Electronics GuilleAcoustic's audio thread

Hi mates,

some of you might remember my messy "GuilleAcoustic's design thread": http://forums.bit-tech.net/showthread.php?t=205983

Since most of the pictures aren't available anymore (auto purge from image sharing site) and the chaos I created in this previous thread, I decided to create a new one.

In order to have more focused things, I'll create 2 separated threads:

• Computer focused thread (case ideas, peripherals, etc.)
• Audio focused thread (amplifier design, speaker cabinets, etc.)

I'll try to keep things clean and focused, it's time to tame my brain . As always with me, it's a participative thread. Any comments are welcomed, especially negative ones as it helps to improve things (as long as you give arguments).

Note: I'll edit this first post ot make a proper and more eye candy one . All apologies for this very basic "home" ... and please excuse my english.

 

Ok, it's time to get serious now. Following posts are going to be a succession of WIP and trying / failing / learning.

I won't post anything in the "project logs" sub forum unless I have a finished project. This current thread will house my ideas, share my precious links, give advises, etc.

So lets start with the first step of my audio asylum : Project GA-HH1 (GuilleAcoustic Hybrid Headamp #1)

This is an hybrid headphone amplifier project based around the Raytheon JAN 6418 sub-miniature and an OPA or its discrete equivalent.



The tube has an output impedance of 100K Ohm, so an transistor stage is mandatory to adapt the output impedance (an OPA with a gain of 1 can also be used).

Here a basic schematic of a 6418 tube headamp (not mine)



Components are on their way and I'll fully document the prototyping process. The idea is to build either a portable C-Moy like amp and a dual mono desktop amp.

EDIT: For anyone curious about "how does a vaccum tube work ?", here are great videos explaining the basics (the first one was made by Walt Disney).

 

Thanks mate ! About price, those little tube are very cheap. They costed me 14€ for 4x tubes and this was on the expensive side (mostly because I got military grade tubes). It's on the same price tag than a CMoy, a $40 kit is available from Oatley electronics : http://secure.oatleyelectronics.com//product_info.php?cPath=100_104&products_id=1027 (at this price you have basic components, but this is a good base for future tweaks).

I've read a lot about CMoy and quickly ended on that one. Completly insane build ! I'm really in love with tube, but I'm planning to build a CMoy to replace my Lian Li front panel jack .

Thanks for the information, that'll be very handy. I have an old Creative Zen but it doesn't read FLAC and I'm not really happy with since I got a pair of AKG K701.

 

Hi fellow bit-techers,

little update to let you know about a great Chrome / Android / iOS application that I discovered yesterday :



This is a circuit simulator with a great user interface. The free version is limited to a very small circuit, but the full version only costs 7€ a year, so not very expensive.

Sorry for the lack of post in this thread, but I don't want to start showing work until I really have something to show. Stay tuned

 

Ohhhh a little audio goodness!
Subbed for sure

 

Little necro bump, but I found this lonely beauty at my residency disposal:





This is a Philips 521A, an old valve radio from 1934. The chassis is in pretty bad condition, but sanding and new veneer should fix it.



The smartphone on the following pic is my humble Xperia M2, its 4.8" screen gives an hint at the vaccum tubes size.



The radio works, but all the capacities must be changed. Nothing surprising for this 81 years old beauty. Here is a rough guestimation of the restauration stack:

- Deep cleanse
- Capacitors replacement
- Sanding
- Veneer
- Front speaker cloth replacement
- Power cord replacement
- Back panel replacement

Here is what it should looks like when in good condition:

 

That bump

Nifty!

 

Thanks a lot, that was quite the surprise when I saw it, lying among wood planks.

The radio has a phono input, still monaural but I can connect a Raspberry Pi with a DAC hat. Gonna bring this beauty to the 3rd millenium.

 

Awww... it's like finding a box with an abandoned kitten in it. It demands to be loved and nurtured and restored to its former glory.

 

So true. The strong mushroom smell really saddened me. This is a legendary radio, Phlips first superheterodyne receiver.

I found the schematics on a TSF specialised site:

 

Even the name sounds cool: "superheterodyne".

 

Never done flood recovery on antique hardware before, but I've done a ton of mold removal. I'd apply a penetrating bathtub bleach, scrub with a toothbrush, and sponge off. You have to let it dry and hit it again a few times. Make sure not to let it soak and separate the veneers.

 

Sadly the cabinet is in pretty bad condition. The veneer is already separating from the corners and is blistering on the top panel. Sorry for the night pics, but this gives an idea of the poor thing's current state.

 

What a precious find! This is very familiar to me: last year I also found an old radio. Of course, not as old as your. In my country such things are very rare, and many museums would fight for the receiver like your .

I found the first-class radiola produced in 1956, huge, weighting more than 40 kilos. When I'm not doing my casemods, I am restoring it.



And I don't think that your radio is in poor condition. I've seen receivers restored from a much worse condition. So I wish you a good luck with this one!

 

Thanks a lot BootSector. Your receiver looks great.

The first receiver that I found was from the early 60's, a stereo Gründig with FM (mono) fully equipped in Telefunken part (tubes and transformer). I haven't restored it yet, it needs a new selenium rectifier, full capacitors replacement and the foam inside the electrostatic tweeters is dry as stone.


Video is not mine

The only missing part is the optional stereo FM decoder module, unless I find one the FM will be in monoral:


Gründig Stereo-Decoder-6

 

That's interesting! I'm sure you will succeed with your new project. Let me show you one motivational photo. You've already seen my chassis in "before" condition, and this is "after":



I'm absolutely not experienced in restoring old radios, this is my first try.

 

I have a valve amp at home that I am going to be making over in the next year at some point. I will get some pictures up for you later when I get home

It works and all the valves fire, but it needs some TLC, potentially a bit of a rewire. I haven't done much testing on it yet. Also needs all the inputs/outputs to be made modern as currently I have no phono cables that will fit on the outputs! Has a very cool magic eye on the front though.

Bootsector - I doubt mine will ever look as nice as that. tremendous work.

 

Oh gosh, that is one damn job you've done there. Very motivational indeed. I'm currently cleaning the chassis from all the rust and one of the electrolytic capacitor leaked. I'm glad that there was no PCB to be eaten by the chemicals. All cable are good for a change too, they are rigid as hell and the plastic insulation is crumbling badly.

 

This is my receiver

















Though some smoke came out and I got scared so I unplugged it Needs lots of attention.

 

It wouldn't hurt to try some furniture polish on that front panel if it's that bad. I think it's still saveable. Veneer can be mashed back down and stuff...