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Old 1st February 2010, 03:41 AM   #51
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Quote:
Originally Posted by danielwritesbac View Post
Okay, have mute to v+ via a 10k resistor. The mute switch didn't need to pull full current--it only needs voltage. Stupid datasheet. lol!
So I need a 10k resistor between pins 14 and 5? In addition to a switch?
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Old 1st February 2010, 06:35 AM   #52
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Quote:
Originally Posted by irishpatrick33 View Post
So I need a 10k resistor between pins 14 and 5? In addition to a switch?
You don't need to add a switch.

Well the amplifier draws less current when you connect pins 14 (mute) and 13 (v+) together with a 10k resistor.

Typically, you'd also cause the 10k resistor to charge up a capacitor (voltage goes through the resistor in order to charge a cap), size from 10uF to 100uF (larger value is longer time delay), and the amplifier won't switch fully on until the cap is charged up. Its a time delay, typically called "soft start".
That's also a luxury item that serves as a sort of speaker protection--the delay stops the pops and clunks when you power-up the amp.

Since pin 14 was meant for this sort of circuit and/or to operate from a digital controller unit, this fact is what gave me the idea to use the 10k resistor (to decrease the current draw of the chip's inbuilt switch).

I have not yet connected a capacitor between pin 14 and ground for time delay start, have not yet determined that 10k is the most appropriate value for mute powering, and have not yet gotten the amp up to high fidelity performance. Currently, my own TDA1558Q sounds exactly like a car radio and this is not impressive. So, bear that in mind--I'm just experimenting at this point.

.

Here's the redo build:
(the main idea here is to get the amp into "expected operation" to create a working baseline)

I'm thinking to bend pins 5 and 13 out just far enough to create a "3rd row" and solder a sold wire across them--makes V+ rail.

Now that they're out of the way, that also allows to solder a sold wire across pins 3, 7, 9, 11--makes ground rail.

These two "rails" can be held apart by soldering a 100nF capacitor between them (as shown in the datasheet).

Next step, connect the speaker wires--the spacing of 20ga zip cord is remarkably convenient as it is the same as the pin spacing (thus the pins don't accidentally touch).

Then I have to figure out the most appropriate value for the resistor between V+ and mute (range probably 1k to 22k, minimum and maximum values).
After that its probably good to connect a 100uF cap from pin 4 to ground, and an additional cap (range is 10uF to 100uF) from pin 14 to ground (when in combination with the resistor, it creates the expected "soft start" function).

After these steps to get the amplifier into "expected operation" the next thing is to figure out the mystery of Pin15 (which can be used to remove noise, completely remove DC offset and several other uses), and fill in the input circuit (such as how to make a load without also making a noise), and fill in the rest of the power circuit.

Wish me luck on the redo!
If anyone has any comments on how to do this better, please let me know!

Last edited by danielwritesbac; 1st February 2010 at 06:40 AM.
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Old 1st February 2010, 04:33 PM   #53
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Default Pin 15, the noisebuster

So far, I found only one thing to do with pin 15, and it has been useful.

I wanted a stout 10k load internal to the amplifier to bust the noise. Well, 15 is the centerpoint voltage internal to the amplifier. Pin 15 = every input that isn't provided on pins 1,2, 16, 17

So, I put two 10k resistors on pin 15--intending one load for left channel and one load for right channel.
-and-
I joined pins 1+2, and also joined pins 16+17 as seen in the datasheet for bridged amplifier.
-and-
As for the 10k resistors that are hooked to pin 15, they are connected, one of the resistors to pin 1+2, and the other resistor to pin 16+17.

This did increase the input load.
It was not completely effective in removing the "guitar amp type noise" but it did reduce noise dramatically.
It also changed the DC offset (as expected) from the previous 52.1mv to 00.6mv. My meter cannot read reliably at 00.6mv, so it may be zero DC offset.

I had to change input filter capacitors (located in-between the potentiometer and the amplifier) to correspond to 10k. I used 47uF//1uF electrolytic (per each right and left). This capacitor size is overlarge, but I'm planning to experiment with 5k input load. 1k is too much (bad tone) and 10k isn't quite enough (not completely silent during no input).

The amplifier is performing much more clearly and the efficiency (45 watts barely warming a 3" heatsink) and power output are prodigious indeed! Still working on sound quality (s/n ratio and stereo seperation) but made major progress with pin 15.

Curiosity problem: This isn't a class AB amplifier (impossible efficiency and output per voltage). So, what is it?
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Old 2nd February 2010, 12:21 AM   #54
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Quote:
Originally Posted by danielwritesbac View Post
Currently, my own TDA1558Q sounds exactly like a car radio and this is not impressive. So, bear that in mind--I'm just experimenting at this point.
Sorry to hear that. Really sorry to hear that.

I hope your experimentation solves the problem. As I will likely follow in your footsteps in such a case.
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Old 2nd February 2010, 08:17 AM   #55
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Quote:
Originally Posted by irishpatrick33 View Post
Sorry to hear that. Really sorry to hear that.

I hope your experimentation solves the problem. As I will likely follow in your footsteps in such a case.
Ah, the pin 15 mod brought the entertainment level up considerably. Its clear as can be, no longer sounding quite so much like a car amp. It is as Wahab reported, clear, detailed and quite lively.

All extreme gain amplifiers are lively and they all suffer a bit of a challenge for noise control. TDA1558Q is not an exception to that. In trade for the bother (extra design challenge), you get a sort of "uncompressor" feature.

Currently, I'm playing with:
1). Pin 15's centerpoint voltage employed (plus 2 resistors, left and right) as an all-bandwidth load upon the inputs. This removes noise at Inside the amplifier and reduces DC offset to zero. Need to find an optimized resistor value.
2). A potentiometer ( also called "pot" "L-pad" "voltage divider") located in-between the input filter caps and the RCA jack. The potentiometer doesn't place any load on dc but it does decrease the level of input input (ac audio), and that also reduces noise (and everything).
Wahab is indeed correct that a potentiometer volume control is necessary because the amplifier's gain is considerably excessive. Need to find an optimized potentiometer load value.
3). Soft start function at the mute pin for about 1/4 second timing. This is mute to v+ with 10k -and- also mute to ground with 22uF.

After this, I think we can have some sketches and photography. Perhaps Wahab can post some construction photos as well? That would be nice to see.
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Old 2nd February 2010, 01:08 PM   #56
wahab is offline wahab  Algeria
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Quote:
Originally Posted by irishpatrick33 View Post
So the signal grounds connect to pin 3... and pin 3 also connects to the other grounds?

Here a picture of what I understanding.

By the way, did I actually get polarity or phase of speaker correct?

all is right, it should work, but it s better to put
a stereo potentiometer at the input...
something like 20K..
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Old 2nd February 2010, 01:19 PM   #57
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Hey man, I just can't seem to get the "zzzzzt!" noise stopped. Any ideas?
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Old 2nd February 2010, 01:22 PM   #58
wahab is offline wahab  Algeria
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Quote:
Originally Posted by danielwritesbac View Post
So far, I found only one thing to do with pin 15, and it has been useful.

I wanted a stout 10k load internal to the amplifier to bust the noise. Well, 15 is the centerpoint voltage internal to the amplifier. Pin 15 = every input that isn't provided on pins 1,2, 16, 17

So, I put two 10k resistors on pin 15--intending one load for left channel and one load for right channel.
-and-
I joined pins 1+2, and also joined pins 16+17 as seen in the datasheet for bridged amplifier.
-and-
As for the 10k resistors that are hooked to pin 15, they are connected, one of the resistors to pin 1+2, and the other resistor to pin 16+17.

This did increase the input load.
It was not completely effective in removing the "guitar amp type noise" but it did reduce noise dramatically.
It also changed the DC offset (as expected) from the previous 52.1mv to 00.6mv. My meter cannot read reliably at 00.6mv, so it may be zero DC offset.

I had to change input filter capacitors (located in-between the potentiometer and the amplifier) to correspond to 10k. I used 47uF//1uF electrolytic (per each right and left). This capacitor size is overlarge, but I'm planning to experiment with 5k input load. 1k is too much (bad tone) and 10k isn't quite enough (not completely silent during no input).

The amplifier is performing much more clearly and the efficiency (45 watts barely warming a 3" heatsink) and power output are prodigious indeed! Still working on sound quality (s/n ratio and stereo seperation) but made major progress with pin 15.

Curiosity problem: This isn't a class AB amplifier (impossible efficiency and output per voltage). So, what is it?

great work, daniel, you modified the thing considerably...
it s a classic class AB amp, with each amp draining about
25mA at iddle...
it s true that the gain is too large, at 46 db for the bridged version,
which make use of an input potentiometer mandatory...
this wasn t missed by phillips that did reduce the gain to
26 db in the successor of this circuit, the TDA8561Q...
i used this one because i had some left, and the output
level of a laptop is not very high, so i retained a high gain circuit
after having exausted a ten different circuits, this one seemed the
most practical...
anyway, good tries, i ll publish some photo of the proto soon...
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Old 3rd February 2010, 03:34 AM   #59
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Originally Posted by wahab View Post
this wasn t missed by phillips that did reduce the gain to
26 db in the successor of this circuit, the TDA8561Q
Looking at the specs of that one.. I sort of wish I grabbed that one. Not a huge difference between the two. But I would trade THD for a watt or two any day of the week. Maybe I should pick that one up.
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Old 3rd February 2010, 04:26 AM   #60
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Originally Posted by irishpatrick33 View Post
Looking at the specs of that one.. I sort of wish I grabbed that one. Not a huge difference between the two. But I would trade THD for a watt or two any day of the week. Maybe I should pick that one up.
For example a 90db @ 1 watt efficiency rating on a speaker:
90db@1w
93db@2w
96db@4w
99db@8w
102db@16w
105db@32w
108db@64w
111db@128w
114db@256w
117db@512w
120db@1024w
You get 3 more decibels every time you double the amplifier power.

Compare the 16w amplifier with the sound you want to crank up -versus- the 64w amplifier with the sound you'd never want to hear again. Only one of these options is useful, so lets make clean amplifiers.

Last edited by danielwritesbac; 3rd February 2010 at 04:28 AM. Reason: This wasn't a comment about any of the amplifiers discussed on this thread but rather the concept about what "watts" will do.
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