Wizard MCII

[kdmay]

I personally believe that the OT variations he offers are steel type, not primary impedance changes. But this is personal view.

I've already done an MC2 layout, but I had a power supply board with rectifier and switching supply already, so this is the preamp section only. You might find it useful. It's for a standard turret board from CED.

https://www.cedist.com/products/turret- ... 0mm-x-60mm

Capacitor types do matter and Friedman uses the 0.68uf Electros for a reason. Just buy the same type for the MC but in 1uf.

[Colossal]

Is the PI tail really 4k7?

PI.png

[kdmay]

Is the PI tail really 4k7?

Good pickup - that should be 10k!! There is a 4k7 to ground, like this.

Wizard MC2.png

[Colossal]

Excellent! Thanks for updating the board layout.

[kdmay]

Excellent! Thanks for updating the board layout.

No worries. Good to have people check it over

[studiodunn]

Does anyone have a layout of the bias circuit for a 100w wizard?

I just got a 100w Modern Classic and someone has done a pretty sloppy job on that I want to fix. I actually reached out to Rick, but to say it isn't cost effective is an understatement.

Thanks

mc100-biasRes02.jpg

mc100-biasRes03.jpg

[kdmay]

It would just be a standard Marshall bias circuit

[studiodunn]

It would just be a standard Marshall bias circuit

Thanks, I assumed so and just went ahead and used a 2203 layout, but used a 21k pot resistor. All seems well now.

mc100-biasFix.jpg

[kdmay]

Thanks, I assumed so and just went ahead and used a 2203 layout, but used a 21k pot resistor. All seems well now.

Hey while you have it on the bench, can you please verify that the lead boost function brings in both bypass caps on the 1st and 2nd gain stages?

[studiodunn]

Sorry, The amp is already on top a cab and rocking. If I get a chance I will pull it and confirm.

[burger]

I've designed a PCB for the MCII based on the schematic earlier in this thread. It will do an MC25, MCII 50w or 100w. Some excellent QA and assistance from Kurt has it complete. We've ordered a small batch and between us will build a couple to verify. I've got a fair bit of interest from other DIY builders to order another batch, if anyone is interested in grabbing one let me know.

[headcrash]

If I may chime in:
KDMay, is that a 47nF PI decoupling cap across the second grid resistor and tail resistor? Standard Marshall value would read 100nF, although it should not make a huge difference. Also, on the infamous handdrawn schematic it says the presence cap value is 470nF instead of the "standard" 100nF, and contrary to your layout. Anyone experimented with that? I always find it annoying how the Presence taper on typical MArshalls does next to nothing until around 1 p.m. ...

Another thing: wouldn't you agree, If I said, that the tube stage with the 1M feedback is a leftover from the Jubilee circiut and might have little to no effect on the sound?
I think, that the signal gets pretty squeezed by the diode network, then gets even divided down a little (even more depending on the lead master on Jubilees), and then there is that pretty clean stage, which originally served to lower source impedance for the FX loop in the Jubilee. I would state, that you could omit that stage without a noticeable change in sound.
What do you think?

[kdmay]

Good observations!!

KDMay, is that a 47nF PI decoupling cap across the second grid resistor and tail resistor? Standard Marshall value would read 100nF, although it should not make a huge difference. Also, on the infamous handdrawn schematic it says the presence cap value is 470nF instead of the "standard" 100nF, and contrary to your layout. Anyone experimented with that? I always find it annoying how the Presence taper on typical MArshalls does next to nothing until around 1 p.m. ...

I've only used 100n as the Presence cap in my mule build (as per the MTL schematic), but I should really try the 470n as per the hand drawn schematic. Having said that, all the gut shots I've seen have standard 100n presence cap (for example as per below).

Another thing: wouldn't you agree, If I said, that the tube stage with the 1M feedback is a leftover from the Jubilee circiut and might have little to no effect on the sound?
I think, that the signal gets pretty squeezed by the diode network, then gets even divided down a little (even more depending on the lead master on Jubilees), and then there is that pretty clean stage, which originally served to lower source impedance for the FX loop in the Jubilee. I would state, that you could omit that stage without a noticeable change in sound.
What do you think?

Possibly. Why don't you try it! What I do know is that when I changed around this stage between the MTL config (FB: 100k/100k; Divider: 100k/100k) to the MC (FB: 1M/100k; Divider 100k/10k) this made a difference, so simply omitting this stage I believe will alter the sound and feel.

[burger]

I've completed the first prototype build with my PCB. I've done a 6V6 25w MC25, although the PCB will easily accommodate 50W & 100W flavours.

The PCB includes a separate rectifier and regulator for either DC Heaters and/or the relay power supply. Room for setting up elevated DC heaters, 5 on-board relays for many combinations of channel, boost and LED switching. Component footprints are sized for orange drop caps.
Grounding is sorted on this PCB and the amp is dead quiet.

A few quick pics and a clip of my MC25 proto. The clip is the unboosted Lead channel, it's a big bold rock sound!

62084770_2367833490168037_361603239499530240_n.jpg

64246430_854675161564854_4410319663620161536_n.jpg

MC25-v0.1.mp3

The PCB is 400mm x 77mm and easily fits into a smallbox style chassis. It comes with a fully synced schematic and example layout diagram.

With the first build up and running and the PCB now tweaked and confirmed, I'm ready to submit a run of boards. Thanks to those that have already PM'd me to register interest.

Boards will be US$30 plus shipping which I'd expect to be around US$20.

Let me know via PM.

Cheers
Jason

[norska]

Put me down for a board. Possibly 2 the clip sounds killer btw!