22 watt per channel stereo amp project

[doug0147]

Hi Everyone,

I have posted some threads about the SS amp I'm making and it's really starting to come together now (circuit wise). I wanted to post my progress on this in case anyone is interested, or if you have any comments, questions, or constructive criticism. Here is what I have so far.

The plan is to make a stereo multiple channel combo amp with the following features:

• mono and stereo inputs, the left jack will be mono, left and right are stereo
• Multiple channels - So far I know there will be a clean, and a Dr Boogie channel
• effects loop
• extention speaker cap out
• whatever I can think of next....

Power Amp - this is the power amp circuit I'm using http://www.aaroncake.net/Circuits/amp20w.asp
It's 22 watts per chanel. I made a PCB layout in Eagle cad and built it allready. It works!

Pre Amp - This is made out of several circuits combined
I'm using stomp box amp emulators to get the distortion channels. I'm using a Don Tillman pre amp circuit with an eq
for the "Clean" channel.

• Clean Chanel- Don Tillman pre amp - http://www.till.com/articles/GuitarPreamp/index.html
   that goes into a Baxandall EQ - http://amps.zugster.net/articles/tone-stacks#Baxandall
   then it goes into a LM386 amp I found here  http://www.elecfree.com/electronic/simple-lm386-audio-amplifier/
   I'm adding a gain pot between the cap and pin 1 of the chip.

• Metal Chanel - Dr. Boogie  - http://gaussmarkov.net/wordpress/circuits/dr-boogey/
   Then into a Tillman pre amp then into a LM386 amp with no cap between pin 1 & 8, so there won't be any additional gain boost.



As of now I have only tested with one side of the amp chip. I've tried out an 8" 25 watt/50 watt musical( I still don't know what that means)  4 ohm Jensen. I also ran it thrugh my Marshall 4X12 cab.

I havn't figred out the effects loop, or stereo parts yet. I think I'm only going to do stereo through the clean channel. I'll just double the clean preamp. All the other channels will just be mono.

I'm thinking about adding a Run Off Groove UNO and a Thor. I might be getting carried away.

I'll post some sound samples and pictures soon. Let me know any ideas you have and what you think.

Doug

[donald stringer]

Keep posting these gain clones have captured my imagination, as a matter of fact I have a little project I am working on my self.

[doug0147]

No problem. I'll keep you updted

[doug0147]

I came up with a way to switch between 4 preamp channels with led status indicators. There will be 2 sets of 2 channels. The 2 sets will be switched between with a DPDT toggle. That switch will go to another DPDT switch to choose one of the channels in the set. I have the diagram below switched to the Dr. Boogie channel.



Now I need to figure out how to ad a footswitch option to this. Any sugestions?

[Taylor]

I'm confused. You're making it stereo with multiple ins, but then you're collapsing it to mono and running it into a single speaker? What's the point of stereo if you're not outputting stereo?

[doug0147]

Taylor, Sorry about the confusion. That wasn't really a complete diagram. I havn't really figured out the stereo part yet. I think that when one input is used it will run bridged mono. When to inputs are used a switch will activate stereo mode.  The other channel will only have a clean preamp. I don't think I would want to use a Dr. Boogie in stereo anyway. It seems like it's going to be a bit tricky.

[donald stringer]

If you scroll down a bit this is how I am going to impliment my effects loop if I utilize one. http://sound.westhost.com/project27.htm  If you look at  http://www.geofex.com/  switching with cd4053 this might be a way to take your channel switching out of your box to a floor switcher. As far as the possibilities ...... they are endless. In  doing something like this you are only limited as to how simple or complicated you want to make it. Thats what I am doing, I dont go off on binge building maybe thats my  problem I examine everything to death but I want to get the most out of the least. For me I dont need it to be floor switchable [one complication eliminated] all though it can be done.

[donald stringer]

 Maybe make up an complete block diagram of just what you might want to do. So we can get a better picture of what you want

[donald stringer]

 In case your interested my project involves an altec lansing multi.subwoofer I bought at a yard sale. The unit works but  one of the speakers are blown. There are a couple of chips on the board I am going to bypass so I can implement my own pre-amp. I have everything out of the box. This is pretty cool   I have an off / on switch, led, vol. a 22watt stereo power amp. This chip suppies stereouts  into  two different speakers. I  want to go a little overboard on the cosmetics of the case in the trad. of these gain clone things.

[doug0147]

Donald, So you're using a powerd sub as a guitar amp. Are you changing out the speaker? I know ISP makes a guitar amp that actually uses a sub woofer! I'll try to draw up a diagram of exactly what I'm going for. I know that first diagram didn't explain much. Also, I like the effects loop idea in the first link, but I couldn't find the switching article on Geofex. Can you post the link?

[donald stringer]

 The subwoofer is blown. I am going to use my old faithful 4/ 10"s [univox] cab. This is wired for 8 ohms. There is an 572 compander on the board that they use as, I suppose an compressor along with an lm324. All I have to do is desolder a couple of components and open up the board a bit. This is doable. Go to geofex and scroll down until the lettering gets small and you will see it cd4053. I have  used these an number of times in some of the few effects I have not torn  apart and scavenged for parts. The chip is still functioning whisper quiet. You can do your switching other ways that would be easier unless you just wanted to kick your build up a notch.

[doug0147]

Donald,  I took I glance at that cd4053. I'm going to have to really read that page, looks complicated, and how can I apply it to my amp. I think I might want a simpler way to make a foot switch.

[donald stringer]

I"ve started my project. Kicked this thing off by isolating the inputs succesfully. This power amp chip is KA621OAH and it can be found on alldata sheet. I can already tell its going have more than enough vol. for what I want. I"ve lost the vol. control though because by taking the inputs off the board it took the other chips out of the way. I think this build is going to be simplified somewhat as I dont want to muck about to much just so much as to keep any unwanted parts out of the way.