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Mezmerize B1 Buffer Preamp
Mezmerize B1 Buffer Preamp
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Old 20th February 2017, 07:18 PM   #191
loudspeakers is offline loudspeakers  Sweden
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Don it again, FAR better than the original pass single ended B1.
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Old 29th June 2017, 05:36 PM   #192
ORNJ is offline ORNJ  United States
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Hey all,

I have downsized houses and have gone from a rather large(for my area) 1300sqft house down to 900sqft.

As I continue to shrink my foot print and minimize I am going from surround sound to a 2.1 setup and part of that is going to be dropping from an AVR to small separates.

I am really interested in going to a DCB1 and some Hypex amps/active speakers

Can the DCB1 be configured to have a sub out?

I am going to use my Bottlehead Quickie right now but would like to have something without the microphonics.
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Old 29th June 2017, 06:14 PM   #193
Salas is offline Salas  Greece
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Mezmerize B1 Buffer Preamp
Yes, enough builders create a further output by tapping signal from the main output RCAs to another parallel pair. They just add 100R buffering resistors in series with the signal hot of the extra RCAs.
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Old 4th August 2017, 07:53 PM   #194
peafarmer is offline peafarmer  United States
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Default Bad luck with LED's

Hi, guys. I'm finally getting around to building my DCB1, and am having trouble with the LED sourcing similar to what was reported by user nkalogridis earlier.

I purchased the 593-VAOL-3HCE4 VCC 1.8V 20mA LED's. I am measuring them using a 9.71VDC battery, and have tried them with both a 1K and 1.5K resistor. I am measuring 1.91V (7.8 mA) with the 1K resistor. I am measuring 1.89V (5.2 mA) with the 1.5K resistor. Earlier, I had checked them with a 460 ohm resistor to get closer to their rated current, and they measured 2.01 V. So, clearly, they are not 1.8 Vf LED's as advertised.

Can these be used? I think not. If not, can I get some part number recommendations from those who have had better luck hitting the 1.8V nominal target. I don't mind waiting a week to get this right.

Thanks,

Andy
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Old 4th August 2017, 09:07 PM   #195
outtek is offline outtek
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Hi Andy, I had some bad luck with the LED's , but the one that actually were almost spot on in the 1.8V were these OSNR3134A, on a previous post in the build thread I was getting these voltages across the LED's :
- over the positive (9240 MOSFET) side 3 LED's I have 5.42V ;
- over the negative (240 MOSFET) side 3 LED's I have 5.44V ;
- on the positive side 5 LED's I have 8.90V and on the negative 8.84V (Here I could play with one or two LED that I have measured with 100mV higher the the red ones to get close to 9V)
- on the test point, the output of the reg. (the 3 little pads behind the 10ohm resistors ) I have 9.52V on the positive side and 9.48V on the negative.
Apparently these were ok values to power up the buffer and have it functional according to Salas and it does work fine. You could do a mix and match to get very close to the required value (I could of done that on the 5LED's sides but removing one or two of them and re soldering another to get what I want implies potential damages to the PCB as one member faced in his build).
As a side note try and solder them a bit higher from the board this way the internals while soldering wont get to hot, I soldered mine at about 5mm height.
Thanks,
Florin
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Old 4th August 2017, 09:33 PM   #196
peafarmer is offline peafarmer  United States
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Thanks, Florin. Unfortunately, these are not available in the U.S., at least, not on Mouser or Digikey. Hopefully there are others that have had success....
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Old 5th August 2017, 09:35 AM   #197
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by peafarmer View Post
Hi, guys. I'm finally getting around to building my DCB1, and am having trouble with the LED sourcing similar to what was reported by user nkalogridis earlier.

I purchased the 593-VAOL-3HCE4 VCC 1.8V 20mA LED's. I am measuring them using a 9.71VDC battery, and have tried them with both a 1K and 1.5K resistor. I am measuring 1.91V (7.8 mA) with the 1K resistor. I am measuring 1.89V (5.2 mA) with the 1.5K resistor. Earlier, I had checked them with a 460 ohm resistor to get closer to their rated current, and they measured 2.01 V. So, clearly, they are not 1.8 Vf LED's as advertised.

Can these be used? I think not. If not, can I get some part number recommendations from those who have had better luck hitting the 1.8V nominal target. I don't mind waiting a week to get this right.

Thanks,

Andy
You are misunderstanding the specifications.
The 20mA figure is the maximum current. Any higher and you are likely to damage them.

If they are lowish light output then a current from 2mA to 5mA would be about right for long life and reasonable dynamic impedance and quantity of light.
High light output could need as low as 0.5mA to 3mA the same light.

Try a 4k7 resistor and a 10k resistor and measure the Vf.

You can use the CURRENT as the trimmer to set the Vref you require from the series string.
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regards Andrew T.
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Old 2nd April 2018, 03:00 PM   #198
kpsthakur is offline kpsthakur  India
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Quote:
Originally Posted by Salas View Post
For down to 8.2R 3W per side setting resistors and circa 200mA will hold for reliability and rectification/filtering capacity as built standard. A 50VA 15+15VAc Tx will suffice. Keep the bridge diodes bit off board for air to can move around them.
Hi Salas, I am not able to understand this part...where are we using the 3W resistors?
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Old 2nd April 2018, 03:18 PM   #199
kpsthakur is offline kpsthakur  India
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Quote:
Originally Posted by Salas View Post
J111 can run high mA through itself, the error amplifier BJT, and the LEDS, compromising long term reliability. All FETS are used at IDSS in this circuit. If one must use some J series better use J112. Its not a different FET for noise and gm while the IDSS is moderate vs J111.

*Any gm any parasitic capacitance and any noise spec for the rest of FETS than those six can change the power supply performance to a degree nonetheless.


Does this mean, that J111's could be used ...if yes, what Idss values could be suitable
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Old 2nd April 2018, 05:07 PM   #200
Salas is offline Salas  Greece
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Mezmerize B1 Buffer Preamp
Theoretically yes but all the J series I have lately tested have excessive IDSS. There is no defined max IDSS in their datasheets. Try with PF5102 instead which tests between 5-11mA roughly.
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