The Valve Wizards preamp layout

[pompeiisneaks]

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

MerlinMediumGainBluesRockv1.2.PNG

Edit: Updated the layout, had the pots wired all wrong (backwards) and I had them off a bit as well, thanks sluckey
Edit1: newest version with corrections again by sluckey.

~Phil

[tubeswell]

FWIW - Merlin's updated chapter on grounding (downloadable for free from his website) has layouts for pre-amps, and power amps (PP and SE).

[pompeiisneaks]

Odd I don't see that on it, this link?

http://valvewizard.co.uk/Grounding.pdf

BTW Have an updated version, sluckey found some errors. I'll just replace the top one.

~Phil

[tubeswell]

Fig 15.10 SE

Fig 15.12 cathode biased PP output

Fig 15.13 Fixed bias PP output

Fig 15.14 preamp incl LTP (multi-star ground)

Fig 15.17 2-channel pre-amp

(what I think about when I use the term 'layout' - although I concede it is very schematical)

[pompeiisneaks]

Fig 15.10 SE

Fig 15.12 cathode biased PP output

Fig 15.13 Fixed bias PP output

Fig 15.14 preamp incl LTP (multi-star ground)

Fig 15.17 2-channel pre-amp

(what I think about when I use the term 'layout' - although I concede it is very schematical)

Yeah to me those are schematics with a slight touch of layout just for the grounding part. Missing to munch information about how to put the components onto a board.

Phil

Sent from my LG-V521 using Tapatalk

[tictac]

The tone stack doesn't look right. The bass control looks Voxish but seems to be connected backwards. It also looks like your missing a tone cap, (.1uf?) is the 200k slope resistor supposed to be hardwired to the bottom of the treble control?

TT

[pdf64]

I'm not sure that Merlin would approve of the input grid stopper being mounted on the board, away from the tube socket terminal

[pompeiisneaks]

The tone stack doesn't look right. The bass control looks Voxish but seems to be connected backwards. It also looks like your missing a tone cap, (.1uf?) is the 200k slope resistor supposed to be hardwired to the bottom of the treble control?

TT

What sluckey pointed out is it's a clone of the Fender Bandmaster but with slightly changed parameters: http://el34world.com/charts/Schematics/ ... ER_6G7.pdf

Are you missing the .1 uF on the board before the 470p and 200k that head to the treble control? or the .01 that's on the bass control itself? As for the connections, they mirror the above schematic as well.

~Phil

[pompeiisneaks]

I'm not sure that Merlin would approve of the input grid stopper being mounted on the board, away from the tube socket terminal

Lol true, I know he beat that into my head, and I should have remembered, 'put the grid stopper as close to the grid to avoid miller capacitance' if I recall

~Phil

[tictac]

OK I see! that 6G7 TC is very unusual for a fender design, so it looks like you've got it hooked up correctly then...

Any idea what you'll do with the un-used triode @ V2?

TT

[pompeiisneaks]

OK I see! that 6G7 TC is very unusual for a fender design, so it looks like you've got it hooked up correctly then...

Any idea what you'll do with the un-used triode @ V2?

TT

I'm not sure yet, if I do build it, that may be a cathodyne PI so I can just go to power output at that point and give er a rip.

I did it on request for someone else, and am just sharing the layout if anyone's interested for now

It's still a possibility for me but like 10th on my list of 'things to try'

~Phil

[modman]

Mod Edit: removed spammy edit by user.

[tictac]

This thread demonstrate why sharing layouts without schematics is counter-productive:
-it's impossible to see what's going on
-it's impossible to detect errors that subsequently get spread over the internet.

So very true....
No disrespect but it's a newbie thing. I remember 25 some years ago that everything I built I wanted a layout. Someone helped me understand I really needed to think in terms of schematics.

Once I did it was like the lights started coming on So put those layouts away and draw the schematic first. Do the layout after the schematic is drawn and refined and I bet you find that the schematic helps you make a better layout

TT

[sluckey]

Then you end up spending 700USD on a Bassman kit that sounds like a 5W solid state practice amp.

Cheap shot!

[modman]

Mod Edit: removed spammy edit by user.