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Old 1st October 2010, 11:08 AM   #2061
Salas is offline Salas  Greece
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OK then, clarified. Enjoy it.
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Old 1st October 2010, 04:25 PM   #2062
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Hi

I've finished stuffing the board and everything appears to be OK.

I am getting +10.17v and -9.52v at the shunt output, and the DC offset is R=0.1mV and L=0.2mV when idling. It does occasionally rise a bit when turning on or off, but I understand this is to be expected. The relay also clicks-in after a few seconds. I will be using this with my F5 so I'll be adding a 1uf cap on the amps input.

Click the image to open in full size.

Is there anything else I should check before connecting my LDR attenuator?

Thanks
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Last edited by Tripmaster; 1st October 2010 at 04:28 PM.
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Old 1st October 2010, 04:53 PM   #2063
AndrewT is offline AndrewT  Scotland
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check the voltage drops across the CCS resistors.
check the output offset from OFF to ON and from cold to operating temp.
The relay should be open when the circuit starts up and open again when the circuit shuts down. You should not see a DC pulse at startup nor at switch off.

1uF for a DC blocking cap seems quite low in value for the input of a Power Amp.
Are you intending to EQ the bass for a particular sound effect?
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Old 1st October 2010, 05:38 PM   #2064
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Quote:
Originally Posted by AndrewT View Post
1uF for a DC blocking cap seems quite low in value for the input of a Power Amp.
Wouldn't that just depends on the input impedance resistor to ground? An RC filter will be affected by both the resistance and the capacitance...
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Old 1st October 2010, 07:58 PM   #2065
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Hi

I thought 1uf was the correct value for an F5. I'm sure I have seen it mentioned elsewhere. But if I'm wrong...

Building a symmetrical psu B1 buffer

All of the LEDs measured 1.8v when testing prior to soldering, the relay clicks after 5 seconds after turn on, and clicks again straight after switch off.

I measured the voltage across the 2x68R (34R) resistors. Negative side 1.76v and positive side 1.64v

I've just rechecked the dc offset whilst 'cold' and there doesn't appear to be any, just a slight bit of interference from the DMM. I will check the 'hot' readings a little later.
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Last edited by Tripmaster; 1st October 2010 at 08:05 PM.
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Old 1st October 2010, 09:04 PM   #2066
Marra is offline Marra  United Kingdom
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2.2uF would work even down to a 20k Zin amp.

Recommended by Salas in the Blue Hypno thread ; post 217 and working well with my DCB1 and Aleph 5.

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Old 1st October 2010, 09:51 PM   #2067
Salas is offline Salas  Greece
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Looks like working perfectly OK Richard. Congratulations. In the graph is the high pass you can expect when coupling 1uF to 100K load.
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File Type: gif 1u100k.gif (14.5 KB, 775 views)
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Old 1st October 2010, 10:26 PM   #2068
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Quote:
Originally Posted by Salas View Post
Looks like working perfectly OK Richard. Congratulations. In the graph is the high pass you can expect when coupling 1uF to 100K load.
Thanks Salas. That graph looks good?
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Old 1st October 2010, 10:34 PM   #2069
Salas is offline Salas  Greece
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If your speakers can go lower than 1.8Hz -3dB then its not enough.

Seriously, you may use more uF for even less infrasonic phase shift but for sheer amplitude you are way well covered for 100K input F5 as you see in the graph.
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Old 2nd October 2010, 09:05 AM   #2070
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Tripmaster View Post
Thanks Salas. That graph looks good?
Have a proper look.
That graph of low frequency response is for 1uF & 100k.
The output of your circuit is already loaded with 100k.
To achieve that graphed response the following Power Amp or receiver needs to have Zin = infinity.

If the actual Zin = 100k, then the resultant load for the HP filter is 50k. This moves the graph one octave to the right.

The F5 has no DC blocking cap at it's input so the 1uF works alone.
The Zin ~ 101k.

This leaves the HP filter F-1dB ~3Hz.
This is OK for many.

If as stated earlier, a Zin=20k were used then F-1dB moves to ~17Hz.
If that Zin=20k power amp had a capacitor of 4u7F as a DC blocker then F-1dB moves to ~22Hz

Summarising:
1uF at the source output only suits very high Zin at the receiver that is DC coupled.
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Last edited by AndrewT; 2nd October 2010 at 09:12 AM.
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