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Old 3rd April 2010, 04:14 PM   #21
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Join Date: May 2008
Audio seemed fine. Altho I have not hooked it to decent speakers yet. absolutely no pop or noise on turnon or turnoff. standby function works beautifully.

The only thing I can say is its much simplier then the one included with the 7265 datasheet. The standby function is done with some simple resistors and a cap and the feedback path is MUCH shorter. He has spots for many components including filters on the inputs. I chose to omit many parts, atleast for now. I did however leave the zobel and input caps.

I'll ask my friend (Randy Rubin) if I can share the schematic\PCB layout. If he says yes i'll post images. Same guy that did my PCBs for my biamp's and crossovers. This board was donated to me for free as a project to mess with, so I'm not really in a spot to willingly give out its design.

Last edited by thetube0a3; 3rd April 2010 at 04:16 PM.
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Old 11th April 2010, 02:11 PM   #22
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Seems to be pretty much complete other then some pieces of blue protective plastic i need to peel off of the aluminum face
I need to put a scope on it tho either i'm imagining it or I'm hearing a very high frequency noise. like 15-17KHz continuously from both speakers. Perhaps noise from the SMPS supplies? Or it may just be completely in my head due to the horrid apple speakers im testing with.

two knobs = bourns 10K pots with a 20K resistor each to ground. I'm using them as volume\balance knobs. due to the 20K resistor they don't make a huge difference on volume but allow me to change the level + balance a fair amount which is what I was after. switch in center = standby/on. Not the best IMO but it does the job and the amp was built 100% with parts from friends and my stash. I didn't have to spend a cent

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Click the image to open in full size.

Last edited by thetube0a3; 11th April 2010 at 02:17 PM.
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Old 19th April 2010, 02:09 PM   #23
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OK I need some opinions.

I have the amp hooked up at work to a dell PC and my gain is insane. I have the mixer all the way down to 0 and still have too much gain.

My feedback is set up for a gain of 32. The datasheet says you want to be greater then 25dB.

My pots on the input are 10K with a 20K resistor in series to ground. The chip has an internal load of 25K. I used the 20K resistor to try and keep my input impedance something respectable.

I'm thinking to drop the input level I can put a 10k or 20K in series with the input between the rca jack and the pot and just running the other side of the pot straight to ground. This will give me far more control with the volume pot as well as still maintain over 20K input impedance.

Reason I have 10K pots in the first place is this amp is built 100% from free parts. I'd like to keep it that way
any opinions?
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Old 19th April 2010, 05:50 PM   #24
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20k to ground in series with a 10k pot means you can adjust the input from ~67% to 100 %, but not below 67%.

What's wrong with 10k input impedance? Skip those 20k resistors and you can attenuate all the way down to zero.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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Old 19th April 2010, 06:36 PM   #25
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Nothing wrong with 10K input impedence I suppose. But keep in mind the TDA-7265 has internal resistors which are 25K.

This will give me approx 7K input impedance I would assume? Seems a bit low for a cheap PC's onboard sound to drive no?
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Old 20th April 2010, 12:25 PM   #26
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Amp is done. Works great now with the 10K pots straight to ground.

$5 chipamp + a free board from a friend + a bunch of free parts, hardware and two samsung tablet 19V switching power supplies from another friend = wow

I am really impressed. I expected the amp to work decent but this by far exceeds my expectations especially driving a 4 ohm load.
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Old 10th August 2012, 12:34 AM   #27
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hey guys,
im new at this site and also in electronics. anyways i am trying to built an amp with the 7264/5. does anyone have schematics for this??
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