hvdcdc

 

Pedaliera Jakec Metalc

I was making a small tube amp with Domen, having everything bought and all, when he came to me with another proposition: with few friends they have a gig at Jakec Scouts orienteering championship and they would like to get some low cost guitar effects. I've told him that the enclosure is usually one of the costliest parts of a pedal , so we settled to put them all in one enclosure. I had a sturdy powder painted enclosure from a 19' rack switch and we decided to repurpose it for that project. To prove it can stand stress I stepped on the enclosure - it bent, but only because I've already tampered with its frontplate.
Next question was what to put inside - which effects would they like to have. As a center we choose Jed's "Klon" (which I wanted to build for quite a lot of time) - I saw it useful to serve as a buffer and as overdrive. Before we planned to put a boost - I've made some LPB-1s before (with added switch to change it to a "Screeming bird" - it really just takes to switch both coupling caps) and even had a Tube town PCB for it, so thas was another building block. Following the drive we put a chorus, "Angel" from Musikding. This was really all the soundchain we made. We planned to use  my "Reverbula" (look at the previous post here) in amp's effects loop, so it was decided we will find a way to control it from the "multieffect" - for this purpose I planned two "control" switches, where essentially a connection gets to open and close - and that is signalled with a LED. This way you can control a remote device, eg.a switching relay or a device in the effect loop of the amp without the need to run the signal back and forth. Because the switching circuit is fully isolated (jacks are plastic) from other circuit it can even serve as an amp pedal if needed. As for the power I decided to put a linear regulated power supply inside to give it quality power (not some noisy whining switcher).
To tune a guitar I planned an output to jack, which gets switched with a momentary footswitch.
Soldering was quite straightforward. I really enjoyed making the Klone, Jed surely knows how to make PCBs - the pads were the right compromise in size and shape. The only complaint I had there was the quality of solder resist, it scratches off too easily (but that may just be a bad batch). For footswitches I used the PCBs I made myself, and they really make wiring a breeze - if the switch is right. Next time it it probably better to make it with pads for a panel mount version (because PCB versions just differ too much) - the same goes for the switch PCB, also my own design.
For the power supply I used an old halogen lights transformer and led AC to a Tube town linear regulator PCB I had. There was some trouble soldering on the diodes, holes were not big enough, so I had to drill them. Caps I used were straight overkill, but I wanted to make sure 7809 doesn't struggle and the power is clean. Through the construction I changed the plan and so attached this linear regulator PCB near the control assembly - control being only a power and not a signal part of project there was no fear that it would cause problems. I've added an external DC jack so also external effects can get a 9v DC.
In wiring I used shielded cable on some parts which I guessed could be problematic. Wiring is not too tidy, but still decent.
In mains part of the power supply I've put a power switch and a fuse.
In putting the enclosure together I had some trouble, because I forgot to take in account it closes with sliding - jacks were in the way and also teh power switch. I had to nibble away the corner where the out jack was and also turn the power switch horizontally.

It sounds more than amazing. "Klon" really shines. Coupled with my "Yahamaha II" on boost seting it produces serious metalized sounds - and obviously serves well in all the spectre leading to it.

At first there were big ideas to paint the enclosure and add a wooden front, but we ran out of time. So here it is in its crude form.

Philips AG4756W into a guitar amp

 TAKE CARE NOT TO HAVE MAINS ON THE CHASSIS (isolation transformer or polarized plug!!)

schematic not posted due to it being copyrighted (google it!)

Stinko - overdrive/fuzz pedal

I kind of got a feeling I know some shit about electronics ... But then I met Staš. And got some reality check. Kudos, man! He made quite a simple design, using various diodes to clip the signal. Due to simplicity I made it my side project. My 850 overdrive had something wrong inside (and I totally messed it with contact-glueing Qs in the sockets (wiggly contacts)), so I took it apart. This left me with an empty pedal enclosure, all the mechanical work and most of the wiring already done. I have drawn the PCB in DipTrace, but made this design on stripboard, it was just a trial really. And I had some unsettled bussiness with the stripboards from forementioned 850 unit and laso from a small buffer, which turned to be annoyingly noisy. Stripboard is a pretty good thing for not so complicated circuits (when drawing in Diptrace, I didn't even have to use both sides of the board). And for overdrive circuit some noise is not such a problem, so also trace layout was not critical. And it is a challenge, to plan in stripboard environment, not just "connect the dots" as you do in real PCB design. So, it was mostly kind of an exercise in stripboard really. And also a trip to circuit design theory.
There were no special things during soldering, except again - as many times before - I managed to make a part of a board far too crowded (it's a big 1uF caps fault). But hey, so I succeded in making the board really compact (due to previous holes in the enclosure the place to mount the board was limited). To mount the board, which featured only one fixing hole on the side, I used a cabletie fixing bracket together with a spacer and a screw - this way I was able to glue the board in an apropriate place and make it fixed.
Testing the pedal first thing was nothing came out of it - then I noticed the input and output are mixed up. Then I noticed that master pot behaves funny - I have put the ground on pin 3. After resoldering the wires there was the time for the final test.
I am quite satisfied, also with the looks. Sound is majestic, with diodes turned on and off. I am used to tube sound, so it sounds a little "plastic" to me, but is good. I used 1N4148 diodes, maybe with the other ones it would be more natural. The setting I like most is with gain pot practically all the way up, diode clipping off and gutar pots to the max. This leads to very sweet saturation of the transistors (2x BC547C used). Next step would be ordering a PCB for it and making few pieces. But I don't need more than one ...

Calcinator Box

When I quite suceeded with Yahamaha MkII (not only myself, but also other people are generally quite satisfied with the sound and power of the little beast), there soon came the idea to realize the same concept with cheapest possible components - I took an old speaker box, used a cheap speaker form TubeTown and soldered scraped components. The only "new" component in the original design was KEMO module. I have included computer PSU as a primary power source and then used homedesigned DC/DC converter to get needed HV for tube preamp circuit. First design included also "Banana booster circuit" - so conceptually speaking I have cloned the Yahamaha. But there was buzzing, bumps and generally low quality sound. I discovered that:
- computer PSU has too "dirty" DC output for audio use (at least it seemed so)
- my HV DC/DC converter fails to produce steady quality power output (it could be a "scrapped" diode I used or the device is genarelly unsuitable for such use - originally it was intended as a high voltage power source for capacitor filling, eg. for electroshockers and airsoft guns) - it heated very much ... I must build another piece and try it in another piece of Alembic, to see what it is about
- there could be a mistake in preamp circuit - but it was extremely hard to troubleshoot, as I have used two back to back pcbs. So instead I have desoldered useful components and used another preamp Alembic board I have already made for another project
At the time I was quite ready to totally scrap the project and was quite doubtful if I will make another electronic project again - it seemed as waste of time.
************
Second try was with the new Alembic plate, put into the chassis of the computer psu, trafo from halogen lighting (used already in Yahamaha Mk1), PSU on the basis of my tiny regulator PCB and for  HV PSU I gave another try to the forementioned unit. Speaker and Kemo module stayed the same.
I made the tone stack from the other schematic, it seemed it will make the tone commands more responsive.
Result: very low output, a lot of noise, random "hiccups" of the system.
Decision: HV DC needs replacement - if anything, I will use ready made eBay module.
I was on the verge of never touching wires again.
******
Third try came when I needed to order a special trafo, for a friend's effect PSU I was repairing. So I ordered a trafo with a HV secondary. I used rectifyer I have experimentaly made on the stripeboard some time ago. With all the modules connected now consistent sound, but very low volume. What now? Still no real incentive to work on the thing - I don't need it myself, and nobody else said he needs something similar.
******
In the middle time I thought what if the different design of the TS is guilty for such a crappy output - I even thought about mixing up the output and input. So the step before me was to disasemble the preamp. (For the other projects: work on only one plane and not so many pcbs. Don't be stingy about the place. Try the sistem before assembling.) I've removed the preamp and started inspecting it. Gain pot wafer was cracked - but that can't be a reason for the problems. Then I looked at the main board (where the tube socket is). I almost concluded everything was right - and then find it! Oh, cremated snail tail, I have mounted the output decoupling cap on the cathode! (it should be on the plate). I've soldered the new cap in the correct position and assembled the amp. Still quite a lot of mains hum (I have made a perfect star ground, what is the problem? With the master pot lower the hum becomes louder.) But the amp was screaming like a stabbed wild boar, just like it should. Yeah, victory!
I have learned previously on the Yahamaha that the Alembic works better (more of a normal gain) with the AU instead of AX tube, so I have replaced AX with 5814, some USA made. Now I can normally use the master pot ...
++++++
THE VERDICT:
All in all, great distorted sound, superb clean sound (but not with two channels, requires some pot fiddling to change), quite noisy and hum with lower volume. Decent amp.
The insides are messy and probably dangerous. Modules fixed on all the inside planes are a bad idea. Make a central chassis and stick to it. Don't scrimp on the room.
The poweramp has 16V input, so it is capable of providing 40W on 4 ohm speaker. I should try it probably sometime on a bigger cab to see the full power of it - it could be impressive.

SPECS:
- Based on Alembic bass preamp design (Fender preamp), single channel only, 5814 tube
- powerstage Kemo module
- two separate rectifiers, HV and LV
- DC tube heater
- combo design
- low cost design (later just partly)

the box

the box - again

the controls: upper row alembic controls, lower row input jack and master pot, lower power button

preamp tone stack

preamp main board

the messy insides (from the top): speaker output jack, preamp in black PC PSU chassis, poweramp module on the cooler, trafo, both rectifiers

Jupiter - effects PSU - ENG+ SLV

It all started, when Čič came for a visit and I've been boasting with my newly done "sand" effects. And he wanted to try "TT Banana booster" too. So he went to plug the mains adapter to the effect to try it. I saw the mistake at once, but it was too late - he's put the Banana adapter into on of the sand effects, the overdrive. There was a loud pop and distnictive smell of an exploded cap. And surely nothing from the unit anymore. Not only was it the polarity mismatch, there were 14V instead of 9. I knew it was a disaster.
But in the meantime I have learned with the TT Voltage pump failure, that passive parts are not so prone to failure (except the said mispolarization of elko caps) - and there are not much active parts in this circuit; so first I replaced the main cap, which exploded. Then I removed and tested both bigger diodes in the circuit (smaller diodes, which were in the circuit for the purpose of overdrive clipping, werw in such a polace that it looked impossible to be damaged by the failure), but they tested ok, so I soldered them back. The heart of the effect was an opamp, and it was available on eBay, so I oredred the replacement. Put it in - and it worked!
But still, the mechanism of the mistake was bothering me, so I decided to make my own effect PSU with so clearly marked connections to never do such a thing again (?). There were components, which weren't suitable for pure ptp wiring, and I really didn't feel like etching, so I kind of invented my new circuit making way - using rivets, solder lugs and laid wires on a board without copper. And as there is no "signal" wiring, hardly anything would go wrong.

BOM:
- ordinary board for etching, etched all copper off, cut to the size of the chassis
- computer PSU chassis - in the making I experiment with HCl and H3O, to get the "dirt" effect, thus the name of the device
- salvaged central tapped trafo, I think it is 15-0-15VAC, VA unknown, but I have marked it when salvaging to be 30W safe (from the device sticker)
- power common cahtode diode - i like it how simple is it to make a full wave rectification with such diode and central tapped trafo
- 6800uF 63V cap - surely an overkill, but I wanted to be on the safe side + I wanted to try to attach a snap-in cap with my methode - it worked great
- 1uF caps (3x) to paralell the existing elkos - main cap, both exit caps
- two DC/DC buck modules
- LED with corresponding resistor and its socket - when attaching I see it is not a critical thing and solder its ground directly to the chassis
- fan - At first I used it only to cover the hole in the chassis, but then the trafo was getting warm, and it was a nice idea to have the cooling on hand, so I connected it. It is a 24V unit, so it's nicely quiet and slow
- copper net for the chassis openings, fixed with rivets
- fuse bracket and fuse
- wiring - done with ease on the riveted solder lugs

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- zadeva dela - testirano čez noč teklo vse kar imam efektov; morda bi dolgoročno stestiral še pri polni prkilopljenosti z osciloskopom glede vzorca motenj.
- ohišje v "dirt izgledu" - fora s škropljenjem hidroksida z razpršilcem ni dobra, pravi bruniran look dobim le, če s hidroksidom polivam (zadnja obdelana stranica) - ampak še vedno izgleda kul.
- hcl+h2o2 skorajda v trenutku očistita ploščo bakra - je pa že majhna sled lepila dovolj, da baker ostane (morda bi bil to še boljši način za jedkanje plošč od Fe3Cl - ampak jedkanje plošč ni prav aktualno trenutno) - drugačew so te plošče krasne za izdelavo, in po mojem izračunu cenejše od fiberboarda s tt; moral pa bi najti še nadaljnjo alternativo, ki je verjetno še cenejša (1,6 ploščo, ki je neprevodna, nestatična in dovolj trdna)
- clip-on brusilkica za dremelj se res dobro obnese - noro dobro; kako hitro se da delat!
- design z rivets & solderlugs je sicer malce zamuden, ampak izjemno estetski in uporaben. Manjše rivets komajda pridejo skoz plato; za manjše rivets solderlug obrnem naokrog in dam rivet skozi luknjo za žico, žico pa skozi luknjo za rivets- pritrrditev dc/dc modulov s trdimi napajalnimi žicami se odlično obnese
- najprej delam GND povrh in DC spodaj, ampak je logično in bolje, da gre dc po vrhu in GND spodaj (torej ob ohišju) - morda bi za naprej veljalo DC še izolirati (heatshrink)
- vse gre tekoče in brez posebnih problemov
- trafo se greje (kasnejša inštalacija ventilatorja to vse zrihta)
- v noči dam mains na output od modula in ga skurim, jao - nov modul (ampak, saj so poceni); me pa šele ta incidemt opozori, da GND ni potegnjen na ohišje - naredim tako, da je (kot v profi inštalacijah, haha) to storjeno preko pritrdilnega vijaka ploščice) - je pa fajn, ker vidim, da menjava modula poteka hitro in gladko
- voiltažo 9 modula dam njaprej na 9,4V, ampak jo potem dam kar na 9,0, ker verjetno tolerirajo efekti tudi malo premalo (če bi že glih blo)
- ko se odločim dati outpute na stran pri stikalu, je ledica prekratka; najprej jo pustim kar noter, nato pa potegnem do mains inputa - ledice imajo, ker niso kritične v sistemu, vedno lahko gnd kar z ohišja ...
- ventilator - 24V ventilator krasno dela na 12VDC, ravno prav je upočasnjen; noter ga dam, da zapre luknjo v ohišju, ampak potem krasno funkcionira
- uf, kako je fajn pravzaprav delat s central tap trafotom, za full wave ne rabš drucga kot eno common cathode diodo, pa še trafo je ozemljen.
- s solder lugsi se res elegantno in hitro cini, potem ko je reč zvrtana in pritrjena - se obnese! - tudi resoldering je hiter in brez problema
- dober je ta koncept, da je vse na plošči in je tako cinjenja ohišje - notranjsot minimalno
- priotrditev izhodnih kablov s penico je fajn

Skupaj gledano, lepo čist urejen projektr brez komplikacij

universal tube preamp PCB - custom PCBs no. 2

When I was looking at different schematics of the tube amps, I noticed there are not much variations in the design, so I thought to myself, why not design a PCB which suits them all. This is the result. I already used two of the boards and they are quite well manageable. Lower portion of the board, made for the tone stack, proved incredibly practical, but requires some planning ahead. There is a mistake with the orientation of the main power cap. It would have been better if the DC and GND rails would be just opposite - DC on top and GND down there - so GND is closer to tone stack and the jacks. The holes for the screws should be closer to the tube socket. Maybe it would be better to make seprate board for around the socket (with  solder lugs - so with a hole and screw places, also for the shield) and separate for the tone stack.

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write me for the gerber files or made boards