Source for Fixed Bias VVR Boards

[strelok]

Does anyone know where I can get some? I seem to remember someone on here was thinking about making and selling them a while back but I don't remember who. Would like to buy a few for my latest and upcoming builds.

[JazzGuitarGimp]

Hi Strelok,

I think you are thinking of me. When this question came around last time, I had suggested that if someone wants to provide me with a schematic and BOM, I would be happy to do a layout and provide boards - but I don't think anyone responded to my offer, which still stands, by the way. Though at this point, I'd need two to three weeks to get the boards back from the fab house.

Cheers,
Lou

[strelok]

Cool thanks, any idea how much each board would cost? Would there be a minimum order? I'll see if I can come up with a schematic and parts list that would be suitable.

[mhartman]

I've always just wired up the "VVR" circuits using a home made eyelet board. The circuit is very straight-forward.

[JazzGuitarGimp]

Cool thanks, any idea how much each board would cost? Would there be a minimum order? I'll see if I can come up with a schematic and parts list that would be suitable.

PM Sent

[Kagliostro]

A member of DIYItalia had some experimentation with Merlin's VVR for fixed bias, he tried to use it on a Marshall, but had problems

related with the source of the voltage

reading on LondonPower site seems that a low impedance supply is required (a separated transformer)

here a bit of documentation if someone want to give a try

VVR Merlin Schematic.jpg

VVR Merlin Layout.jpg

VVR Merlin PCB.jpg

Franco

[MakerDP]

You also need a tracking circuit to adjust the bias voltage as you adjust the B+ voltage.

[Kagliostro]

Is the low part of the schematic

The sensing input point is labeled "dal nodo alimentazione G2" on the schematic

Franco

[andresound]

Don't mean to hijack the thread, but I ordered VVR boards for Cathode bias from Hall about 6 months ago. Still waiting!!! Does anyone know if he is still around?

[Kagliostro]

On the red rectangle the whole circuit

On the blue rectangle the Bias & "Bias Sensing" circuit



The red cap was added by Merlin because of some cases of auto oscillations of the circuit

You can use the Top circuit (without the Bias & "Bias Sensing" part) for Cathode Bias Amps

(the advantage of this circuit is that a common pot can be used as there is a lower voltage on it)

--

...... I ordered VVR boards for Cathode bias from Hall about 6 months ago.

Have you tried to write an e-mail to Hall ? Are you sure they received your orther ?

Franco

[M Fowler]

Don't mean to hijack the thread, but I ordered VVR boards for Cathode bias from Hall about 6 months ago. Still waiting!!! Does anyone know if he is still around?

Yes Dana Hall is still around. You should contact him again and see what's up.

Mark

[andresound]

Thanks Mark. I know we have a REALLY slow postal system, so wanted to give Dana the benefit of the doubt