Lovepedal - Dover Drive  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
ivan H
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Post by ivan H »

That's great if one is looking to change the original effect into a high gain distortion (I already have high gain distortions), however I put this together because I wanted the original effect for some Reverend Billy G type tones which it can do quite well. A search on transistor gains for silicon fuzz face type circuits led me to info that the first transistor gain is best somewhere around 65% ~ 85% of the second transistor. Actual gains aren't so important (allegedly) so long as this ratio is kept. Apparently this gives the best interaction between the guitar & effect, allowing cleanup with the guitar's volume control, touch sensitivity etc. Also mentioned experimenting with input/output cap values along with the transistors to get tonal response desired. Cheers

Manfred
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Post by Manfred »

A search on transistor gains for silicon fuzz face type circuits led me to info that the first transistor gain is best somewhere around 65% ~ 85% of the second transistor.
I am interrest in this theme too and going to work on it.

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Post by di-anno »

Manfred wrote:Thanks, sounds good!
I further step could be to hook in the blend circuity of the Lovepedal Silicon Fuzzmaster.
http://tagboardeffects.blogspot.de/2012 ... aster.html

Thanks for reply, it's fairly clear that bassy/clarity of this pedal strongly depends on its input impedance and probably in your link there is the best solution to manipulate it. However I found in buffered version a better sound than the original (..for my ears and for my rig..) so i experienced in that way introducing a dual gang pot in buffer to control clarity/bass and volume pot responce. i still have some noise problem but promises good.
dov_buf_1.jpeg

I think that in front of fuzz face type pedal it would be very useful something like this:
http://www.stompbox.de/buffer_english.html

cheers

ivan H
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Post by ivan H »

Manfred wrote:
A search on transistor gains for silicon fuzz face type circuits led me to info that the first transistor gain is best somewhere around 65% ~ 85% of the second transistor.
I am interrest in this theme too and going to work on it.
Cool, I'd be interested in your results. I'll do the same when time allows. Cheers

ivan H
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Post by ivan H »

Ok, I know its been a while, been pretty busy but I have spent a little time tweaking. Went back to 209 hfe for Q1 & 271 hfe for Q2 (Q1 @ 77% of Q2). This gives the best performance & interaction with the guitar, just bass heavy. So, I lowered the value of the FF output cap by half to 0.047uf which did the trick. Still have the resistor in series with the gain pot at the moment. Cheers

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Post by Kennc_dk »

I have measured key bias nodes on the Dover Drive that i traced the schematic from:
Battery measured to 9.43 volts.
On the IC :
pin 1,2,5,6 and 7 = 3.04 Volt
Pin 3 = 2.88 Volt ( hmm, I’ll recheck this one)
Pin 8 = 6.17 Volt
Pin 4 = 0 Volt
On PNPs :
Q1: 6.17 V, 5.89V and 4.85 V
Q2: 2.07 V, 4.85V and 5.49 V
I’ll measure HFE on both of them very soon.
Note to PNPs: gain is set to 1’oclock. Internal trimmer is Stock, as on the schematic.
Last edited by Kennc_dk on 05 Nov 2017, 09:57, edited 1 time in total.

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Post by Kennc_dk »

Yes, the pedal i quite bassy, so i have added an external switchable low-cut a’ka ‘The fuzz face Eric Johnson mod’ on the output of the Dover drive. Adding the low-cut between fuzz stage and OD stage causes nasty biasshifts.
I use the low-cut mainly on solos that are not to take too much Sound space in the band. In a trio constellation i almost never use the low cut.
Yes, due to the High gain of this pedal and the PNPs (AM detectors!) at the input, the pedal i prone to Pick up radio signals, mobile phones ect.
Despite bassy’ness and radio moskow, I LOVE MY DOVER DRIVE PEDAL!

ivan H
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Post by ivan H »

Thanks heaps for the voltages Kennc_dc, I'll check through mine against them. I did a quick google search but haven't found anything on the Eric Johnson low cut mod yet, I'd be interested to know about. I'll look a bit further. I did look at the the axis fuzz mods, might try a couple of. Cheers

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Post by Kennc_dk »

ivan H wrote: I did a quick google search but haven't found anything on the Eric Johnson low cut mod yet, I'd be interested to know about. I'll look a bit further. I did look at the the axis fuzz mods, might try a couple of. Cheers
on this www: https://www.electrosmash.com/fuzz-face its stated that:
"Eric Johnson seems to prefer a 100KΩ level resistor over the stock 500KΩ. Using a smaller resistor, the filter will cut more lows out (fc=160Hz) which will result in a brighter sound."
This makes sense regarding Erics solos, so I added the 160Hz LF/bass cut on the output of the Dover drive as I described previously. if your solo is to ride on the top of a crowed band, this preferably selectable -mod/option makes sense, both for the fuzz faces and the dover drive ;-)

ivan H
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Post by ivan H »

Kennc_dk wrote:
ivan H wrote: I did a quick google search but haven't found anything on the Eric Johnson low cut mod yet, I'd be interested to know about. I'll look a bit further. I did look at the the axis fuzz mods, might try a couple of. Cheers
on this www: https://www.electrosmash.com/fuzz-face its stated that:
"Eric Johnson seems to prefer a 100KΩ level resistor over the stock 500KΩ. Using a smaller resistor, the filter will cut more lows out (fc=160Hz) which will result in a brighter sound."
This makes sense regarding Erics solos, so I added the 160Hz LF/bass cut on the output of the Dover drive as I described previously. if your solo is to ride on the top of a crowed band, this preferably selectable -mod/option makes sense, both for the fuzz faces and the dover drive ;-)
This is exactly why I am experimenting to brighten it up. In a 3 piece setting it might do ok as is, but trying to use for leads in a 4 piece, well, you already know. Thanks heaps for the tip, greatly appreciated. Cheers

MoonWatcher
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Post by MoonWatcher »

It just dawned on me that there's no real reason to have the silicon Fuzz Face portion of the Dover Drive use PNP transistors, is there? Wouldn't it almost make more sense just to translate that circuitry to be NPN-based (2N3904)?

Epiphany number two - it might be cool to have both a Fuzz Face and a Zendrive in a pedal enclosure, together, and make each switchable, so that you would essentially have three pedals vs. the Dover Drive's one. You could also end up with more variations in sound by including the voice and gain controls with the Zendrive.

Ben N
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Post by Ben N »

@Bugg, are you still planning to release a board for this?

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Post by Frank_NH »


Kennc_dk
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Post by Kennc_dk »

!! MADE A MISTAKE DURING THE TRACING !!

I own 2 orignal Dover drive pedals myself, and they sound rather different, one has much higher gain than the other. Thus I traced the second Dover drive pedal also and found out 2 things:
1. A capacitor (c4) is inserted/traced incorrectly in the first schematic that i did!
2. There is no difference between the two pedals, except that HFE is different in the bipolar transistors between the 2 pedals.

example: HFE of 'Q1' is 200 versus 140

Here is the updated schematic. The capacitor now tames the high end of the Fuzz part. It forms a ~3.5kHz low pass filter:
Lovepedal Dover Drive rev2.jpg

Manfred
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Post by Manfred »

I have this PCB-layout in accordance with the schematic above
created in two versions.
The versions are the same except for the resistors ( 121k, 81k2 ) of the factory setting.
In the first version both resistors appear in the second version they are replaced by a trimming potentiometer ( 200k).
I have checked the layout twice with the test function of the SprintLayout6.0 but I still ask for recheck.
Dover1Layout.JPG
Dover2Layout.JPG
Ready to print PDF-files:
Dover1ComponentSide.pdf
(18.73 KiB) Downloaded 12 times
Dover1SolderSide.pdf
(4.93 KiB) Downloaded 12 times
Dover2ComponentSide.pdf
(18.5 KiB) Downloaded 10 times
Dover2SolderSide.pdf
(4.96 KiB) Downloaded 10 times
SprintLayout6.0-file:
Dover.zip
(44.82 KiB) Downloaded 21 times

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