Earthquaker Dunes stripboard clone - no drive

Sesh · Post by **Sesh** » 23 Aug 2020, 15:54

Hi there

I've buillt an Earthquaker Devices Dunes clone in stripboard/vero using the tagboard effects layout: http://tagboardeffects.blogspot.com/201 ... dunes.html

Schematic is here: https://www.pedalpcb.com/docs/Oasis.pdf

I've double-checked the layout and reflowed the solder pretty thoroughly.

Everything works fine, there's audio through, the switches work as intended, it audibly boosts the volume and two of the clipping selections work. Everything except when the "None" clipping mode is selected it barely overdrives the signal, but just turns harsh when I turn the drive knob. Which leads me to believe the issue is with the clipping amp part of the circuit. But that's as far as my schematic/electronics knowledge will take me.

The readings from the LM833 pins are as follows:

1 4,5
2 4,6
3. 4,4
4 0
5 9,15
6 4,55
7 4,55
8 4,55

From these readings it doesn't seem the opamp is bust?

Attached is a couple of pictures.

andy-h-h · Post by **andy-h-h** » 24 Aug 2020, 05:05

Hello

9v on pin 5 doesn't look right. Are you measuring the pins this way? Pin 8 should have 9v

1 - 8
2 - 7
3 - 6
4 - 5

Do you get a decent increase in level in the N mode? It should really jump up a bit, as there's no reduction from clipping. I have a Plumes, which is similar in that regard. The diode bypass mode should act more like a clean boost at the start, and then get dirty towards the end of the gain range. I think that mode is primarily intended to just hit your amp / anything after it with some level.

examples on the scope:

no diode, clean, lots of level (it does eventually clip with gain on 100%)

no diodes - cranked. This is the opamp clipping, which not everyone likes compared to diodes

silicon diodes - clipped nicely, and much less level

This is my Plumes layout too https://vero-p2p.blogspot.com/2020/08/e ... ayout.html

Sesh · Post by **Sesh** » 25 Aug 2020, 08:48

Woops! Noob alert. Yes, my pins are incorrect. My 5 --> 8, 6--> 7, 7 --> 6 8 ---> 5

I should say I'm using a Yamaha THR-5 modeler... with headphones even. I think that might be the source of the harshness and lack of drive, if you say that the "None"-mode is supposed to be more of a boost. I compared my pedal to the pro guitar shop demo which is a miced up amp, and it sounds waaay more distorted (on "None" mode with full drive). But if it's a tube amp and he's already pushing it, that might explain the difference in distortion.

I'm gonna try it with my Peavey Classic 50 in the practice space and see how that sounds and get back to you

andy-h-h · Post by **andy-h-h** » 25 Aug 2020, 11:59

Hard to say with a lot of demos online - they always sound great. I checked out some demos, and Dunes appears to have more dirt on the N setting than Plumes, maybe as the Plumes is running +9 / -9v on the opamp. Might get more clean level as a result of this. But hey, only one way to find out... See what Mr Peavy has to say.

Sesh · Post by **Sesh** » 26 Aug 2020, 18:24

Mr Peavey said "this is how it's supposed to sound".

The "none"-diode setting is supposed to be a bit trebly and doesn't compressand darken in the same way that the diode clipping selections do. So I messed around with the tone switch and the bright/normal toggle and could get it to sound perfectly fine.

Indeed, it's supposed to just push the amp a bit. The other two modes sound excellent. It just took a proper amp to demo it - let that be a lesson! And now to box it..

andy-h-h · Post by **andy-h-h** » 27 Aug 2020, 05:59

Great - it works! I think the N mode might be something EQD added because it's easy to do, more so than for any great need (at least for me anyway). But hey, either way it's a good sounding Tube Screamer.