Double Decker: Pass B1 CLONE build completed and happy
This is my first build I am posting here. I would like to thank Nelson Pass for making this available for us.
Let's start! I won't describe it in words. Rather than let pictures speak themselves.
All PCB boards were assembled for mounting in chassis. All PCB layouts are designed by me except source selector and of course PASS B1 Clone is from NP. Thanks to Uriah offered significant help during initial build of LSA.
I started with metal box and perforated screen for making DIY chassis.
After cutting in sizes time to bend and make it in shape to fit in everything.
There was some issue with one source (CDP) causing drop of LF because of LSA impedance of 13KΩ exposed to source. To hide the LSA behind buffer I added SSP - DIY Super Simple preamp (from another forum). This is another version from previous one where I used SSP at the input to accept selected source and drive LSA within PASS B1 where B1 driving output power amp.
e.g. Source -> (SSP->[LSA->B1])->Power amplifier
This sounded excellent. But SSP is having unity gain which was not my requirement, I wanted no (zero) gain, pure buffer. Hence I replaced SSP with another bulky B1 (shared PS with first B1).
Now it looked like: Source -> (B1->[LSA->B1])->Power amplifier
in above statement, PS is not shown but present there and
() - inside preamplifier
[] - second B1
This made input impedance of B1 exposed to source (1MΩ) and first B1 drives to LSA. Second B1 shows output impedance of 50Ω, drives power amplifier. This make it B1 buffer at both the ends, make any source in the world happy by means of very high input impedance. All power amps are drivable with very low output impedance and LSA in control of volume level.
This made no loss of frequency response and adequate driving of source and power amp made life easy with net result cleanest possible I listened in my setup.
This is my first build I am posting here. I would like to thank Nelson Pass for making this available for us.
Let's start! I won't describe it in words. Rather than let pictures speak themselves.
All PCB boards were assembled for mounting in chassis. All PCB layouts are designed by me except source selector and of course PASS B1 Clone is from NP. Thanks to Uriah offered significant help during initial build of LSA.
- PASS B1 Clone,
- LSA - Light Speed Attenuator, a LDR based volume control (reference DIY Lightspeed Attenuator - Passive LDR Volume Control (optocouplers))
- input selector
- CNC Phono stage for my turntable (reference Another Super High End Phono Stage! No expense spared... - AudioKarma.org Home Audio Stereo Discussion Forums)
- SSP, DIY Super Simple Preamp (op Amp based), not in picture (reference DIY Simple Active Preamp - AudioKarma.org Home Audio Stereo Discussion Forums)
- Power Supply for all of above feed from 30VA r-core transformer.
I started with metal box and perforated screen for making DIY chassis.
After cutting in sizes time to bend and make it in shape to fit in everything.
There was some issue with one source (CDP) causing drop of LF because of LSA impedance of 13KΩ exposed to source. To hide the LSA behind buffer I added SSP - DIY Super Simple preamp (from another forum). This is another version from previous one where I used SSP at the input to accept selected source and drive LSA within PASS B1 where B1 driving output power amp.
e.g. Source -> (SSP->[LSA->B1])->Power amplifier
This sounded excellent. But SSP is having unity gain which was not my requirement, I wanted no (zero) gain, pure buffer. Hence I replaced SSP with another bulky B1 (shared PS with first B1).
Now it looked like: Source -> (B1->[LSA->B1])->Power amplifier
in above statement, PS is not shown but present there and
() - inside preamplifier
[] - second B1
This made input impedance of B1 exposed to source (1MΩ) and first B1 drives to LSA. Second B1 shows output impedance of 50Ω, drives power amplifier. This make it B1 buffer at both the ends, make any source in the world happy by means of very high input impedance. All power amps are drivable with very low output impedance and LSA in control of volume level.
This made no loss of frequency response and adequate driving of source and power amp made life easy with net result cleanest possible I listened in my setup.
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This is the final outcome of the project.
Knobs were sourced from fleabay and Faceplate was homemade by me. I used 6mm Aluminum plate which is fixed by 4X M3 screws from behind. I have plan to anodize it but so far put one thin layer for metal primer, 2 thin coats of silver color spray (available for Car paint shop) and 2 coats of clear coat.
Knobs were sourced from fleabay and Faceplate was homemade by me. I used 6mm Aluminum plate which is fixed by 4X M3 screws from behind. I have plan to anodize it but so far put one thin layer for metal primer, 2 thin coats of silver color spray (available for Car paint shop) and 2 coats of clear coat.
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Thanks!
LSA do match nicely. Only problem is it exhibits low impedance for source if exposed to source without any buffer. I could not figure out why LF was getting lost for CDP but addition of source buffer solved that issue. Definitely it was working fine with all other sources in absence source buffer too.
Now how LSA works? Its very smooth and transparent. I used linear pot so I can have better control at lower volume levels. Matched LDRs do trick for balancing stereo image.
Uriah offered significant help during initial build of LSA which was part of group buy we ran at another Indian forum.
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Thanks! It sounds very clean. Background is dead silent. Frequency response is flat and no gain - no loss of signal level. Overall total transparant within chain. No coloration of sound, I can listen every detail of Music. And this exposed limitation of speakers which are DIY. Now working on GR research speaker DIY as well as F5turbo V2.
Nice Build Mishra ji
Hi thanks!
I used simplest but dc operated relay based source selector from flebay. My intension was to keep only audio signal and DC PS within box and keep away all clock genrating circuits etc out of enclosure.
Andrew's idea is good but as I explained, I would like to keep digital boards out.
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