Rack mount power amplifier 1.

Another idiotic (never finished???) idea of mine.

As I go back to build audio equipment and bought enormous amount of old audio gear, I eagerly need something to test it in my lab. I started to build my test equipment into 19" racks (than disassembled everything. 😂)

For testing, I need a set of speakers, and a power amplifier.

Requirements:

• Built into a 1U rackmount enclosure (I hate things on trays in the rack)
• Use modul parts: Switching PSU, Class D amplifier board
• Put all of the connectors to the front, to be easily accessible
• Optional: back connectors with front/back switch

Ordered:

• 500VA 24V PSU - $16.45
• TPA3116 120W Class D board - $10.71
• 1U Rack Chassis - $44.82 + $56.73 (Shipping)

Whaaaaat?????

No way.

Once more:

• 500VA 24V PSU - $16.45
• TPA3116 120W Class D board - $10.71
• 1U Rack Chassis - $44.82 + $56.73 (Shipping)

Think a bit, look around.

Buy the chassis locally

• 1U Rack Chassis - $50

Whaaaaat?????

No way.

Next iteration:

• 500VA 24V PSU - $16.45
• TPA3116 120W Class D board - $10.71
• 1U Rack Chassis - $50

Look around more thoroughly:

I found quite a few outdated or broken 1U network switches. $12-$15 each

Much better.

The things arriving:

The Amp:

The PSU:

The Switch for repurpose:

My new A3 printer and sheet laminator is on the way to me. So the plan is to throw away the parts from one of the switches. build the connectors, volume pot on the front of the switch chassis or add some holding consoles (probably 3D printed) and design a new front panel, print laminate, cut and finally glue it with a double sided adhesive tape.

This is the plan. Looks super fast to me. Hopefully not another half baked, shelved project.

New Arrivals 6. - (special edition)

Today, I only want to write about one thing arrived, as it is a bit special to me and need some more attention.

This is a bit strange, nostalgic story.

In my childhood I was living behind the "iron curtain". There we have very little possibilities to get things from the western part of the world. I had obsession to music, the audio electronics in my teenage years. Even I was "working" as a DJ in the school. I had two cassette decks, built a mixing station for this.

I was eagerly need a headphone. My mother time-to-time had the opportunity to travel to the west. Once she bought a headphone for me (some no-name thing, but I was really happy with it).

Years elapsed, more and more Hi-Fi things arrived to the country. To support the music and Hi-Fi loving audience, a magazin appeared on the local market: http://www.hifimagazin.hu/

Once they was running a headphone test: http://hifimagazin.hu/HFMCD/HFM/CIKKEK/HFM2410.HTM

There were AKGs, Beyerdinamics, Sennheisers, etc. the good big names. Those were first unavailable in the country and also as a moneyless student, I can't afford them even if it would be on sale locally.

I just find the KWH HOK-80 on the list, what got good verdict, was available for the money acceptable to me, so I bought it based on the article.

It had great sound, but you had the feeling when you put it on, like your head would be in a machine vice.

You can't tolerate this "comfort" for a long time.

I was a gadgeteer kind of guy already these days. So I built the orthodynamic panels from this headphone to the one I got from my mother years ago. Case closed, I had a good enough headphone (Also built headphone amp for it).

Few years later after the "iron curtain" fallen, I got other interests, turned to the computers instead of the audio electronics. Once I landed the already unused mixing console and the headphone to a friend.

Never seen them again.

Two-three weeks ago (30 years after the story above) I read an article about some highend Technics loudspeakers https://longkft.hu/audioblog/technics-sb-afp1000/ (it was a repost on the facebook).

The article is talking about the east-german headphone I had previously also as the technology is the same as the one used in the Technics monster.

When I read it, the long forgotten story above pop into my mind.

Looked around on the eBay, and found a HOK-80 for a few bucks. Today arrived.

Even this one arrived in the original box, with the original documentation and warranty card.

What a surprise, the original east-german invoice was also in there.

165 east-german mark. I was looking around the exchange rates. If I'm not mistaken, it would be €33 today.

Nothing changed regarding the comfort. The vice feeling on your head is still there.

My son has a gamer headset. He completely destroyed the cabling, the switch and volume knob of it. Finally I bought a bluetooth one for him (can't hurt the cable). I just throw the headset to a drawer years ago with the thought "I'll repair it later" - never happened.

Now I picked it. It would be a good donor candidate for my new project. I want replicate, what I did in the '80s (sort of).

I will build the orthodynamic drivers into this Gigabyte headset's shell, add a proper, detachable headphone cable and done. This will be one of my next projects.

Akai - Media Player 2. Volumio

I dowloaded and put on a microSD card the Volumio
Connected to HDMI, keyboard, switched on - nothing on the screen (maybe the screen resolution)
Moved the set to a 4K TV - nothing on the screen
Removed the Wi-Fi module - nothing on the screen
Switched the Pine64 board to completely new - nothing on the screen
Changed the microSD card to a different piece, manufacturer - nothing on the screen
Changed the microSD card to my previously used Android TV distribution - screen on, booting
RTFM - you are an idiot. The Volumio is headless on SBCs

Connect to the LAN, wait for IP, connect via browser

First task accomplished
I need a few plug-ins for the complete system:

Tidal (I'm using mainly as music streaming)
Looked around. I'm not happy. Looks like the native integration doesn't exists. You have a few choices:
1. Subscribe to MyVolumio and use Tidal through it
2. Download your music locally with AudFree
3. Stream through UPNP/DLNA from your Android phone
I can tell, I'm not happy with either choices. Not yet decided, what to do.
Further reading:
https://forum.volumio.org/tidal-playback-t8894.html
https://www.audfree.com/tidal/tidal-on-volumio.html
https://forum.volumio.org/tidal-native-plugin-myvolumio-t10682.html

16x2 (20x2) LCD display - hopefully my VFD use the same communication protocol
It looks like there is quite a lot information exists on the internet. I just need to grab them, and build. The question is, how will it work on the Pine64 as all of the descriptions for Raspberry Pi.
Here are the Github repositories for the code:
https://github.com/Saiyato/volumio-pydpiper-plugin
https://github.com/dhrone/pydPiper
https://github.com/JedS/Raspdac
Connection:
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDN0xib8RQp84p4BqSTxCumE6uhyphenhyphen2iqGubwXm-KATwOJx0sHPCs1NKIhWuSWM56k99GLX91C0lwPjYfspIR3Jhl_yviuIMxvLpiiFX3ck0547TcxwAUciyi3cRbKmU0u9lV6lM20T8SfBj/s1600/Volumio+LCD+1.jpg
I2C Interface (not yet decided, if I'll use it):
https://forum.volumio.org/display-16x2-and-i2c-interface-t9549.html

Rotary Encoder
It looks like the rotary encoder plugin already in the stock firmware, so I installed it already.
Here is the documentation and connection:
https://github.com/Saiyato/volumio-rotary-encoder-plugin
I read on various pages, that this is unreliable. Here is a different solution:
https://forum.volumio.org/getting-rotary-encoder-working-t9690.html
We will see, what is the working solution.

Buttons/GPIO
The chassis contains three buttons already. My plan is to keep them, and use them for... I don't know yet. I'll figure out later. probably I'll relabel the buttons.
Anyway. Here is the plugin:
https://github.com/tomatpasser/gpio-buttons
https://github.com/volumio/volumio-plugins/tree/master/plugins/system_controller/gpio-buttons

Bluetooth
I'd like to play music from my phone through bluetooth. So looked for the solution. Here I found one:
https://forum.volumio.org/volumio-bluetooth-receiver-t8937.html

Infrared Remote
Here is a starting point for the infrared remote I plan to use:
https://forum.volumio.org/control-guide-for-raspberry-t9700.html

Now I collected all of the information I think is necessary for my VolumIO project. I'll continue from here connecting, setting up piece-by-piece.

Akai - cannibalized

As I wrote previously, I want to add streaming media capability to my retro Akai Hi-Fi set.
The plan was the following:
Pick up on the market a low cost unit, fits into my set.
Remove everything from inside.
Build the following set into it:
- Raspberry Pi + VolumIO
- Some power supply
- Some DAC
- Some alphanumeric display
- Rotary encoder
- IR receiver

I was looking for the possible "donor" units. Finally my choice is an Akai AT-A1 tuner. I bought the one I have in my hand for GBP 17 from UK

Opened the box. Here is the original inside:

Then I removed everything what looks unnecessary:

Ordered a few things what will go into the box:

This is the current status. More will come soon.

Akai - old love

I didn't write this blog for a while. I had good reason for this, what is not public. From now on it looks like my reason went away, so I'm back.
Along with my passion for electronics, CNC milling, 3D printing and many more, I have an old love. Music and Hi-Fi. To be honest originally this was bringing me into the world of electronics almost 40 years ago (38 to be exact). I was 11 when the first Hi-Fi set landed in my family. Right from the beginning I was thinking how can I expand its capability, later on I was thinking how can I rise its sound quality. This lead me into the word of audio electronics, building amplifiers and other things.
As I raised behind the "iron curtain" in the '70s and '80s. At that times not to much goods arrived from the western part of the word. Here in Hungary mainly one company namely Akai was available, based on the fact that Videoton (Hungarian audiovisual manufacturing company) acted as a manufacturing base for Akai here.
At 1984 even they had a trade show in a restaurant in Budapest. I was there and picked up a brochure, what was almost a Hi-Fi bible, a source of wishes for a long time. I just wanted to own a full set of highest ranked equipment from this brochure - what unfortunately don't have anymore.
In the last year somehow pop this desire into my mind after a long time forgotten.
So I started to collect.
Today I can tell, I almost have the full set I wanted. Actually even a bit more, but the "project" not finished. I'll probably sell a few, switch a few from it.
Here is the current collection:

Some of the units are in a good shape. Some of them need care both outside and inside. In the following months even years I plan to restore those into working, aesthetically good condition (also with some external help).
In addition to this I plan to create a shelf to accommodate all of the units I intend to keep, and add some capabilities what fits into the design, but was not available at the time this equipment was built, like internet streaming audio.

Chain of events

I always think, why I start more projects than I finish.
One cause is the chan of events. I start something, than something is missing is missing from it, what forms an other project, than I miss something from it - other project and the chain of events formed. Have several open things, nothing finished.
Check the current one:
I wanted to recreate my music listening environment. The first path is from vinyl.

1. Repaired the crossovers in my Mission 705 loudspeakers (replaced a few ancient Tesla caps)

2. Repaired my NAD 5120 turntable (removed the original built in cable, added a few RCA connectors, replaced the belt, adjusted the arm lift)

3. Wanted to build a new RIAA corrector. It is based on the award winning design from the '80s. Created by a local HiFi Magazine here in Hungary named HFM-I. Actually built it, but just wrote about it on my Hungarian language blog (http://it-pro-hu.blogspot.com/2019/02/hfm-i-ujragondolva.html, http://it-pro-hu.blogspot.com/2019/03/hfm-i-2.html, http://it-pro-hu.blogspot.com/2019/04/hfm-i-3.html

4. And here is the place where my "chain of events" starts. It came into my mind, that I'd like to measure what I built before put it into my system. Bought an HP 8903B Audio Analyzer (not just for this project, it was in my plans for a while already).

5. U1. I have a good set of instruments, but it wasn't a requirement to connect them to a PC until now (I was thinking, I'll do that once upon a time). For generating a graph from the 8903B it become absolutely necessary. Unfortunately didn't find a GP-IB interface what I like, so the first unplanned project born. Found an Arduino based interface, but absolutely hated the hardware, so designed a new one (http://pakahuszar.blogspot.com/2019/04/gp-ib.html, http://pakahuszar.blogspot.com/2019/04/gp-ib-2.html)

U2. Didn't like the software of the interface, neither the license, nor the implementation. Started to write a completely new code from scratch (still unfinished, it will be testable soon, if it doesn't end as unfinished project as many before).

U3. Somebody asked upon my posts, if I want to sell the GPIB interface boards I created. Started to think - why not?
If I sell it, I want to organize the hardware designs and the software correctly. Don't want to publish unfinished design, or software, so I built up a git branching model for myself to achieve this. Here surfaced my old problem again. The library handling of the KiCAD is horrible. I want to publish the hardware design without external dependency (I mean, if somebody opens the schematic, get real components instead of boxes with question marks). Tried to use KiCADs archive plugin. Unsuccessfully. Registered, but it not even started. After few days of searching, asking, got no solution.

So, the Unplanned-3 project born. Create an application (not a KiCAD plugin) what automatically manage this mess on my hardware projects (I started it in .Net Core 2.1, got some progress, but this is a topic for a further post)

Let see! This is one way how my unfinished projects are born.

Status

It's been long time since I didn't write anything on this blog.

Actually I just didn't have lust to write. It doesn't mean, nothing happened.

The main reason I writing now is the status of my Curve Tracer project. After a long struggling period I achieved the first milestone of the project. It started to work. I mean the whole measure chain is working, but there is a long road ahead still, until the finished product.

As I'm talking more and more a few "audio related" people, I went back a bit into my childhood, and started to work on my audio equipment.

Repaired and modified my good old NAD5120 turntable. Repaired my Mission 705 speakers, collected a few retro audio components from the eBay.

Now I have a fairly good sounding system. I'm planning to add some DIY components in the future (going back in electronics, where I started)

There is something itching inside me, since I first saw a Fostex full range horn speaker in a DIY book. It was at least 5 years ago. Since then I'm thinking about to build a pair. As my audio equipment started to work, I felt, it is just the right time to make my hands dirty.

I started to build a Fostex FE108E Sigma based box. To be precise, the recommended enclosure from Fostex's web site.

Headphone holder

As my 3D printing started to work, I wanted to create some additional things also.

Yesterday, I put in work my long unused (today nonexistent) knowledge in trigonometry. Here is the result:

Meet with my shiny, new headphone holder.

Printed:

And in work:

The files are on the thingiverse