22 watt per chanel amp. Will this work?

[doug0147]

I found this schematic for a stereo 22 watt per Chanel amp.

http://www.aaroncake.net/circuits/amp20w.asp

I was wondering if this would work for a guitar amp. Would there be any way to bridge the 2 channels to make it 44 watt mono? Is there any reason this would be bad to use as a guitar amp?
Thanks for your comments.

[JKowalski]

It would work fine for guitar - however, audio playback amplifiers usually have a response quite different from guitar amplifiers. Their "ideal" frequency response for an amplifier is a completely flat line - no alteration from the origianl source. The ideal guitar amp - well, it depends on your preference - but it typically has a dynamic response. Correct me if I am wrong on this.

Like I said though, it will work, it just maybe wont sound that great to you without some tweaking.

[tommy.genes]

It looks like that TDA1554 is already bridging four channels to get the two 22-watt channels, so you could not bridge them again to get 44 watts mono.

You could run them in parallel mono, however. Split a single source into both inputs, and then have each channel drive its own load. I know some 2x12 guitar cabinets offer you a separate amp channel input to each speaker for stereo rigs (and some 4x12 speakers can work as two separate 2x12s).

Also, as JKowalski noted, this is just a power amp. It would not have any of the character that an actual guitar amplifier would have. That could be corrected by running a BSIAB, ROG Thor or any of the other preamp circuits to be found here in front of it.

-- T. G. --

[doug0147]

Thanks for the advice. I was thinking that it probably need a stomp box pre amp to make it sound good. Maybe the Dr. Boogie. Anyway, keep the advice coming. I'll let you know how it turns out!

[Nasse]

I have had for years about similar amp, I have used it as utility amp for testing and what ever. My amp uses TDA7370 chip. A week ago I tried a modelling preamp trough it and it was very nice, that modelling cheapo has stereo output and some fx sound nice in stereo, like ping pong delay and some time based fxs. And my cheap modelling box has stereo aux input for some backing trax...

I think my amp works quite nice with modelling stuff because it is quite nice quality hi-fi amp (what ya can get with 12 volts suply) and quite loud too. My power supply is not 5 amps only 2 or 3 amps but it works just nice at moderate bedroom/living room volumes. Indeed I had the voltage set at 10 volts...

http://www.elektor-electronics.co.uk/magazines/2003/july/quad-bridge-car-amp.55320.lynkx I think this might be nice design with slightly newer version chip

[doug0147]

Thanks for the link. I found another amp on that site that looks interesting.

http://www.elektor-electronics.co.uk/magazines/2006/july/simple-hybrid-amp.58346.lynkx

It has a tube pre amp and a mosfet power amp.

[Ice-9]

Marshall use the TDA series  chips quite a bit in some of there amps. For example one of the best sounding little amps i had, used the the TDA1514A chip this gave 40w output it had 2 of these to give a stereo 40watt per chanel, if you want 40w mono just use one. BTW the schematics for the marshall amps that use these chips are available to look at.

[doug0147]

The TDA1514A sounds really good.  I found this schematic and layout for it.

http://www.electro-dan.co.uk/electronics/tda1514.html

[Ice-9]

Yeah that is very similar to the marshall schematic, i think marshall pretty much used the TDA datasheet for the power amp with a few changes. Here is a link to the schematic, the power amp is in the bottom right corner of the schematic on the second page.  I think its ok to post this link but if not mods should delete.

http://www.schematicheaven.com/marshallamps/stereochorusrev_2x40w_8240.pdf

[doug0147]

Ok, I'm seriously thinking of building the amp based on the TDA1514A chip. This would be the first thing I've built that requires more than a 9V battery or wall wort. The 25+/- power supply is new to me. He says in this link
http://www.electro-dan.co.uk/electronics/tda1514.html

That I will need an 18-0-18 transformer. Where can I find a transformer like this. Can anyone post a link? How is the transformer wired to the circuit in his article?

Thank you for your help!

[Ice-9]

The link you supplied has a schematic of the PSU already there for you. The secondary of the transformer is like 2 secondary 0- 18v windings in series, so the center wire is tapped off to give the 0v- gnd wire. The two outside wires go to the bridge rectifier. (in the diagram the rectifier is a one piece affair, same can be made from 4 diodes to make a full bridge rectifier.) I hope this makes sense

[Ice-9]

This is the type of thing your looking for

http://www.rapidonline.com/searchresults.aspx?style=0&kw=88-2622 about £10

http://www.rapidonline.com/searchresults.aspx?style=0&kw=88-3371 about £20

[doug0147]

Is that type of transformer used mostly in Europe? The type I see mostly in America is like this one

http://www.radioshack.com/product/index.jsp?productId=2102703&CAWELAID=107594935

[Ice-9]

Here in England we use both types. The torriods are used in many amps especially where space is important as they can be made smaller than the other type. This makes them very suitable for rack gear. You can use either type.

[doug0147]

Thanks Ice You've been a big help.

[doug0147]

OK guys,  I went and built the fist amp I was talking about in this thread. Like you guys said. The frequency response is not good for guitar. I put by dist+ stomp box in front of it and it was a little better, but still not that great. My biggest surprise was that it wasn't as loud as expected. I'm powering it with a 12V DC 5AMP adapter I got from a LCD computer monitor. It's no where near as loud as my 15 Watt Vox Pathfinder. Any theory to why 22 Watts of this amp is quieter than my 15W Vox? Also, any suggestions on getting a better tone out of it?

thanks

[Tubebass]

Well, first, what are you using for speakers? Speaker efficiency is generally higher in guitar speakers than in, for example, home stereo or car speakers. Another point is that the power chips will want to see line level, so your guitar signal will need boosted quite a bit. Try driving the power chips from the preamp out of another amplifier, or put an EQ pedal in front with bass and treble boosted, and mids cut.

[doug0147]

I'm using the 8 ohm speaker in my Vox pathfider combo amp.

[doug0147]

I forgot to mention. I used a 47k resistor instead of the 39K . There is only one resistor in the circuit. I don't know if that makes much difference.

[Tubebass]

So you're using one channel of the power chip into 8 ohms? With 12 volt supply you'll be making about 6 watts.