Modified AB763 schematic question?

[markmalin]

Hey guys,


Back in April of 2015, I think it was Tubenit who drew up a schematic for me.  (Tubenit, I don't know if you'll see this, but if not, maybe someone else can help.)  There's what looks to be an extra 220K resistor in the center of the drawing attached to the wiper of the Reverb control, between the wiper (and the 470k feeding the reverb return) and ground.  Would this have been put into the schematic on purpose, or is this just a mistake?  Tubenit (or was it someone else?) graciously drew this up during a thread discussing this build.  I'm thinking he may have put this 220k to ground in by accident, but I wanted to be sure...  I'm attempting to draw it myself in Express PCB's Schematic program (another story!), but I want to be sure it's right. This does not match the way I've been building these, and is not present in the Fender AB763 (or similar) schematics.  I need a sanity check here! 


I've attached a scan of the schematic.  I also attached a ".sch" file, but I am unable to open this so it may not be the right one.


Humbly,
Mark

[sluckey]

That resistor should not be there.

[kagliostro]

To me the .sch file is corrupted (and didn't open)


Franco

[markmalin]

Thanks so much, guys.  And Tubenit, thank you!!  You didn't have to do that!  But I sure appreciate it :)


I don't know what happened to that other file, it wouldn't open in my downloaded version of the schematic program.  I'll try to load in the version you just drew up.

[markmalin]

It was a mistake.  Sorry!

I tried to redraw it for you with some corrections.  However, I could not see on the PDF file what you did at the end of the OD section.

With respect, Tubenit

Sorry I didn't get the whole schematic in the scan.  It was late last night.  :P  So what I did was add your "5E3'ish tone stack" at the end of the OD section.  I'm hoping I can figure out the schematic program and add that in.  Again, thank you so much for re-drawing this!


Mark

[tubenit]

Mark,

Regarding the "pseudo 5E3 tone stack",  it works great on my Tweed BluezMeister.  I originally had it on my D'Mars, but eventually changed it to a simple .0047 to ground which sounded a little smoother on that amp.

I've tried to draw it in the schematic for you.  Please post some pics of your build at some point.

With respect, Tubenit

[markmalin]

Mark,

Regarding the "pseudo 5E3 tone stack",  it works great on my Tweed BluezMeister.  I originally had it on my D'Mars, but eventually changed it to a simple .0047 to ground which sounded a little smoother on that amp.

I've tried to draw it in the schematic for you.  Please post some pics of your build at some point.

With respect, Tubenit

Dang.  How can I thank you! 

I'll post pictures of this particular build in a couple weeks when I get it done.  I've built/sold several of these amps, but not with the pseudo 5E3 tone stack.  Also, I've added a relay and footswitch for the OD.  For what it's worth, here's a demo of my "demo" amp, which includes a fixed version of your extra tones tack.  On that one I dialed it in and then used resistors rather than a pot.  The recording is raw (dry) and unprocessed and no effects. I could have doctored up the recording but this is simply a Senheiser mic direct into my iPhone.   (youtube seems to compress everything anyway)  https://youtu.be/ofjwtpB-Vu0 .  You can skip all the yacking in the beginning if you like and f.f. to around 4:00+ when I switch in the overdrive.  (would I love to have someone like Stelligan from Amparage playing this thing - he'd make it sing!  But alas...you get Mark Malin, Hack Guitarist!  lol)

Mark

[PRR]

> an extra 220K resistor

Does no harm, and maybe no good.

For 12 cents you can try it both ways.

[markmalin]

> an extra 220K resistor

Does no harm, and maybe no good.

For 12 cents you can try it both ways.

Thanks for your input, PRR. Good point.


Mark

[tubenit]

Mark,   

That amp looks and sounds great!  Very nice job and I enjoyed your playing also!  Thank you for sharing your fine work.

With respect, Tubenit

[markmalin]

Mark,   

That amp looks and sounds great!  Very nice job and I enjoyed your playing also!  Thank you for sharing your fine work.

With respect, Tubenit

That means a lot. Thanks.  I couldn't have done any of this without the help of guys like you, and everyone who's been so helpful on the Hoffman forum over the last several years!

[markmalin]

Mark,

Regarding the "pseudo 5E3 tone stack",  it works great on my Tweed BluezMeister.  I originally had it on my D'Mars, but eventually changed it to a simple .0047 to ground which sounded a little smoother on that amp.

I've tried to draw it in the schematic for you.  Please post some pics of your build at some point.

With respect, Tubenit

Tubenit - you asked for pictures.  Here are a couple of this build.  Expecting the cabinet next week.


Mark

[tubenit]

Wow!!  That is one beautiful build!  Very impressive.  THANKS for sharing the photos.  You really do nice work.

With respect, Tubenit

[markmalin]

Wow!!  That is one beautiful build!  Very impressive.  THANKS for sharing the photos.  You really do nice work.

With respect, Tubenit

Thanks, that really means a lot.  Thanks for all the help!
Mark