Dx Blame MKIII-Hx - Builder's thread

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#842
a.wayne said:
Sounds like the input stage gain is too high or being overdriven , what is the source driving the amplifier ...?
Rudy , turn the gain on your pre down until the sound is soft, do you still hear the distortion ....?
Click to expand...

@ Evette and a.wayne, here is no distortion I had the volume too high, the microphone of the camera makes the distortion 😉

The preamp is Fettle (Pinkfaun) I think also high output preamp.
Tomorrow I am solder the 10R resistance and test again.
If sounds better than I connect the other speakers.

Rudy
p.s. The volume control is now:
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#843
TECHNICAL DATA Fettle preamp:
Input impedance: 100kΩ
Gain: x 10 (+20dB)
Output impedance: 600Ω
Max output voltage: 6Vrms (10mA)
Frequency response: 12 Hz - 120 kHz (zero feedback)
THD% (1 kHz): 0,07 % 2nd, 0,00% 3rd, with output voltage 1Vrms
Noise: around -100 dB

Which resistance is responsible for the input sensitivity of the Dx Blame MKIII-Hx?

Regards,
Rudy
 
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#845
a.wayne said:
Output impedance ......
Click to expand...

If I connect the DAC output directly on the amplifier the white noise is gone.
Note, I use a CD recording with a very quiet number.

Which resistance is responsible for the input sensitivity of the Dx Blame MKIII-Hx?
And which resistance value should I use?
Video now uploading: http://www.youtube.com/watch?v=j_FSvC2edYk

Regards,
Rudy
 
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#846
Am I right that the 390 ohm resistor responsible for the input sensitivity of the Dx debt MKIII-Hx ?
Can I use a 10K resistor, so I can use my Preamp ?

TECHNICAL DATA (according to manufacturer):
Input impedance: 100kΩ
Gain: x 10 (+20dB)
Output impedance: 600Ω
Max output voltage: 6Vrms (10mA)
Frequency response: 12 Hz - 120 kHz (zero feedback)
THD% (1 kHz): 0,07 % 2nd, 0,00% 3rd, with output voltage 1Vrms
Noise: around -100 dB

Regards,
Rudy
 

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#848
The input impedance of your power amp is set by a resistor.
The input sensitivity of your power amplifier is set by a ratio of two resistors, neither of them are that first impedance setting resistor.

I don't have a schematic to hand, otherwise I would give you references.
 
#849
AndrewT said:
The input impedance of your power amp is set by a resistor.
The input sensitivity of your power amplifier is set by a ratio of two resistors, neither of them are that first impedance setting resistor.

I don't have a schematic to hand, otherwise I would give you references.
Click to expand...

@ Rudi, Thank you.
@ Andrew here you have ...
 

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#855
BMW850 said:
I have here a 8K2 resistance to soldering in from the other board and not a trimpot 😉
Edit: 10K change to 8K2
Click to expand...
I have only one clue to what you are proposing.
I see one resistor with an 8k2 value, but that resistor has nothing to do with input impedance nor input sensitivity.
Label the components and then we can explain what you need to know.

Sorry, this is all back to front.
You should know basic operation of your amplifier before you delve into changing anything.
 
#858
MKIII Hx input volume control connection, start video at 1.15 min:
MKIII Hx input volume control connection - YouTube

So, is the 8K2 resistor, good to solder in?

Label the schematic, so we can see what you are referring to.
Click to expand...
I don't have the knowledge to do that, that is why I question.

It's nice I have a little sense of electronics but it is my hobby.
And the amplifier plays with help of forum members, otherwise this amplifier has never playing.

I have almost all components, self created via schematic with help from forummembers
Speakers
Battery Preamp
Power Amplifier
CD Transport.
DDDAC
All the power supply

Thank you all,

Regards,
Rudy
 
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#859
The 8K2 resistor, is not good, the amplifier playing now direct from DAC out but to soft, with the CD Dire straits.

The 8K2 is not a succes hopefully somebody helps me with the good value.

And with my preamp I have still to much wite noise, when the volume going up the white noise get lower 😕
My preamp has a volume control with steps, each step still give a crack on the speaker.

Regards,
Rudy
 
#860
According to Carlos u don't have an input impedance mismatch ,my question to u is what happens when the pre amp output gain is low do u have any noise or distortion?

I would try what Carlos suggest keep increasing until u have the gain u desire ...
 
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