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Topics - polo16mi

Preamps and Effects / Spring reverb tank info
August 30, 2012, 11:25:59 AM
Researching about make myself a spring reverb tank, founded this site with info.

Posted here, but not sure if it is right place. please move it if not.
Hi there:

I want to modify a sansamps gt2 clone tonestack. It has a baxandall tone control with 2 bands and i want modify it to 3 bands.

I thinking take a look to some commercial solid state amps, to see how they implemented it.

Somebody of you remember some model like that?
Hi there:

I already mounted an amp, using a SansAmp clone as a preamp and a LM3886 as an amp.

I very happy with results. I sound very good.

Im unhappy just with the fact that the bass tone control dont change so much the sound.

It has a baxandall tone control as you can see in the pdf file that attached.

I wondering which mod can i make for obtain better response on bass control variation?
Hi there:

I made an amp using a sansamp clone as preamp, and LM3886 Chipamp as amp. It is wired straight the output of sansamp to LM3886 input.

I wondering how can i add an CD/MP3 input as, say, MG15CD, so i can jam a backing track.

My first idea, is wire a jack in parallel with sansamp output, directly to poweramp input, join Left and Right channels to + signal input, and gnd-gnd. Not sure if any trouble in that way.  :-\

I see MG15CDR squematics, and it use a 10uf cap in series with a 10K resistor from preamp output, and a 3.3K from cd input. Joins resistors terminals and go to the power amp input.

Why they use that resistors? Not sure if it is for protection purpose or impedance dealing.

Can any help?
Hi there:

Has been long time since last post:

Here some pict for my last proyect.

I had inspired in a JCM900 1x12, and make my self version.

It has a 50W chipamp, and kind of GT2 clone as a preamp.  Its sound good enough to my, and already tested in a coupled of jam sessions last night.

I need some suggestion about how to record some samples to load here....

I returned back to work in my last project.

I trying to mount kinda of a JCM900 1x12 combo clone (at least, its format).

Using a gainclone as amp, and a Sansamps as preamp.

Worked fine assembled on the table, but still rest to resolve some "detailed engineering", and mount all together inside cabinet, and that work well for some jam in a bar.

First one, mounted all stuff, and potentiometers cable are soldered straight to SanAmpClone PCB. Tracks are very thin, so soon they lifted up as moved the pcb to test it. Using dead pc power supply cables. Very nice cables, several colors to choose, as you can see in pictures.

What work best? Do a simple pcb to mount potentiometers, and wire that pcb to sansamps pcb? O put some terminal/screw or something like that in sa pcb?

Second one: SansClone works with 9V. For try it used a cheap multiple voltage supply, but now, i need to resolve its feed inside of cabinet.
Ideas are: use another trafo with its rectifiers and 7809 (JM says dont like it, in addition, i think that will need to couple its 4,5v with 0V of LM3886): Or use zeners. I need to feed it with 34V and put out of them 9V, with i guess about 200ma for feed SansAmp. Calculed a 25V of drop with 200ma. Ill need to use a 120 ohms resistor with 5W of power disipation? Am i right?

Here a couple of picture....

Can you suggest some ideas? Beside, feel free to improve my english  :-[

The Newcomer's Forum / Gainclone 3886, Vcc- fuse blows
November 10, 2011, 07:28:51 PM
Hi there:

Had been a long time since my last post.  We survived Puyehue´s eruption, and my new house building, so here i m again.

Now i return to guitar amp construction hobby, cause i still playing with my ruby version, and last week try to play with other guy´s, equiped them with a Roland 30 cube & Gibson SG  8|, other guy with a Traynor 20 and a Squier, and i with my old Faim and Ruby  :grr.  It is like trying to scream at front of Boca Juniors hooligans. I cant ear my self nothing at all.

So now i working in a Gainclone like

I mounted a power supply with a 24/24 6A trafo, rectifiers, 2 4700uF electrolitical per rail, so i have +34.9V,0V,-34.9V.
I put a fuse between each rail and V+ and V- of the gainclone, so goes like this:

---Vcc+ --> Fuse----Vcc+(gainclone)

---Vcc- --> Fuse----Vcc-(gainclone)

I switch on, and fuse at Vcc- blows.

I checked disconecting the gainclone, new fuse, at -34.9V ok. No blows.

I checked the pcb and founded a short between Vcc- and Pin11 (pin 11 says datasheet that not conected, anyway, i removed the short). Regard of this, every looks ok.

The tab of LM3886 are insulated from heatshinker with a mika film and a plastic ring in the screw. I measured continuity between the tap and heatshinker, and read something, and quickly goes infinit.

Can you help with some tips?
The Newcomer's Forum / Best home made DIY PCB method?
February 08, 2011, 01:55:47 PM
Hi folks:

I had been making some pcbs, for ruby and for a bluesbraker.  In past, i had been etched other PCB in my secondary school (around 90's) , i.e. for a laboratory power supply, really, no big deal, big traces, no very difficult at all. I used to make it with a couple of indeleble marker´s (a thin and a thick one). Then, it goes to Perchloride ferric bath.

Lately, when i mess around with ss-amp hobby, start using the "print with a laser printer, transfer to the pertinax with an iron and put the pcb in to Perchloride" method.

Its looks easy and better than pencils for difficult designs, but i can´t find the optimun combination between:

- wich paper best to use?: i tried regular bond paper and illustration coated paper, always printer with HP Laser. Bond worked acceptable, but not good enough, cause some track looks slighly corroded. Illustration coated paper didn´t work well with the printer. Looks like toner cant fix properly to the paper and see some "ghost" appear on the sheet.

- I use an iron of 1200W. Wich better? The hottest temperature that it can reach? I´m affraid that if too much hot, take off/detach copper of the pcb. How much temperature? How much time?

Any know a cheap, home made, method better than mine?

Can any name his own method that use? No industrial, of course.

Not sure if it is the right place of the forum to put it post. Please move it if not.
The Newcomer's Forum / Question about rele
April 26, 2010, 05:52:13 PM
Hi guys:

Its a long time since my last post. Im had been working a lot. (thanks god).

I maked a TDA2005 amp, and used a marshall bluesbkr clone as a preamp. Its sounded very nice for my, but i made the preamp with a universal pcb, so it isnt  very reliable, so.. sometimes worked, sometimes not.

I have a radio program too, where we and our guests, just play a backgrond track, and just jam over it. We use a Marshall VS102 of my partner, conected to the studio console. It sound very good  <3)

Cause of the sound of it, i get the plans of it from, and begin to study it.  It has 2 channels.It has one clean, and one overdrive channel, each one selectable, and the overdrive is switcheable beetween OD1, and OD2.  Kind of two differents overdrives. I thinking (and planning) to make some kind of clone of it, but, its has some ICs that i cant get easely. It is the M5201 wich are a dual omp amp selectable by tension. It use too a 4316, wich are apparently a cuadruple switch.  They use those IC, for switch beetween differents chanels setup. i.e, in the overdrive first opamp chanel, they use the 4316 for setup differents gains loop for OD1, and for OD2.  Another case of use of the M5201 is when they select clean or overdrive chanell.

I wondering if its razonable to use some relays and simple TL07XX instead of them, properly wired. Electrically i think that is no difficult to make that changes, but since of point of view of the signal quality or better to say, sound quality, i afraid if it will causes no troubles like pops sounds when use the relays for change the channels.

Please, can you say something about this?

Thanks a lot for your help.
PD: I making a box for all the stuff. When i finish it i ll post some pictures, im promises.

The Newcomer's Forum / Preamp circuit wanted
February 01, 2010, 05:17:23 PM
Hi everybody there:

Since last year that i don´t write any post, so happy new year. I back again, and have some to tell you.

Following my "roadmap", i already maded a Ruby with a tone control big muffed style with pretty success. (Coihue Micro).  I had learned that for my, about 50% of the sound is the speaker.  After, i used the ruby like a "test amp stage" for severals pre. I tryed ROG thor, thunderchief, and tonemender, with some succes just with the tonecontrol. The others, well,  :grr  Reading the forum, that circuits, no work at all, so, i put them a side.

Then, i made a TDA2005 datasheet BRIDGE power stage using a power supply maded with a rectifier bridge and a dicroic feed tranny. (about 50VA)  It work pretty nice, using just a buffer stage with a MPF102 direct from the guitar, and i sound very nice, clean.  Regrettably, in that time just have a cheap 6" speaker, so it sound like sh... when i hit hard the strings.

Since about two weeks, i purchased a 12" - 8 ohms speakers at J M FAHEY and with it, is a peace of cake <3).

I used like preamp, then, a Marshall BluesBraker clon, mounted over a perfboard, and it works no so good, (when it worked).

I planing to etch a board of that Marshall BluesBraker, then see what append.  I looking for a versatile circuit of a preamp, that gimme a "marshall-like" sound, (going from nice clean, to medium distortion, Hells Bells?, you know?) with a good tone control, and foot swicheable distortion, and a effect loop.

I founded the circuit of a Trace Elliot SuperTramp, and looks pretty nice, but, no idea that what FET them uses...

Any suggestion about a circuit?

Founded a good pre, next step is make a TDA7294 power stage.

The Newcomer's Forum / What about this preamp?
September 16, 2009, 10:41:53 AM

I looking for a nice preamp for my future amp and founded this....

May ask what our masters think about it?

EDIT: Done. Loaded the jpg.
The Newcomer's Forum / Dicroic Lamp Trann for TDA
September 12, 2009, 12:29:08 PM
Hi there:

Some question stickin in my mind.

I had been looking for a cheap tranny for a simple power stage made with a TDA2005 like its datasheet, bridged version, and i wonder if a can use a transformer that i seed used for feed dicroic lamp, cause....

a) a 220Vca-12Vca 5 amp transformer worth around $70  ( +- 17 u$s)  (electronic stores)
b) a 220Vca-12Vca  50W for dicroic lamp sales around of ¡¡$16!!  ( +- 4 u$s )  (electric stores)

I think that the fact that factories make hughes mount of dicroic lamp transformer they are very cheap.

Is 50W (around 4.16 A) enough for a TDA2005 bridged?

thakns guy for your pacient answerings


The Newcomer's Forum / Why they dont use tweeters?
September 07, 2009, 10:48:31 AM
Hi everobody:

Im just curious about something:

Why regular SS Guitar amp (at least that i see here, in Argentine) dont use tweeters?

Any idea?


I had been studing the TDA7294 datasheet and noted something that im in doubt.

At the page 6/13 they says there that the RMS Continuos Output Power is:

Vs=+/-35V,  RL=8 ohms   60 W min   70 W typical.
Vs=+/-31V,  RL=6 ohms   60 W min   70 W typical.
Vs=+/-29V,  RL=4 ohms   60 W min   70 W typical.

I dont understand fully something.  I have a 24+24/6A  tranny, and maked a power source with a rectifier bridge with 4 diodes (6A60), a 100nf ceramic cap in parallel with each of them, 4 electrolitic cap (4700/63v each, 3 for rail), and 2 100nf poliester cap (one for rail).   I guess that i ll get around 34V CC for each rail.  If i use this power source, i wont use a 4 ohms speaker with this tension?

I hope expresed clearly enough.... :-\

The Newcomer's Forum / Coihue Micro
August 21, 2009, 05:46:09 PM

Finally i putted all the stuff intha box, and called it as  "Coihue Micro" (aka Ruby with MS-2 tone control "tweaked" in cheap proto wooden box)

With yours......Coihue MIcro.

coming soon  some mp3 and  PCBs in dwg,
The Newcomer's Forum / Speaker impedance question
August 20, 2009, 09:42:26 AM
If you may have to pick a speaker, what incline your decision to an impedance or other? 

Wich is best for what?   4 or 8 ?   I mean.... imagine that you have  100W over 4 ohms and 100W over 8 ohms?

I guess that the same power over 4 ohms push the amp output twice the current that 8 ohms, but if you get a side this, how affect your choice at the sound?  ???

The Newcomer's Forum / Mono preamp supplying two amps
August 20, 2009, 09:29:35 AM

I have a question sticking in my head, and i ll  shoot it here, just for curious....

If i make two amp stage, identical, mono, can i supply them with just one preamp?

Like this...


The Newcomer's Forum / Speakers questions
August 11, 2009, 11:44:20 AM
I readed the excelent job at the Loudspeakers and Loudness thread of  Teemuk and  J M Fahey !  :tu:

I have a couple of doubt and question about the stuff.

I here in the south, wich are the best chances that have if i looking for decent speaker for any SS amp? 

I researching where is the garbage site in Villa La Angostura, to look for some junk usefull, as suggested JM , looking for old car or radio speakers for equipe my version of ruby.

I had been in a little electronic store here, and the attendant showme the "A" speaker and the "B" and thats all that they have! I requested about the frecuency response, but....  ??? 

Ok, no good stores at the hand, so, second try, google...

I downloaded the Jahro catalog at and see a couple of that maybe are useable for guitar amp, but how about the curves? If i call for it to them? Not breakballs for them to give that info for a couple of models? The same about  If i contact them?

And a last question....

If you have a ready to work power amp, lets say a TDA7294 o LM3886 based amp, for example, whats best for it? Imagine that you´ll do a combo, and the options for speakers are:

A -   2 x 12"
B -   4 x 10"
B -   4 x 8"

Wich are best for?  ???
The Newcomer's Forum / Gonna make a guitar chipamp
July 17, 2009, 10:06:34 PM
HI there:

I studing and reading this magnifical forum.  I downloaded the teemu´s book, and i reading it too. Great job, congratulations! It´s excelent stuff, but a little dificult to me in some´s point´s to understand, so... i chew a little of it every time i got a break. :-[

I wanted to purchase a guitar amp, but i change my mind a little and here a couple of razons.

- I´m an technic electronic from the secondary college. Here i was studing in the ENET 2, from Neuquen, and i had graduated in 1992. I havent a lot of experience in audio but i work fixing computers and his related stuff. I had been working since that time in them. I love that kind of junk. I like to fix myself my car too, and i had make it several times with pretty nice results... I homebrewer too. So.... i like to mess around with anything else.... Its a shame for my that i cant make myself a ss guitar amp.

- I´m used to think that the cost of a trafo and a good speaker are too high and in adition, the work and time that takes to do the amp, dont make any sense to make one, and the best way is to buy one, but i get at a very good price a 24+24/6A tranny, and somes TDA 7294, a 3886, a TDA2005, and a couple of LM386 of a good friend of mine almost for free....... Still have the problem of get a couple of decent´s speaker for a guitar amp.

- I use to hit a old FAIM ( a cheap argentine copy of a STRAT)... not a very good player, but getting more experience with a teacher. We want to make an ensamble with other guys and just jam! So... we need an amp at least! The FAIM has some improvements such as Schallers and another neck. Not a big viola, but is my first girlfriend, i love it.

So, well....what the hell..... it worth the try.

Going to "the bifes".....i had looking around and reading somes datasheets of TDA7294, LM3886, TDA2005.....  I think that with this stuff and a few cheapers components i have enough to make a decent amp for jam with a drumer and a bassman.  If a could call for a wish to my hada madrina,  i want a 2x12" 100 RMS combo :P :P xP, with clean sound, and that the thing should be more "expresive" as a punch the strings! Kinda ACDC bluessy distortion if us permit me the term.

I plan to start making a Ruby or kind of it, something that looks simple, to practice and remember the cloruro, the soldering iron and all this stuff. Get practice and make a little amp for practice in a bedroom. Perhaps a simple preamp?

I thinking to make all modulars stage parts, so i can upgrade each with one more powerfull or better when i make a better part. Maybe a stage with the 2005?

At the end of all, i want to do the "big one" for the power stage..  I guessed that a good option are maybe a couple of 7294 in a bridge configuration, but i had reading around that isnt a good configuration. Them tend to explode in that bridge. Someone of us have one of them working in that configuration? I found a video at youtube, in that a mexican guy i guess, presents its chipamp and i says that he suppouse that the thing has BRIDGED TDA7294. 

In the second hand, i still have a LM3886T.  Looks like the net is plenty of well tested chipamp with it.

I confusing about if the path that i plan to follow is razonably or not. BTW,  i planing to purchase 2 12" of Mr FAHEY when i have the $$$. :)

Best regard for all of us and sorry about my english.  Sorry if i sound in any way bad for any of us, im not a great english writer  ??? ???