So, i wanna build a 100watt amp. Its just a simple affair, im ripping the guts out of my 10watter, putting in new electronics, and putting in new electronics. I plan to put a ~70watt speaker into it, and then using the enclosure of another 10 watt amp for a makeshift "cab" to put a 50watt speaker into it. I plan to put in celestions, or peavy speakers. But, i have no idea of what schematic to use. Hopefully one of you can give me a link to a schem, with a parts list, and also where i can buy a ready-etched PCB for it. Im looking for a simple schem, not too hard to build, this is just going to be a learning experience.
(http://i56.photobucket.com/albums/g186/bird_flu_02/10wattamp.jpg)
^^thats the amplifier im gutting.
Well, it won't be plug and play so to speak, but if you are careful, you should be able to use all of your preamp stuff from the old amp (I'm assuming it works), then put in a LM4780 for 100w of power. You can buy a PCB for that at chipamp.com, but if you wait a little while I might be able to get you one just for the cost of shipping. Brian is sending me some to distribute here.
And welcome to the board btw.
A couple of other alternatives... I've never tried these and may have, in fact, found the links in the schematics part of this site. Anywho, for what it's worth:
http://europa.spaceports.com/~fishbake/amp/ca100.htm
And this is more of a complete project... I think RDV sent me this one:
http://sound.westhost.com/project27.htm
I haven't tried either, so I can't say how easy they are to get up and running... they seem simple. Chipamp.com is probably the easiest, though.
It's definetly going to be easiest to just do it via a kit from chipamp, but just because its easy doesn't mean its the best option. Now thats not to say that chipamps aren't great, because they are...but they aren't the only way to do a SS power amp.
I wouldn't trust the "Cheap 100 to 150 Watt Amp" at http://europa.spaceports.com/~fishbake/amp/ca100.htm to work reliably enough. Why:
1. Bias adjust and thermal coupling is done with only 2 x 1N4007 diodes. I sense a serious threat of thermal breakdown. I'd also suspect that the circuit has a high amount of crossover distortion since it has a darlington output.
2. High supply voltage and only one pair of output transistors. With 150 watts even the maximum ratings of TIP142/147 are way exceeded. For watt ratings such as these i'd recommend at least another pair of output transistors in parallel.
Yeah it's simple and i'm quite sure it would work, but it could destroy itself in a matter of milliseconds as well. With decreased rail voltages, i would trust it to run a maximum of 40W amp or so. With slight modifications to improve stability maybe an amp of 50 to 60 watts. But 100 to 150? No way!!!! The designer has not been on the level with the output transistor specs or demands required for stable enough high power applications. I'd recommend anybody to stay away from this design as it is.
The Rod Elliot's project looks a lot more like a design that i would choose from the two. Actually, i think it could be quite educative for anyone planning to build an high power amp to compare both circuits and find out why the ESP design is so much more complex. Even if they choose to build a chipamp afterwards.
Quote from: joecool85 on April 22, 2006, 09:27:48 PM
Well, it won't be plug and play so to speak, but if you are careful, you should be able to use all of your preamp stuff from the old amp (I'm assuming it works), then put in a LM4780 for 100w of power. You can buy a PCB for that at chipamp.com, but if you wait a little while I might be able to get you one just for the cost of shipping. Brian is sending me some to distribute here.
Wow, i would definitly be interested in the PCB, thanks very much!!! :) Can you email me with info to:
born2lose_out2lunch@yahoo.co.uk
BTW, where could i get these components for that^^^? Im a poor guy, little money (only 16...) so i would probably have to buy the components somewher else.
The components are part of the kit. So you'd get the PCB and all components needed to make the power amp, minus heatsink and transformer. Keep checking the forum, I'll post as soon as the stuff from brian comes in. Otherwise, you can check out chipamp.com
Ill keep checking, im off school at the moment, so i have plenty of time. Thanks a lot man!!
Hi! Ive been gone for 3 weeks, just getting back into the swing of my amp now. I have the whole enclosure ready, the plywood cabs are ready, and theres plenty of space for that PCB on an aluminum enclosure. Unfortunatly, i dont have a camera at the moment, so i cant take pictures.
Joecool85, did you get those chipamp PCB's, im still very interested in getting one! Thanks a lot.
Well, the good news is yes, they came in. The bad news is that they are all gone :(
Aw *s!!t*. Is there any chance that more could come in?
Not unless someone else wants to spear head it. It's a substantial amount of work getting all the kits in, separating out all the parts, ordering missing ones, getting people's money and shipping them out.
Ah, okay. Well, im willing to help out with whatever, i have plenty of time at the moment to do some stuff, so if you want, im here to help.
ok, i've tried the "cheap 100W to 150W amp". It works fine but after a few weeks, filter caps in the PS suddenly begins to SMOKE!!!!!neither it blows but then I stopped using it..
And the rod elliot design is the one i'm using for 7mos. now...
If they blow or smoke in seconds they´re wired backwards. Since they worked for weeks,I must assume that their voltage rating is marginal at best. Replace them with caps that support at least 10 volts more than what´s nominally needed and you´ll have no problems. The "100/150" *will work*, but it´s just a regular classic schematic stripped to the bone and then some. You should at least: 1) add a 100pF ceramic cap from Tip41´s base to collector ; 2) add a Zobel network: a .1ceramic in series with 10 ohm 1/2 W resistor, from "hot" output to ground (or across output jack) ; 3)split the 22k resistor into two 10k´s in series and wire a 100uFx35V capacitor from the midpoint to ground ;4) add a third biasing diode in series, the three of them should be epoxied to the heatsink, the amp will still be somewhat underbiased but usable ; 5) definitely not "150W" but will pull around 90W into 8 ohms with the +-45V or, (much safer) into 4 ohms using +-35V. By the way , avoid shorts at all cost because it has no protection whatsoever.
Hi JM,
I'm going to make sure to you that there's no mistake on that one. I guess your right, that 4,700uF cap is rated only at 50V and my transformer is at 6A, 35-0-35 sec. The rectified voltage was at +/-43V as far as I can remember. Maybe I'll try what you have said though.
So did I take your mod correctly like this?:
(http://)(http://i303.photobucket.com/albums/nn156/DimebuGG/100Wto150Wpoweramp.jpg)
The sketch is horrible and can be very confusing. I suggest you draw it out in the conventional way to visualize the circuit better. Mr. Fahey's recommendations for modifications are on point and most of them are correct in the shown diagram. However, the 22K resistor he advises to split in half (and filter from the junction) is the one far left. The resistor you have split now is the feedback resistor. If you split it and shunt the junction point to ground with a large capacitance it practically removes all negative feedback and runs the amp at full open loop gain. Even small input signal will overdrive the amp to clip to rails. This can be catastrophical!
With the original feedback resistor values (22K/220R) the closed loop gain is still about 100. I'm pretty sure something closer to 20 – 40 is a far better value for gain. Try replacing the 22K resistor with 27K and the 220R with something between 1K and 560R.
Dear Bugo, you got it quite right, sorry if I wasn´t clear enough, so, as "one image is worth 1000 words) here you get two. #1) is a hand-drawn schematic of my "breadmaker", my P100 module. I´ve built around 10000 of them, the first 9000 or so with 2N3055H+Tip31/32 drivers, which lately had to be replaced by Tip141/142 because nowadays it´s almost impossible to get a genuine 2N3055H. The current version uses IRFP250 which are close to indestructible. #2)Is a poor scan of the board "ready-to-mount": : the 100W/4 ohm amp is the center section, on the right is the +-42 power supply, and on the left are the +-15V preamp supply outputs. When I get my camera back I´ll post better pictures.
Dear Teemuk, thanks for clearing Bugo´s doubts.
The amp´s sensitivity is around 700 mV, it has mixed voltage and current feedback. Power output is 20 clean volts into 4 ohms and supports many "ooops!!! sorry!!!" shorts.
Bye.
JM
Teemuk,
Oops sorry. my bad..i didn't notice the leftmost 22K resistor. :) :)..