My Tubelab SE unanswered question

Nikon1975 · 4th August 2011, 02:32 PM

Dear All,

I'd like in my new Tubelab SE to reduce the voltage for the power drive to 200V to limit the heat consumption.

The question is: how much current should I make available ? I tried to measure, but it looks like the current drain is almost zero.

Thanks,

Davide

tubelab.com · 4th August 2011, 03:30 PM

The average current drain is set by the resistor from the source of the fet to the negative supply. I usually aim for 5 to 10 mA to limit dissipation in the mosfets. If your positive voltage supply is lower, then you can increase the current to improve the dynamics a bit. I have found no benefit to going beyond 20 or 25 mA. These current numbers are per channel.

For my test amps, I use an isolation transformer with two 120 volt secondaries which I put in series. With a bridge rectifier and filter I get a +/- 160 volt supply for PowerDrive. That works well.

Nikon1975 · 6th August 2011, 06:48 AM

Thanks!!! I will be using the regulator from diyhifisuppy, that has -120v supply. For the positive suppy of the powerdrive i will use a secondary winding of the main transformer. As I will have it custom made, i will request 50mA 150v. That should make.

We will see what will come out.

Davide

Nikon1975 · 21st August 2011, 04:38 PM

George,

Another question: what filament voltage are you aiming for the 5842 tubes ? I notice that with the current arrangement it is below 6.3 V. Do you think there is any advantage to run a separate filament supply for the drivers ?

Thanks,

Davide

tubelab.com · 22nd August 2011, 12:10 AM

Quote:

Another question: what filament voltage are you aiming for the 5842 tubes ? I notice that with the current arrangement it is below 6.3 V

I aim for 6.3 volts. The 5842 is the most variable tube that I have ever used and that includes the heater current. I have seen 5.4 to 6.7 volts with the stock configuration. The 5842 heater voltage depends on the power line voltage and tube current. I usually just tweak R3 as needed.

If you were building the ultimate amplifier with off board power supplies a good DC source for the 5842's might be a good idea. I did that in my 845SE amp which used a Tubelab SE for the driver.

Nikon1975 · 22nd August 2011, 11:38 AM

Will do like this.

Then I think it makes sense also to lower the AC for the 300B filament, so I reduce the heat production of the regulator. Am I correct ?

Thanks,

D.

Nikon1975 · 23rd August 2011, 03:12 AM

As I am pretty flexible with the power supply at this stage I was thinking something like this.

The module that I am using needs the rectifier, so I am using the rectifier on board, mainly to hold the tube in place.
The output of the module will be +400V and -120V. The B+ from the module should be mainly ripple free.
I will have a separate supply CRC for the power drive.

Now I can feed the B+ directly to the OT and feed the board with the power drive supply of around 200V. Like this the drivers and the power drive will share the supply, and I will reduce the heat also on the CCS.

The disadvantage is that the driver will not have a supply as clean as the power tube, but I noticed that the CCS makes his own work to reduce ripple.

Am I correct ? Does it make sense ?

For the filament, I will use the on-board supply for the 300B, feed with something around 5.5VAC and a separate PSU feeding 6.3 V 0.8 A regulated to the drives. I will have an ACof around 7VAC.

Please comment on my plan. Maybe I am missing something.

Thanks,

Davide

Nikon1975 · 23rd August 2011, 03:18 AM

And the other disadvantage is that the drivers will be feed with a supply done with diodes rectification, not tube.

D.

Nikon1975 · 26th August 2011, 11:30 PM

Any input?

Thanks,

Davide

Nikon1975 · 30th August 2011, 05:35 AM

So I think I will use the separate supply only for the mosfet. I set on 160 VAC 220uF 270R 220uF. Does it make sense here to have something like PP caps at the output, let's say 10uF or something smaller.

Additionally, I have two ammeter to connect instead of the resistors. Now they will be directly in the signal path. Should they bother me ?

I plan to connect one pp cap for each channel right at the OT. I think this should mitigate any possible negative effect of the meter. Am I correct ?

Thanks,

Davide

4th August 2011, 02:32 PM	#1
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	My Tubelab SE unanswered question Dear All, I'd like in my new Tubelab SE to reduce the voltage for the power drive to 200V to limit the heat consumption. The question is: how much current should I make available ? I tried to measure, but it looks like the current drain is almost zero. Thanks, Davide

4th August 2011, 03:30 PM	#2
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	The average current drain is set by the resistor from the source of the fet to the negative supply. I usually aim for 5 to 10 mA to limit dissipation in the mosfets. If your positive voltage supply is lower, then you can increase the current to improve the dynamics a bit. I have found no benefit to going beyond 20 or 25 mA. These current numbers are per channel. For my test amps, I use an isolation transformer with two 120 volt secondaries which I put in series. With a bridge rectifier and filter I get a +/- 160 volt supply for PowerDrive. That works well. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

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6th August 2011, 06:48 AM	#3
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	Thanks!!! I will be using the regulator from diyhifisuppy, that has -120v supply. For the positive suppy of the powerdrive i will use a secondary winding of the main transformer. As I will have it custom made, i will request 50mA 150v. That should make. We will see what will come out. Davide

21st August 2011, 04:38 PM	#4
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	George, Another question: what filament voltage are you aiming for the 5842 tubes ? I notice that with the current arrangement it is below 6.3 V. Do you think there is any advantage to run a separate filament supply for the drivers ? Thanks, Davide

22nd August 2011, 11:38 AM	#6
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	Will do like this. Then I think it makes sense also to lower the AC for the 300B filament, so I reduce the heat production of the regulator. Am I correct ? Thanks, D.

23rd August 2011, 03:12 AM	#7
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	As I am pretty flexible with the power supply at this stage I was thinking something like this. The module that I am using needs the rectifier, so I am using the rectifier on board, mainly to hold the tube in place. The output of the module will be +400V and -120V. The B+ from the module should be mainly ripple free. I will have a separate supply CRC for the power drive. Now I can feed the B+ directly to the OT and feed the board with the power drive supply of around 200V. Like this the drivers and the power drive will share the supply, and I will reduce the heat also on the CCS. The disadvantage is that the driver will not have a supply as clean as the power tube, but I noticed that the CCS makes his own work to reduce ripple. Am I correct ? Does it make sense ? For the filament, I will use the on-board supply for the 300B, feed with something around 5.5VAC and a separate PSU feeding 6.3 V 0.8 A regulated to the drives. I will have an ACof around 7VAC. Please comment on my plan. Maybe I am missing something. Thanks, Davide

23rd August 2011, 03:18 AM	#8
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	And the other disadvantage is that the drivers will be feed with a supply done with diodes rectification, not tube. D.

26th August 2011, 11:30 PM	#9
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	Any input? Thanks, Davide

30th August 2011, 05:35 AM	#10
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Vienna	So I think I will use the separate supply only for the mosfet. I set on 160 VAC 220uF 270R 220uF. Does it make sense here to have something like PP caps at the output, let's say 10uF or something smaller. Additionally, I have two ammeter to connect instead of the resistors. Now they will be directly in the signal path. Should they bother me ? I plan to connect one pp cap for each channel right at the OT. I think this should mitigate any possible negative effect of the meter. Am I correct ? Thanks, Davide