I am trying to undersyand clearly about the inductors: I red about 10uH being ok (on the blue/black board) for 8ohm speakers and 22uH for 4ohm ones (even the wiki page states that).
Then... I red even the opposite!
Could someone please clarify about that refering to blue/black board?
Thanks in advance
BTW, I even asked about the use of the amp6 inductors rated 10uH because soneone told they could saturate if run over 24V. But I plan to use 18/20V max. Would it be ok..?
Then... I red even the opposite!
Could someone please clarify about that refering to blue/black board?
Thanks in advance
BTW, I even asked about the use of the amp6 inductors rated 10uH because soneone told they could saturate if run over 24V. But I plan to use 18/20V max. Would it be ok..?
Generally, lower load impedance = lower inductor value. On my 'wiener' card, I use 10uH for 4/6 ohms and 15uH for 8 ohms, though 22uH will also work for 8 ohms. You also have to change the output capacitor based on the load and the chosen inductor, I'll write up a post later describing how to calculate the parts you need.
I had a pile of stuff written up in the past for calculating L droop/saturation for toroid cores, but no longer have access to it. I do distinctly remember the T106-2 saturating too much at higher currents, when I was looking at output inductor options for my boominator card.
I suggest going through the datasheets of inductors, and find a curve giving the inductance versus current. You want this curve to be a flat line (say 5-10% droop max) from 0 amps to your maximum output current (eg, 24V/4 ohms = 6 amps). For example, Coilcraft MSS1210 looks great:
Typical Inductance vs Current - MSS1210 Shielded Power Inductors
If your inductor supplier can't give you one of these curves, find another supplier.
I had a pile of stuff written up in the past for calculating L droop/saturation for toroid cores, but no longer have access to it. I do distinctly remember the T106-2 saturating too much at higher currents, when I was looking at output inductor options for my boominator card.
I suggest going through the datasheets of inductors, and find a curve giving the inductance versus current. You want this curve to be a flat line (say 5-10% droop max) from 0 amps to your maximum output current (eg, 24V/4 ohms = 6 amps). For example, Coilcraft MSS1210 looks great:
Typical Inductance vs Current - MSS1210 Shielded Power Inductors
If your inductor supplier can't give you one of these curves, find another supplier.
Great: lower inductance for lower impedqnce as I was assuming, thanks.
So these could work ok for the blue/black board, and the curve inductance/current is particularly flat.
http://www.coilcraft.com/pdfs/rfs1412.pdf
I will check my toroids for having the same informations, but considering that I would run my mps on the 18/20V range I hope they will be ok with the T60-2 ferrite toroids...
Waiting fir your next post in case you decide to show the calculating formula.
Thanks!
So these could work ok for the blue/black board, and the curve inductance/current is particularly flat.
http://www.coilcraft.com/pdfs/rfs1412.pdf
I will check my toroids for having the same informations, but considering that I would run my mps on the 18/20V range I hope they will be ok with the T60-2 ferrite toroids...
Waiting fir your next post in case you decide to show the calculating formula.
Thanks!
Hello
I have the tpa YJ 2.1 board and want to use a subwoofer but the xo is not very good. Does anyone know how could I hack the existing filter to change the xo or is it better to just make a new low pass filter? And does anyone know the best LPF I could make for this board if the xo can not be changed? I could not have negative voltage for the filter because the amp is operating on 12v-19v.
Thanks
I have the tpa YJ 2.1 board and want to use a subwoofer but the xo is not very good. Does anyone know how could I hack the existing filter to change the xo or is it better to just make a new low pass filter? And does anyone know the best LPF I could make for this board if the xo can not be changed? I could not have negative voltage for the filter because the amp is operating on 12v-19v.
Thanks
Regarding calculating the T60-2 saturation/impedance droop, I don't have a quick answer. There's a lot of literature up on the Micrometals website regarding inductor design, and I don't have the time to dig into it myself. I'd pick a known flat inductor, the Colicraft MSS1210 will solder directly in place of the existing inductors on a YJ blue/black card.
How to pick TPA3116/8 output filter parts... you'll have to do a bit of math:
Start by choosing Rload (say 8 ohms) and arbitrary L and C values. TI's default filter is 10uH + 0.68uF.
Wo = 1/sqrt(L*C) = 1/sqrt(10e-6 * 8e-6) = 383.4Krad/sec
Fo = Wo/(2*pi) = 61033Hz.
Q = Wo*(rload/2)*C = 0.521.
You want Fo to be in the 40-70KHz range, and Q to be in the 0.5 to 0.8 range, ideally 0.707 (zero peaking). Low Q values will roll off early and have less treble response (lower Fo's will move the roll-off further into the audible range), and high Q values will have a HF peak.
Here's what I recommend:
4 ohm = 10uH + 1.5uF.
6 ohm = 10uH + 0.68uF (standard TI config) or 15uH + 1uF, both perform about the same.
8 ohm = 10uH + 0.33uF, or 15uH + 0.47uF (recommended) or 22uF + 0.82uF.
Next thing is, make sure your speaker has a flat impedance over the whole audible range. I strongly recommend adding zobel networks to speakers - without this done, the speaker's rising impedance will cause peaking in the output filter, and you could end up with particularly nasty resonances which could burn components with the right input signal. I'd give this site a read and add a zobel following their guidelines.
TA Speaker Topics - Neutralizing L(e) with a Zobel
How to pick TPA3116/8 output filter parts... you'll have to do a bit of math:
Start by choosing Rload (say 8 ohms) and arbitrary L and C values. TI's default filter is 10uH + 0.68uF.
Wo = 1/sqrt(L*C) = 1/sqrt(10e-6 * 8e-6) = 383.4Krad/sec
Fo = Wo/(2*pi) = 61033Hz.
Q = Wo*(rload/2)*C = 0.521.
You want Fo to be in the 40-70KHz range, and Q to be in the 0.5 to 0.8 range, ideally 0.707 (zero peaking). Low Q values will roll off early and have less treble response (lower Fo's will move the roll-off further into the audible range), and high Q values will have a HF peak.
Here's what I recommend:
4 ohm = 10uH + 1.5uF.
6 ohm = 10uH + 0.68uF (standard TI config) or 15uH + 1uF, both perform about the same.
8 ohm = 10uH + 0.33uF, or 15uH + 0.47uF (recommended) or 22uF + 0.82uF.
Next thing is, make sure your speaker has a flat impedance over the whole audible range. I strongly recommend adding zobel networks to speakers - without this done, the speaker's rising impedance will cause peaking in the output filter, and you could end up with particularly nasty resonances which could burn components with the right input signal. I'd give this site a read and add a zobel following their guidelines.
TA Speaker Topics - Neutralizing L(e) with a Zobel
i did this according to irrebeo's advice a few months ago.
different online calculators gave different values for my speakers.
but i had a good starting point from there to play around with boxsim to find a good compromise.
and voilà...
it makes a big difference!
If I correctly understand:
Impedance is 8ohm
Coil inductance is 0.54mH
R1 should be 8ohm (10W)
C1 should be close to 8.54uF (I have 8.2uF 250V film caps, sounds ok...)
And the very simple scheme should be this one, RIGHT?
An externally hosted image should be here but it was not working when we last tested it.
Yes or like this (and anything in between):
Just wandering about resistor power: 10w is enough??
In general their might be benefits from using Zobels on every speaker unit, just search the threads (usually ending in war on this forum). But here it is just a suggestion to have a grip on behavior of outputfilter of just these ampboards🙂
Looks good.
Make sure you use a non-inductive film resistor instead of a wirewound resistor for the snubber resistor. I use wirewound resistors as test loads for amps, and I had to put zobels on them 🙂
Four 33 ohm, 3W film resistors in parallel give 8.25 ohms with 12W of power handling and very low inductance.
Make sure you use a non-inductive film resistor instead of a wirewound resistor for the snubber resistor. I use wirewound resistors as test loads for amps, and I had to put zobels on them 🙂
Four 33 ohm, 3W film resistors in parallel give 8.25 ohms with 12W of power handling and very low inductance.
Yes or like this (and anything in between):
This "optimal" equation will generally overcompensate the impedance to be close to or below Re, and will have significant loss. A better approach is to have Rzobel = Znominal x 1.207. This will give a more linear impedance compensation with less phase change and as a bonus have less loss.
And as gmarsh points out above, please make sure a resistor in series with a capacitor in parallel across the speaker is absolutely non-inductive. Not just "non-inductive" as in wire-wound so-called "non-inductive" power resistors. Metal film or carbon composition works best although for the power ranges required here metal film would be preferable as carbon composition would probably drift too much and wear out too soon.
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Going back to output LP filtering:
I am to go for 8ohm speakers with 15uH inductors + 0.47uF caps, but I was thinking if with this configuration the snubberizing addition (330pF cap + resistor) is still recommended.
Any advice, please? 🙂
I am to go for 8ohm speakers with 15uH inductors + 0.47uF caps, but I was thinking if with this configuration the snubberizing addition (330pF cap + resistor) is still recommended.
Any advice, please? 🙂
All my 3116 ampboards got the 330/10 snubber now, but listen yourself. None of my speakers have rising impedance with frequency, they either have zobel or have slightly dropping impedance with frequency like electrostatic or ribbon speakers could show.
Got it, thanks!
I have another, different, question:
Planning to use my board with a linear variable PSU, and I ordered a toroidal trafo 15V 120A, that means about 7A.
The PSU I plan to use has ER206 diodes (here the datasheet ER206 ... - Datasheet Search Engine Download )
These diodes are rated for 2A max average current, and 50A max peak current.
Will I have any problem using these diodes..?