Recently it has been archieved to capture, store, propagate and play back audio with the full human hearing frequency range (16 to 16000 Hz) and contrast (7 Bel). Still, if a big sound source or several sound sources at once are the matter of content, such play-back sounds artificial, because all is emitted from one acoustic source. In order to hear, what is going on, we use both ears simultaniously, turn our head in different directions and will detect the electro-acoustic device.

While an indetectable electro-acoustic reproduction incorporated six microphones, storage and transmission channels and a house-sized sphere covered by loudspeakers on the inside and containing the listener, we can help imagination at least a little bit by introducing sonic differences between left and rite. We also want this stereo, after Greek stereos shape, to integrate thoroly and easily with already existing mono electro-acoustics. We may double transmission and storage channels, for example...

Over in the Low-distrotion, Audio-range,
Oscillator thread (LINK) some posts
about getting lower distortion before taking
the measurement of a DUT (Device Under Test).

Our own RNMarsh posted some good results
running his Panasonic through a miniDSP
box configured as a Low Pass Filter.

He had good results. So I thought and told him
so, and suggested he might get better results doing a band pass filter.

So instead of doing my diode homework for
my Solid State Devices class, I thought I'd
better check, that is put up for shut up.

So, I did and here is what I discovered:

Before filtering:


https://www.diyaudio.com/forums/attac...r-baseline.jpg...

...

This is an unfinished design idea.

*****

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 (but with neither the original transistors nor the original resistor values).

I changed just about all the resistor values slightly for one reason or another, and changed all the transistor types. I've run my own simulations to check my version basically works as it should. Output BD135(39),136(40) are shown on the schematic as being leftovers from my headphone design, they will work to play music but to meet high current output specifications something bigger in TO-220 or similar thermal package will be needed.

As I hope you can see from the circuit schematic, the design - for a power amplifier - is unconventional. There is no feedback...

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!

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.

These are available on my web page.

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...

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.

The natural solution is a symmetrical arrangement of lo-pass monopoles embracing a hi-pass one, combined with a cross-over of first order.

When Germans started to loose ground in World War II, wide-range drivers playing from Large E to 10 KHz were state of the art. Mister Eckmiller developed a co-axial two-spectra-paths driver consisting of hi-pass encircled by lo-pass piston. But for mass...

I started a thread at https://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...

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...