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Discrete Operational Amplifier - Open Source (SMD)

Posted 8th January 2017 at 02:35 AM by googlyone
Updated 8th January 2017 at 02:49 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, 33 views)
File Type: pdf SMD OpAmp Top layer.pdf (18.7 KB, 55 views)
File Type: pdf SMD Opamp Schematic.pdf (114.4 KB, 123 views)
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Old

Levels- and spectra-pathing symmetrical arrays of monopoles

Posted 6th January 2017 at 05:23 PM by Grasso789
Updated 4th February 2017 at 08:33 PM by Grasso789 (Bits)

This is about spectra-pathing ("multi-way") loudspeakers 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 loudspeakers, not stadium ones. While spectra-pathing enables large power at wide bandwidth, 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 beamwidth. But the natural solution is a symmetrical arrangement of lopass drivers embracing one hipass 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, widerange drivers...
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Old

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

Posted 3rd January 2017 at 08:32 PM by bwaslo
Updated 3rd January 2017 at 08:41 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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File Type: zip Current Hog Calc v2.zip (27.8 KB, 13 views)
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Old

Building a DOA SeNNator Headphone Amp

Posted 3rd January 2017 at 04:56 AM by disfunctionalshadow
Updated 3rd January 2017 at 04:26 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, 53 views)
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Posted in Headphone Amp
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Old

Small tline for 8"

Posted 29th December 2016 at 12:52 PM by HumbleDeer

I think I'll be painting my small subwoofer in some shade of cherry or wine red. I just need to sand it down once more and give it one final layer of MDF Primer. Hopefully, all dents and small damaged points will be gone. I won't get my hopes up though.
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Old

Can a double blind test really be double blind?

Posted 27th December 2016 at 12:48 PM by jan.didden
Updated 27th December 2016 at 12:51 PM by jan.didden

This blog is not about audio. Or at least not in the sense of a design or equipment discussion. It's about how we as humans tick, and possible (probable?) implications for how we form opinions and views about what we hear, about a particular design or sound.

My long-standing interest in this area was recently triggered again by a couple of posts from Mark4w, and a book he recommended (Thinking, Fast and Slow, by Daniel Kahneman). At about the time I received the book I also fell into a scientific discussion on the TV about the process our brain goes through to form an opinion and serve that up to our conscience as 'this is how it is'.

I thought back about all the discussions I've had on diyaudio about sighted versus blind listening. Without opening up Pandora's box yet again, in a nutshell: The brain uses every input it can get its hand on to form an opinion. So when you listen to, say, a new amp, the brain not only uses the sound coming in through your ears,...
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Old

How to Spell Checking Posts - Firefox

Posted 27th December 2016 at 04:12 AM by SyncTronX
Updated 31st December 2016 at 05:26 AM by SyncTronX

How to set up the spell checker.

Surprise!

Spell check is NOT in the DIYAudio software,
it is part of your browser.

Set up is simple. Follow these
general steps:

On the menu bar select and hold tools:
Click the image to open in full size.


Then, drag down and selection Options:
Click the image to open in full size.






Then from the tool options scroll down and select Advanced:
Click the image to open in full size.



Then at the bottom click on the check box, to
put a check in it:

Click the image to open in full size.


Close the window, restart your browser, that is it.
...
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Old

Project Unity Board Layout

Posted 27th December 2016 at 01:33 AM by rjm (RJM Audio Blog)
Updated 27th December 2016 at 11:11 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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Old

Pictures of my Audio Equipment

Posted 23rd December 2016 at 09:44 AM by BasicHIFI1
Updated 23rd December 2016 at 09:58 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 06:02 AM by rjm (RJM Audio Blog)
Updated 28th December 2016 at 12:46 AM 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, 25 views)
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