I thought I'd go with a 50 ohm resistor and a 1k variable resistor / trimmer in parallel.
Anyhow, which size transformer would you pick (for a 12vac secondary perhaps and double filtering:317/337 and then something better)?
Anyhow, which size transformer would you pick (for a 12vac secondary perhaps and double filtering:317/337 and then something better)?
Just come across this B1 Rev 2 preamp when search around for my still build in progress balanced ACA amp (I am a total newbie and this is my first DIY Hifi build, finger crossing). I mainly will using DAC or computer to steam the music to the ACA amp, and seems people are suggestion B1 Buffer as preamp.
The setup in my mind is as I will need to convert from unbalance (DAC/Computer) to balance (ACA monoblock) and looking at audio transformer path. Which is reason somewhere in the over 400+ pages forum and suggest need buffer amp, as ACA cannot just use audio transformer/passive amp.
I am thinking:
- DAC/Computer (unbalanced) --> Audio transformer (convert to balanced)--> 2x B1R2 (with 12 pin 50k pot for volume control to two board) --> ACA Monoblocks
Questions:
1. Am I on the right track?? Or it will not work?? Any other suggestion?
2. Do I need to swap the path of 2xB1R2 and Audio Transformer, so it is DAC to B1R2 first then Audio Transformer? (sorry I still not sure about input/output impedance matching, and what effect of audio transformer will do on impedance)
2. What ratio of Audio Transformer should i using?? 600:600, 10K:10K, or 600:2k4 (for V stage), 10K:40K??
Stan
The setup in my mind is as I will need to convert from unbalance (DAC/Computer) to balance (ACA monoblock) and looking at audio transformer path. Which is reason somewhere in the over 400+ pages forum and suggest need buffer amp, as ACA cannot just use audio transformer/passive amp.
I am thinking:
- DAC/Computer (unbalanced) --> Audio transformer (convert to balanced)--> 2x B1R2 (with 12 pin 50k pot for volume control to two board) --> ACA Monoblocks
Questions:
1. Am I on the right track?? Or it will not work?? Any other suggestion?
2. Do I need to swap the path of 2xB1R2 and Audio Transformer, so it is DAC to B1R2 first then Audio Transformer? (sorry I still not sure about input/output impedance matching, and what effect of audio transformer will do on impedance)
2. What ratio of Audio Transformer should i using?? 600:600, 10K:10K, or 600:2k4 (for V stage), 10K:40K??
Stan
Those 10 ohm resistors... are they “grid stoppers” to serve for HF / oscillation protection? Could another small mkp capacitor be used on the filtering rails after those?
no tube - no grid ........ but there are gates ....... but these aren't gate resistors
simply, that is RC filtering and - even more important - inrush current limiters , for moment when juice is flowing to empty caps
small caps across electrolytics ..... your choice
simply, that is RC filtering and - even more important - inrush current limiters , for moment when juice is flowing to empty caps
small caps across electrolytics ..... your choice
Oh, that 10 ohm reistor is just part of the CRC filter, to lower the noise from the PSU. If you have a clean supply, feel free to omit it.
The pcb I mentioned in post #146 is put to good use for my new b1 r2. I did the mods Zen mod suggested, put a couple of vishay mkp1839 from supply rails to ground center. With the new SH pass x150 and ancient dynaudio contours its working swimmingly.
Just in case I run it with a cap now, but I'll try small isolation transformer to have a taste of the "iron pre"
Just in case I run it with a cap now, but I'll try small isolation transformer to have a taste of the "iron pre"