2 watt speaker?

[jtroutt19]

Sorry if this has been discussed before I couln't find anything. I was watching a video last night showing the differences between 4 types of speaker in the 9xr pro. The very last one was a 4 ohm 2 watt speaker. That being said there was no information about what type of speaker it was as far as brand name where to get it and so on.

Today at work I took apart a beats pill. Perfect size speakers and they have great sound. Plus they are 4 ohm speakers. Got home tonight and installed one and its loud but crackles and pops. So I cant use these speakers. So what 2 watt 4 ohm speakers are people using?

[jhsa]

I will check later when I get to the computer but I think a 4 Ohm speaker might not be recommendable for the PRO's audio amplifier.

João

[DaveyP]

A speaker that has been used with 'great' success is

http://www.reichelt.de/Full-Range-Speak ... &OFFSET=16

Compared to the OEM version its a great improvement, its like hi-fi Jim, but not as we know it

[jhsa]

Yes, that is what I use on my PRO.

João

[jhsa]

as I said, the datasheet of the amplifier chip does not mention a load of 4 Ohms. Only 8 and 32 (Phones).

So I would not install a 4 ohm speaker. Also, do not expect much improvement on the sound volume side. This chip is not very powerful.
This chip seems also to be quite sensitive. Mine got half damaged. the speaker sound was distorted while the earphone sound was good. That means half of the amplifier output circuitry is damaged. I had to install another digital amplifier board on my radio to drive the speaker. The earphone is still driven by the original chip.
Attached is the datasheet of the TPA711 audio amplifier.

João

[MikeB]

The amplifier is powered from 5V, so it provides 700mW into an 8 ohm speaker, 4 ohms will overload it.

Mike.

[jhsa]

Thanks Mike.
I don't think My radio was outputting 700mW before. I would say, not even close.. And I did replace the gain resistor on my test radio as recommended when we were beta testing it..
But i guess I still have some problem on my radio. After installing a 1.5W amp (3W stereo but i use only 1 channel), my sound is still not loud and when I try to increase the volume it starts distorting.. This amp board uses the same chip as the Ar9x board, and that radio IS loud

I think that when I have some time for it I will try to probe the signal right out of the DAC with an external amp, and go down right to the amp. Maybe I find out the source of the distortion. The weird thing is, I have the phones connected to the original chip (1 out and gnd) like they were before, and the sound is clear at full volume. I thought it could be the speaker itself, but the distortion is also there with another speaker connected. Weird??

João

[jtroutt19]

would it be possible to install a more powerful amplifier? I will get that speaker thats recommended and go from there.

[jhsa]

would it be possible to install a more powerful amplifier?

Unless you really know what you are doing, I wouldn't recommend it. I only did it because the amp in my radio is deffective..

João

[DaveyP]

The weird thing is, I have the phones connected to the original chip (1 out and gnd) like they were before, and the sound is clear at full volume.

That's not weird...its fault finding,

The chip contains 2 amplifiers and is used in 2 modes, for loud speaker mode both amplifiers are working and in a push pull configuration, the earphone mode just uses one of the amplifiers.. ergo 1 of the amps is duff (technical description for not meeting specification)

[jhsa]

if you read my post above, you will see that I also have distortion with the other amp I have installed They can't be both "duff"
I am well aware of how the original chip works

What is weird?
- The sound of the phones is clear at higher volume and the sound on both amps is not. Distortion of the external amp is not the issue as I have the same amp working at higher volume on another applications.
- Different speaker also has the same problem, so, the speaker is not the problem. I also tried a speaker from some stereo equipment I have here.
- The signal source for both amps is exactly the same as for the original amp driving the phones.

Anyway, this thread is not about my radio's sound problem, so.......

João

[jtroutt19]

As far as knowing what im doing...in what respect are you talking. I have jedi soldering skills. I repair small electronocs all day for my jobs. Board level repair stuff. Multi layer board repair. Hot air/infrared reflow work pad replacement. The kind of stuff that requires a microscope to do.

Now if you are talking electronic theory then i am not as good. I know enough to get me in trouble.

I dont mind you discussing your radio sound issues. In my thread good way for me to learn!!

[jhsa]

Ahhh, ok, you are a skilled person as far as soldering irons are concerned

Now to install another amp, there are a few points to consider:
- What Amp? I used this one for the speaker, the phones are still driven by half of the original amplifier:

http://www.ebay.com/itm/3pcs-PAM8403-2X ... SwstxVWJcQ

And here is the datasheet for its chip, the "PAM8403"

PAM8403_Audio Amp.pdf

(194.56 KiB) Downloaded 240 times

This amp can also be modified so it mutes the sound when the phones are inserted in the radio's 3.5mm jack socket. This involves cutting tiny tracks on the AMP board, as I think one or both of the control pins (MUTE and SHTDN) pins are tied to VCC. If you try to drive them low (as we need to) without cutting the track(s), BAAANNNNGG!! If you know what I mean

The thing is, the PAM8403 has 2 different possibilities to do this. "Mute" (turns outputs OFF when mute pin is pulled low) and "ShutDown" turns the AMP OFF when is pulled low.
I used Mute I think. The problem is that the original chip (TPA711) disables the speaker when the relevant pin is high while the PAM8403 works the other way round, as you can see if you check the datasheets. My workaround was to use a transistor to invert the level so the PAM will turn the speaker OFF when the phones's jack is inserted.

I also had to solder some resistors to the input, to make some kind of audio mixer as one input was loading the audio signal too much. But i don't remember this part very well. You would have to experiment. I don't think I documented this mod unfortunately.

All this, together with fine soldering are the reasons I said that this mod is only recommended if you know what you are doing

João

[jtroutt19]

Fair enough! thanks for all the info. Sounds like a fun night to me! One question though. Are you still having issues with distortion?

[jhsa]

I remember that when I did this mod I limited the signal to a level that would keep the distortion low.
The general sound volume of the radio is not very loud, but it is certainly better than it was.
My other radios are louder than this one. But even like that it is still enough for me..

João