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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
The YARRA Preamplifier/HPA for Melbourne DB Group Buy
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Old 6th July 2020, 11:42 PM   #1311
redjr is offline redjr  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
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Originally Posted by xrk971 View Post
Not yet, Vunce just built the verification build and testing it. Looks like we also need some higher current 5v for the RPi? Is 1 amp enough or is that a 3A requirement?

It’s the red “Vpower” board.
Looks good. Very interested. I'd want a 3A supply for the RPi. It nominally uses 2.5A, and most RPi wall-warts supply that.
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Old 7th July 2020, 12:02 AM   #1312
Vunce is offline Vunce  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Hi Redjr,

Pretty fancy setup you’ve got there, lots of goodies packed in that chassis. Nice!!
I’m keeping it simple and going with an old school R-2R AD1862 DAC chip in NOS mode. My application doesn’t require big time current draw, the Vpower psu would not be adequate for >200mA.
But, the pcb’s are small and a pair of them can be powered from a single 12v dual secondary trafo. I’m using one of the Talema’s (12v) we use in the Yarra psu.
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Old 7th July 2020, 01:35 AM   #1313
xrk971 is offline xrk971  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Let’s see if we can make one with an integrated 3A at 5v supply. Probably a CMC in between it and the RPi.
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Old 23rd July 2020, 08:54 AM   #1314
donovas is offline donovas  South Korea
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Xrk, excellent stuff! My hats off to you. I too have been working on a modular preamp and we have ended up with a lot of parallel design choices- from dual mono capmx to input boards and even the use of curved traces (yes they look the best! &#128513 i too am putting mine in a custom case tho mine wont be good enough for a group buy.

Have you thought about including a dc relay on the board, or even a delay network for a turn on thump? I need one on mine and cant decide how to power it because i dont wanna ruin the prestine dual mono architecture not knowing how much the relay circuit is going to affect the supply line.
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Old 23rd July 2020, 11:41 AM   #1315
xrk971 is offline xrk971  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Thanks for the kind words Donovas! I have turn on delay and DC protect solid state relay for a speaker but it would work fine for a preamp. It has been measured to add no distortion to the signal. Uses 20mA and can be supplied with a single rail voltage from +18v up to +150v as it has a built in linear regulator. The relays are actuated by an optoisolator so there is very little danger of the SSR degrading your power supply. You could always pull it off before the cap Mx if you were concerned. I also have a headphone amp / preamp version of the SSR but it’s not RTR - you need to solder your own SMT parts.

Ready-to-Run (RTR) SSR DC Speaker Protection and Delay GB

Here is thread on headphone version to gather level of interest but there was not enough to make a RTR production run. The headphone version is in stereo and uses both +/- power supply rails as it uses bipolar comparators rather than an optoisolator to check for DC offset.

RTR SSR Headphone Amplifier DC Protection Modules GB
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Last edited by xrk971; 23rd July 2020 at 11:46 AM.
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Old 1st August 2020, 02:30 PM   #1316
xrk971 is offline xrk971  United States
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I have a new solution for converting balanced to single ended and vice versa. Can be a useful addition to the Yarra to give it flexibility of inputs/outputs. Uses SOA opamps so very neutral and transparent. Most of all, absolutely quiet with no audible self noise with audio source off.

BTSB Buffer - SE/Bal to SE/Bal Buffer GB
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