Tube Driver Question.

[milkwasabadchoice]

I am going to build one of these, from General Guitar Gadgets, and I was just wondering how clean it can be when the drive is all the way down? and how warm it is? Is the generalguitar layout good? I am hoping to use this as a clean boost and a warm overdrive can this be done? Sorry for all the question.  Hope to here from you all.

Thanks,
Jason

[milkwasabadchoice]

anyone?

[JimRayden]

Sadly, there have been reports of some hum in the GGG layout.

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Jimbo

[Phorhas]

HI.
I haven't build onw but I own a tock one and it can get quite "clean". you can also use a lower Mu tube.

[Paul Marossy]

Sadly, there have been reports of some hum in the GGG layout

I have heard the same. But, I haven't been able to confirm whether it's the actual layout, or if it has to do with how people laid it out...

[guitar_199]

I can't say that I know for certain...... and I am most certainly no expert......

But I've looked that PC board over and compared it to another one from Germany......and I too have heard about that issue.....

One thing that I notice about the GGG layout....is that right where the 12 vac comes on the board... it goes into the two diodes
that rectify the AC and split it up for the voltage doubling.  Now.....if you look where the input comes  on to the board... it goes through R1
and C1.....then takes a turn right under C15 and goes right directly under the two rectifiers.  That is probably a fairly high impedance
input on the IC and a fair bit of copper trace running to it passing right under 12 VAC coming in.   If that 12 VAC is coupling over to the input line it will get picked up and boosted and I bet you THAT will hum.

The German board that I saw has a different rounting so this proximity of AC to input trace does not exist.  I do not know if
that board is reputed to have a hum problem.

I just thought I'd throw that out there......

What do you think? 

[JimRayden]

Hmm, besides, why use a 2-diode-setting when you have the opportunity to wire up a bridge rectifier? The cost of additional filtering is higher than of a few more diodes, to my knowledge.

And I'd make a separate PCB for the power supply and the circuit because we've got AC going on here, Watson! 

------------
Jimbo

[Paul Marossy]

If that 12 VAC is coupling over to the input line it will get picked up and boosted and I bet you THAT will hum.

That sounds reasonable. 

[Paul Marossy]

Hmm, besides, why use a 2-diode-setting when you have the opportunity to wire up a bridge rectifier? The cost of additional filtering is higher than of a few more diodes, to my knowledge

Umm... wait a minute. :icon_exclaim: 

I see your reasoning, but that circuit employs a voltage doubler circuit. Doing a full wave rectifier on it won't work because it also is creating the bias (V- & V+) at the same time. 

[JimRayden]

Whoopsydaisy, my bad. 

Hmm I wonder how can I work on tube amps with this kind of concentration and attention abilities. But well, it hasn't zapped me yet.

---------
Jimbo

[Paul Marossy]

Hmm I wonder how can I work on tube amps with this kind of concentration and attention abilities. But well, it hasn't zapped me yet.

LOL.