"Hazen" Mod on Simple SE?

Davec113 · 31st December 2009, 10:39 PM

Looks possible on the Simple SE, you'd need to cut a trace on the board, then solder a cap between G3 and Cathode on the power tube sockets.

Anyone try it?

tubelab.com · 3rd January 2010, 04:53 AM

I haven't tried it, but I would proceed with caution. This mod leaves G3 with no DC connection whatsoever. Ordinarilly G3 should not draw any current, and stray electrons that strike G3 (inevitable) will eventually build up a negative charge. However if the tube is even slightly gassy (common with current production tubes) you could wind up with a positive voltage on G3 leading to more distortion and a possible runaway condition.

If you do this, I would leave a meter connected across the cathode resistor for a while and watch for unusual current changes. G3 doesn't have too much effect on tube current, but I still like to have it connected to something (DC wise).

There was a post about a year ago by a long time tube amp designer that claimed connecting G3 to a low (about 10 volts) negative bias made G3 "dissapear". This was only supposed to work on EL34's. I never got around to trying it. The cap could be doing exactly the same thing.

Davec113 · 5th January 2010, 08:40 PM

It's tempting to try it, but I'm not sure I want to risk damaging the amp. I guess I need to build a 2nd amp with cheaper parts to experiment on.

tubelab.com · 6th January 2010, 02:53 AM

Quote:

It's tempting to try it, but I'm not sure I want to risk damaging the amp. I guess I need to build a 2nd amp with cheaper parts to experiment on.

I don't mind blowing stuff up. In fact I have a Simple SE board that I have blown up and fixed countless times. There are pictures of different itterations of blown parts scattered throughout the "Tubes" forum. In fact the necessary runners on the PC board are already cut (for another experiment). Once I get caught up on the Simple P-P manual, I may try it just to see what happens. I imagine the results will depend on the output tubes. I have plenty of less than perfect examples to try.

Davec113 · 08:02 PM

Bump???

Since my post I've finished my ME degree and moved, nothing new happening with my system, which I'm pretty much satisfied with... as long as it stays in a small room "nearfield" it is hard to beat.

Now I am wondering if anyone tried this mod to the Simple SE yet? I will do it first if I have to...

Edit... this only works on el34s because there is no internal connection to G3, so this shouldn't have any affect when running kt88s I'm guessing as the internal connection will be present, and the cap in parallel probably won't do anything, but correct me if I'm wrong please.

rock4016 · 15th February 2011, 07:44 PM

You are correct, you need a 6CA7 or EL34 to do the mod.

31st December 2009, 10:39 PM	#1
Davec113 diyAudio Member Join Date: Jul 2007	"Hazen" Mod on Simple SE? Looks possible on the Simple SE, you'd need to cut a trace on the board, then solder a cap between G3 and Cathode on the power tube sockets. Anyone try it?

3rd January 2010, 04:53 AM	#2
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	I haven't tried it, but I would proceed with caution. This mod leaves G3 with no DC connection whatsoever. Ordinarilly G3 should not draw any current, and stray electrons that strike G3 (inevitable) will eventually build up a negative charge. However if the tube is even slightly gassy (common with current production tubes) you could wind up with a positive voltage on G3 leading to more distortion and a possible runaway condition. If you do this, I would leave a meter connected across the cathode resistor for a while and watch for unusual current changes. G3 doesn't have too much effect on tube current, but I still like to have it connected to something (DC wise). There was a post about a year ago by a long time tube amp designer that claimed connecting G3 to a low (about 10 volts) negative bias made G3 "dissapear". This was only supposed to work on EL34's. I never got around to trying it. The cap could be doing exactly the same thing. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

28th August 2010, 07:59 PM	#5
Davec113 diyAudio Member Join Date: Jul 2007	Bump??? Since my post I've finished my ME degree and moved, nothing new happening with my system, which I'm pretty much satisfied with... as long as it stays in a small room "nearfield" it is hard to beat. Now I am wondering if anyone tried this mod to the Simple SE yet? I will do it first if I have to... Edit... this only works on el34s because there is no internal connection to G3, so this shouldn't have any affect when running kt88s I'm guessing as the internal connection will be present, and the cap in parallel probably won't do anything, but correct me if I'm wrong please. Last edited by Davec113; 28th August 2010 at 08:02 PM.

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5th January 2010, 08:40 PM	#3
Davec113 diyAudio Member Join Date: Jul 2007	It's tempting to try it, but I'm not sure I want to risk damaging the amp. I guess I need to build a 2nd amp with cheaper parts to experiment on.

15th February 2011, 07:44 PM	#6
rock4016 diyAudio Member Join Date: Aug 2005	You are correct, you need a 6CA7 or EL34 to do the mod.

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