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Old 23rd January 2013, 10:16 AM   #21
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So, how big are the woofers on these front speakers?
Do you intend full audio band or a bit less bass?
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Old 23rd January 2013, 10:53 AM   #22
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Originally Posted by danielwritesbac View Post
So, how big are the woofers on these front speakers?
Do you intend full audio band or a bit less bass?
just small sony xplode car speakers,,possibly around 5''/6" even im planning to update my druvers.I need mid and tweeter,,I have another amp for woofer.
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Old 23rd January 2013, 11:11 AM   #23
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Yes, okay. If 23x gain is loud enough for you, that schematic, post 20, should work fine with those speakers.
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Old 27th January 2013, 12:56 AM   #24
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Hi,
Daniel, great project. I have been wanting to do a point to point amp for a while, and this really intrigues me. So in doing some initial planning I have my first question. In refering to your original schematic, are all of the resistors 1/4 watt? In another post you mentioned that you were using a 1/2 watt for your feedback resistor, but you thought the sound quality degraded with higher wattage value. What composition do you recommend for the resistors? Would you recommend somthing like a riken for a feedback resistor (or somthing from mouser as I have already submitted an order to partsconnexion today)?

Sorry, that is more than one question. Thanks
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Old 27th January 2013, 07:23 AM   #25
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Quote:
Originally Posted by SoIL4x4 View Post
Hi,
Daniel, great project. I have been wanting to do a point to point amp for a while, and this really intrigues me. So in doing some initial planning I have my first question. In refering to your original schematic, are all of the resistors 1/4 watt?
Thanks.

They are all 1/4w.

Output RC can be used with a 1/4w 10R and 10n capacitor--That's pretty minimal but usefully retards RF and can't shunt any audio.
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Originally Posted by SoIL4x4 View Post
In another post you mentioned that you were using a 1/2 watt for your feedback resistor, but you thought the sound quality degraded with higher wattage value.
That's seems backwards, for (bad) example: An 1/8w feedback resistor will degrade audio because there's a Power Amp pushing at it--Higher current into smaller wattage resistor is bad for quality.

In a different way, 1/2w, 1w, 3w, might be bad for feedback resistor due to their larger size = higher inductance, and higher inductance puts MOAR gain on HF, which we don't want to do.

Ordinary 1/4w feedback resistor is unlikely to degrade the audio when there is low current. But, there may be room for improvement.
Parallel 1/4w resistor for feedback, as shown in the photos is great because it withstands higher current without degrading audio and because it cuts inductance in half. It also allows convenient values, such as 60k and 75k. . . of really really non-inductive resistors. I fluxed the leads before soldering, so that connections will be solidly operating as 1 piece for good quality.

Xicon and Koa 1/4w Carbon Film are suitable. Radio Shack apparently carries Xicon. Mouser has both. The leads on these products are nice and thick, and that's desirable. Approximately, 12 cents for a paralleled pair of good quality carbon film will have less inductance than a single expensive carbon comp.

P.S.
Entertaining spot for 1/2w carbon film is the feedback-shunt resistor (2.7K on the schematic). Xicon and Koa are suitable. Now, the entire voltage divider has 1/2w capacity.

P.P.S.
When the lower inductance feedback resistor (parallel quarter-watt resistors) is set against the higher inductance feedback-shunt (solo half watt resistor) in a voltage divider, then gain is decreased for HF. This is apparently what people are trying to accomplish with expensive boutique resistors except that I've done it for pennies and on purpose. The effect is miniscule and you can notice it only because there's gain on it.
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Old 27th January 2013, 07:27 AM   #26
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I'm not saying that such tweaks are necessary.
What I'm saying is that paying a lot is unnecessary.
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Old 30th January 2013, 10:13 AM   #27
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Originally Posted by danielwritesbac View Post

Here are the 2200u caps:
Click the image to open in full size.
Daniel,,I don't have 1.3 R,3W but I have 1.5R,1W only,I don't hav 6A05 ,,but I have 6A04 diodes.Any alternatives ?
how about carlos psu.
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File Type: gif schematic-psu.gif (17.1 KB, 421 views)
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Old 30th January 2013, 11:19 AM   #28
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Daniel, I don't have 1.3R 3W but I have 1.5R 1W only; I don't have 6A05 but I have 6A04 diodes.
6 parallel 1.5R = 0.25R, 6W and ok. 6A04 is fine.

You may want to find higher current resistors; however, the good news is that 6A04 assists in managing the surge current.
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Last edited by danielwritesbac; 30th January 2013 at 11:26 AM.
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Old 30th January 2013, 12:57 PM   #29
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thank you so much for your quick reply.
Should we not put a 100nf in the psu board ?
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Old 30th January 2013, 09:04 PM   #30
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Can I use 2.2K instead of 2.7k,is the color of LED specific ?thank you.
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