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Topics - Oooscar

#1
Hello all,

Maybe a bit off topic, but maybe you can give me some help...

I am trying to add an aux input to a boombox radio I have at home
I have not found the schematic of the main board, it's a MX-Onda
MX-MCP6428Mp3. So far, I don't want to use the tape player or the
CD player. I want to modify the circuit on the radio Mode.
It has an analog volumen pot with six pins, and the following ICs,
SA2111 is the radio IC, and NEC1316C is the power amp IC.
I can't see any sort of Jumper wire that would allow to connect an
stereo 3.5 female Jack with 'two poles' to keep the radio on, but
connecting an aux instead of the radio. Everything seems printed
on the board.

I have tried to connect directly my smartphone to one of the inputs
of the NEC1316C ic, but the sound is barely heard, It's like the IC
ignores that signal, and the radio signal keeps there. The volume pot
does not improve the situation. Something is going on, but I am lost.

Anyone here has any clue how can I make It if it's possible?

Thank you very much for your attention. Thanks for stopping by.

Cheers


#2
Hello,

I have around two small speakers from a pair of phones. 8 ohm 0,25 watt each one.
I have tried It today with an lm386 amp I have. And the sound from the low strings is not as good as the sound of the first three ones. I know small and tiny speakers have problems with low frequencies, I even tried It with the smartphone, and It sound quite high, bright, treble. Is there any way to balance the sound at least a bit? Changing the output capacitor, etc. I would like to make a very small guitar amp, like a smokey amp, but with the "best" possible sound.

Regards, cheers
#3
Hello all,

Recently I bought a Zoom G1xon effects processor, and I am trying it with a homemade amp I did based on an LM386 ic. I didn't expect to work properly. What happens is that any guitar I connect to the g1xon and to the amp produced in general a lot of noise, and if I turn the volume of the guitar up, a high pitch squeal, like feedback sound starts to sound. Have you had these sort of sounds in any unwanted situation? Maybe I can get some tips to solve it. The amp by itself with just a guitar works well, with a bit of hum of course, but fine. I attach a photograph of the diy amp.

#4
The Newcomer's Forum / Tda ICs Pentawatt PCB
May 28, 2020, 04:29:39 PM
Hello,

I have some TDA ICs, 2030A, 2003, 2006. The Pentawatt package pins do not fit on a typical perforated board. Is there some specific socket to use it with a perforated board? Otherwise I have to make bigger holes. Any suggestion? Maybe some of you have more experience.

Another question. I heard that Jfets with low pinch off voltage are better to use them as buffers, boosters? I guess it affects to the clipping, taking into account that a guitar signal has 200 mV peak to peak, let's say.

Thanks.

Cheers
#5
Hello,

I am studying different preamp schematics. I am inclined to minimal amps or amps with not so many parts, just the ones needed to produce a given sound for guitar practice/bedroom playing purposes. I have several questions:

1.- Is it good to add a boost stage initially before any overdrive/soft clipping in terms of sound?
2.- Is it better to add a tone control stack before any clipping or after, in terms of sound?
Let's say you make: guitar, boost, tone control/tone stack, soft and/or hard clipping, out.
3.- Does it worth to add a classic tone stack with bass, trebble, mid respect a single pot tone control, or a BMP with some mid control (Jack Orman mod I believe...)?

It seems to me that with a simple tone control (or maybe two pots) you can get a wide range of sounds, but I am learning, and I would like to understand how many stages can have a guitar amp, and the purpose of those, to see how can I simplify or minimize them, and still get a good and wide range of sound. For instance, adding preamp stages to an LM386 can give you a good sound with control. I have tried hard clip diodes with a TL072, and the sound to me gets better. Nicer.

Thank you very much for your attention.

Regards, cheers.

#6
Hello,

I am starting to experiment with opamps as preamps, and/or headphone amps.
I am trying to add a tone control, and the big muff pi seems a simple one. I put it between the two op amps of a TL072CP but the sound I get is very bad. When there is not tone control, I get at least a clean sound when I listen with my headphones, but when I introduce the big muff pi tone control, the sound is noisy/distorted (in a unpleasant way). What I am looking for is a clean and filtered sound. If I want musical distortion I will add it later. But just to go step by step.

I have tried also to add the big muff pi passive tone control to the output of a JRC386D simple circuit, with just a capacitor at the output, and I get no sound at all. I am thinking if the output current of the opamp is not enough for the tone control circuit. When I remove it, I get sound in my headphones. I know that there is a circuit called Smash Drive that has a tone stack in the output of a LM386, but it is used as a pedal, and I have no tried and don't know if it has enough power the signal to drive headphones.

I am trying things with ingenuity, just step by step. Maybe some of you here have tried the same circuits or similar ones, or have more knowledge, and can give me some clues to help me get those circuits work.

Cheers,

Oscar.