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Project Unity Board Layout

Posted 27th December 2016 at 12:33 AM by rjm (RJM Audio Blog)
Updated 27th December 2016 at 10:11 PM by rjm

Two boards, each board configurable for line and headphone variants. Powered by nominal +12 V -12 V split regulated supply, though 9-15 V rails can be used without modification.
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File Type: zip pcb-unity-10e1-bom.zip (150.2 KB, 74 views)
File Type: zip pcb-unityB-10b1-bom.zip (98.7 KB, 66 views)
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Old

Pictures of my Audio Equipment

Posted 23rd December 2016 at 08:44 AM by BasicHIFI1
Updated 23rd December 2016 at 08:58 AM by BasicHIFI1

Images of the audio equipment I have access to.
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Old

Introducing Project Unity

Posted 23rd December 2016 at 05:02 AM by rjm (RJM Audio Blog)
Updated 27th December 2016 at 11:46 PM by rjm

Following on from this post and this post, we arrive in time for the holidays with Project Unity. Merry Christmas everyone.

Four circuits: Unity, Unity H, Unity B, Unity BH. line preamp, Headphone amp, line Buffer, Headphone Buffer respectively, all derived from a common base circuit called Unity Root. Unity Root is conceptual, it exists only as a reference so you can see more clearly how the four working variants relate to each other.

It's the "all for one, and one for all" approach to diyaudio, a single research and development line applied to a range of applications, feedback from any of the applications brought back to apply to the line in general.

This simplifies not just the circuit development, similar efficiency is also brought to the documentation, board layout design, and BOM... about which I'll have more to say in a bit.
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File Type: zip Unity 10 LTSpice.zip (5.6 KB, 47 views)
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The (Xross-type) X-Reg Voltage Regulator (Stabilizer)

Posted 20th December 2016 at 04:47 AM by rjm (RJM Audio Blog)
Updated 7th March 2017 at 07:09 AM by rjm (BOM 16b2 uploaded)

I've come this far so I might as well complete the trifecta.

This is the X-Reg circuit, with a new layout and component numbering to match the new S-Reg and Z-Reg boards. Each is a drop in replacement for the other.

Like its siblings, the X-Reg is a low current voltage regulator for line level audio. The output is about 9 V (adjustable up to 12 V) and the maximum load current is 50 mA without heatsinks, 100~150 mA with small heatsinks on Q1,2.

It is not a true regulator as there is no fixed reference and instead the output voltage is defined relative to the input voltage. The high open loop gain of the op amp is harnessed for very low noise and very high ripple rejection. It is necessarily a high feedback approach.

So, there you are: three mix-and-match power supply options for all your low voltage, low current audio needs.
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File Type: zip X-reg-16b.zip (63.6 KB, 55 views)
File Type: zip pcb-xreg-16b2-bom.zip (93.3 KB, 26 views)
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Old

The (Zener) Z-Reg Voltage Regulator

Posted 19th December 2016 at 12:55 PM by rjm (RJM Audio Blog)
Updated 7th March 2017 at 07:11 AM by rjm (BOM 11b2 uploaded)

Companion regulator to the S-Reg. Same board dimensions and connection layout. For line level audio.

Same idea as before rectified 2x12 VAC input, +/- 11 V output. 50 mA max output current unless the transistors are heatsinked.

There is a small amount of over-current protection afforded by R3,4 but do not short the output for all but the shortest of transients.

Eagle/Gerber files attached, so you can go get this made yourself, optinally with whatever modifications you need.

I've use this regulator circuit in my Sapphire headphone amplifier. It's a simple and modest circuit but I feel it works really well in practice as long as the audio circuitry it powers has reasonable PSRR. No feedback means no out-of-band noise or instability, even as the output impedance remains low.
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File Type: zip Z-reg-11b.zip (51.1 KB, 39 views)
File Type: zip Z-reg-11b1-Eagle.zip (63.8 KB, 36 views)
File Type: zip pcb-zreg-11b2-bom.zip (70.3 KB, 13 views)
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Old

The (Shunt-Source) S-Reg Voltage Regulator

Posted 19th December 2016 at 11:09 AM by rjm (RJM Audio Blog)
Updated 4th May 2017 at 12:39 AM by rjm (added BOM)

S-reg voltage shunt-source regulator for line-level audio circuits.

This is designed to accept rectified 12x2 VAC input, producing +/-12 V output split rails.

Features soft-start and over-current protection, standard configurations for load currents up to 50 mA. High performance: 80 dB ripple rejection up to 100 kHz.

update: BOM uploaded
update: web page (stub)
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File Type: asc sreg10e.asc (5.0 KB, 106 views)
File Type: zip pcb-sreg-10f5-bom.zip (88.2 KB, 2 views)
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Old

RJM Audio in 2017 [modular simplicity]

Posted 19th December 2016 at 12:11 AM by rjm (RJM Audio Blog)
Updated 27th December 2016 at 11:50 PM by rjm

The time of year where I like to draw up some plans for the next 12 months.

This year’s output looked something as follows,

At the end of all this I find myself sitting on four different voltage regulator circuits, several variants of the transistor output diamond buffer, five phono stages variants, and a couple of nebulous ideas about developing a discrete voltage gain amplifier.

I'm considering how to package this all up in such a way as to best appeal to diyaudio builders of widely varying application needs and skill levels while keeping a simple...
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Old

CFA audio gainblock - a second take

Posted 16th December 2016 at 01:21 AM by rjm (RJM Audio Blog)
Updated 16th December 2016 at 01:28 AM by rjm

This is either an ingenious interfacing of the output buffer and current feedback amplifier by adding second arm to the central current mirrors ... or it's another really bad idea(tm).

It simulates nicely though.

[What's happening here is current output of collector Q9 is no longer being asked to bias and drive the buffer Q16. Instead Q2 and Q17 do that job. The change lowers distortion, improves bandwidth, and even raises the PSRR a little.]
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Old

A slightly different kind of voltage amplifier

Posted 12th December 2016 at 10:44 AM by rjm (RJM Audio Blog)
Updated 21st December 2016 at 04:50 AM by rjm

(which is a current feedback amplifier)

Lately I have been looking again for a discrete transistor voltage gain amplifier for line level duty that isn't just another op amp.

I keep coming back to variations on this circuit. It's a diamond buffer input with current mirrors in the mid-section strapped around a voltage divider / feedback loop that provides the gain. This backs out into either another diamond buffer or, in the revised version below, a standard Sziklai output stage which can be more easily scaled up as needed for a headphone amp for example.

An offset bias adjust circuit could be added to trim the output offset voltage. Or use a coupling cap. It's a few hundred mV otherwise.

Circuit gain is R4/R6, approximately. The total value of R4+R6 should be kept about 20 kohms. C1 is a compensation capacitor. Circuit gain as shown is 14 dB, -3 dB at 250 kHz.

As with all CFA, the choice of the feedback resistance...
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Old

Lynx and RME Sound card pinouts

Posted 7th December 2016 at 05:28 PM by 1audio

Attached are the pinouts for a Lynx (L2 or L22) sound card and for an RME HDSP(e) sound card. The host end is a standard Dsub connector
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File Type: zip Connector pinouts.zip (49.1 KB, 24 views)
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