SLO Lead channel mods

[evh_slash]

So I love my SLO 100 DIY preamp clone for its Crunch (mid gain tones) . It's unbelievable !! My only issue is when in full blown Lead mode I find it way too compressed/congested ?? The presence / top-end seems a little choked & the gain seems out of control, even when set very low !!

It's a bit confusing because on the one hand it does sound pretty bright/ fizzy, but then on the other hand its like its ever-so-slightly blocked off at the highs.

In other words it has a lot of treble and bite, but its not quite open (clear) at the top due to the sheer amount of gain/compression and High Frequency cuts throughout the circuit. I'd like to reduce the overall gain a bit, and open up the top-end a bit more.

My First thoughts are to change:
- V1 Plate Resistor from 220k down to approx. 170k by soldering a resistor in parallel to bring the Plate voltage back up & reduce some of the Mush/Gain at the 1st stage (But also affects my beloved Clean/Crunch channel as well though)
- OD volume Bright cap mod - Change from 1000pF to 500pF for slightly less drastic Mid/Gain boost
- V2b Plate Bypass cap (change the 1000pF Plate Bypass to 750pF for slightly less aggressive upper mid/treble cut. Hopefully 750pF will still be enough to prevent oscillation and unwanted squeals)





My soldering skills are not great so I would have to wait until after christmas to get my friend to do these mods for me .

If anyone with any experience modding SLO's or amps in general can add anything else to that please feel free, also let me know if the suggestions I've made should get me closer to what i'm looking for, without spoiling the overall feel of the amp ?

[DonP]

Re: SLO Lead channel mods

I'm not afraid to mod amps, having built many tube amps. But lately I've been finding I can tweak them with external devices. My Marshall 3203 has an odd preamp that gets really high gain, but also a treble cut as you turn it up past 7. I found an MXR 10 band EQ in the loop can solve the issue.

I used to be guitar -> amp only, but in the past few months I've found pedals are good for tweaking tone.

It's your amp so mod away if you want to. But what you are asking is sort of trial and error, and can get expensive going back and forth unless your tech doing the mods gets very lucky on the first try, or if you bite the bullet and mod it yourself. The mods you've identified are pretty simple. It might be a good way for you to start being a DIY'er.

[evh_slash]

Re: SLO Lead channel mods

Thanks .. Yeah I mean my theory is pretty decent I just dont have much confidence in my soldering . Its just a little messy ! I'm just looking for specific guidance regarding the SLO circuit . As I said, I just want to reduce some gain and compression whilst retaining the high end without it being harsh ! I'm definitely gonna drop the V1 plate resistor down + the bright cap value !