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Topics - m-Kresol

General Questions / headtrip 2 diodes
November 13, 2020, 05:54:12 AM
I ran out of 1n914 diodes and so did my regular supplier. Am I correct in assuming, I can exchange them for 1n4148?
General Questions / Pepperspray/Percolator transistors
November 08, 2020, 04:42:59 PM
I recently gave my pepperspray board to a motivated colleague at work and we're having a hard time finding the transistors. Are there any good substitutes for the PNP Ge (Q1, 2n404a) and NPN Si (Q2 2n3565)? I have AC128 around and plenty of Si NPN. If there's a substitute, does hfe matter? thanks

Also, I think there are some errors in the doc:
*) schematic and BOM call for a 2n3965 for Q2. Only the text specifies 2n3565.
*) the shopping list shows a BAT41 as a possible alternative to Q2. I guess this was meant for D1-2
Build Reports / 1590LB Headphone Amp
August 20, 2019, 05:19:46 PM
So, my brother's birthday is coming up and he asked me some time ago to build him a bass headphone amp. naturally, I wanted a challenge and decided to make it as small as possible. After some research, I settled on the MXR Headphone amp, but added a charge pump to 35V to give it some more headroom.
I've designed the pcb as a sandwhich, with the top one being the charge pump and the bottom one having the actual amp on it. In case of heterodyning or other noise, I could have just removed the charge pump and add a small vero for the power supply. Luckily, everything turned out flawless and I managed to put it in a 1590LB. Thanks Brian for the enclosure library in Eagle. that helped a lot!
The graphics are laser engraved after base coat and spray paint. After the laser, I put on 3 coats of clear. works great, and is quick, but it will not remove the base coat (I guess it has some inorganic particles that don't just burn off).

I will work out a build doc and publish this soon, also have some spares that I'm going to sell very cheap.

During building. the two boards are soldered together with 3 pins. I cut the leads very short on both boards, and covered one side in hot glue, just to prevent any shorts.

I did add a whole to the bottom board for fixing it into the enclosure, but ended up just hot glueing it in place. The bottom pcb is slightly smaller so the DC jack is partly under the top pcb.
Build Reports / 2 pedal pcb builds
July 30, 2019, 12:27:41 PM
I've recently build two effects using pcbs from for a friend that is playing in the band "Cynic Circus". Not quite my cup of tea, but all of the guys are cool to talk to and super friendly.

First build is a Fortin 33 boost (basically a TC electronic Integrated Pre), the second a Airis Savage Drive. Went together well and I am happy with the results. The 33 has too much treble for his taste, so I'll install an internal trimmer to alter that.


My brothers birthday is coming up in August and he asked me some time ago, if I could build him a headphone amp for his bass.

Do you have any recommendations or is any headphone amplifier doing the trick? Any suggestions are welcome, also strip- or veroboard is fine for me.
A friend asked me, if I heard of the Airis savage drive and if I could possibly built him something along those lines. Obviously he was shooting for a clone, but I have found next to nothing about it online.

It's a 4-knob drive pedal (vol, drive, bass (tight), tone (bite)) using one IC (likely an opamp) and 2 transistors, so I'm thinking it could be some kind of cranked tubescreamer.

Any input? Thanks
Hey guys,

as always, I have a problem with a build. And as with my last view builds, I'll put out a reward for the person that gets me to a working pedal: You get a pcb shipped to your door. The pcb was also included in my BOTY package in the hopes I get it working, so there's that.

So this is my take on the DBA Echo Dream 2. I basically took the schematic that is out there, redrew it in Eagle (it's basically identical) and made a layout. You can find the ,,original" schematic, the redraw and the layout in the zip file linked below. Several people commented on effectslayout and tagboardeffects that they managed to build it on vero, so the schem should be fine and the project doable.

It generally works, all the functions do what they are supposed to except for at long delay times. I get this weird ,,dog farty thing" (© cooder) going on, where the delay chip is motorboating like crazy. It is dependent on the settings of the VCO chip. You can hear the problem in the clip below.

In addition, I got a serious white noise problem, which I didn't notice at first but is very strong at high fuzz and vol settings. (it is possible that it wasn't there in the beginning, but I can't say for sure) could likely be improved by boxing it, but I doubt it would remove it entirely. More likely this is related to the AC ripple I found on the DC supply, which is amplified. More on that in the pdf.

Things I've tried so far:
First, I had fake XR2206 chips, but got decent ones and the oscillator is working (checked via oscilloscope). Also got some original ones from the 70s from a coworker. They are a bit different, but still lots of noise. Overall, I think the chips I've got are decent
I switched out the PT2399 and tried 3 overall, all with similar results
Checked my soldering
Checked component values and schematic on original schem, tagboardeffects and and compared it to mine. Seems to check out.
Checked my actually soldered components for value and orientation.

Brian suggested to increase R28 (on my schematic) to around 270k. Played around with it, but couldn't eliminate the noise.
He also said that R18 makes more sense to go to pin 13 of the Pt2399 instead of the junction of R16/17. Tried that, didn't make much difference.
Also tried the green LED from pin 7 of IC3 (Pt2399) to GND. Didn't do the trick either.

I populated 2 pcbs overall and both behaved similarly.

The voltages were probed with a DMM and an oscilloscope and can be found in detail in the pdf in the zip file along with the schematics, board layout and pics. In short: the DC input is straight DC, but there is a slight AC overlay after the input resistor, when the VCO chip is inserted. The noises are highly dynamic depending on the settings, but generally are related to depth, rate and delay time settings (amplified by fuzz and vol obviously).

Obviously, I could not find the culprit after about 5-6h of debugging. This is were you come in. I would really appreciate it, if someone finds the time to compare schematics, check the layout for obvious design rule mistakes,  give some tipps on where to search, etc.. I'm busy at work again and hardly motivated for this atm to be honest, but having no idea where to start and always ending without any progress doesn't help either.
Imho, it is likely either a systematic error that I did twice and did not see or a design mistake with the pcb layout. This is my first delay and they are tricky to do right. Especially since DBA is known for their notorious out of spec parts and childlike layouts, this is ok for me. It could just well be that the 8Vpp swing of the VCO is coupling into some other nets or similar stuff. I should have given the VCO it's own seperated ground plane to begin with.

ZIP-FILE thanks for looking!

Build Reports / Dreamtime delay
January 20, 2019, 02:16:07 PM
Here's my latest build, madbean' Dreamtime FV-1 delay.
If you haven't built it, I highly recommend it. It's glorious. I never cared for modulation, but the slow tremolo modulation is crazy good.

Random space invader laser engraved onto a tayda powder coated enclosure. I tried some new jacks, which was a huge pain (11mm holes etc.) and the pcb just barely squeezed in despite thin wires.
I also had to make an extra small optical bypass board to fit the 1590a. it's basically a copy of THcustoms mini bypass, using 0603 parts. The difference is only that I have an extra resistor for the indicator LED and one for the optocoupler. I ordered a set of 40 pieces with V-scores from elecrow, but got 120 (they extended my 2x2 design to 5x6, no idea why). this will suffice for eternity.

Open Discussion / NOD - New Oscilloscope Day
November 02, 2018, 02:13:46 PM
So this landed today, going to have a lot of fun:

Got a good deal for it. Unused, original packaging for almost 50% off second hand. the guy who bought it, did not use it after all. Capable of up to 50 MHz (way too much for what we do), 2 channels, can add/substract and so forth, FFT and some other bits and bobs I will hardly use.

The image is a "sine" wave btw. from the output of a XR 2206 function generator chip when underpowered (input voltage to the chip around 6V. should be around 10V)
Build Reports / 3Li-Vibe (EQD The depths)
October 13, 2018, 08:59:53 AM
This is my take on the EQD Depths vibe. Went with the yellow LED/Tayda LDR option after all.
Reverse etched enclosure with envirotex on top as per my etching tutorial (link in my signature, shameless advertisment). I still have a few pcbs to share. if someone is interested, just shoot me a PM.

Build Reports / Helium OD - EQD Palisades
August 27, 2018, 07:52:05 PM
Finally, this is done. After my first prototype failed in December, it took me forever to find time and motivation to give it another go. With the help of reddesert, I got this working the second time around and corrected all the design flaws, the first pcb had. The circuit is stock EQD palisades with minor changes to the power section. I also added onboard optical bypass and made it fit into a 1590BB. The major add-on is that the boost can be used individually from the OD. The DIP switch lets you choose between the independent mode and the stock master bypass switching (OD is master, boost only working when OD is on)

I actually made 3 enclosures for this. The first was riddled with flaws in the layout/labeling, the second one didn't turn out as I wanted it to with the laser engraver, so I etched another one. Since I didn't want to spent too much time on it and the enclosure I had was in bad condition after some experiments from at least 3 years ago, I went for a used look. I dig it.

I have several pcbs to spare, there will be a thread in the BST section sometime this week. thanks for looking.
thank you again reddesert!

Open Discussion / Show some holiday pics!
August 18, 2018, 01:13:28 PM
I thought I change things up a bit. Holiday season is still ongoing, so I thought it would be nice to see what everyone was up to. So, if you like, post some pics of your vacation destination. I bet we will collect some beautiful places from all over the world.

I was hiking a lot the last two weeks, here's a best-of including the "Hohe Tauern" and some parts of Vorarlberg, both in Austria.

More pictures on my blog linked in my profile, if someone is interested.

I finally found some motivation and time to go back to my take on the EQD palisades, which basically is a TS with bells and whistles with subsequent boost. The original unit has it wired with the TS bypass as master bypass, meaning that the boost can only be used when the TS is engaged.
I added optical bypass to the system and while I was working that out, I figured it would be cool to have the boost available seperately. So i added this option via internal DIP5 switching to go between the master bypass and stand-alone configurations.
This is when it turned bad. I did not consider that when I used the stand-alone switching and optical bypass, the circuit would always be in the chain. or at least the part pictured below. BO1 is the TS out/boost in. IC3B is the optocoupler LDR for the optical bypass.

Like this, I always have a path to GND formed by R17||R15+R16 (approx. 9k9). This way I loose a lot of bypass volume as well as volume going into the boost, rendering it useless. With the TS on, everything works fine. I'm not quite sure why I loose that much signal. 10k is quite a lot, especially considering that in bypass IN and OUT are directly connected (checked the resistance). However, I couldn't find any other explanation.

I started tinkering around with R15 (emitter resistor of the collector-circuitry). The transistor is only used as a buffer, the gain is around 0.9 so no drastic changes in voltage, however current is boosted.
I tried going up to 100k and 1M (also adjusted R14 without any changes). While DC voltages are not really affected and change only a bit, I got gated distortion when R15=1M also during bypass.
I started modelling in LTspice and found the same (clipping of emitter voltage and output currents). I also tried varying R16, but had no luck and always lost quite a bit of volume in bypass. Also, increasing R16 would lead to volume loss of the TS, if activated.

I tought about how to actively remove a connection via a switch, but it would have to be added if the TS is activated, but that would require a 3pdt switch, which I wanted to eliminate with optical switching (so it's a nogo for me)! I'm at the point where I think this was not meant to be. I really would have liked the feature, the pcb is basically ready to go (but needed revising, I screwed up the rotaries big time). Do any of you have any input for me? I'm not sure what else I could vary (the transistor does not change a lot since it's a buffer) or how to get this to work out. I still suspect something obvious that I missed...
I'd appreciate any advice or feedback. To make it worth your while, the person getting me on the right track will get a pcb for free once it's done. thanks for looking.

well, at least I learned some LTspice in the progress. 8)
Build Reports / 1590a Wooly Mammoth - Hydrogen Fuzz
November 23, 2017, 07:19:29 PM
Here's my 1590a layout for the Wooly Mammoth. It works great and the layout is shared through my osh park account.

First laser engraved enclosure. It took a lot of tries to get there and I'm still not satisfied. To get down to the metal (or to be able to remove the charred powder coat residues) you need more than one pass with my machine or slow speeds. Both of those options reduce the detail drastically. Lessons learned: 1) Only make simple graphics for the laser. 2) it stinks like hell (also the residue) 3) Envirotex doesn't make the residue look darker. I cleaned the enclosure with isopropanol after engraving and the wet graphic gave a better contrast so I put on Envirotex, but it's not the same effect.

Anyways, the wooly mammoth is a great fuzz, gnarly like a fuzz factory, but without oscillations and knob settings that don't do anything.


Build Reports / Fluorine Fuzz - Clusterfuzz
October 01, 2017, 05:37:58 PM
Hi guys,

when the Clusterfuzz was traced a while back, I had to do a pcb layout for it. I altered it only a little: power section was a bit altered, used a ON-OFF-ON switch for 3 clipping options (any diodes, FET and none) and put the filter switch internal on a DIP. Since the guys from function f(x) were very helpful in verifying the schematic, I hope it's cool to post my build. I play less frequently these days and only play at home, so there's no commercial application of this clone, otherwise I might have gone for the Clusterfuzz Junior (which btw. came out after I finished my design. sure you didn't copy my layout? ;) ) I won't share the layout out of respect for the function crew, although Keefe got the extra one in a trade.

Also in there is the first batch of my optical bypass board. The 1776 board is too big for my taste and the Lumen is out of stock since forever... I managed to flip the connector pads to the main pcb , so there's already a 2.0 design with that corrected as well as discrete CLRs for the optofet-LED and the indicator LED.

Enclosure is reverse etched, spray painted and topped off with epoxy as described in my tutorial. Had to repaint as I wasn't content with revealing the etch and screwed up. It's not perfect, but good enough. Next one will hopefully be done with my laser engraver 8)

It's obviously missing one knob...
Build Reports / Yorkshire Echo
April 26, 2017, 06:57:16 PM
this is the Yorkshire Echo by "juansoloFX", which was part of the pcb bundle I got for the BOTY contest. Thanks to John and Cleggy for their noble donation.

The build itself went together really smooth and it sounds great. I'm very happy with how it turned out, one of my best builds so far, if I might say so myself. The sparkling of the metallic paints goes very well with the space theme. The bezel will get replaced with a round one, as soon as they come in. I used this build to write up my etching tutorial in all detail, if anyone is wondering how I do it. LINK


Hi fellas,

I bought a new guitar a few weeks back and it's my first offset guitar. I was aiming for a Jazzmaster when I found this one locally for a very good price and it pretty much is everything I could have wished for (eg. no tremolo, satin finish neck, not the ugly Fender strat headstock). It only has two minor scratches on the back but otherwise is like new.

It's a Hohner Reno and I have almost no info about other than it was build from 1998 - 2002. Timbo is winding some new pickups for me, which will make this one near to perfect.

When I was home for easter I used my dad's workshop to build myself a multiple guitar stand. Thanks to Brejna for posting his build a while ago. I was hoping to get some dark wood, like walnut, but I couldn't justify paying more for a piece of lumber than what I paid for most of my guitars, so I went with cheap spruce from the hardwarestore instead and gave it an oil finish.

Open Discussion / hohner guitars - any good
March 26, 2017, 11:11:49 AM
There's a jazzmaster/tele mashup Hohner guitar for sale locally - for very little money I have to add - and I was wondering if any of you have experience with their electric guitars. This one is a "Reno" modell, which is not produced any longer apparently, they only have acoustic and headless nowaydays.

I was planing on getting a jazzmaster, but this one is very nice optically and I didn't want a trem anyways. Do you think exchanging the pickups for regular jazzmaster PUs would be hard, ie. especially the cavity for the neck PU?

any advice is appreciated, thanks.
Tech Help - Projects Page / PSU HiFi Amp
November 23, 2016, 04:55:51 PM
You can ignore my request. It's not working yet, but I got a professional to look at the schematic and he confirmed it's good as is. Wasn't sure if he would reply to my email, so I posted it here too. thanks anyways.

I'm not quite sure where to put this, as it's neither Etcher's paradise nor a madbean project, but one of my own.

So, I was hoping to get a second set of eyes on my schematic for the PSU for my HiFi amp. I tested it yesterday and I the rectifiers work. The heater side is ok. But the high voltage side, which is supposed to give 285V DC only gave 40V at first, the second try only gave 10V, and now I'm down to below 1V. The transformer works correctly, I have 250V AC at the input to the PSU and 360V DC at R1, but after R1 the voltage breaks down. Also the primary fuse blew one time, which is weird because I thought the secondary fuse would go first as no heater current is flowing anywhere (wires disconnected/floating). I should mention that I measured every component before soldering and suppliers are trustworthy.

I checked all components, reflowed everything and desoldered C5 and C6 as I suspected those (I had to desolder C5 before which is a pita because of it's size and feared that I overheated it). with only C5 or only C6 the result is the same. Only very little DC voltage after R1. I also checked the datasheets for pinout of the transistors.

I'm suspecting something might be wrong with my schematic to begin with. I'm not entirely sure about the voltage stabilisation parts. The Zener diodes bring the voltage down to 285V and open the MOSFET, which should give also a little below 285V at the output, which is stabilized by C8.

I'm appealing to the electronics gurus (Brian, Jon,...) to have a look, I'd appreciate it. Thanks

Build Reports / Liquid Mercury Phaser
November 21, 2016, 01:15:25 PM
drolo's fantastic Liquid Mercury phaser. Came together nicely without problems and the combination of yellow 5mm LED and 2 tayda LDRs works well and sounds nice. thanks to chuckbuick for the tipp.

I added a Tap sync jack which is basically just synchornising the 5V tap of the tap switch with other taplfo devices (in my case Jon's Cardinal tremolo). I might resolder it to the other lug of the jack. This way, if someone accidentally inserts the 9V supply there, it will only put GND on the 5V pad instead of 9V, which might damage the IC. I need to add the jack to the tremolo to confirm it works, but according to the datasheet it should work.

The etch turned out really well and the epoxy really brings it to live. Lots of detail on this one. First attempt at a multi-coloured theme as well. Lots of work putting tiny pieces of masking tape on there. I didn't have 6 knobs of the same kind, so it's missing one and the waveform selector will also get a white one in the future.