Using TSE 45 to drive a GM70 (or other big power tube) - diyAudio
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Old 22nd October 2012, 06:40 PM   #1
cotdt is offline cotdt  United States
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Default Using TSE 45 to drive a GM70 (or other big power tube)

If I remove the output transformer on my Tubelab SE and connect the output of the 45 to a GM70 tube, would that work well? I would like a modular setup that I can swap around.
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Old 23rd October 2012, 02:11 AM   #2
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You need a method of connecting the 45 to the GM70. The usual coupling capacitor / bias resistor will work but will not be optimum. Big tubes like the 211, 845, GM70, and 833A need a low impedance drive source, with a low DC resistance path to the bias source. These attributes are needed for low distortion and good overload recovery.

The usual method is to replace the OPT with a driver transformer that matches the 45 to the grid circuit of the tube being used. That works if a good quality transformer is used.

I chose to replicate the drive circuit that is currently in use between the 5842 and the 45 on a small PC board using larger parts to handle the higher voltages present. My circuit design is here:

845SE
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Old 25th November 2012, 08:32 PM   #3
cotdt is offline cotdt  United States
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Can the TSE 45 PCB be used as driver stage for GM70/845? I would just replace the 45's 10ohm resistor with a CCS? GM70 would then just be a drop-in replacement for 845 in that circuit except with 20V heaters.

Is there a PCB for Powerdrive or a universal power supply that you sell?
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Old 15th January 2013, 02:20 PM   #4
jrobson is offline jrobson  South Africa
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Quote:
Originally Posted by cotdt View Post
Can the TSE 45 PCB be used as driver stage for GM70/845? I would just replace the 45's 10ohm resistor with a CCS? GM70 would then just be a drop-in replacement for 845 in that circuit except with 20V heaters.

Is there a PCB for Powerdrive or a universal power supply that you sell?
Hi

I'm researching something similar... In another post George said he doesn't have any powerdrive PCB's.

Essentially yes you remove the OPT's, R18&R29 and plug in a powerdrive circuit at T2-2 and T3-2.
On the schematics the 845SE also has +150V going into both 2SK2700's, where in the TSE board it is connected to B+... This should still be ok I think? The second powerdrive 10M45's are set for 91ohms which is about 30 something ma...
Other than that you need a good power supply.... I've posted a GM70 one on another thread that you can use to get going...
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