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Mezmerize B1 Buffer Preamp
Mezmerize B1 Buffer Preamp
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Old 7th July 2019, 04:46 PM   #381
Salas is online now Salas  Greece
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Mezmerize B1 Buffer Preamp
Quote:
Originally Posted by duckanddexter View Post
Hi,

Can I run an op amp off the existing 10v rails on the mezmarise board. opa 1692 650 ľA per Channel. Using the input relays to have a gain position on the input rotary, for each input. Thus accommodating the rare occasion my system requires more gain without permanently introducing another stage.

Wonderfully transparent pre amp with drive, Many thanks.

Any thoughts gratefully received,
Kind regards Nick.

Yes you can, it's a clean rail to tap from, only make sure no noise or oscillations will be introduced and shared. Check all is well in the full configuration with op-amp using a scope. AC coupled at 5mV vertical and 50uS horizontal will show. Looking for a thin clean DC line. Nice that you like the preamp, cheers.
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Old 7th July 2019, 09:00 PM   #382
duckanddexter is offline duckanddexter  United Kingdom
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Brilliant, Many thanks Salas.
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Old 12th July 2019, 02:13 PM   #383
glennjarrett is offline glennjarrett  United Kingdom
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Default leds

Hi
My Mezmerize DCB1 10 years after board has arrived from the site shop
I have had trouble getting hold of the kingbright leds as discontinued i had a few leds in my parts bin this is what i have managed to get

3 x red leds tested with 10v and 1K resistor 5.50v 4.2ma
5.48v 4.3ma

5 yellow leds tested with 10v 10.01v 11.6ma
10.01v 12.2ma
is this ok or should i try to get a better 5.4v match ?
kind regards Glenn

Click the image to open in full size.20190712_134613 by glenn jarrett, on Flickr
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Old 12th July 2019, 02:52 PM   #384
glennjarrett is offline glennjarrett  United Kingdom
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also the 2 18r 2w resistors could i use just 1 10r 5w instead ?
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Old 12th July 2019, 03:36 PM   #385
Salas is online now Salas  Greece
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Mezmerize B1 Buffer Preamp
Yes you can use all of the above Leds or 10R set resistors without any significant deviations from intended biasing. Maybe expect somewhat higher than +/- 10V rails. There is the bias current for the quintets bringing them to total Vf, depends on their tail JFET's IDSS, plus one Vbe added in the circuit, coming from the error amplifier BJT. Inconsequential differences. By the way amber Kingbright Leds from the same series as the listed discontinued reds are adequate as well.
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Old 12th July 2019, 06:25 PM   #386
glennjarrett is offline glennjarrett  United Kingdom
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Thank's Salas
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Old 19th July 2019, 12:53 PM   #387
glennjarrett is offline glennjarrett  United Kingdom
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BCB-1 build coming on nicely
decided to go for the kingbright as the leds i had were from China via ebay with no info .
just waiting for the R set resistors to arrive and mount the 4x mosfets on the sinks .
Going to power up first check voltages then solder the 4 amp fets in which way round would you place the 4 fets ?

would 7.57 - 7.46 - 7.47 - 7.49 be ok ?
or 7.57 - 7.47 - 7.46 - 7.49


Click the image to open in full size.20190719_122305 by glenn jarrett, on Flickr

Last edited by glennjarrett; 19th July 2019 at 01:06 PM.
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Old 19th July 2019, 04:31 PM   #388
Salas is online now Salas  Greece
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Mezmerize B1 Buffer Preamp
7.57 - 7.49 - 7.46 - 7.47 is the better order

The first pair is going to naturally produce more DC offset but that's the nearest arrangement with what IDSS samples you got in hand
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Old 19th July 2019, 06:36 PM   #389
glennjarrett is offline glennjarrett  United Kingdom
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Thank's Salas
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Old 17th September 2019, 06:44 AM   #390
Junebugvinyl is offline Junebugvinyl  United States
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Default Have two B1s but getting on board with the Mez B1!

Hello All!

I have built and enjoyed two B1 units (one balanced) and now want to give the Mez B1 a go. Four questions:
1) I see the boards are still for sale but the SK170 sources seem sparse since the 10 years later board and BOM was issued. Suggestions for sources of well-matched sets for the signal path?
2) I want to build balanced (all the more need for good matching) so is it just a matter of doubling up all parts and the board except using a single tranny that has twice the specified current capacity?
3) I want to integrate a remote controlled relay based ladder type attenuator. See The δ1 relay-based R-2R stereo attenuator Other than space and power supply what other cautionary notes would you have for me?
4) What is the purpose of the 100 ohm resistor on second set of outputs? I intend to have multiple balanced outputs on my unit.

Thank you!
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