Soldano X88R preamp

[Sensei Tim]

I finally got DIYLC installed and spent some time with it over lunch today.  I had issues with getting the nice component templates so i had to use the default ones.

Using this schematic  http://www.prowessamplifiers.com/schematics/images/Soldano%20X88R%20Redrawn.pdf i've done a layout, but left off the portion after the master volume.

Hopefully my first kick at the can has no errors (i can always wish!)

edit: first error - typo in the notes

[Ciaran Haslett]

Hi Tim!

Great job! Based on values I assume you went with the High Gain Channel?  If so, there are a few problems (sorry)

1. Coming out of Q1...the 47n should go to a 220p not 220n (typo?)
2. The 220p on Q2 doesn't appear on the schematic
3. Coming out of Q2...the 22n should go to a 470K THEN to the Gate of Q3.  At the minute it goes to the Gate and the 470K is left in limbo. The 39K is on the Gate when it should be the source.  

If you move everything to the left you can shift the top leg of the 1M to the bottom of the 470K, cut between the 22n and Gate of Q3, and add a link from 1M/470K junction to gate.

4. Mid 3 labelled as 2.  No Bass Cap?.  Treble 2 should go through the 330K then to Master 3.  Also 330K shouldn't connect to Treble 3.

These are all pretty simple fixes and congrats for going after a preamp on your first attempt!!!  I struggled with a buffer on my first go!

Well done!

[Ciaran Haslett]

I should add...having done a few preamp layouts...it's definitely a good idea adding a resistor between gain 1 and ground.  It seems weird to me having 2 pots on a pedal that will make it go silent.  With said resistor you can set it so that, with the gain pot fully CCW, there's still signal going through the pedal.  

Maybe add a few low value caps to simulate the Miller effect too.

Good luck.

[Sensei Tim]

don't apologize for pointing out mistakes!  i knew there would be some!

here are the updates...

no bass caps because there were none in the schematic (that i saw?)  and yes, this is the high gain channel.

This circuit was so similar to the dr boogie that i used that as a starting point and made the adjustments as necessary :)

[rocket88]

hey man looks great!! especially for a first layout. my only suggestion looking at it is that it might be better to add a row or two on top so you can move the trimmer farther from the fets cause it's going to be a tight fight. plus with the width it's already at it's going to go in a 1590bb anyway, so why not make life easier.

if you take my suggestion you'll just add a link from the trimmer lug to drain of each fet. nothing wrong with how it is, you know me, i can be a little overly anal sometimes. lol

[Sensei Tim]

yeah. i don't use those square trimmers.. i use round ones, but for the life of me i couldn't figure out how to import templates - i dl'd mark's templates that were posted in another thread here, but couldn't figure out ow to import them.  regardless, the 6mm rounds will fit with no interference.

If anyone can help me figure out how to get the nice pretty component templates loaded into DIYLC 3.x i'd be greatful ;)

[rocket88]

the templates mark uses and posted work only with V2 not V3, so that may be why you couldn't import them.

[Sensei Tim]

tag it as verified.

found an error in the revB layout. revC is built and verified.

[Travis]

Nice work Tim! How does it sound?

[Sensei Tim]

it sounds pretty good so far. i was only able to play through a small practice amp late last night so i wasn't able to turn it up too loud. i biased the JFETs as best i could at a low volume.

Lots of saturation and usable throughout the gain range.  the EQ is very usable across all the range, too.

I'll try and bias it thru my normal amp and 12" speakers and do a playthru of it this weekend.

[Sensei Tim]

https://www.youtube.com/watch?v=PPdTeLWLUYw

pardon the shitty playing ;)

[MetalRules]

hi
thats a nice one !
what trimmers did you use?

[Sensei Tim]

100k

[MetalRules]

thanks !

[Sensei Tim]

Thanks to |V|ark for his library i cleaned up my layout.

also noticed in my original build that the treble control was backwards. editted the layout to reflect the changes

[J0K3RX]

Nice work, and the youtube demos sound damn good!

I was surprised that you were able to get some usable range from the tone stack with the 100k source resistor on Q5. You may want to try a 10k or 22k there and see if that improves the overall range? You might also try to lower the 47k in the tone stack to maybe 22k or throw a trim pot in there and dial it in where you like it...

[Sensei Tim]

Thanks!

Personally, i did find it to be a bit on the bright side. will have to tweak the tone stack, but no time right now.

Cheers!

[alltrax74]

Thanks for this nice a layout !
Does the bottom end stay tight (palm mutes) ?

[Sensei Tim]

have a listen to the youtube video.

It's not bad, but not as good as some of the others.  The x88R is not a modern preamp - i think it's from the late 80s - so it's not really going to be able to compare against some of the modern designs

On Wed, Nov 2, 2016 at 4:03 AM, alltrax74 [via Guitar FX Layouts] <[hidden email]> wrote:

Thanks for this nice a layout !
Does the bottom end stay tight (palm mutes) ?

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[alltrax74]

Didn't see the link
Sounds pretty good I might give it a try
Thanks