Actually I could get a 3 phase connection but then I would have designed the amplifier to take full advantage of it (for one the large screen caps could have been much smaller).
The two lines are "fused" inside the amplifier....also the HV depends on the filament voltage. If the latter fails (the fuse blows) the softstart relays will open and the HV immediately cut so that no damage comes to the tubes. the GND connections of the gu81m will be fused to prevent runaway. I am quite happy about the project so far. Everything seems to be going well. Basically the amp is rady for testing. I just need tto sort out some minor problems (warping of the top plate - 3mm thick aluminum) is on the to do list. The rest is ready: voltage boards, driver boards, output transformer and tubes. Also I want to add handles to the front panel to emulate this specific model of enclosure:
Useful when the amplifier needs to be tilted on the side.
Also I would like to minimze AC hum so careful routing of the "2 miles" of heater wiring is required.
I estimate first run before the end of june, possibly before then. I am quite busy with some other non aurdio related things so progress may be slowed down.
Don't worry...I am not giving up
You will here this amplifier sing the Soviet national anthem. Not sure about the quality but it will sing.
A tribute to the gu81m engineers.
Also I found out that there is a gu80 tube around. Larger and with a longer life. perfectly compatible with the socket.
The two lines are "fused" inside the amplifier....also the HV depends on the filament voltage. If the latter fails (the fuse blows) the softstart relays will open and the HV immediately cut so that no damage comes to the tubes. the GND connections of the gu81m will be fused to prevent runaway. I am quite happy about the project so far. Everything seems to be going well. Basically the amp is rady for testing. I just need tto sort out some minor problems (warping of the top plate - 3mm thick aluminum) is on the to do list. The rest is ready: voltage boards, driver boards, output transformer and tubes. Also I want to add handles to the front panel to emulate this specific model of enclosure:
An externally hosted image should be here but it was not working when we last tested it.
Useful when the amplifier needs to be tilted on the side.
Also I would like to minimze AC hum so careful routing of the "2 miles" of heater wiring is required.
I estimate first run before the end of june, possibly before then. I am quite busy with some other non aurdio related things so progress may be slowed down.
Don't worry...I am not giving up
You will here this amplifier sing the Soviet national anthem. Not sure about the quality but it will sing. A tribute to the gu81m engineers.
Also I found out that there is a gu80 tube around. Larger and with a longer life. perfectly compatible with the socket.
The easiest way to deal with this is to use some 3mm thick aluminium angle, this will provide all the stiffness you need, plus it makes a convenient surface on which to fit all the bits you might have forgotten! (Also makes a useful heatsink for say, voltage regulators or power resistors).
Paul
small detail required for mercury rectifier operation. Since a mercury tube can (and will) require a long warmup once tilted or stored for a long time I have devised a solution. I have a 2 channel 3 position lever switch. One channel controls the relays for all transforme. the second channel toggles between the jumper selection you see in the picture (sec/min)
Up position will start the amp with a 30min delay before HV is applied. Down position will activate the amp with a 30s delay (normal operation). Center position is obviously amp OFF mode.
internal jungle...
aluminum angle fitted...warp is reduced but not eliminated. Maybe it is acceptable.
I believe the angle would have to run the whole width of the amp (if possible) to be effective.
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Added front handles
Inviato dal mio GT-I9001 con Tapatalk 2
An externally hosted image should be here but it was not working when we last tested it.
Inviato dal mio GT-I9001 con Tapatalk 2
Maybe fit it the other way around? with the extrusion facing the front (as we look in the photo)
large portion of the amp completed. the entire backside (only two connectors are missing).
I tested the B+ delay and it works like a charm. I will post a small video of the thing in action. For now a view of the amp during assembly.
As you can see it is *quite* organised. Obviously something must be reworked. All AC wiring has been drill-twisted as much as possibile without damaging the insulation. I hope this will be enough to protect against hum. I am ready to move the inputs to the front of the amp closer to the driver section.
Also the indicator lights behind the panel are for safety. I must see both glowing before even thinking of switching everything on.
For now Enjoy!
I tested the B+ delay and it works like a charm. I will post a small video of the thing in action. For now a view of the amp during assembly.
As you can see it is *quite* organised. Obviously something must be reworked. All AC wiring has been drill-twisted as much as possibile without damaging the insulation. I hope this will be enough to protect against hum. I am ready to move the inputs to the front of the amp closer to the driver section.
Also the indicator lights behind the panel are for safety. I must see both glowing before even thinking of switching everything on.
For now Enjoy!
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Wow, you work fast Alex. You started this thread on Jan 12th of this year and look how far you've come in such a short time. Very impressive. About the angle plate for your top plate. With that little amount of weight, you could use 1/4" or so bar stock all the way across and grind out the area with the rec tube sockets are. Can't wait to hear your impression of its sound.
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