Covert Overdrive too wooly

[stevtron]

I'm fighting since weeks with this little buddy, 'cause I can't believe that the sound should like it is (and yes, I have done everything right, all the right parts etc. - this is my 180th pedal or so) … too muddy, too wooly - no crispy highs, nothing nearly like that (like a 70's Marshall), even with treble and pres full open … but bass amount is massive ! So , I searched and found some mods wich brings me in the right direction, but not a perfect solution. There must be something wrong with the schematic , I have build a DLS MKI and this is totally different, crunchy highs and mids etc … is there a bullet proof original schematic somewhere in the www ?

 

[Chuck D. Bones]

180?!?!? Does your pedal board look like this?

DLS mk I and mk III are very different beasts. The schematic in the Covert build docs is correct. One some early boards, the BASS & MID controls were backwards. That won't affect the sound, just the direction you turn the knobs. Mine sounds good. Tone is well balanced. All the controls do what they're supposed to do. Buckets of gain in the Super Lead (up) position. There's quite a bit of distortion even with the PREAMP control dialed all the way down. Deeper bottom end and much less gain in the Super Bass (down) position, but the tonal balance is still there. The only place I deviated from the build docs is I used an A50K instead of a B250K for the VOL pot. I gotta believe that one of the caps is wrong. C2, C5, C9, C12 and C18 are all there to cut some of the treble, I'd verify those first. Or you can use an audio probe, listen to every stage from front to back and see where the sound goes south.

How 'bout some pix?

 

[stevtron]

No no, I‘m using very less for live on my board, but that keeps me not away building more and more ... it‘s a big fun !

So I‘m gonna check these caps again ... btw. I used ceramic caps for the 680n , is this a problem here ?
Thank you

 

[stevtron]

btw, I have absolutely no clean sounds, in both positions. Even with gain full down there is a good crunch character and no volume difference between both "channels"

 

[Chuck D. Bones]

Yeah, something's not right. Super Lead distorts even when the PREAMP is at zero, but Super Bass is pretty clean unless I really dig into the strings, then there is some mild crunch. And there is a big volume difference between the two channels when PREAMP is at zero. Maybe there's a problem with the 4PDT switch? It's very easy to overheat them during soldering. If the plastic starts to melt, then the internal contacts get misaligned. You can check the switch for continuity with a DVM (power off).

 

[stevtron]

Thanx again ! I'll have a lot to check ...

My ceramic caps having a tolerance from 5-10% , could that be a problem with the filter caps ? ... for example 450pf instead of 470pf and so on ... ? But when I calculate a simple RC filter f.e. 470pf/470k and change 470pf to 450pf I get no big centerfreq change ... so, I can't imagine that these tolerances will have a big impact ... mmh

4PDT is ok

 

[Chuck D. Bones]

10% tolerance on caps is fine.
If you're not getting a gain change when you switch channels and you're positive that the switch is good, then we have to turn our attention to R20 and C19. When SW1.1 is closed, R20 & C19 provide negative feedback around Q1, lowering its gain by at least 20dB. With power off, check continuity from Q1-1 to C19, from C19 to R20, from R20 to SW1 and from SW1 to Q1-3. Something in that feedback path has to be broken. Verify R2 is 33K and not something a lot lower.

Still no pix? You hiding something?

 

[ThePodsInterrobang]

Assuming the circuit was all built correctly, there are mods mentioned on this Tagboardeffects page by John Kallas that help reduce the amount of bass and gain in the circuit.

Catalinbread DLS MKIII

Collection of vero (stripboard) & tagboard layouts for 100s of popular guitar effects, with over 1000 verified designs. DIY your own boutique effects!

tagboardeffects.blogspot.com

I used them on my Covert overdrive and to my taste the sound was improved and the usable ranges of the bass and preamp knobs were increased.
The mods I ended up using were:
Change C18 to 22nF - This reduces the bass and wooliness. Probably the most useful mod.
Change R4 and R11 to 220R - This reduces the amount of distortion
Change R3 and R10 to 1K - Makes the sound subtly smoother and thicker
Change C19 to 220nF - Smooths out the superbass mode a little

There was also another mod for the Superlead mode mentioned in the thread, but I tried that and did not prefer it. It reduced the gain but also reduced the sound clarity.

 

[Chuck D. Bones]

C18 - yeah, that pedal is too dark for my taste with C18 at 100nF. I have the Presence trimmer maxed out on mine. Making C18 smaller doesn't reduce the bass, it increases the mids & treble. In my next build, I'm reducing C18, moving the Presence pot to the front panel and wiring it a little differently.
Lowering R4 & R11 increases the headroom. At 9V that's important. At 18V maybe not so much.
You mentioned increasing R3 & R4, I think you meant R3 & R10. That will reduce the gain a little.
C19 & R20 have a 2.2ms time constant. That means below 72 Hz the gain in the first stage rises. Increasing C19 moves that frequency down, eliminating the 12dB gain hump at 10 Hz. This and C18 made the biggest difference.
The source resistor mods have to be taken in the context of changing JFETs since different JFETs need different biasing.
I just read John Kallas's posts on tagboardeffects, very informative.
Thanks for all the great info!

 

[Jiuk]

I always using DLSmk3 with other drive pedal(like Tubescreamer, treblebooster, MXR dist+). Those pedal cuts the low frequency and make high frequency brighter. Do not mod DLSmk3 pedal.

 

[ThePodsInterrobang]

C18 - yeah, that pedal is too dark for my taste with C18 at 100nF. I have the Presence trimmer maxed out on mine. Making C18 smaller doesn't reduce the bass, it increases the mids & treble. In my next build, I'm reducing C18, moving the Presence pot to the front panel and wiring it a little differently.
Lowering R4 & R11 increases the headroom. At 9V that's important. At 18V maybe not so much.
You mentioned increasing R3 & R4, I think you meant R3 & R10. That will reduce the gain a little.
C19 & R20 have a 2.2ms time constant. That means below 72 Hz the gain in the first stage rises. Increasing C19 moves that frequency down, eliminating the 12dB gain hump at 10 Hz. This and C18 made the biggest difference.
The source resistor mods have to be taken in the context of changing JFETs since different JFETs need different biasing.
I just read John Kallas's posts on tagboardeffects, very informative.
Thanks for all the great info!

I did mean R3 and R10, I just edited the post in case anyone new reads it.
I agree about the C18 increasing the mids and treble, that's more accurate.

 

[daria]

I Just stumbled across this post No. 24 on TGP from Catalinbread. There's apparently no 100nf in a DLS MKIII. I'm going to experiment.

What are your Dirty Little Secret Mk III settings?

I find unity at around 9-10 o'clock. I'm running two of these, one in SL one in SB. The SL is set with Bass, Mid and Treb at noon and gain cranked. I use the volume on the guitar to vary the tone. The SB I use as a platform for Fuzzes, Bass at 9 o'clock, mid and treb at 10 o'clock and gain at...

www.thegearpage.net

A question. What volume setting is supposed to be unity? At lower to mid gain settings in Super Bass mode I'm having to set volume at about 4 oclock to hit unity.

 

[Chuck D. Bones]

Interesting. I always found the Presence trim to be too dark, now we know why. Now I'm intrigued to know what's inside the DLS Red.

I have a ROG Thunderbird on deck, it employs a completely different approach to Marshall emulation.

 

[daria]

I haven't had a chance to experiment with the 100nf yet but, with it in, my presence trimmer at Full CW was super bright and shrill. I have a some bright range to play with between 3 o'clock and Full CW but at 3 o'clock it's like an on/off switch, jumps straight to darkness.

 

[jjjimi84]

Assuming the circuit was all built correctly, there are mods mentioned on this Tagboardeffects page by John Kallas that help reduce the amount of bass and gain in the circuit.

Catalinbread DLS MKIII

Collection of vero (stripboard) & tagboard layouts for 100s of popular guitar effects, with over 1000 verified designs. DIY your own boutique effects!

tagboardeffects.blogspot.com

I used them on my Covert overdrive and to my taste the sound was improved and the usable ranges of the bass and preamp knobs were increased.
The mods I ended up using were:
Change C18 to 22nF - This reduces the bass and wooliness. Probably the most useful mod.
Change R4 and R11 to 220R - This reduces the amount of distortion
Change R3 and R10 to 1K - Makes the sound subtly smoother and thicker
Change C19 to 220nF - Smooths out the superbass mode a little

There was also another mod for the Superbass mode mentioned in the thread, but I tried that and did not prefer it. It reduced the gain but also reduced the sound clarity.

I highly recommend these mods, I did not change r3 and r10 but the other mods made this pedal way more useful and it sounds phenomenal.

 

[Jiuk]

R3 is 1k, R10 is 680. Both are correct values. 820 and 560 is wrong values.

 

[mr_de_fursac]

I also thought this pedal was too wooly and muddy till I turn up the presence pot to 3 o' clock. Dramatic change and much more useful and good tone!
Give it a try before going crazy with the mods

 

[zgrav]

180?!?!? Does your pedal board look like this?

Just wanted to acknowledge that is a great link. Crazy, fun and musical.