Salas hotrodded blue DCB1 build - Page 168 - diyAudio
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Old 24th February 2012, 10:29 PM   #1671
evanc is offline evanc  United States
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OK so we are figuring the current by the voltage drop across the power resistors only....Leave it to me to try and make it more complicated.

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Old 24th February 2012, 10:32 PM   #1672
Salas is offline Salas  Greece
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On which one rail you got the most drop on Rset? Use a bigger value there so to match the less drop one by Iccs=RsetVdrop/Rset. But 50mA differences won't change them transconductance when you are around the 0.5A mark. So don't strive for very good matching of CCS currents per rail.
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Old 24th February 2012, 10:48 PM   #1673
evanc is offline evanc  United States
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The plus rail is dropping more voltage. I like the don't do anything option the best....This thing sounds soooo nice.
Thanks for the help, Evan
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Old 24th February 2012, 11:32 PM   #1674
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The power resistors imply the current available from the ccs. Your DCB1 will never come close to using that much. I beleive it has more to do with impedance and the ease at which the current is delivered.
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Old 26th February 2012, 08:31 PM   #1675
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Default help

Hi,

I'm a relatively new guy with a new guy question.

My understanding is that the black Hypnotize board, offered by Tea-Bag, does not have volume control, and the hot rod supplies a higher current that supposedly increases the soundstage. Other than impedance matching, what do you feel is the sonic advantage of the B1 buffer?

I'm using a four channel MiniDSP with an on-board potentiometer, but I've read that it's non-optimal to attenuate the line-level volume in the digital domain because of SNR and "bit conversion accuracy" issues.

I would use two Hypnotize boards for all four channels. I don't require the Mezmerize board because I don't need more than one input source for each board. However, for reasons stated above, I would like to have some volume control in the analog domain, after the digital signal processing, and before I feed the signal to my power amplifiers... i.e. I need a good preamp with unity voltage gain and volume attenuation.

I could control volume from the DSP, and feed the Hypnotize board, but how would this be an advantage in regard to the audio quality? Isn't the B1 just one more potential noise source added to my audio chain? What is the advantage of the B1 without volume control?

Thanks,
Mason
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Old 27th February 2012, 12:21 AM   #1676
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I will sum up why the DCzb1 is excellent. I recently built a new tube preamp and didnt have a 50k pot for it, so i just wired it up and used the dcb1 as a volume control. Today i added the pot to the tube pre and removed the dcb1. Removing the dcb1 changed the sound so little that i would have a hard time telling whether it was in the chain or not. For a passive pre, you cannot say more. to Nelson and Salas.
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Old 27th February 2012, 07:40 PM   #1677
Pboden is offline Pboden  Norway
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Click the image to open in full size.

Just finished mine, but the leds are not giving me the complete lightshow. V- is ok, but the V+ is around 7vdc

Any idea where to start looking ?
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Old 27th February 2012, 07:41 PM   #1678
Tea-Bag is offline Tea-Bag  United States
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Check Polarity of LEDS?
VgS measure across the FETS, voltage across the 10Rs.
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Old 27th February 2012, 07:48 PM   #1679
Salas is offline Salas  Greece
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Usually one or more LEDS are put the wrong way around in the dim strings or are dead. A DMM in diode tester mode if able to light an LED, can be used to touch each and one up, as they are installed no problem, to see if some are dead due to too much iron. Else it can be some semis but one check at a time.
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Old 27th February 2012, 07:51 PM   #1680
Pboden is offline Pboden  Norway
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Quote:
Originally Posted by Salas View Post
Usually one or more LEDS are put the wrong way around in the dim strings or are dead. A DMM in diode tester mode if able to light an LED, can be used to touch each and one up, as the are installed no problem, to see if some are dead due to too much iron. Else it can be some semis but one check at a time.
So.. if there is a dead led one place, the others will no light up ?
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