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Old

For Sale - Reference DAC PSU for Red Baron / Tube-I-zator

Posted 28th January 2017 at 10:16 AM by dvb projekt
Updated 8th February 2017 at 05:19 AM by dvb projekt

Reference DAC PSU
for Red Baron / Tube-I-zator

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Custom made "Galaxy" housing with 10mm front panel from modushop.biz

Custom made Transformer with double C-cores, made for Vacuumschmelze Germany for Siemens military equipment

Tube-Rectifier circuit (6106/GZ34 or equivalent) with High-End Parts for B+ of the Tube-I-zator

The C-L-C-R-C Network with no electrolytic caps!

Yamamoto Teflon socket
...
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Old

A power amplifier.

Posted 19th January 2017 at 10:37 PM by rjm (RJM Audio Blog)
Updated 23rd January 2017 at 10:55 PM by rjm

Another request.

The Sapphire4 and Unity (H) boards were based on the 47 Labs Treasure 0347 amplifier circuit, and the original was not so far away that I couldn't "de-modify" the Unity (H) board back to what is essentially a 0347.

Here's what else you need to know:

Runs off 100VA or higher power transformer, 2x15 VAC secondary, bridge rectifier, 2200 uF filtering or more on the power supply rails in addition to what is on the main boards.

The outputs go to a mute toggle switch and then a 2A fast fuse before connecting to the speaker terminals.

In the original, Q9 and Q10 are taken off board and glued to the face of Q13 and Q14 packages. This provides overtemp control, as the output transistors heat up the Vbe of Q9, 10 decreases - reducing the output bias current.

C2 was not present on the original. I include this compensation capacitor as an optional tuning option, though my own tests show it shouldn't...
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File Type: zip unity47-10a.zip (97.3 KB, 65 views)
File Type: asc Unity 10a (H) 47 mod.asc (5.5 KB, 150 views)
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Old

Phono Stage Cartridge Loading Auxiliary PCB

Posted 18th January 2017 at 06:02 AM by rjm (RJM Audio Blog)
Updated 19th January 2017 at 04:33 AM by rjm

By request.

Simple 4 option loading for MC or MM cartridges. Stereo board, 80x50 mm. Part of the "useful elements" series.

Inputs are bidirectional (pass through), the signal only has to be connected to one set to function. What more loading choices? Use two boards!
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Old

Dual Bridge Rectifier PCB

Posted 18th January 2017 at 04:33 AM by rjm (RJM Audio Blog)
Updated 19th January 2017 at 04:32 AM by rjm

I'm sure there are dozens of people on diyaudio who could do up this layout, but hey, it was a super-quick modification of the cartridge loading board I was doing anyway ... so to continue the series of 50x80mm "useful elements" boards, here is a dual bridge rectifier board for a transformer with two secondaries.

It will work with just about all of my projects, or anyplace you want to have the diodes separate from the rest of the circuit.

If there is interest I may get a set made up, or make the Gerbers available.
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Old

Discrete Operational Amplifier - Open Source (SMD)

Posted 8th January 2017 at 01:35 AM by googlyone
Updated 8th January 2017 at 01:49 AM by googlyone

Well here I am at the end of another summer holiday - with yet another thing I have built for which I have absolutely no plans at all!

I have over the years built several (several dozen I would expect!) discrete operational amplifiers. The challenge I set myself here was:
- Actually get some proper measurements of it's performance, now that I have some test gear that is up to the job.
- Make the device in something close to a DIL-8 package. (slight fail here but close enough)
- Discrete
- Use some of the multitude of parts I have collected of late.
- The ability to configure the op amp as a buffer or amplifier with non-inverting gain. This means adding feedback resistors and a DC block cap.
- The ability to include input RF filter (typical few hundred ohms series and 1nF across the input)

The schematic won't surprise anyone - over the years I have designed ridiculously complex and simple amplifiers, and have run...
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File Type: pdf SMP Opamp Silkscreen.pdf (18.7 KB, 44 views)
File Type: pdf SMD OpAmp Top layer.pdf (18.7 KB, 68 views)
File Type: pdf SMD Opamp Schematic.pdf (114.4 KB, 154 views)
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Old

Levels- and spectra-pathing symmetrical arrays of monopoles

Posted 6th January 2017 at 04:23 PM by Grasso789
Updated 14th April 2017 at 12:59 PM by Grasso789 (Bits)

This is about spectra-pathing ("multi-way") loud-speakers made of several monopoles, in explanation omni-directional sound sources, but I really mean direct radiators as opposed to horns, which are more uni-directional. I think about home, rehersal and club loud-speakers, not stadium ones. While spectra-pathing enables large power at wide band-width, seams between paths are usually audible, altho that could have been avoided rite from the start, at least technically. But instead of fixing problems at source, one has relentlessly used power to paint over them.

Computers can cover up phase distortion, which has been introduced by common spectra-pathing, and improve beam-width. But the natural solution is a symmetrical arrangement of lo-pass drivers embracing one hi-pass driver, an arrangement commonly referred to as D'Appolito arrangement, combined with a cross-over of first order.

When Germans started to loose ground in World War II, wide-range drivers...
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Old

Calculating ballast resistor values to to control current hogging in paralleled BJTs

Posted 3rd January 2017 at 07:32 PM by bwaslo
Updated 3rd January 2017 at 07:41 PM by bwaslo

I started a thread at http://www.diyaudio.com/forums/solid...t-hogging.html on this subject, and after some time and many helpful suggestions, here is the calculation I came up with.

The goal is to find out how large the ballast resistors must be to prevent current runaway and to control "current hogging" to a given limit. Current hogging is a phenomenon with bipolar transistors when operated in parallel in which the hotter of the set draws more current than the cooler one(s) and so heats up even further. The fix is to put series resistors ("ballasts") in the emitter circuits (see the drawing), but I've not been able to find anything published that says how to calculate the value of the resistors.

The model is for two BJT transistors, with their collectors and bases commoned and their emitters summed through individual ballast resistors. You need to know what the process-variation-caused...
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Attached Files
File Type: zip Current Hog Calc v2.zip (27.8 KB, 23 views)
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Old

Building a DOA SeNNator Headphone Amp

Posted 3rd January 2017 at 03:56 AM by disfunctionalshadow
Updated 3rd January 2017 at 03:26 AM by disfunctionalshadow

In a search to replace a modified SMSL headphone amp that I use at work, I decided to build a DOA SeNNator, a variant of the filtering headphone amp for the Sennheiser HD 650, published by Solderdude over at - diyaudioheaven along with measurements of the HD650's responses.

It's based on the "HD 650 SeNNator" and "SeNNator build tips" pdfs. In adapting the design, DOAs were used. An upgrade to the filtering caps from polyster to polypropylene. To the original circuit, circuits and design ideas from:

  • Sam Groner - +/-30mv DC offset adjust and DC bypass cap.
  • Layout idea lifted from Jeff Steiger's CAPI-2 Line Stage Amp, from Capi-gear.
  • DC filter from Collective Cases, reducing the numerous different electrolytic caps and upgrading the linear regs. from LM217/337 to LT1963/3015.

Minimized mechanical assembly, using the default PWBs available in Kicad, each channel and the DC filter/regulator boards are in a Euro card form factor...
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Attached Files
File Type: pdf DOA_SeNNator_V1.5p.pdf (43.5 KB, 59 views)
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