a tube rectifier, I'm not sure why you would need an inrush limiter at all, unless C1 is causing the tube to arc over. Maybe keep the one on the mains side of the PT. Does the new PCB have a position for one?
Either way, you just need one. It could also be located right after the diodes, before C1.
jeff
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Thanks Jeff - yeah, the new boards have space for the CL-140 (digikey KC014L-ND) and two diodes (digikey UF4007TR-ND) before the rectifier tube.
There was another thread (and I'm at a loss to find it now) detailing how the inrush on just the mains doesn't necessarily protect the rectifier? Or sort of does, but the separate inrush on the rectifier was helpful. As I've learned with all this stuff, you read 20 threads, some of which are conflicting, and seem to make no sense at the time, but eventually you sort it out.
I haven't had anything arcing over (but have also had the CL-90 in place there going into T1 Red-Yel screw terminal before the rectifer), but had been mentioned that the rectifier tubes in this design were operating near their limits voltage-wise, and the Sovteks could take it, but lesser tubes tend to fry (thus the inrush).
There was another thread (and I'm at a loss to find it now) detailing how the inrush on just the mains doesn't necessarily protect the rectifier? Or sort of does, but the separate inrush on the rectifier was helpful. As I've learned with all this stuff, you read 20 threads, some of which are conflicting, and seem to make no sense at the time, but eventually you sort it out.
I haven't had anything arcing over (but have also had the CL-90 in place there going into T1 Red-Yel screw terminal before the rectifer), but had been mentioned that the rectifier tubes in this design were operating near their limits voltage-wise, and the Sovteks could take it, but lesser tubes tend to fry (thus the inrush).
If you have both installed now, leave them.
The CL 90 on the power transformer primary softens the hit on the tube heaters and the power transformer when the amp is first switched on. This is especially important if a solid state rectifier is used. The tube heaters are a low resistance at turn on and can draw considerable initial current. This can cause hot spotting if the heater wire is not made of uniform thickness, or evenly coated. The CL 90 slows these events down a few seconds causing a bit less electrical and thermal stress.
The CL140 and the added diodes softens the hit on the rectifier as it starts to conduct. It does not come into play until after the CL90 is finished. There is a second surge of current as the rectifier begins to conduct. It begins to charge the empty C1 cap while its cathode is not fully heated. If the cathode coating is not perfectly uniform, or the cathode is not perfectly concentric within the plate, this current surge will occur over a small portion of the cathode's surface causing an arc.
On an amp the size of the SSE neither device can be considered mandatory. The CL140 and diodes did stop the rash of rectifier arc overs, but maybe JJ and Sovtek just stopped selling their bad tubes. In a bigger amp I always use a current limiter in each place. It is cheap insurance against damage, that sometimes can get expensive.
The CL 90 on the power transformer primary softens the hit on the tube heaters and the power transformer when the amp is first switched on. This is especially important if a solid state rectifier is used. The tube heaters are a low resistance at turn on and can draw considerable initial current. This can cause hot spotting if the heater wire is not made of uniform thickness, or evenly coated. The CL 90 slows these events down a few seconds causing a bit less electrical and thermal stress.
The CL140 and the added diodes softens the hit on the rectifier as it starts to conduct. It does not come into play until after the CL90 is finished. There is a second surge of current as the rectifier begins to conduct. It begins to charge the empty C1 cap while its cathode is not fully heated. If the cathode coating is not perfectly uniform, or the cathode is not perfectly concentric within the plate, this current surge will occur over a small portion of the cathode's surface causing an arc.
On an amp the size of the SSE neither device can be considered mandatory. The CL140 and diodes did stop the rash of rectifier arc overs, but maybe JJ and Sovtek just stopped selling their bad tubes. In a bigger amp I always use a current limiter in each place. It is cheap insurance against damage, that sometimes can get expensive.
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