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Preamp/crossover DIY

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Saturnus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2015 at 11:42am
Originally posted by slaz slaz wrote:

Top job that man !!

Very close to something I would love to have actually (been muttering/murmuring about it for a whle, never done anything).

Ideally I would have  an additional HP filter (switchable) at about 55-60Hz or so - 12dB/octave should do..... and possibly bring the EQ pots out to proper external ones with knobs.



I think the idea is very much not to have anything but the tone button be externally adjustable but you can extend them if you like. I'd warn that they'd pick up much more noise though.

I see it as meant for active speaker use where you set the whole speaker up using the pots and adjust the EQ frequencies manually based on measurements. You can adjust the input section to function as a 2nd order subsonic filter if you like (it's already 1st order which combined with the amp after is really a 2nd order already if you adjust the output capacitors on both accordingly).
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[Djo] View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote [Djo] Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2015 at 3:59pm
Yes, the idea is exactly that, a compact and effective way to make a bi-amplified active speaker. ;)

But, you can adapted the principle to your needs. ;)

I've just upload all my files here :

https://drive.google.com/folderview?id=0B5FND3hVDS53fl9zakhLZHNGM3NKTEZDN012X0h0QTluWjFKcHZ5TEtxSnc1SEpORXhoWkE&usp=sharing

You'll find the project files, so you can modify what you want.
I use Kicad for the schematics and DIYLC for the components layout.

http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software+Suite

http://code.google.com/p/diy-layout-creator/


Originally posted by Saturnus Saturnus wrote:

You can adjust the input section to function as a 2nd order subsonic filter if you like (it's already 1st order which combined with the amp after is really a 2nd order already if you adjust the output capacitors on both accordingly).

Is there an easy way to calculate a second order filter made from two first order in series?
Imagine two filters R=20k C=400n in series should make a fc -6db at around 20Hz but what about fc -3db. Should be around 30Hz, right?


Edited by [Djo] - 11 May 2015 at 4:01pm
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Saturnus View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2015 at 4:59pm
Originally posted by [Djo [Djo wrote:

]Is there an easy way to calculate a second order filter made from two first order in series?

EDIT: 2nd order LR filters are realized by cascading identical first order BW filters. The -3dB point will be f*2^0.5 for a HP and f/2^0.5 for a LP.


Edited by Saturnus - 11 May 2015 at 5:17pm
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davey t View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davey t Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2015 at 9:49am
wow impressive. I'm surprised you went for prototype board and managed to get good performance without a ground plane. A PCB would have been easier but only if you have made PCBs before. Good to see some old school analogue circuit there. 


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[Djo] View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote [Djo] Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2015 at 11:24am
@Saturnus : Thank you! I will try to improve my HP filter section. Thumbs Up

@davey t : Thanks! I don't have the equipment and knowledge to make my own PCB, so I stay with veroboard. I quite like them but I always fear trouble or noise. It all depend but from my experience it's better when we try to use small/moderate value resistors, lot of decoupling caps, and HF filtering to avoid AOP oscillations.
Oh, and I learned electronic by myself with the help of datasheet and forum, so yeah, I'm very proud to show you something that works really great. LOL


Edited by [Djo] - 13 May 2015 at 11:30am
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PetaLue View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PetaLue Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2015 at 6:17pm
I appreciate your design. it looks very cool and helpful.Also thanks for sharing with us. I want to know that what you used to process the signal in different bands? Also how you set the octave values? What is the purpose of knob, i mean in which way it is controlling the parameter.




Edited by PetaLue - 02 October 2015 at 5:23pm
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[Djo] View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote [Djo] Quote  Post ReplyReply Direct Link To This Post Posted: 25 September 2015 at 11:38am
Hi!
Thank you for your interest in this project. I use it now for several months and I'm very happy with it. These board works very well.
To answer you, well, I think it's best that you follow the links on the first post. I'm not a native english speaker so my explanations could be imprecise.
Here, it is only a compilation of existing designs that work flawlessly.
Good luck!
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