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RJM Audio

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Sign of times past. #hismastersvoice  

[sign reads: Victor / Stereo / Fuji Wireless Inc.]
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RJM Audio

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Chez RJM Audio. Giving the Twilight headphone amp a spin, after a long spell in storage. I never offered it as a kit - too specialized - and it probably won't win any measurement contests, but it has a certain magic. If you just want to curl up and spend an evening listening to LPs, this is the amp to do it with.

http://phonoclone.com/diy-twi.html
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RJM Audio

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A collection of headphone amplifiers. But which one is the best!? It's all so very complicated...

(left to right: Sapphire, J-Mo II, and Twilight amps)
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Several layers of changes had left my original Sapphire 20f boards looking pretty ratty so I built a new set and installed them this weekend.

The input cap (Multicap) has been reduced from 0.47uF to 0.33uF, and I left out the ceramic bypass caps and Zobel filter. IC1 is socketed OPA134, transplanted from the old boards.

FYI: normal operation is for V+, V- to be +/-11.5~12 V, and output offset voltages seem to clock in at about 15 mV.

#rjmaudio   #headphoneamplifier  
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Kenneth Rørås's profile photoRJM Audio's profile photo
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A dual mono power supply is a completely optional, highly worthwhile, upgrade.
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Building a second set of Sapphire boards. I'll try it without the ceramic bypass caps first, then with.

#rjmaudio   #multicap   #headphoneamplifier  
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I have a pair of tested, working Sapphire 2.0 boards available. As per the current kit, configured for gain 5x (R4=4.7k). Drop in replacement for the earlier boards, if you are thinking of a quick-and-easy upgrade. Asking $100, same price as the kit.

(edit: sold)

#headphoneamplifier  
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Victor Panics's profile photoRJM Audio's profile photo
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+Victor Panics The Sapphire is class A. The J-Mo Mk. II is class A, and single-ended, which is what you are probably after. I have a set of those built too.
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RJM Audio

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Some boards up for grabs: a set of voltage regulators for the J-Mo Mk. II (tested, working) I thought I would use these but ended up using the old prototype regulator board instead. Also, the prototype J-Mo Mk. II boards, working but flawed design, for parts or experiment.
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Yesterday's little job was replacing the custom prototype boards on the J-Mo Mk. II headphone amplifier with the stock version. The power supply is custom built, but its the same MOSFET regulator described in the project page, just shared between channels. http://phonoclone.com/diy-jmo2.html

#jmo2   #headphoneamplifier  
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RJM Audio

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This is my current setup for quickly matching up pairs of 2N5486 JFETs. The devices come with quite a a lot of scatter in drain currents, but its easy to find pairs efficiently once you have a pool of 10 or so to work with.

#jfet   #jmo2  
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Reading over the details, I've warmed towards this project after learning it plays standard FLAC format, up to 24/192, with no ecosystem lockdown to the dedicated music store. Its got a high-end DAC (ESS9018), a custom I/V converter stage, and 128 GB of solid state storage. I'm not in, but I approve - tentatively. Even the price seems pretty reasonable.

#ponomusic   #ponoplayer   #flaclossless  
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A resource for the design and construction of high-fidelity audio equipement.
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RJM Audio is my hi-fi hobby site. I design and build audio circuits, from interconnect cables to headphone amplifiers to voltage regulators. Best known, I guess, are my VSPS and Phonoclone phono preamplifier circuits.
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