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Topics - Max

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1
Build Reports / Reboxing a couple of pedals
« on: August 22, 2020, 02:25:25 AM »
The first is a Tonemender I had in a multieffect that has been torn apart long ago. I thought it would have been nice to have it back on my board so there it is. The second is a TriVibe (THcustoms PCB) where I made some mistake in the enclosure the first time. The graphic was fine, but the inside was a mess, so after a couple of years I decided to clean it up a bit. Of course it got a brand new graphic as well.
Funny enough, when the Tonemender was in the multieffect there was a loud POP when the toggle switch was flipped. Well, now it's gone  ;D

2
Build Reports / My take on the Distortion+
« on: July 23, 2020, 12:31:15 PM »
OK, nothing fancy, classic distortion circuit from MXR. But.
I had a look at the mods proposed here and there, I tried some and decided I didn't like them.
Two of the mods (bass and compression) were very subtle (i.e. I couldn't hear the difference) so, I discarded them. And I didn't like the way the tone control was implemented: instead of a potentiometer in series to ground with the shaping cap before the volume pot, I replaced the 10k resistor at the op-amp output with a 10k potentiometer, and put a capacitor on the centre pin of the pot to ground. Actually, I put two caps, with an on-off-on switch, so I can have two settings or disable it entirely.
Then the diodes: since I'm dumb, I misunderstood the circuit, and the result is unexpected: I have an on-on switch that connects the diodes EITHER to the op-amp feedback (soft clipping) or to the output (hard clipping), but I can't have them together. Plus, and here comes another mistake, I ordered the wrong switch, an on-off-on instead of an on-on, so when it comes to switching diodes types I have three options:
- fully symmetric (parallel of 2 1N34 in series)
- "slightly" asymmetric (parallel of 2 1N34 and 1 1N4148 + 1 BAT41)
- "very" asymmetric, that is, 2 1N34 in series to ground only.
The effect is very pronounced, also the tone control is much more effective. I think I tried a 741 and an LF351 as opamp, but I don't remember which one I left in, I suspect the 741.
Ah, yes, the graphic: I didn't really know what to do so I made this sort of faded grey&white which includes part of the schematic.
OK, enough talking (or writing... or reading? whatever) here's a couple of pictures (and the final schematic, maybe it's clearer than my attempt at explaining it)
Ah, there's a lot of space in the top of the enclosure because it's recycled from another project.
Enjoy!

3
OK, nothing fancy, classic distortion circuit from MXR. But.
I had a look at the mods proposed here and there, I tried some and decided I didn't like them.
Two of the mods (bass and compression) were very subtle (i.e. I couldn't hear the difference) so, I discarded them. And I didn't like the way the tone control was implemented: instead of a potentiometer in series to ground with the shaping cap before the volume pot, I replaced the 10k resistor at the op-amp output with a 10k potentiometer, and put a capacitor on the centre pin of the pot to ground. Actually, I put two caps, with an on-off-on switch, so I can have two settings or disable it entirely.
Then the diodes: since I'm dumb, I misunderstood the circuit, and the result is unexpected: I have an on-on switch that connects the diodes EITHER to the op-amp feedback (soft clipping) or to the output (hard clipping), but I can't have them together. Plus, and here comes another mistake, I ordered the wrong switch, an on-off-on instead of an on-on, so when it comes to switching diodes types I have three options:
- fully symmetric (parallel of 2 1N34 in series)
- "slightly" asymmetric (parallel of 2 1N34 and 2 BAT41)
- "very" asymmetric, that is, 2 1N34 in series to ground only.
The effect is very pronounced, also the tone control is much more effective. I think I tried a 741 and an LF351 as opamp, but I don't remember which one I left in, I suspect the 741.
Ah, yes, the graphic: I didn't really know what to do so I made this sort of faded grey&white which includes part of the schematic.
OK, enough talking (or writing... or reading? whatever) here's a couple of pictures (and the final schematic, maybe it's clearer than my attempt at explaining it)
Ah, there's a lot of space in the top of the enclosure because it's recycled from another project.
Enjoy!

4
General Questions / Repairing a Pride of Texas
« on: April 04, 2020, 05:07:18 AM »
I just put my hands on a broken Danelectro Pride of Texas. Honestly, I was hoping for something easier to repair. Damn it, this thing is all smd, also tracing it (  ;) ) will be a nightmare. However, it looks like the problem is on the switching board, so hopefully it is the relay that's faulty.
More to come when I have time to work on it...
PS: according to a couple of stickers on the box (that were casually covered by some white labels...) this was already on offer on Amazon as reconditioned.

EDIT: I just realised that probably I picked the wrong forum for this thread, if anyone reckons appropriate to move it somewhere else please go ahead.

5
General Questions / Amp-in-a-pedal and negative feedback
« on: March 14, 2020, 05:09:51 AM »
Hi All, I've had some experience building some distortion pedal derived from famous amps, especially from runoffgroove, and after experimenting with my take on the Orange MkII (check the 2019BOTY contest for more) I'm now trying to understand a bit more about the negative feedback.
From what I get, this is used to bring part of the signal from the output transformer back to the cathode of one of the preamp valves, where the signal phase is opposite w.r.t. the anode, in order (for example) to tame the highs or increase/reduce the distortion.
Now, some of the older projects from runoffgroove (i.e. Professor Tweed, Thunderchief and Flipster) as well as the orange project I started from, follow the original amp schematic 1:1 leaving out the final tubes and the output transformer, but include the negative feedback which, instead of taking the signal from the output transformer, takes it from the output of the pedal, which, correct me if I'm wrong, is equivalent to taking it from the output of the preamp.
My question is: without the output transformer, doesn't the negative feedback just suck signal from the output without really affecting the tone as in a real amp? Maybe this is one of the reasons runoffgroove moved away from this 1:1 philosophy to get better sounding circuits in terms of fidelity to the inspiring amp.
EDIT:
this is probably the best explanation I've seen of the negative feedback:
https://youtu.be/H5fFb5_9xyA?list=PLhv-fcfLlQdrnP4wn5wWaaO8_Y8IFrPxx

6
Build Reports / My take on the DSOTM aka Skreddy Lunar Module
« on: March 05, 2020, 11:54:06 AM »
After playing a bit with a breadboarded fuzz, starting from a simple VOX fuzz (from a VOX Double Sound Wah-Fuzz), then turning it into a Jimi Hendrix FF, I decided to go for something more flexible and built the Skreddy Lunar Module.
I designed the PCB to fit a 1590A with two pots for Level and Fuzz, two pots with the small plastic shaft for Body and Bright and a trim for the Bias with the possibility to put a shaft on it and bring it out of the enclosure (which I did, and recommend).
At first I was really disappointed with the sound, until I checked the schematic and found a missing trace, nothing important, only the input signal to the base of Q2  :o Now I'm surprised I got any sound at all  ;D ;D
Anyway, fixed that and voilą, sounds great without any tweaking and with a lot of different settings. I still have to try it with a Wah.
Here's a couple of pictures. The graphic was recycled from another pedal that I didn't really like and is long gone in the spare parts bin.
PS: the LED is purple  ;)
Enjoy:

7
Open Discussion / Of Fuzzes, Opamps and Buffers...
« on: November 23, 2019, 07:26:01 AM »
I have a Hendrix Fuzz Face breadboarded that works fine (with an additional mod, but this will come later) and I was thinking about adding a dry/wet option, so I took the Madbox circuit from THCustom and put the fuzz on one channel while the other send is connected directly to the return to get the dry signal.
Result, the dry signal works perfectly, the fuzz is nowhere to be heard, maybe just a tad.
Now, I know that fuzz circuits don't like too much opamps (or anything else in front of them), so what would you guys suggest, maybe a little jfet buffer between the input opamp and the fuzz might do the trick?

8
General Questions / Fidelity of some amp-in-a-box distortion pedals
« on: July 09, 2019, 07:18:02 AM »
Hi All,
I've built some of the effects from Runoffgroove that aim at reproducing one or the other famous amp sound, like the Azabache or the Ginger, and despite the sound being very nice, there's something missing.
As an example, take the use that Don Felder makes of muted notes in his solos with the Eagles, which according to him have been played through a Fender Champ at max. volume: if I try to play those muted notes, doesn't matter the amount of overdrive I get from the pedals, I never get that fat CHICK out of the guitar, it just doesn't seem to drive the effect hard enough, and of course it's reflected in the overall sound, the attack of the notes is different.
I'm currently using an Epi ES339, which of course is not an original Les Paul '59 like Felder's. Ah, I play through a cabinet sim (condor) and headphones, real amps are unfortunately out of question.
Anyone has any idea on how to tweak for example the Azabache to obtain that kind of sound, if possible at all? Or maybe it's a problem of my setup?

9
How Do I? Beginner's Paradise. / Two channels, one stomp
« on: March 02, 2019, 06:51:45 AM »
OK, let's say I need to switch between two pots in order to have two different settings for the volume at the end of an effect. With a 3pdt stomp it would be fairly easy to do all the switching including two LEDs. But in reality I need to switch 4 pots in total, that is gain and volume per channel, so a 4pdt stomp would do it but there would be no room for a status-LED.
So, here's my question: if I only switch the output (connected to the wiper) between the two pots and leave the input and GND connected then the circuit upstream will see half the resistance, i.e. the two pots in parallel.
Shall I double the pots' resistance to get the same impedance of the original circuit?
If this would be enough I could still do everything with a 3PDT, which would be great especially because I already have it!

EDIT: Obviously I wouldn't be able to exactly double the values, I should do 1x10k replaced by 2x25k in parallel and so on...

10
Open Discussion / VOX Double Sound Fuzz vs BJTs
« on: December 11, 2018, 05:17:12 AM »
A long time ago ('96 maybe) a friend of mine borrowed a VOX double sound wah vintage that was sounding great, so I decided to copy the circuit and make a stand alone fuzz (at the time I couldn't find a wah inductor, so no point in replicating the wah...).
It came out a little nasty fuzz with no controls, just two BC238B and few other things. Now, after all this time, I found a VOX V847 broken for a few euros and fixed it and then I thought: let's build that little fuzz again, I still have the schematics (check attachment)!
And so I did but with MPSA18, that are also used in the newer VOX wah replacing the BC238B.
Since I was not really happy with the sound, or maybe it's just my memory failing, I decide to put in two BC238B as I did the first time.
After struggling a bit to find them (on EBAY) I checked the hfe and it's in the specs, so I put them in the circuit but it doesn't work.
What's puzzling me is that a BC238B as T2 doesn't work, really no signal at all, while as T3 together with an MPSA18 works but the sound is crap (and I've tried ten of them).
How come that 22 years ago it worked right away without even checking the transistors?

11
Open Discussion / Bass Cab Sim (or speaker response)
« on: July 31, 2018, 10:56:58 AM »
Dear All,
I'm thinking about getting me a cheap kit bass guitar just to have some fun. With this idea obviously comes the following: what pedal can I build for it ;) ;) (but this is not my question)?
I don't have an amp, I only have a Condor cab-sim for my guitars that works wonderfully, so, first thought was, what if I play a bass through my Condor? But, hey, I still have two PCBs for the Condor, what if I adapt the Condor to the different frequency response of a bass amply speaker? It shouldn't be too difficult, but I don't know where to find a frequency response to start from.
Any suggestions?

Max.

12
Build Reports / New build: ROG Omega
« on: March 27, 2018, 02:43:37 AM »
With all the amazing builds I've seen on this forum I'm almost reluctant to post this little circuit in a tiny 1590A, but it's really nice sounding. It's the ROG version of the Range Master, basically a FET based treble booster. Since the drain bias of the FET allows for different sounds, I made a small change to the circuit adding a second trimmer and a switch. In this way I'm able to dial in two different biasing for the FET and get a broader sound spectrum from the same effect without having to open the enclosure.
The PCB is (obviously) from OSHPark, while the first build was on Vero.
One day I'll be able to post audio or video samples, for the moment here's a couple of pictures:
https://drive.google.com/open?id=1ToKCMsHZgK1daGZQ3gIPXvvdDHh3OQWB
https://drive.google.com/open?id=1ZpTcurx7Vt-Zih4XUowIBMdX6YRAe-Lg

13
Open Discussion / Enclosures with vertical vs slanted sides
« on: January 16, 2018, 07:56:07 AM »
All the enclosures I've used so far [1590A, -B, -BB, and -DD] have the side walls slightly slanted, probably because of the manufacturing process. Now, I have a project where the jacks are PCB mounted and it fit exactly in a 125B. Do you know if the 125B available at musikding have the sidewalls vertical, or eventually, where to find such a box? I seem to remember that the enclosures used by MXR have the side walls at 90 degrees square, but it's been a long time since I've seen one.

14
General Questions / Piezo Pre, Pick Ups and impedance matching
« on: October 22, 2017, 07:49:08 AM »
I almost finished a solid body with three single coils and electronics more or less like a strat.
As an experiment, I added a piezo transducer with a little preamp built around an MPF102. I have another preamp like this in my acoustic and works very well. In the acoustic, however, the piezo is under the bridge saddles and has a higher output, while here I have a single piezo element (aka buzzer) somewhere stuck to the body (well, under the neck pick up). First thing, I'll try to replace the jfet with a j201 to have a bit more gain and try to balance the output a little bit wrt the magnetic pick ups.
The main issue, however, is that I used an ON-Z-ON toggle switch, so that I can have both magnetic and piezo circuits together but there's some impedance problem and the result is that when they are in parallel the pick ups are basically inaudible. If I remove the battery, the pick ups can be heard as a far far away sound.
Here's the schematic:
https://drive.google.com/open?id=0B5Uj9BTxpfvLR3VwR2dkaFFTbnc

Any idea? I'd like to leave the magnetic pick ups passive...


EDIT: I just realised that I open this thread in the wrong forum, can someone please move it to the proper place, like "Open Discussion"? Thanks ;)

15
Build Reports / Another ROG: the Tri-Vibe from TH Custom
« on: September 09, 2017, 03:33:01 PM »
Hi guys, I finally managed to put together this nice little circuit. I had some issues with the decal and the colour printer at work and it took me way too much time to finish the enclosure. Not to mentioned that when I got the decal printed to perfection the first time, I didn't spray enough coating on it and the ink started to smudge during the application :'( :'(
I borrowed the image for the graphic from some website, I'm not that creative  ;D ;D

About the circuit: the central position of the switch (Vibe) is so subtle that at first I thought it was not working at all. Is it how it should be?
I find the other positions just great.
Enjoy:
https://drive.google.com/open?id=0B5Uj9BTxpfvLbXdUTUNSYWRqams
https://drive.google.com/open?id=0B5Uj9BTxpfvLeVMxS0NPZVF3Rlk

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