| Rodo |
Hi. Iīm testing last version of TDA8920: TDA8920B. PCB is not in datasheet so Iīm starting from begining. Iīm making a versatile PCB but I need some assistance with schematics and lay-out issues. I plan to use 2 TDA8920B in BTL mode but also with 4 x SE ouputs. Imputs will be selected whith jumpers. Also all design will be modular.
I have experience with PCBs development.
If somebody wants to work with me in project is wellcome. I use Protel but I can share any format output (.pcbs, gerber files, png, corel, etc.). Post is opened. |
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| Ipanema |
| There's lots of crosstalk between the channel when I tested the evalution board. Maybe you should consider only use it in BTL mode. |
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| Rodo |
| quote: | Originally posted by Ipanema
There's lots of crosstalk between the channel when I tested the evalution board. Maybe you should consider only use it in BTL mode. |
Hi Ipanema.
Datasheet specification for channel separation is about 70 dB. Only reference I found in both datasheets (8920 and 8920B) about advantage of using BTL is because pumping effect in supply.
Did you tested 8920B with evaluation board PCB in datasheet for 8920 or you made a new lay-out?
Schematic for 8920B has some changes in components and supply. Could it be reason for crosstalk?
I have not tested any of both so I have not idea.
Reason to use SE as BTL is because I have some Hifi speakers with low RMS power limit (about 35 W 8Ohms). Also I plan to use BTL for SB and any other configuration I could test with more powerful speakers. |
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| BWRX |
| quote: | Originally posted by Rodo
Datasheet specification for channel separation is about 70 dB. |
At what frequency? |
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| Rodo |
| quote: | Originally posted by fumac
hi Rodo
i had make 8920B
use 2 TDA8920BTH in BTL mode but also with 4 x SE ouputs
IS JUST LIKE ME
RG
FUMAC |
Hi fumac.
I followed some posts you made for PCBs for hi frequencies considerations and I learned a lot! Also I surfed your site and amplifiers you made are amazing! You could make a lot of money with UPS and swithching power supply boards because hi frecuencies for that devices are very dificult to use.
Returning to amplifiers: I will try some easier one.
I found 8920B very interesting for beginers.
Did you have any problem with crosstal in SE configuration? |
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| Rodo |
| quote: | Originally posted by BWRX
At what frequency? |
Hi BWRX.
Thanks for you post.
1W / 0 Ohms / 1kHz.
But have in mind for class AB hybrid amplifiers, testing parameters are more than enough.
Do you think for class D channel separation varies more than AB amplifiers with frequency? |
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| fumac |
rodo
when i was a beginer(even this day ,i am newb )
i tryto design class-d for my project a wireless speaker
i'm start at 8920
but it's not very easy to dowith it
inside the chip, low signal and high power mixer
so must to attention to the decoupling
i design 3 versions pcb, then make 8920 ok
after that, i found the chip of class-d is not good at high power
so changto other way
good luck
rg
fumac |
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| Rodo |
| quote: | Originally posted by fumac
rodo
inside the chip, low signal and high power mixer
so must to attention to the decoupling
i design 3 versions pcb, then make 8920 ok
after that, i found the chip of class-d is not good at high power
so changto other way
good luck
rg
fumac |
Hi again fumac.
Do you think a chipset solution is better way? It means using a chip to PMM and other for power output?
I donīt need hi output power. 80+80 W is enogh for me but I donīt want to use a huge heatsink.
I couldnīt find other chips to use with easy board lay-out.
Idea is to use double side boards but without metalized holes using top layer for ground plane.
Trypath has some different options than 8920 but I canīt get chips in Argentina. |
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| fumac |
| quote: | Originally posted by Rodo
Hi again fumac.
Do you think a chipset solution is better way? It means using a chip to PMM and other for power output?
I donīt need hi output power. 80+80 W is enogh for me but I donīt want to use a huge heatsink.
I couldnīt find other chips to use with easy board lay-out.
Idea is to use double side boards but without metalized holes using top layer for ground plane.
Trypath has some different options than 8920 but I canīt get chips in Argentina. |
i have tested 8920 and class-t(100w@4r) in same speakers(tannoy), personal chiose 8920, the bass of 8920 is better than the class-t, the treb of class-t is better than the 8920.
no one is better than other one in all test. so i delete all of them in my new projects.
about chip set
i did not find any chipset is good Enough at class-d ,(i just read the pdf of them,no interest to test them again),
rg
fumac |
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| Ipanema |
| I tested the evaluation board PCB as posted in the datasheet. It may be PCB itself causes the crosstalk. I didn't investigate further. BTW, this chip sounds fine just like the class T. But I still prefer GC over class D thus far. Enjoy building...... |
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| Rodo |
| quote: | Originally posted by Ipanema
I still prefer GC over class D thus far. Enjoy building...... |
Thanks for your answer. I have a lot experience with STK based amplifiers. I avoid using STK because the size of heatsink. Also they generate a lot of heat with a huge heatsink. I have not use GCs.
As you tested GCs, do they have same problems with heat?
Thanks a lot, Rodolfo:) |
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| Ipanema |
| GC does not generate much heat as with most Class AB amplifier. However the heat does increase proportional with the supply voltage. If you face heat problem with your heatsink, then just lower the supply voltage will do. :-) The lowest supply I use for LM3875 is +/- 16V and they are stone cold with just a puny heatsink. |
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| Rodo |
Hi. Iīm finishing first PCB for TDA8920B (SMD Version). I will make it public soon.
As I plan to use 2 chips in same amplifier I will make one PCB for each chip and use connectors to joint modules. Third module will be inputs, mute control, osc. and supply circuit.
I want to reduce redundant parts of circuit. Is it possible to joint both chips starting with a common VDDP, VDDA, VSSA and VSSP? It means using just one supply circuit?
Thanks for your help, Rodolfo |
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| Rodo |
| quote: | Originally posted by Ipanema
GC does not generate much heat as with most Class AB amplifier. However the heat does increase proportional with the supply voltage. If you face heat problem with your heatsink, then just lower the supply voltage will do. :-) The lowest supply I use for LM3875 is +/- 16V and they are stone cold with just a puny heatsink. |
Thanks for your answer. If I canīt build this class D amplifier I will start with GC.
;) |
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| fumac |
| quote: | Originally posted by Rodo
Hi. Iīm finishing first PCB for TDA8920B (SMD Version). I will make it public soon.
As I plan to use 2 chips in same amplifier I will make one PCB for each chip and use connectors to joint modules. Third module will be inputs, mute control, osc. and supply circuit.
I want to reduce redundant parts of circuit. Is it possible to joint both chips starting with a common VDDP, VDDA, VSSA and VSSP? It means using just one supply circuit?
Thanks for your help, Rodolfo |
phps before u send it to make it, u can post it here, many people can tell u some thing;)
rg
fumac |
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| Rodo |
Hi.
I finished first board.
You could find images at:
http://www.bairesshopping.com.ar/pcb/pcb.html
or here at the bottom.
There are 2 boards:
- TDAīs one: It contains TDA8920B, complete output stage as describes datasheet, some components from input circuit and some components from filter power supply input. Plan is to use 2 boards per amplifier. I think Itīs finished.
Itīs double side through hole but TDA. To avoid using metalized holes, I used some capacitors that let connect both layers soledering pads of both sides. Top side is most for GND ground plane.
- Main board: It contains common parts to use 2 x TDA8920B boards. I made it just single side PCB. Some components from Power Suppy, Mode Control, External Oscillator and audio inputs are in this board to reduce redundant circuit. Main board is not finished yet: just 1 TDAīs board is connected and to use with internal oscillator. Also some space at right is keept to include audio preamplifier or just to fit Power Suppy rectifier and capacitors.
I have some questions about this project:
- Is it ok the way a separate supply stage in both boards?
- Same question for audio inputs.
- Is it ok lay-out?
- Plase check GND and FGND as I separe tracks to balance load. Is it the idea?
Thanks, Rodolfo
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| Rodo |
Top side PCB
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| Rodo |
Bottom Side PCB
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| Rodo |
Highlighted Schematic from original NXP datasheet.
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| fumac |
Rodo
hi thanks ur mail
i cant read your pic,
and i cant goto ur web :)
pehaps u can post in diyaudio, or email me:)
rg
fumac |
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| Rodo |
If somebody canīt see images and want to me to send them by mail, send me a e-mail to rodolfocasaubon$yahoo$com
Thanks, Rodolfo |
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| Rodo |
Here is new TDAīs module board with some errors fixed. Also I removed solid ground plane from top layer to see board better. Obviously in final board Solid GND plane will be present.
Mainboard (board to connect both TDAīs modules remains the same.
Please evaluate this.
Thanks, Rodolfo
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| fumac |
i think ur l3,l4 , move close to the output of the chip, it will be better then now.
rg
fumac |
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| fumac |
hi classd_fromru
long time no see:)
do u have skype or others
let's make friend
fumac |
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| Rodo |
Hi classd_fromru. Your board was first that makes me think in using TDA8920 to this project. You made it very small, just one layer and just one wire-jump!!!!
TDA8920B (upgrated version of TDA8920) schematic in NPXīs datasheet is quiet different to TDA8920 (without "B"). GND and supply are diferent. Also some components are removed or changed.
First approach was using your layout instead PCB in datasheet for TDA8920 because simplicity. But I got 8920B instead 8920 so none of PCB layouts are designed for this version.
TDA8920B has not any PCB from NXP datasheets.
Because changes in schematic for "B" version and the fact that SMD capacitors and other components are very hard to find in local market, I decided to start from schatch. Also in a new design, I decided implement other features as BTL-SE jumper setting, mainboard with 2 x TDA8920B modules support for BTLx2 or SEx4, etc.
Since Iīm not so good in electronic issues, I started this post.
Could you please take a look to my design?
Thanks a lot, Rodolfo |
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| audiodesign |
| Do you sell this pcb or the complete board ? |
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| Rodo |
Hi.
I don't sale PCB or complete board since I made it just for me to test chip. Anyway I have a hard to find datasheet fot 8920B that has evaluation PCB (Datasheet found in NXP has none). Datasheet is not posted in NXP website. Developers of NXP sent it to me by mail.
So, if you have in mind to build your board to test 8920B, I could send datasheet or my own designed board (Protel) that could help you.
NXP board is very similar to 8920: SMD components, double side ond very small. Mine uses just SMD 1205 100uf caps and 8920B chip. Other components are all trough-hole. Board is single side.
Write me to rodolfo@kashima.com.ar if you want any file.
Rodolfo |
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