Custom ss guitar amp build!

[J M Fahey]

HEEEEEEEEEEEEEEEEEEEEYYYYYYYYYYYYYYY !!!!!!!!!!!!!!!!!!!!!!!!!!!!! :trouble
Who said you could post pictures of MY workshop ?? :trouble
I can only forgive you (a little) because thanks to your pictures I could find my girlfriend's white cotton panties, which she misplaced a couple nights ago, since we were last ... er ... adjusting bias on a Twin ...
Now not kidding: terrific place to work in, *loved* the dual purpose work/pool table , the bar/workbench and the sight through the window.
Well, the combination bar/workbench is not too original, I've seen a few already.  :lmao:

[mgcasella]

A big day has arrived!

Just thought I'd let everyone know that the LM3886T's and TDA7293's came in the mail.  Due to the overwhelming amount of recommendations we will most likely be using the LM3886T's, but we decided to buy some TDA7293's just for the fun of it  :tu:

Here are the LM3886T's:



Here is one of the TDA7293's:


Tom and I have decided on a small simple circuit to use for a mini-prototype of the amp (basically, we will be building a practice amp version of the beast).  Hopefully, we will be blowing stuff up within the next few weeks!   

[DJPhil]

I love the smell of new parts.

Somehow I totally missed this thread earlier. If you ever want to talk tech stuff and happen to be up in Omaha let me know. Not too many folks around here seem to be into electronics.

Keep us posted, I'm slowly working on a 3886 build here too, though I'm only after about 40W.

[mgcasella]

I love the smell of new parts.

Somehow I totally missed this thread earlier. If you ever want to talk tech stuff and happen to be up in Omaha let me know. Not too many folks around here seem to be into electronics.

Keep us posted, I'm slowly working on a 3886 build here too, though I'm only after about 40W.

Me too  :tu:

Yeah man I'll totally hit you up if I'm ever up that way - thanks for the offer 

[J M Fahey]

Start with the LM3886, simply because it's logically laid out, and its PCB will be *much* more reasonable.
The guy who designed the pinout of the 7294/94 should be shot.
You need to join pins which are far away, with tracks crisscrossing each other, what were they thinking?
Why didn't they join them internally?
Stupid designer.
This *forces* you to use double face PCBs *and* to run tracks on the "back" side of the chip, making it very difficult to seat it against the back panel or a properly seated heatsink, as customary in guitar amps.
All examples show a big, heavy heat sink mounted *on* the PCB, "floating", that's to say unattached to the chassis.
Obviously the stupid designer aimed at TVs and  5.1 home theater systems, which do not take the bumping of guitar amps.
Or ... you have to take the very unreliable Marshall approach, with miniboards and 15 wire connectors per chip.
Oh well.

[mgcasella]

That's nuts about the TDA's - I had no idea    I have a feeling we'll be going with the LM's unless the TDA's sound a million times better  :tu:

[J M Fahey]

Hi MGCasella, see for yourself.
Draw a line (which would be the back panel or a heat sink bolted *somewhere*), draw the chip package "bolted" to it, then all other components spread on "this" side of the sheet, meaning inside the chassis / inside the PCB and start penciling connection lines as needed.
With the LM3886 you will solve the maze in between 15 minutes and 2 hours, depending on the tightness you want to achieve , then use the PCB design software to draw it professionally.
Try that with the TDA !!!
All published solutions draw copper lines below the heat sink, which should then float over the pcb *or* hold the PCB "in the air" held by the chip pins.
All homemade projects I've seen show the PCB on a table, unmounted.
One demands a special heatsink with a much thicker center extension, to reach the chip.
Commercial users (Marshall) go the "spaghetti" way.
What irks me is that the chip designer could have easily solved it in 15 minutes extra work.
It must have been Friday afternoon indeed.
Oh well.

[mgcasella]

That's so strange that the TDA's were designed that way.  I know they were originally meant for stereos, TV's, etc (and not for guitar amplifiers) but still it seems, from the way you describe it, that it would be hard to use the TDA's regardless. 

I wonder why Marshall decided to use them?  I bet they probably just got a deal on a huge batch and said "f!!* it - let's make some money" 

[mgcasella]

Sorry it's taken so long to update this page but things have not been going so well. To make a long story short, the guy I hired to build the amp didn't work out.  After repeated visits and discussions with this builder, I had to file claim with my credit card (I'm SO glad I didn't pay in cash).  The waiting period is over and the money is mine again, which is why I'm now just starting to continue with this thread.

As for my continuing search, I've gotten some "bids" where people have said they would charge me $800/hr for the design, which I can't afford (and personally, I think the quote was that high just because they didn't want to do it).

I suppose I could always try Craigslist.  If I could get someone just to draw up the schematic of the design, I'm sure I could find someone who could build it on the cheap, and then I could just tweak it. 

I've thought about just modifying an amp I already like to my specs.  This would be a chore (especially since I have limited knowledge of electronics) but it may be necessary.

I've already put so much time into this I think it would be ridiculous to just let it go.  Does anyone know how/who I could contact? Does anyone have any ideas?

[J M Fahey]

Sory to hear that, but please remember you were warned fron the beginning that your goal was unrealistic.
That's why I suggested "keep it simple".
Truth is, what you wanted *can* be done, technically, but does not pay to build "just one".
Being a new design, (since you are not "exactly cloning" any commercial product) means that first
1) a general "block " design must be made, even on the back of a paper napkin (you got so far, I guess)
2) that design must be refined.
3) Decide power, PSU, transformer, size, chassis, front panel layout, etc.
4) Design a power amp, including its Layout, PCB, how/where it will be mounted, heatsinking, heat flow, etc.
5) Design, layout, PCB, for the clean channel.
6) Ditto for the basic dirty one
7) Ditto for interconnection, effects loops, (foot) switching.
Building a rough prototype, to check that the general idea is reasonable, start debugging ground loops, interference, radio, buzzing, oscillation, etc.
9) Rebuild the resulting rats nest into something more usable
10) Only now that it works, sort of, start polishing the sound.
11) This will *very* probably need a major re-design , back to step 4 (no kidding).
12) this is interactive re-design and sound polishing, will probably need 3 or 4 iterations until you are :
a) reasonably happy with results
b) too fed up to continue polishing.
13) you redraw the final PCB version and do the same with the front panel, you order the definitive set of silkscreens to print them, you also get a new blank front panel to be perforated and printed, since the old one is full of holes and permanent marker labels.
You build the amplifier's final version (which is the 5th or 10th since you started with this project)
14) Enjoy.
15) You have already spent from $2000 (you lucky guy) to $20000 (more realistic), you have a truckload of discarded stuff, including the "definitive" cabinet, because you realized too late that the chassis slid-in perfectly, *without* Tolex, but not at all (or maybe it needed a hammer) after you covered it.
16) Did I mention that it takes about a year to go through all this?
That for an established Company, with all its resources.
Even so, every year we see examples of "Frankfurterosis" or "NAAMMitis", when not-quite-finished products are rushed there to meet Marketing Dept. deadlines.
Oh well.
Been there, done it (for the last 42 years).

[mgcasella]

Great news!

I recently was connected with a guy named Damon Mar who should be able to help me get a prototype of my amp going!  He's a musician, is about to receive his Masters in Engineering, and is also an entrepreneur.  He builds pedals that can be used with synthesizers, as well as guitars and they seem pretty cool.  He makes stuff more for people who like to make ambient-type noise, but I told him that I could definitely see metal bands (more like black/experimental metal) experimenting with his stuff.  Check out his website if you're interested: http://marsyth.com

We met for about 2.5 hours last Thursday and I told him all about the design and he says it's definitely something he can do.  Also, because he makes foot pedals and get stuff wholesale, I'll be able to get a deal on the parts.  Hopefully by next Thursday, he'll have an idea of most of the parts I'll need to buy.  After that, the plan is to make a protoboard with lots of sockets so we can swap out parts.

The best part is that he has an oscilloscope – that will be fun to use when we're measuring/messing with sound waves.

I'll be sure to keep this thread updated as the amp progresses.  When the amp starts making noise, would everyone like to see YouTube videos and listen to soundclips?

[joecool85]

Great news!

I recently was connected with a guy named Damon Mar who should be able to help me get a prototype of my amp going!  He's a musician, is about to receive his Masters in Engineering, and is also an entrepreneur.  He builds pedals that can be used with synthesizers, as well as guitars and they seem pretty cool.  He makes stuff more for people who like to make ambient-type noise, but I told him that I could definitely see metal bands (more like black/experimental metal) experimenting with his stuff.  Check out his website if you're interested: http://marsyth.com

We met for about 2.5 hours last Thursday and I told him all about the design and he says it's definitely something he can do.  Also, because he makes foot pedals and get stuff wholesale, I'll be able to get a deal on the parts.  Hopefully by next Thursday, he'll have an idea of most of the parts I'll need to buy.  After that, the plan is to make a protoboard with lots of sockets so we can swap out parts.

The best part is that he has an oscilloscope – that will be fun to use when we're measuring/messing with sound waves.

I'll be sure to keep this thread updated as the amp progresses.  When the amp starts making noise, would everyone like to see YouTube videos and listen to soundclips?

Great news indeed.  We definitely want to hear sound clips and see videos.  I'd like to see video of the oscilloscope in action as well - those things are cool!

Good luck and have fun!

[mgcasella]

Damon's website is marsynth.com/

Oops!   

[mgcasella]

GREAT NEWS!

Finally, Damon and I were able to make time to sit down and determine what parts need to be ordered.  Soon, we will have the parts to begin constructing the protoboard of the preamp!

I'm so excited because now - in the foreseeable future - there will actually be something tangible/physical to show for all my work 

I will be sure to post updates as things progress  :tu:

[joecool85]

GREAT NEWS!

Finally, Damon and I were able to make time to sit down and determine what parts need to be ordered.  Soon, we will have the parts to begin constructing the protoboard of the preamp!

I'm so excited because now - in the foreseeable future - there will actually be something tangible/physical to show for all my work 

I will be sure to post updates as things progress  :tu:

Good to hear, thanks for keeping us posted