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

linear PSU - custom made PCBs no. 1

When I started working with electronics, there was a nice little PCB in TT shop, which handled the power supply for the TT pedals, made with 7812 linear regulator. But later I needed more than 1A, which is the limit for that IC, so I started looking around. When working on G5 project, I came across Micrel 29502, a LDO linear regulator with very simple other component requrements, knowing also about 1084 and Lm317 ICs. I wanted to make a simple PCB, which will be useful for all those ICs. Work was much easier, becouse with PSU design there is not so much to worry about the parasitics and similar. Still it was quite a challenge to design it in a way suitable for all different pinouts (roughly speaking, 29502 and 78xx class are compatible, and 317 and 108x are the same) - now the pcb is designed in such a way that first two go on one side, and second two on the other - with all other components of course. The other pin alignment task is made through "the cross" - how to connect is figured out from the application section of the IC datasheet. Both axial and SMD diodes can be used. The design lacks the fixing holes (I counted PCB to be fixed through the IC tab and main cap) - if there is a new version, I am probably including them.

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write me for the gerber files or made boards

Jackee - TT Peppershredder - SLV

Glede na to, da je proces trajal toliko časa, je dejansko težko zajeti celotno zadevo. V tem času sem se veliko naučil, končni rezultat pa je presenetljivo dober. Zvok je res vrhunski, bruma prajktično ni (v primerjavi z ppsh1 je ogromen napredek). Strošek je bil kar precejšen, je pa res, da sem nabavil še veliko dodatnega materiala (ki mi ga potem zdaj ni treba kupovat).

a) zvok

Zadeva ima soliden overdrive, žal mu pač kot analognemu efektu jaskost z zmanjševanjem gaina/drivea zelo pada; zato je v začetku potem zelo opazen pok Dcja pri preklopu. Glede zvoka drugače dejansko ni pritožb, efekt je solidno tih, tudi pri največjem ojačanju ne daje od sebe nič hrupa, kot da bi bil „tovarniški“

b) uporabnost

Ne vem, kako bo efekt dolgoročno deloval, to bo pokazal čas (verjetno bi znali prit na dan kakšni problematični loti ali poškodovane komponente. Drugače pa je je efekt neuničljiv.

c) izdelava

Proces je trajal res dolgo, verjetno kar ene pol leta, je pa res, da sem zdaj enoto osvojil in posvojil, v procesu sem se veliko naučil. Načrtoval sem zadevo prtecej preveč škrto s prostorom - in tudi preveč natlačeno. Lampama sem dal precej preveč prostora, seveda pa ne morem vedeti, koliko je lahko medsebojnih motenj. A če sklepam po svojem compressorju za bas (kjer je lampa „v srcu“ vezij), to ni tak problem - in bi lahko prihranil ogromno prostora, če bi načrtoval ploščo sredi med lampama. Ali če bi dal lampi zadaj ven (kot sem pač šele zdaj dobil idejo). Velik delež k gužvi prispeva tudi „mode switch“, ki je bil dejansko čisto nepotrebna komplikacija, popolnoma bi zadostoval TS bypass switch. Gneča žičk ob lampah je neznosna! Problem zase je dolžina napeljave - zaradi manj motenj sem jo skušal držati čimkrajšo, a je potem pač tako, da je silno težko bilo delati. Za naprej so verjetno najboljša rešitev konektorji – ali pa „solid“ žica, kjer se izdela vse skupaj in potem vstavi. Ploščici – moji prvi za rabo – sta uspeli kar lepo, edino po izdelavi ju nisem obrusil, kar je verjetno povzročilo slabše prijemanje cina. Tega je bila kriva tudi prenizka temperatura spajkalnika; mora kar imeti 300°C, za odspajkanje in masivne komponente pa raje še več. Zato sem – ker je bil kontakt spajkalnika s komponentami predolg – uničil verjetno kar nekaj komponent in zadeva najprej ni delala. Za naprej velja, da raje malo daljše nogice pustit kot pa cvret komponente. Problem zase je napajalnik TT, ki je usmerjen – in je bila zato napetost na enoti prenizka, morda je bilo celo zato noter „rožljanje“ diod. Za prihodnje je vprašanje, če je sploh še smiselno naročati napajalnike, raje ga naredim sam, po vzoru Moosepotamusovega za Alembic, pa še napetost lahko reguliram (morda bi celo vgradil ločeno regulacijo za heater in pa plato). Pri načrtovanju sem včaish malo pretiraval, kot da bi načrtoval serijsko proizvodnjo oz. imel malo problematičen workflow – v naprej velja pač najprej naročit komponente, potem šele načrtovat notranjost in layout plošče. Če povzamem, pa je izdelava lična in zelo privlačna, sploh bakrene rešetke (še vključi). 

I have included some data from TT page, which is not available anymore (?), so instead of linking I loaded my saved files.

Yabox - former Yamaha guts in new box

I previously wrote about the Yamaha 10W amp I fried, and about trying to fix it. When I asked a friend - electrical engineer- what could go wrong if I have shorted the output, he told me it could be generally 3 thinghs: driver Q, main Q or power resistor (that is also a problem with some other project of mine). In problems at Yahamaha II I learned, that passives can hardly get damaged and that they're actives which fail usualy, so I was brave enough to buy both ICs which are present on the board. As I saw a lot of ceramic caps on the pcb, I also said that I would try and change them to polies, as I had scrapped a lot of them. When plugged in the amp was working. There was an old speaker box in my basement. I made a cut in the back panel and painted it. Then I made chassis for the board from my scrap metal. PCB is pretty narrow, so there was not much need for more than a faceplate - I took an old sign plate (later I found out the material is too thin). I drilled the needed holes (and made some stupid mistakes in process), found and connected power switch and reconnected the AC wiring. I used pcb and speaker from the original Yamaha amp. When connected, the result was quite impressive. Specially distorted sound is fantastic.

When revising my work, I figured out:
- faceplate is too loosely attached, so the air is "leaking" through, making annoying sounds and deteriorating the sound
- the vibrations in the box could break the poweramp IC, which is on the basc part of the chassis
- the device is quite heavy, so the screws for the handle need some help

So I later attached faceplate to the backplate with multiple screws and used some foam tape to seal the faceplate, and made a simple bracket to fix the back chassis, to keep it from vibrating. And drilled a piece of metal to support the handles from the inside.

Rich sand sounds.

simple hacks and workarounds - ALWAYS IN PROGRESS ;)

1) how to atach a LED diode to the chassis? there are many solutions, with its good and bad sides ...
- on many older and cheaper electronics the led light is simply glued in the hole with the thermoplastic glue - the problem is to remove  the led from the hole without destroying it ... another problem is that LED has some volume and if put in thinner faceplate it tends to stick out of it so ugly. For that purpose I use an ordinary nut (for a d5mm LED M6 nut), glued to the faceplate (for the "ordinary" look on the inside, for the more "rock" look on the outside). The threads hold the LED just right in its place, that it doesn't slip out and is pretty easy to remove.

2) pcb rivets - they offer so many advantages in pcb design:
- you can mount components on both sides of the board with ease
- the components are much easier to remove (it is said that it is practically impossible to remove the soldered noval socket from the board without damaging both of them, I did it easily) - this is specially useful for the wires soldered to the board
- the components are soldered on much bigger area, so the joint is better, electrically and physically

The main disadvantage is price, they tend to be really expensive. If I could find a cheaper supllier, I would be very happy ...
Another one is additional work needed - to put the rivets in holes and fix them (I do it with the hammer and a center punch on metal surface)

3) use solid wire to secure jacks and switches having solder lugs to PCB (went great with my custom pcbs)

TT Banana booster

Banana booster is one of the oldest TT DiY projects and it always fascinated me how simple it is. I must have drawn tens of different layouts for it. In preparations for my bigger (half finished) project G5, and waiting for some "sand" kits to arrive I took a cardboard box, an obsolete noval socket and looked for the parts in my drawers. 2 caps and 7 resistors in pretty common values - check! TT LoV PSU from past projects - check (and I had to add two monster caps instead of originals   ) jacks, knob, led, switch, wires ... Not a thing someone wouldn't have as remains ... Chassis, pot - missing > ordered (can wait). The model in cardboard was made in approx. 2 hours. With direct PTP approach - my way: messy as hell and hard to troubleshoot, also prone to parasitics, but small. When the chassis arrives there is a complication, because the insides are smaller than thought. When plugged in, sound is great, practically no noise. This kind of tube booster on the begining of sound chain is practicaly all the tube in it you need ...
But I am left wandering: what does the "kick" option in the kit add ... A transistor (as in Vanilla)? Later I see it's a switchable cathode cap - and I am kind of dissapointed; also in me, for not getting the idea myself ... I am thinking of putting it in this project, but where ... Maybe.

Design:
- tube socket is mounted with two L brackets - belton noval chassis sockets are made for this mounting (and can prove a difficulty to mount from inside the chassis >> make hole a square OR use nuts as spacers)
- led is an oval sort (3,7x3mm) and so it is mounted noly by frocibly pushing in 3,5 drilled hole - not too cosmetic, but it works
- caps are (again haha) overkill,  this time in the voltage, but I had those home
- DC input terminal is turned to the middle of PCB (so it can be directly at the chassis)
- as the later 14V power adapters from TT are DC, the diodes are replaced with corresponding jumpers
- on the other side of PSU PCB I used an old pin terminal (neither currents nor voltages are too high for that) - and the distance is just right
- oh, and the second overkill: wires - i used the remains of silicon ones from G5 project >> better use solid 0,14mmm, soldering those to the tiny connectors is nuisance
- 1uF cap goes directly from socket to pot
- all ground is wired directly to the input jack; I tested with multimeter, that contact with chassis is made there

My G5

Two years ago I came across G5 project. At the time it seemed to me like a rocket science, i still had complications with the hum and noise in TT pedals.
But then my friend, who is dedicated guitar player and tube fan, announced he is getting married - and I made a promise I would make him an amp head for his wedding gift. Approximately a year ago I had some time and made a plan to the extent that I did all the needed shopping. From the very beginning I had certain mods in plan, so I didn't order the "all inclusive" kit, but bought parts separately.
Almost a year passed before i was able to dedicate myself to the project again. So the friend is already married - but with all the parts there was no turning back!
So after quite some hours of work here is my rendition of G5 amp.
With following mods /variants)
- DC heater
- LineOut (as in version 1)
- Send/return is omitted but possible to add, as there is a jumpered conector on the preamp pcb
- Q regulated bias (Dymo mod) - with typ3055 transistor
- swithable "safety resistor" on the output of OT

DC heater was qite a task, since EL34 draws 1,5A when hot and even more when cold. First I planned to use a MIC295092 circuit, but then a friend gave me a cheap DC/DC stepdown module with 3A threshold, which is quite enough (and there is really no need for perfectly clear DC for the heaters, just not grossly noisy), and I hooked it after a gretz bridge and a prominent 10uF cap - I was afraid there would be problems, because the bought mains transformer had 8VAC output (I tried to plan voltages as close to the needed as possible to avoid too much of a dissipation of then planned linear regulator - so I used low dropout diodes on the bridge and planned to use low dropout regulator -well, now I know I shouldn't be so afraid of an IC warming up a little (or 100°C), and there are also heatsinks ... So, quite a lot of complication for nothing ... well, nothing, I learned: a little overvoltage is easier to regulate and cool down than to get good linear out of too small of a boundary. Well, when all hooked up, the DC supply is quiet and nice. On precisely 6,3VDC, grounded from the module to star ground. My headphones hear nothing. Ozsi shows some noise on micro scale. So, I can call it sucess. For the next time: plan power transformer heater secundary with few volts overhead so there would be no need for monster filter cap and low dropout bridge diodes.
To be able to plan the "guts" without drilling (and ruining with mistakes) the chassis, I made the model from the cardboard box. It proved really fantastic, much more sturdy than I thought it to be. Before that I made all plans for my projects in Corel Draw, and it was a time consuming work, but still prone to mistakes - it was much easier to work with real components - and much more fun. So all the wires, all the "modules" and parts could be positioned and dimensioned correctly (but still I made some stupid things haha).
The biggest issue was preamp board etching and drilling - the later much more. I don't know, is it me, are the late hours in which I was working on the project or it is a common thing, but almost no 1mm hole was on the right place. For the etching I used a lack paper (from net from China) and pressed toner on the copper board with the help of salvaged copier fuser (I don't like to ruin my laminator; this was a separate project of mine which turned worse than I thought - on a salvaged fuser I mounted a 250°C thermostat instead of thermal fuse, but I have problems with the wheels assembly, not sure why. Still, it works quite good) . To be on the safe side with the crappy preamp board I tinned all the traces. I also put rivets in mounting holes for tube socket (so it was easily soldered on the "wrong" side) and also in all wire terminations (to be able to remove them any time without ruining the traces). Populating the board was easy work then. I have put also complete tone stack on the board - as I always leave the notches on the pots I don't beleive there is much damage done to the board through pot fiddling. But the tube socket it the other question - there is no chance you would put in or out the tube without holding the board - so for the next time: build point to point (preamp is really straightforward easy), or at least plan screw attachment holes very close to the socket.
I was afraid, if the biasing board would really work (I am not used to work with sand), but it was OK. Still it would be much simpler to use a 250kLin more powerful pot. But, as it works, this design could be used on all the other future projects ...

"Switchable safety resistor" was part of the plan the whole time, the reasons are two:
1) Filip is my friend. I wouldn't like him to ruin his amp's OT by not plugging in the speaker
2) G5 is a weak amp - to get the real "sound" it should be connected through "line out" to a more powerful power amp - and then it is a nuisance to plug in its own speaker
So I bought a 50W 7,9ohm power resistor and mounted it on a switchable jack for the speaker out. I was afraid if I did all correctly, because OT's are not cheap stuff. But, it works.

I have managed to wire the line out pot in opposite (how?!?), but as it works, I will not resolder it.
Final result?
The first thing, looks are amazing (let us ignore my ugly handwriting, OK?). Hammond made a fenomenal job with the chassis cover, and you don't need a lot to make the amp look like a boutique hi-fi. The "G5" letters are from automobile part of harware store, and look just right. I have put the main power led on the top of the chassis to make leads as short as possible (from the DC heater supply), but with the amber led the looks are fenomenal - amber glow of led mixes with amber glow of power tube and it's just - magical ... Power resistor on the back protrudes from the main shape, but not too much, and looks like some alien "super powered" add-on. There are some drill holes which I made out of stupidity and sloppyness, but don't bother too much.

The guts look messy as hell, after I made it I was quite ashamed of it, compared with neat insides of other amps on the net. But still, everything is on right place and there is claritiy of logic; the sonic results correspond with careful design (perfected star ground near the input jack, safety distances between modules, generous separation of signal, power and GND wiring). For later projects I work more with solid wire to ensure more neat wiring. Oh, I used speaker wire for heater supply - I am a serial overkiller, if you haven't noticed yet.
The other overkill are the capacitors: I parelelled practically all power caps with lower poly ones: for the power tube, by the OT, and used only 10uF poly for the preamp ... Probably this is far too much, but I don't know a reason this could be wrong.
You probably noticed, I am a "chocholate freak" (at least in Slovene electricians call those plastic enclosed screw terminals chocholates) - they are probably not very good in the signal path, but with high voltages in power sections they are perfect for modular building. And there are allways few there in your box. Around the OT I used them to enable easier switching between primary and secundary windings - if they prove unreliable through time, they still can be replaced with terminals. But, jacks are also just slide contacts, right? In power section use of "chocs" is logical - why solder (and then desolder, and solder ...), when screw terminals work just fine. The whole rectifier board is based on those chocs, because I planned to etch it, but then didn't feel like it. Later I will use cancaps with solder lugs attached to the chassis and also the bridge - this board is a disgrace and is bulky (and don't ask me how to remove it from the chassis). You can see the power supply is not on one place, but near the corresponding modules: a)rectifier with reservoir cap b) power tube caps (with all the psu resistors) c) preamp cap d)OT cap (parelell to reservoir cap) e) caps of DC heater. Behind is the logic, that caps must be close to parts they supply (to "embrace" the circuit).

Sound:
I hoped for a low noise build, but such ... It is a success. There is no hum, no mains, on both knobs at full there is some static, but, it's on the level of "out of shop" amps ...
At full gain overdrive is magnificent, with correct adjustments on the guitar you can get crazy things. And if you also add banana booster in the sound chain ... Sweet!
Clean sound is nice, but weak. Real tubey sound, but not at band practice volume. 25W max dissipation SE design has it's toll. Here comes handy line out jack, and with the connection of external power amp you can hear the sweetness. Tone stack is less effective than expected, with the "sweep " switch practically unnoticeable (is there some mistake?)
next builds (if when and why - takes lot of money and time):
- preamp in point to point arhitecture (not Fender like, but "real" ptp, with components directly on the socket, and supported with singular terminals on other side - also the TS in PTP >> on pot lugs
- rectifier: "cube" bridge and can capactior attached to the chassis
- 9VAC secondary for the heater (to use normal diodes), maybe separate DC/DC modules for preamp and power sections
- connections made with solid hookup wire for neater (and less parasitic /capacitance) problematic guts
- bias board made on protoboard
- power psu made on terminals
- OT connections made on terminals
- use rackomount chassis with internal brackets - not so beautiful, but significantly cheaper, makes the amp more useful
>>forgot:
- I used a custom made power transformer - toroid, which was 28€, much less than original
- regarding the sound: I suspect the treble is some way attenuated, but this could be also due to the fact I tested the amp mostly on my bass cab
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and now the soundfile - not edited, recorded with a phone; with variable degrees of different gain, master and tone stack settings ...
https://dl.dropboxusercontent.com/u/7791647/My%20recording%20%2313.wav

shema: http://www.projetg5.com/Projets/G5/G5V3/G5V3officielle.pdf