Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pompeiisneaks on February 11, 2018, 12:50:55 pm

Title: The Valve Wizards preamp layout
Post by: pompeiisneaks on February 11, 2018, 12:50:55 pm

I've been asked by someone to try and create a layout for the Valve Wizard's (Fig 14.4 pg 256) Practical Medium Gain Blues/Rock preamp. I figured I'd share here too if anyone would like to try it out. I can't share the schematic, due to it being in Merlin's book, but if you want to see it, I highly suggest buying it, I love it "Designing Tube Preamps for Guitar and Bass" Second Ed.

IF you've got the book/schematic, let me know if you think I've missed anything obvious, or should do something different.

Optional easy tweaks to the layout would be to run grounding wires between grounding points on the preamp sections and only run one wire off the board, (except for the power filtering which should be separate, unless you want to do 100% star ground) and you could also separate the power filtering into a separate board somewhere.)

I may eventually get around to building it myself, but have too many items on my build list at this point :P

Edit: updated with the pot wiring right.
~Phil

Title: Re: The Valve Wizards preamp layout
Post by: sluckey on February 11, 2018, 02:39:14 pm

The wrong side of the volume and gain pots are grounded.

Edit...

The tone controls are tangled also. Since Merlin copied the Bandmaster 6G7 tone stack (but using different values) take a look at this to straighten it out...

     http://el34world.com/charts/Schematics/files/fender/Fender_BANDMASTER_6G7.pdf

Title: Re: The Valve Wizards preamp layout
Post by: pompeiisneaks on February 11, 2018, 03:32:16 pm

Oh you're right, lol, I'm thinking from the front but that obviously is showing the back of the pot, inside. 

DOH!

~Phil

Title: Re: The Valve Wizards preamp layout
Post by: sluckey on February 11, 2018, 03:37:57 pm

Since we were posting at the same time I thought I better repeat this so you would see it...


The tone controls are tangled also. Since Merlin copied the Bandmaster 6G7 tone stack (but using different values) take a look at this to straighten it out...

     http://el34world.com/charts/Schematics/files/fender/Fender_BANDMASTER_6G7.pdf

Title: Re: The Valve Wizards preamp layout
Post by: pompeiisneaks on February 11, 2018, 03:39:22 pm

Yeah I realized it was also backwards,  I just was doing it 123 instead of 321 due to mapping it in reverse in my head, the latest upload there should be right I hope :P

~Phil

Title: Re: The Valve Wizards preamp layout
Post by: pompeiisneaks on February 11, 2018, 03:41:28 pm

Oh man I have that bass wrong too, yeah it should be between the wiper and top of the pot, and treble connects to that point too... fixing

~Phil

Title: Re: The Valve Wizards preamp layout
Post by: pompeiisneaks on February 11, 2018, 03:47:37 pm

Ok that I 'think' is now right :P

~Phil

Title: Re: The Valve Wizards preamp layout
Post by: sluckey on February 11, 2018, 05:02:18 pm

Bass pot is still backwards. Look at the 6G7 layout I posted.

Title: Re: The Valve Wizards preamp layout
Post by: pompeiisneaks on February 11, 2018, 10:26:36 pm

I did before but somehow still had it off in my head, think I got it right this time, see v1.2.

Thanks!

~Phil

Title: Re: The Valve Wizards preamp layout
Post by: sluckey on February 11, 2018, 10:47:45 pm

 :thumbsup: