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Author Topic: Audio amplifier for electric guitar  (Read 1699 times)
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jeanninemtv
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« on: August 09, 2014, 08:37:30 08:37 »

Hello,

This is a personal projet for an audio amplifier for electric guitar

I am looking how to improve teh quality of power of this  old ampli, perhaps if i change the old TDA2050 for another one better that equivalent, do you know about another composant better or equivalent to TDA (tunel diode circuit ) ? or how to improve it ?

http://www.st.com/web/en/resource/technical/document/datasheet/CD00000131.pdf
there are many projets with TDA like this that you can do for youlself and it is cheaper

http://construyasuvideorockola.com/downloads/tda2050.pdf

I just bought TDA2050, 4 amplificadores de potencia y un transistor J111 for to change, because the circuit is working bad,

i send the circuit  and schema take a fun Smiley

http://support.fender.com/schematics/guitar_amplifiers/Frontman_15G_15R_schematic.pdf




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metal
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« Reply #1 on: August 10, 2014, 08:12:24 08:12 »

very weak, no power indeed.. Good guitar AMPs usually use tubes or discrete transistor power AMPs, the schematic depends on the power rating you need.

I believe www.diyaudio.com is the place where you can ask such a question.
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pickit2
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« Reply #2 on: August 10, 2014, 02:12:29 14:12 »

I would check your caps, c6 looks like it is blown.
as a practice amp, the quality is ok, if you want it louder. try converting output stage to a bridge amp.
http://www.diysmps.com/forums/showthread.php?245-Bridge-Chipamp-based-on-TDA2050-60W
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Sideshow Bob
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« Reply #3 on: August 10, 2014, 09:32:10 21:32 »

If you want to upgrade the output power. You will also have to upgrade your power supply. Have you given that any thought Wink
Are you on a tight budget for this? If I was on a thight budget doing something like this. I would have kept the preamp part of your current amp. Then build a new power stage, and go scavenging for expensive parts like the power transformer
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TucoRamirez
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« Reply #4 on: August 11, 2014, 04:04:24 04:04 »

anyway the schematic is available, thus you could do what sideshow bob says on a new pcb in order to not to do frankenstein maneuvers cutting and wiring a working amp ^^ :p    btw, could you post details of your power supply?
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CocaCola
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« Reply #5 on: August 11, 2014, 07:44:24 07:44 »

Is it really worth the trouble to even save the pre-amp section?

From the looks of it, this is just your bare bones cheap consumer grade practice amp, thus even the pre-amp end and tone/effect controls are likely sub-par...

IMO if you keep the pre-amp you will probably find yourself putting garbage into the secondary amp and thus garbage out, although louder...

If it was me, and I wanted to use what I could I would design a new 'moderate' level amp that fits in the existing housing and upgrade the speaker to accommodate and match the new amp...  Lots of guitar amp schematics to be found to use as a starting point...
« Last Edit: August 11, 2014, 08:04:14 08:04 by CocaCola » Logged
TucoRamirez
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« Reply #6 on: August 11, 2014, 12:05:00 12:05 »

yep,  anyway,  do we now the "customers" specs?  what the guitar player (him-her)  wants now from the actual amp and what are the "don't like" specs with the existing amp?    

anyway, check and compare this design if you want in order to check for replacements for stages ( assuming of cours you still want to use a single IC amp to manage all the stuff) (purist of sound and power will say you to avoid that and use tubes or transistor arrays in order to get better sound and les noise/distortion at max power )

Code:
http://320volt.com/wp-content/uploads/2010/01/gitar-anfisi-tda7294-preanfi-ses-ton-kontrol.rar
« Last Edit: August 11, 2014, 12:11:32 12:11 by TucoRamirez » Logged

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« Reply #7 on: August 11, 2014, 12:17:17 12:17 »

TDA7294 sucks, very sensitive to PSU fluctuations, burns very quickly under heavy loads and very difficult to work with most of the time, not really suitable for guitar AMPs. You are from the modern AMPs school, what a pitty.. Hau ab...
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jeanninemtv
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« Reply #8 on: August 11, 2014, 08:54:03 20:54 »

Hello collegs,

On the circuit use an TDA2050 that use +-23 volts, i am looking better power perhaps if i change the TDA2050 for another composant i would to have better power, i send the caracteristics that i found for anothers TDAs and LM1875 for instrucctions,

characteristics :

................... Voltage .... Power ....... THD %

TDA2030 ..... +-14V ...... 28W ............. 0.5
TDA2040 ..... +-16V ...... >30W ............ 0.5
TDA2050 ..... +-22V ...... >40W ............ 0.5
LM1875 ..... +-25V ...... >40W ............ 0.5

How to improve the signal finally, in order to have less distorsion ?

Thanks for your answers
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Sideshow Bob
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« Reply #9 on: August 11, 2014, 10:06:12 22:06 »

Well still as said before. Your output power is very much limited by the transformer in your amp, and how much power it can supply. Power transformers are not cheap. So my 02 cent is that the transformer in your amp do not have much (if any any at all) headroom for extra power. Just swapping out the main power amp IC will not help much.
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CocaCola
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« Reply #10 on: August 11, 2014, 10:24:37 22:24 »

How to improve the signal finally, in order to have less distorsion ?

As I said previous, garbage in equals garbage out...  Redesign the entire amp from input to output using a quality design then you will have better sound...  Just slapping on a bigger solid state amp chip, is only going to increase volume not quality and as said you will only get more volume if the power supply can provide the amp with what it needs...

You could go with some of the new low power digital (Class D) amp chips if you want to use the existing power source, they are far less power hungry but it has it's trade offs...
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jeanninemtv
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« Reply #11 on: August 13, 2014, 08:17:26 20:17 »

Hello,

The circuit is working good now, the wrong was only TDA2050,

Good ideas for improving this circuit,

Thanks
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Danish
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« Reply #12 on: December 19, 2014, 05:05:17 05:05 »

I would recommend you to look into the Class D Reference Designs from International Rectifier:

http://www.irf.com/product/Gate-Driver-ICs-and-Controllers-Class-D-Audio-Solutions-Class-D-Audio-ICs/_/N~1nje2e#tab-tab3



Posted on: October 17, 2014, 06:42:05 06:42 - Automerged

Alternatively LM3886 if you insist on Class AB amplification. This is probably the best of the integrated amps in terms of sound quality. But as others also mentioned, you will need to beef up your supply for this.
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Vineyards
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« Reply #13 on: January 09, 2015, 12:29:10 00:29 »

-There seems to be no magic trick to revolutionize this design. It was meant as a cost-effective solution which will help the brand owner make some money by featuring their brand name on this possibly over priced entry level equipment.

-A PSU upgrade could help but you'd probably not feel this improvement since there is no audiophile grade quality elsewhere on your board.
-You could try upgrading the caps but you would not get apreciable improvement due to the same reason.
-You could upgrade the opamps and perhaps get a marginal improvement.
-As you wrote yourself if you have a way to upgrade the output IC with another more quality unit or if still better if you can adapt a discrete output stage here you would achieve a real improvement. Then you can go start back from the item one and expect to get further improvements.

Since this is a guitar amp; the general tendency is towards the mellow and warm sound of an valve amplifier but that would be a tall order plus you would have to start from scratch. (Also there is the risk of getting electrocuted while building and operating such an amp if you are not absolutely careful).

Good luck.
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