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Author Topic: guitar amp diagram revision help  (Read 453 times)

watermelon33

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guitar amp diagram revision help
« on: January 22, 2020, 09:57:36 AM »
Hi guys! I make my own guitar amplifier. I found this circuit diagram. It has a marshall and fender-like design in general. Are there any regulations you want to suggest about the circuit? how can i make it better? I also want to add a distortion channel, how can I do? I am waiting for your revision suggestions and help.

joecool85

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Re: guitar amp diagram revision help
« Reply #1 on: January 22, 2020, 11:12:09 AM »
I would build the amp as-is and see how you like it.  As far as building in a distortion channel, it's as simple as choosing your favorite diy distortion circuit and building it out in front of the input on the amp!
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
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watermelon33

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Re: guitar amp diagram revision help
« Reply #2 on: January 22, 2020, 12:35:14 PM »
Thanks for your answer. I think it would be better to add 'internal' overdrive as in Marshall amplifiers. For this, if I add 2 reverse diodes to the first buffer, will it work? I draw the scheme as a pcb and now I have to make all additions, I have no chance to add it later.

joecool85

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Re: guitar amp diagram revision help
« Reply #3 on: January 23, 2020, 11:30:46 AM »
Thanks for your answer. I think it would be better to add 'internal' overdrive as in Marshall amplifiers. For this, if I add 2 reverse diodes to the first buffer, will it work? I draw the scheme as a pcb and now I have to make all additions, I have no chance to add it later.

If you were to modify the preamp section to be similar to one with overdrive, that should work.  Here is one that is easy to work with: https://www.ssguitar.com/index.php?topic=1885.0
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
thatraymond.com

phatt

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Re: guitar amp diagram revision help
« Reply #4 on: January 24, 2020, 07:39:05 PM »
BTW, X1 is NOT a buffer. As for distortion, just adding diodes won't work well, you would need to add an extra stage to get a reasonable outcome.
You could add an input buffer stage and alter X1 to work like the link *Joecool* noted above.

Also, I believe the TDA2050 is no longer made, though you could use LM1875, others here will know more.

The reality of this is that you it would work out a lot cheaper and many times easier to just purchase a small amp. xP
Phil.
« Last Edit: January 24, 2020, 07:41:40 PM by phatt »

joecool85

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Re: guitar amp diagram revision help
« Reply #5 on: January 24, 2020, 08:07:30 PM »
BTW, X1 is NOT a buffer. As for distortion, just adding diodes won't work well, you would need to add an extra stage to get a reasonable outcome.
You could add an input buffer stage and alter X1 to work like the link *Joecool* noted above.

Also, I believe the TDA2050 is no longer made, though you could use LM1875, others here will know more.

The reality of this is that you it would work out a lot cheaper and many times easier to just purchase a small amp. xP
Phil.

TDA2050 is marked as obsolete anywhere I've looked.  You could probably source one on eBay though.  That said, LM1875 is a great chip and I think it is a direct replacement pinout wise (you'd want to double check).

I disagree on the just buying a small amp though, unless money is the most important aspect.  Building an amp is fun and a great learning experience - well worth the money involved.  That said, buying a kit could be a good way to go.  Or buy something like this 5w unit and then build an overdrive to sit in front of it: https://www.parts-express.com/footnote-electric-guitar-5-watt-amp-assembly-with-power-supply--249-404
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
thatraymond.com

phatt

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Re: guitar amp diagram revision help
« Reply #6 on: January 26, 2020, 07:44:48 AM »
Thanks Joe, yes I was fairly certain that was the case. :tu:

Yeah I get your point about the fun of building your own rig,,,,but you have to buy and build everything. xP
Yes a kit is a good way to go, assuming you are talking just a power amp kit?
BUT you still have to pucha$e; a speaker, transformer, face plate, knobs, maybe some paint and vinyl covering,, add speaker cloth, a cab handle, rubber feet, corner caps.
Then you have to design a circuit from scratch that may end up no better than a $40 bargain from a second hand store. The circuit posted is a small 10/15Watt basic circuit and these can be found on landfill sites if you hunt around and you may even get lucky and pickup a whole amp for nicks. (well that depends on where you live I guess)
Having built a lot of amps from kits and from scratch,, I can tell you that the chance of success at first attempt is very low. Even worse if it's a first attempt. :-X

On the other hand ""IF"" *Watermelon33* has played an amplifier that uses this EXACT Design and it delivers the sound he wants,, then yes it then makes logical sense to build one because you have already heard the result.

My advice would be buy something cheap and back engineer it, you will learn a lot faster and avoid the eternal frustration of building a circuit only only to find it sounds nothing like what you hoped for.
cheers, Phil.

edvard

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Re: guitar amp diagram revision help
« Reply #7 on: January 26, 2020, 07:04:37 PM »
...
TDA2050 is marked as obsolete anywhere I've looked.  You could probably source one on eBay though.  That said, LM1875 is a great chip and I think it is a direct replacement pinout wise (you'd want to double check).
...

Beware TDA2050s from anybody but reputable parts sellers.  Some folks may have made a "reserve buy" when they were going out of production and are selling NOS, but NEW production is all counterfeit.
Obligatory JohnAudioTech video: "Counterfeit vs Authentic TDA2050 audio amplifier IC test"
https://www.youtube.com/watch?v=R2J5xrSiNrI

Looking at the datasheets, I can confirm the LM1875 is a pin-for-pin match with very similar performance.
« Last Edit: January 26, 2020, 07:53:57 PM by edvard »