My TPA3122D2N BTL proto

[kenpeter]

You didn't seem to leave yourself room to drill holes for standoffs.
Many components perhaps too close to the edge for snap track.
What was your plan? Or is this only for the bench?

[theAnonymous1]

Originally posted by kenpeter
You didn't seem to leave yourself room to drill holes for standoffs.
Many components perhaps too close to the edge for snap track.
What was your plan? Or is this only for the bench?

Zip-ties!

I don't even have any extra standoffs on hand, so holes for them would do me no good.

Looking at the middle pic with the board on its side; I figure one tie around the PCB where the inductors are, and then one around the large electrolytics.

I think I will do dual mono-blocks with these. There are some really small 19v laptop SMPS available I plan to power them with.

[kenpeter]

I got a wacky wacky abuse to try... Gotta look through the
scrap for one with an old rev chip or eval board with some
cosmetic defect, nobody will care if I blow one of those up.
If it works, I might then try with a current rev board.

I got a pair of RCA 814 directly heated transmitter tubes.
I want to try them for audio output. Filaments need 10V
at 3.25A, and I hear bad things can happen to one end
of a directly heated filament after extended periods DC?
I am no fan of filament hum to try plain old AC. They do
light up with a bright golden glow like the 32.5W bulbs
they are, with DC on my Agilent bench supply.

Suppose I take a clean ultrasonic 50KHz sine wave instead?
From a Wien Bridge or whatever... And pump that through
one of TI's tough little Class-D amps with a real high frame
rate? The filament would then be about a 3 ohm BTL load?
Wonder if output inductors would be an issue at 50KHz?

TI may have some more appropriate part# to suggest?
I'll discuss this tomorrow (if an engineer has time) before
I move any further. I can still breadboard a Wien Bridge in
anticipation of some future experiment.

[przem]

Hi
Currently i'm making pcb layout for tpa3106d1. I have noticed that you connected Vcc to Fault and Mute through a resistor - could you please explain why?

And what's the cap between INP and INN for?


Btw. How is the sound from this little baby?

[theAnonymous1]

Originally posted by przem
Hi
Currently i'm making pcb layout for tpa3106d1. I have noticed that you connected Vcc to Fault and Mute through a resistor - could you please explain why?

And what's the cap between INP and INN for?


Btw. How is the sound from this little baby?

If you look really close you will see that the Fault pin is actually connected to the Mute pin. This way when there is a Fault condition it will pull Mute high and mute the amp. The 100k to ground on the Mute pin is to pull it low when there is no fault condition.

The cap between INP and INN is a 10nf NP0. I was just experimenting and it isn't required.

I really like the sound of this amp. Plenty of punch and very clean. I suggest using it with the lowest gain setting though as the the background noise increases quite a bit with a higher setting.

I haven't built the other channel yet due to a recent move and broken laser printer; plus I need to order some parts from digi-key.

[Eva]

Originally posted by kenpeter
I got a wacky wacky abuse to try... Gotta look through the
scrap for one with an old rev chip or eval board with some
cosmetic defect, nobody will care if I blow one of those up.
If it works, I might then try with a current rev board.

I got a pair of RCA 814 directly heated transmitter tubes.
I want to try them for audio output. Filaments need 10V
at 3.25A, and I hear bad things can happen to one end
of a directly heated filament after extended periods DC?
I am no fan of filament hum to try plain old AC. They do
light up with a bright golden glow like the 32.5W bulbs
they are, with DC on my Agilent bench supply.

Suppose I take a clean ultrasonic 50KHz sine wave instead?
From a Wien Bridge or whatever... And pump that through
one of TI's tough little Class-D amps with a real high frame
rate? The filament would then be about a 3 ohm BTL load?
Wonder if output inductors would be an issue at 50KHz?

TI may have some more appropriate part# to suggest?
I'll discuss this tomorrow (if an engineer has time) before
I move any further. I can still breadboard a Wien Bridge in
anticipation of some future experiment.

Put a capacitor across the filament, an inductor in series and apply a square wave. The waveform at the filament will be sine like. You will have to choose component values carefully so that the LC filter removes enough high frequency components and the filament resistance when hot provides enough damping to the filter. That's all. Electronic ballasts for fluorescent lamps work much in the same way.

[przem]

Originally posted by theAnonymous1


If you look really close you will see that the Fault pin is actually connected to the Mute pin. This way when there is a Fault condition it will pull Mute high and mute the amp. The 100k to ground on the Mute pin is to pull it low when there is no fault condition.

I have seen that MUTE should be connected to FAULT (datasheet says that) but didn't know about the resistor. As I can see you have also connected GAIN to VREG thru resistor - can't it just be connected directly?

Thanks for your answers!

[theAnonymous1]

Yes, GAIN0 and GAIN1 are connected to VREG via 100k resistors. This is to pull both GAIN high when no jumpers are installed (giving the highest gain setting of 36dB). Installing a jumper will pull the relative GAIN pin low changing the gain configuration.

If you plan on only using a single gain setting you don't need the resistors. Say for instance you want the lowest setting (20dB), you can simply connect both GAIN to AGND and leave out the 100k resistors to VREG.

Have you taken a look at the schematic in the evaluation module datasheet?

http://focus.ti.com.cn/cn/lit/ug/slou191b/slou191b.pdf

[przem]

I looked at it only once, some time ago and just forgot about it ;>
Thanks for reminding

[przem]

Ok, finished. Looks similar to theAnonymous board but there aren't much things that you can change. Coils are on Top layer, probably I'll put them on bottom.