Quote from: THChrist on October 11, 2009, 01:20:48 PM
Hello everybody!

I wanted to share this with you. It's a simplifyed version of the pramp I'm desingning. It consists of multiple bypassable stages, switchable mods and it was designed using 3 Marshall Amps: 1959SLP (1 stage + pre-eq gain), JCM800 2203 (2 stages + pre-eq gain) and JCM900SL-X (3 stages + pre-eq gain). Each stage consists of a Noiseless biased SRPP using FETs

There are switchable mods: Bright cap, Boost (only for modes 2 and 3), Thick (for the 3 modes) and modable Tonestack (33k-470p/56k-220p/46k-690p).

I recommend you to use @15-18v

Here's the schematic:

http://i20.photobucket.com/albums/b228/Anti-Idiot/MPD-SingleVersion.jpg

EDIT: I forgot, please excuse me for not numbering each component, i'll do it ASAP. If you need to point something out, the reference is: 1st stage, 3rd stage, 2nd stage and pre-EQ stage. Also, the LED is a multicolored LED (R/G).

This is a single version. the other version should have 3 gains and 3 tonestacks with volume per channel (15 pots), output buffer, master volume, internal switching using relays (for bypassing stages and switching the gain/tonestacks), external channel switching (using this switching) and poweramp w/presence & resonance (this one). BTWm there's a mistake in the PA section, change the value of the 100u cap to 1u.


Please ask.

I was really excited about seeing this schematic until I got to the "page not found error" on photobucket.  Why not post it here?

Quote from: J M Fahey on October 26, 2009, 11:25:34 PM
As a very general "rule" that has a lot of exceptions, on the secondary side, the one that goes to the power supply board you should have 3 wires: 1 center tap (grounded) and 2 that go to the power diodes or bridge.
You *might* have also a separate 12+12V or 15+15, to power the preamp, although many don't use that, just get their +/- 15V from the main DC supply.
On the primary side, the one that goes to the power switch, main fuse, etc. you should have 2 wires, in that case they are 220V *or* you might have 4 wires, 2 connected to the power cord, through a fuse and a mains switch and 2 wired together and insulated (tape, heat shrink or some plastic cap) from everything else, *or* going to some spade connectors on the PCB that go nowhere else, are there just for neatness.
In that case only, you usually can re-wire it for 110/120V.
Post a couple pictures from each side of the power transformer.
I think you have a bargain, even if you have to buy some external transformer.
Good luck.

Thank you very much.  I'll post relevant pictures as soon as I receive it.  I don't have this masterpiece in my posession yet.  Interestingly enough, I found a few other ads on the internet where I found this amp for sale but I couldn't find any official web site or anything that had information on it.  Anybody have a URL for the company that makes this thing?

Thanks a LOT JM !

Quote from: jfetter on September 08, 2009, 10:15:20 AM
I'm giving it a go with the TPA3106D1 and dsPIC33 for a combo unit. The dsp will let me do in software what I've been trying to accomplish in analog. The target is a smooth overdive with mild reverb. The dspic33fj128mc804 has a 16bit dac and 12 bit A2D. I'm planning on trying oversampling to get 14bit. We'll see.

Running on 24vdc I guess about 35w.

Strange no one is using this part.

What ever happened with this ?  Did you get this to work well?

Quote from: J M Fahey on October 26, 2009, 06:35:30 PM
Hi Zappacat. Were you the bidder?
Anyway, it's the exact same amplifier.
Very Chinese, probably a knockoff of some equivalent Laney.
It should be good.
A 110/220V autotransformer of at least 60 VA, preferably 100/120VA will do.
"Hot" in that case means high temperature, it is also written in French where the words used are different.
It will be cheaper and easier to use an external autotransformer than to replace the original one.
It might even have dual-primary which would make the voltage change possible, but don't count too much on that.
In that "outsourced" market, 5 extra cents are a fortune.

Thank you very much.  What should I look for on the transformer for clues that it might have dual-primary?

No, it's this one :

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370264138909&ru=http%3A%2F%2Fshop.ebay.com%3A80%2F%3F_from%3DR40%26_trksid%3Dm38%26_nkw%3D370264138909%26_fvi%3D1&_rdc=1

I just got one of these amps.  It has a european power connector on it and I'm in the United States.  What do I need to hook it into AC mains in US?  Will I need to change the power transorfmer?  I know it's not the greatest amp but it is very unique.  I've never seen one before.  I don't want to blow it up before hearing what it sounds like.  I can't find any official tech pages on the web for information on it.  Any help greatly appreciated!

I've been doing a LOT of research on this topic.  Mostly because I'm a complete newbie and I need to learn.  Recently I got around to purchasing the chipamp.com boards and I've started to assemble the.

My first question is:

There's a lot of talk on the internet about using the LM3886 as a guitar amp but none of the posts/discussions ever really get to the point of someone actually posting finished projects with information on how they took the guitar signal and fed it to the LM3886 inputs.  Does anyone have a SIMPLE schematic(even without tone stack) explaining how to do a simple preamp stage from the guitar output to the LM3886 input.  I'd like to either use Phatt's passive tone stack or the eighteen watt DIY pedal at GGG for a preamp.  I'm missing the part about attenuating the signal exiting the preamp(Phatt or eighteen) and getting it to the amp input.

Second question:

What would I need to implement a switchable tonestack/preamp.  Ultimately I would like to have the Phat passive and Marshall eighteen on the same amp with a switch to toggle between them.


Any help greatly appreciated !

Quote from: Minion on October 17, 2009, 01:36:35 PM
I"m pretty sure that when talking about chip amps the differance between and Dual mono and a stereo chip amp is that a Dual Mono with have a seperate power supply and Transformer for each channel were a stereo will use the same PSU and transformer for both channels ... the advantage of Dual mono is that there is no Crosstalk between channels and the grounding is easier , the disadvantage is that Dual mono takes up more space in your chassis and is heavier and nearly twice as expensive ......


Cheers

That's what I wanted to know.  Thank you very much.

Quote from: phatt on October 13, 2009, 10:53:25 AM
Hi Zappacat.
            A stereo amp is effectively the same as a two mono Amps.
A stereo amp that recieves two mono signals is just a two ch Amp but the signal is still *mono*
It is only when efx like chorus or trick dely (ie,ping pong) are engaged that you can here stereo.

Remember all these fancy *Stereo* efx do little for live gigs, they are far more suited for studio work.
My advice is get a great *Mono* Guitar Amp sound *First* ,,,an worry about all the fancy stuff when your famous.
My 2 cents worth.  Phil.

This isn't for live performances.  Mostly for me sitting at home screwing around playing/recording things that noone else will probably ever hear.  I'm VERY familiar with the do's and don'ts when it comes to stereo effects live.  15 years ago I was convinced that was the route to take.

If I were to be playing it live I wouldn't be using a 2x12.  I'm too old to carry those cabs around anymore.

Thanks for your input.  I agree with you.  I need to get it working in mono first.

I'm having second thoughts about dual mono vs. stereo chipamp kit for guitar amp build.  I purchased the non-inverting LM3886 stereo kit.  My intentions are to use it as the power amp for my various preamps.  For example PodXT, home built Marshall eighteen, Digitech 2101, etc...  Some are stereo pres, some are mono.  I plan on driving a 2x10 or 2x12 stereo cabinet with it.  The more I read about this stuff the more confused I get.  Can someone explain to me the advantage of using the dual mono kit for this application vs. the stereo kit ?  Thanks for any help.

I'm putting together my first chipamp.  The instructions say that you need Phoenix 22Kohm SFR16S resistors.The parts search on digikey brings brings me hundreds of matches that appear to all be very similar.  Is the manufacturer important when acquiring these components?  How do I know which one to choose when they're all so similar?

Can you tell me what the following specification choices mean when searching for components:

Temperature Coefficient (which of the following are better for this application?)

+- 100ppm/C VS. +- 250ppm/C

packaging

cut tape VS. tape and reel

The instuctions also don't mention anything with respect to TOLERANCE or POWER RATING.  Maybe I'm missing something in the documentation.

Is there a predefined BOM (build of materials) on digikey or mouser?

Thank you.

Hey Phatt, can you elaborate a little on what "semi-passive" tone stack means in your diagram?  Thanks!

I'm putting together my first stereo chipamp circuit boards that I intend to use as a guitar amp.  I'm assembling the the amplifier PCB at this point.  In section 1.7 it refers to a feedback capacitor being optional.  Should I be using the feedback capacitor for guitar?  Please help me with this I'm stuck.  What are the implications either way?  Thanks

The following is an excerpt of the LM317 datasheet:

Output Current    500, 1500, 1000 mA
Input Min Voltage    4.2 Volt
Input Max Voltage    40, 37 Volt
Adjustable Output    Yes
On/Off Pin    No
Error Flag    No
Temperature Min    -40, 0 deg C
Temperature Max    125 deg C
RegType    Linear Regulator

What do the 40, 37 volt input max voltage figures mean?  Why are there 2 figures?  Thanks in advance.

Quote from: joecool85 on August 19, 2009, 07:27:19 PM

Quote from: Zappacat on August 19, 2009, 02:34:45 PM
Where are you at on this project?  Just curious as I'd like to do something very similar.  I need a stereo guitar amp and I'm looking at this setup for a foundation: Non-Inverting LM3886 Stereo PCB Sethttp://www.chipamp.com/orders.shtml  Have any of you used this setup for a stereo guitar amp setup?

Which specific transformer did you end up using?  Are you implementing a tone stack into it?

I've used the mono version of that kit, I ran mine with a 330VA toroidal transformer from partsexpress.com - I only went so big because I was planning on running it dual mono later.  It was the loudest "50watt" amp I've ever heard in my life.  I'm not joking either.  It doesn't color the sound at all (some consider this good, others consider it bad - I like it, that way whatever comes out the preamp comes out the speaker).

What speaker did you end up using?