Mezmerize B1 Buffer Preamp

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#521
glennjarrett said:
Using the 4 matches i made up a B1 buffer with a Alps black beauty 20K pot,
regulated supply lm317 & lm337 @ 10v dc
playing radio on computer though Khadas tone board dac to 2x 50w ice power amp
sounds very good 😀 indeed
Click to expand...

glennjarrett said:
yes it will cool them
also it will thermally connect the 2 fets
Click to expand...

The doubled 2SK209GR substitution idea fully works on test. That's cool to start with. 🙂
 
#528
I also have the 20MHz version of your scope. HM204-2. Good models those. An adequate soundcard like Focusrite Scarlett 2i2 and free software like ARTA, REW etc. would allow small signal FFT and other interesting charts. Maybe something to pursue at a point. You will like it.
 
#530
I have owned the Focusrite 2i2 gen 2 for a couple of years and really liked it. To me the absolute THD value is not as important as it is for matching channels which I now find indispensable. I have replaced it with a gen3 and the THD levels are substantially better. Here is a pic of a loopback test:
 

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#533
Hi,

I'm slowly starting to order parts needed for this preamp and one question came to my mind when searching for the parts.

Do I need WP113IDT leds which are not available in Poland or can I order other leds and match them ?
Another question is: how do I match those leds ?

This is my first time building preamp so please be gentle 🙂
 
#534
Yes you can order alternative LEDS. They should be red. Easiest sorting process is switch a DMM in diode check mode, read voltage one by one and note it down on paper. Stick each LED next to its noted reading.

Try a random red LED to verify measuring ability first. DMMs must be putting out enough voltage to light up LEDS. Many do, some don't. If your DMM doesn't cope, another method is use a 9V battery and a protection resistor in series with the LED. Say 1.5K to 2.2K. And you measure the voltage across each lit up LED.

Then sort them out in groups of alike added voltage numbers for each side. Two triplets and two quintets. Give priority to matching than to absolute indications. Also, don't mix results from those two test methods. They produce different enough indications due to different levels of test current.
 
#536
Use the 9.4s as signal quad and the 3s for everything else.

As for why, that's because at 10V rails 94mW per unit is split between two back to back smd. So it's long term reliable and you take advantage of the little extra gfs (transconductance) over the 7s.
The 3s in the PSUs will run cool when 3mA is fine to light up the LEDs well.
 
#537
Hi folks: I am in the process of assembling my ACA kits. What I would like to add is a preamp to each so that I can add a "volume" knob option to them. I've been doing some reading and shopping and it appears that the forums have recommended the addition of Mesmerize B1 buffers to my set up, but just this morning I discovered that there is an ACA preamp board available as well. So . . . what are the differences in the Mesmerize B1 buffer and the ACA preamp and which would be more appropriate for my purposes (and why 🙂 )?

GrassyAss Amigos
 
#538
You are talking about the ACP+ I suppose.

That one has 9dB voltage gain and can also drive headphones.
DCB1 has no gain and drives amps only. With a digital source it will not overdrive the ACA allowing more pot rotation in the top volume settings range. Its typically more transparent due to its better measurements and lack of capacitors in the signal's way.

The ACP+ has a nicely tailored negative phase second harmonic tone. Its also more versatile when using lower output legacy sources like phono, tuner, deck. Due to having gain.
 
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