ba5417: adjust gain - Page 2

AndrewT · 7th January 2012, 10:41 AM

Is automatic gain control (AGC) fitted?

Could the AGC be switched off? or giving too high an output signal?

guitar89 · 7th January 2012, 11:19 AM

I don't think there is any AGC installed.

picowallspeaker · 7th January 2012, 01:08 PM

The gain is given by the speakers attached !

But...I think that the problem to be overcame is to be found where
Guitar 89 has pointed it : if the amp picks some unwanted signal , maybe
that is to be investigated .
I think that great corporations like Sony make such indestructible products if they are not worked beyond their purposes
My English today is...TOO MUCH !!!

If the socalled DAP is a cheap PC not engineered for good sound , that is a cause.
Poor supply ( decoupling ) and some junk traveling along the lines .
Because...the gain is never enough !!

Some Gain-BW product may tell the truth ..

guitar89 · 7th January 2012, 01:12 PM

hey yo, Mr. pico tony ! Well.... i think it wasn't power supply problem, just some hissing from the chip itself.
I think also contained some RF/EMI noise, since the enclosure itself is not shielded.
The gain is also too high for me. At least what I thought is to increase NFB for better THD, etc.

picowallspeaker · 7th January 2012, 03:45 PM

So you may try that odd value resistor -2K7 - at the input of the amp , to form a an RC filter together with a 1nF cap...well ,I see there just one already

3K9+3n3 ! Did you remove the emitter of the transistor at the input joint ?
I see many 'Cdp tweakers' often remove the mute transistors at the output

Now ; you reported the fact that the amplifier is not shielded ...shield it !!
Perhaps the whole pcb containing amp's circuit is too big because it houses also radio and cd traces and components ? Rip it !
I remember that IC ( Ba 5417 ) being very ( fairly )good , capable of producing
a loud bass...with 4Ω woofers and 2nd order lowpass .
Bye !!!

guitar89 · 8th January 2012, 10:04 AM

haha, I agree that it is very capable !
For your information, the input transistor is remove. argh.... I have to find a metal case for it X.x

guitar89 · 16th January 2012, 12:45 PM

sgrossklass, I have done trying with 2.7k resistor, and no problem seems so far (tested few minute only though)
The hiss is reduced significantly, nice sound is retained though. However, The amplifier isn't sound nice when using direct PC soundcard (compare to other amplifier), however when i use a good quality external soundcard, its sounds nice.
Does this have relation to input impedance ? Maybe the soundcard was driving the amplifier hard ?

I'm also thinking to bypass headphone, how should I connect ?
Could I just bypass C234, R219, L201 ? means can I connect positive side of C134/234 to positive post of each speakers ?
(My main purpose is because those component leave the main circuit very far, wanted to dispose of them for smaller board)

AndrewT · 16th January 2012, 04:15 PM

Quote:

Originally Posted by guitar89

.............. Maybe the soundcard was driving the amplifier hard ?..........

Measure it and compare to the measurement/s from your other source/s

guitar89 · 16th January 2012, 11:12 PM

andrew, may I know what you mean ? and how to measure ? what to measure ^^

AndrewT · 17th January 2012, 09:00 AM

Measure the mVac from each of your sources when they reproduce the same signal level.

7th January 2012, 10:41 AM	#11
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Is automatic gain control (AGC) fitted? Could the AGC be switched off? or giving too high an output signal? __________________ regards Andrew T.

17th January 2012, 09:00 AM	#20
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Measure the mVac from each of your sources when they reproduce the same signal level. __________________ regards Andrew T.

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7th January 2012, 11:19 AM	#12
guitar89 diyAudio Member Join Date: Dec 2010 Location: Malaysia, Selangor	I don't think there is any AGC installed.

7th January 2012, 01:08 PM	#13
picowallspeaker diyAudio Member Join Date: Apr 2007	The gain is given by the speakers attached ! But...I think that the problem to be overcame is to be found where Guitar 89 has pointed it : if the amp picks some unwanted signal , maybe that is to be investigated . I think that great corporations like Sony make such indestructible products if they are not worked beyond their purposes My English today is...TOO MUCH !!! If the socalled DAP is a cheap PC not engineered for good sound , that is a cause. Poor supply ( decoupling ) and some junk traveling along the lines . Because...the gain is never enough !! Some Gain-BW product may tell the truth ..

7th January 2012, 01:12 PM	#14
guitar89 diyAudio Member Join Date: Dec 2010 Location: Malaysia, Selangor	hey yo, Mr. pico tony ! Well.... i think it wasn't power supply problem, just some hissing from the chip itself. I think also contained some RF/EMI noise, since the enclosure itself is not shielded. The gain is also too high for me. At least what I thought is to increase NFB for better THD, etc.

7th January 2012, 03:45 PM	#15
picowallspeaker diyAudio Member Join Date: Apr 2007	So you may try that odd value resistor -2K7 - at the input of the amp , to form a an RC filter together with a 1nF cap...well ,I see there just one already 3K9+3n3 ! Did you remove the emitter of the transistor at the input joint ? I see many 'Cdp tweakers' often remove the mute transistors at the output Now ; you reported the fact that the amplifier is not shielded ...shield it !! Perhaps the whole pcb containing amp's circuit is too big because it houses also radio and cd traces and components ? Rip it ! I remember that IC ( Ba 5417 ) being very ( fairly )good , capable of producing a loud bass...with 4Ω woofers and 2nd order lowpass . Bye !!!

8th January 2012, 10:04 AM	#16
guitar89 diyAudio Member Join Date: Dec 2010 Location: Malaysia, Selangor	haha, I agree that it is very capable ! For your information, the input transistor is remove. argh.... I have to find a metal case for it X.x

16th January 2012, 11:12 PM	#19
guitar89 diyAudio Member Join Date: Dec 2010 Location: Malaysia, Selangor	andrew, may I know what you mean ? and how to measure ? what to measure ^^

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