Drew ][ TDX Production Cards – Plates Galore!!

March 23, 2010

Finally I have recieved the back plates! 🙂 As it is quiet on then laptop card front going to focus on sorting out the first production run. If you are waiting for a card please be patient as I am almost there….honest lol

Drew ][ TDX Production Cards – Update

February 17, 2010

I have now recieved the first plate and all looks good. I just now need to choose the right 3.5mm jack :).

TDX Stereo Card – Jan Update

January 28, 2010

Ok firstly have been a bit slow this month with finalising the various bits that finish of the overall card. I have now got a prototype back plate completed and just trying to get price down for the manufacture

New Year updates…

January 5, 2010

Some New Year Updates

*Drew ][ TDX Card*
Now have some sample back plates and 15 PCBs have turned up 🙂

*Portable GS Stereo Card*
Have moved away from the LM386 pwr amps and now using a single dual power amp TDA2822M. This was primarily to keep component count down as the dual pwr amps are actually more expensive.

I am also testing with the DS1802 dual digital pot (this provides a single IC with mute function, but doesn’t remember the wiper position unike the DS1669 though its more designed for volume control). I would say I am almost there for a completed circuit and just ironing out some minor issues to avoid instability in the circuit.

It is looking like the prototype board for the GS laptop will consist of:-

  • MC14052B – DeMux
  • TL082 – Op Amp
  • DS1669 x 2 – Digital Pots
  • TDA2822 – Dual Pwr Amp

The GS Laptop project have tight timescales so at the moment focus is on this rather than the Drew ][ TDX card…

Michael Mahon has been a real mentor for this project and massive thanks goes out to him.

TDX Laptop Stereo Card – Progressing..

December 7, 2009

Well finally hit some good headway with this tonight and have a fully working circuit with dual channels and volume control and works happily with headphones.
This uses the base of the original circuit (as per the FAQ) but removes the 2nd stage op amp and introduces 2 x LM386 power aps and 2 x DS1669 Digital Pot ICs. There are 2 push buttons that control up and down volume.
Massive thanks to Michael Mahon who has been very patient with me over the last couple of weeks :).
Still have quite a bit of work to do as I also plan to look at other ICs that might be able to simplify the design..as currently the power amp section requires 4 ICS….


Well I plan to do a small run of the version 1.0 card (15 cards or so and will be offered to the CSA2 community first). The output is designed to go via power speakers. My website will get updated at some point to reflect availability :)(www.drew2gs.com).

I have stopped working on getting input functionality working, but rather have decided to focus on making a card that can fit in the portable GS that is being made by http://www.a2gs.com.

The portable GS will need to be able to run via headphones or un-powered internal speakers. This means I need to redesign the existing card to contain power amps. This has also made me think that once I get input working I can make a version 2.0 stereo card that has Line-out, headphone-out with vol control and Line-in/Mic-in. There is potential here to obvious make a completely slotless design.

**It was pointed out that I can get rid of the line-out and just use headphone out to connect to powered speakers**

Well tonight have had 100% success getting headphone output to work with volume control and zero distortion :). This happily worked along side the line out with no obvious issues. Was only able to test one channel as currently only have 1 potentiometer. To get it to work successfully I bypassed the 2nd OPAMP.

There is still hiss/white noise which I am not happy with until I have eliminated the bread board, but am going to continue with the current design. I  will use a version 1.0 board along with a hand made board to see what it all sounds like before i start looking at layout and how to get it to a size the portable GS guys are after :).

Schematic with the output from the low pass filter opamp going into a LM386

Working breadboard (one channel powered) utilising bother lineout and headphone out.

TDX Stereo Card – Prototype Complete

November 23, 2009
25th November **Update**
It seems the white noise wasn’t helped by using headphones to do my testing. As soon as I used a set of powered speakers the sound seemed much much better. There is still some white noise over the right speaker but much less so than my Audio Animator. Therefore I would say card is all good for production, once i decide if i want to add input capability or not :).
24th November **Update**
Prototype was completed tonight. Didn’t take long to solder together and all worked (kinda). The only issue is hiss coming from right speaker, similar to the bread board. Will investigate. Anyway some pictures are below.



The prototype boards have turned up. Will try to get something built over the next couple of days to see if all works and how it sounds.

The card has 4 mounting holes and also a space for a connector for +5 and -5 volts to power the board without a slot. How this will get housed has not yet been decided, but at least base design can potentially be used for slotless application.

My current thoughts are now to encompass a digitiser, using info from CSA2 and also the hyperstudio audio card as an example circuit…so will be back to the drawing board once I have a working board.

TDX Stereo Sound Card – Update

November 2, 2009


I have decided to wing it 😉 and have sent the latest PCB layout to have a prototype made. I should be a in a position within the next 10 days to actually make my first card.

Still awaiting quotes for back plate fabrication…:(


I am planning on making an audio cable similar to the Sonic Blaster one, but with only one 3.5mm jack:-


Today I have been thinking about what I can really achieve in this project as a lot of things are new to me. At this point I have decided to go with a slot based design with connectors for J25 connection and audio out. This will allow the Stereo out connector to be screwed to one of the plates at the back.

One thing I don’t like with the stereo card is mono sound only comes out one speaker (same as my Audio Animator, so nothing specific to the TDX), so I am planning to now put a switch to allow the mono sound to come out of both speakers giving a stereo effect if desired. This switch will be mounted on the back plate.

Work has now started on getting quotes together for PCB boards and plate manufacture while I work on the prototype card. I have had some initial quotes back. They look very promising and now just waiting for back plate fabrication quotes.

I fully plan to investigate slotless design and ADC after the initial run is completed.

TDX Stereo Sound Card – Breadboard Complete

October 28, 2009

Bread Board is complete. Surprisingly all worked (well had an initial issue where i wasn’t providing +5 and -5 volts properly to the board), bit of hiss in the background, but suspect this is because its on a breadboard.

(56k Resistors still arn’t here but put some in series to get the resistence needed)

29/10/2009 – RS Stuff has all turned up, but I had forgotten to add the 56K resistors to the order…3.5mm Stereo PCB jacks also turned up…but suspect they are too close to the board to accept a jack unless at end of the card..Will be fine for breadboard and prototype, but will most likely look at some that are slightly raised to allow cable to not impact back of case. (ideally i want to use a cable from the board to the the back of the case to fit in one of the ports…but finding parts seems difficult)

Connector seems to work well with the ribbon cable and though its a bit of a tight fit on the motherboard it does fit, and didn’t need any crimps. Also started the bread board…not sure its big enough, but its what i had available :).

I have been busy getting parts together for this new project and have just ordered the following parts from RS.

  • 517-3181 – TL084I quad 3MHz 13V/uS op amp, DIP14
  • 197-2669 – 16 way turned pin DIL socket,0.3in pitch
  • 519-0316 – Dual 4-1line mux/demux,MC14052BCP DIP16
  • 135-910P – RES HYSTAB 0.25W/10K
  • 135-932P – CFR16 carbon film resistor,15K 0.25W
  • 365-4234 – NHG min Al electrolytic cap,4.7uF 50V
  • 365-4240 – NHG min Al electrolytic cap,10uF 50V
  • 122-4235 – FKS2 Polyester Cap,100Vdc,1.5nF
  • 622-4397 – Plastic film capacitor,100nF 63V 5%
  • 157-547  – MBA0204 M/F Res, 0.4W 50PPM 1% 56K
  • 289-9846 – Speedbloc(R) 10 way IDC ribbon cable,5m
  • 189-9592 – HE14 AUTOCOM cable socket 26/28awg 7W

I have also ordered a selection of connectors/headers to see what will be best for connecting to the mainboard.

Andy at work likes his circuit diagrams and has kindly drawn up a schematic and a PCB layout based on the TDX diagram and Polymorphs use of the Quad Amp. He still has to add the connector layout for the GS slots, but I am well on my way to having a bread board ready for some testing.

Version 1 Schematic and PCB Layout

I am just going to be using a single sided copper board for the prototyping stage (once breadboard testing is done) this will mean that I will not have the +5V, so will plan to add a L7805 Reg to bring the +12V down to +5V. This will mean only pins 34 and 50 will be used on the connector.

TDX Stereo Sound Card

October 22, 2009

Right on to my next project…. I am now going to attempt to make the TDX sound card i have seen in the FAQ and on Polymorph’s site.

I don’t actually need one as I already have an AE Audio Animator, but again things get older and i could also do with the external box not being on my desk. More importantly more electronics fun 🙂

I have several goals with this project

  1. Re-Produce the above using the information available and assistance from the A2 Community.
  2. Do a more complex electronic’s project
  3. Possibly look at mass production….

I will start ordering kit and getting people at work geared up to help 🙂

Things to think about….

  • Cable to GS ?
  • Audio Output ?
  • Making more than one…

J-25 Connector
1  Analog to digital in
(end nearest front of computer)
2  Analog ground
3  Waveform out
4  Channel address zero
5  Channel address one
6  Channel address strobe
7  Channel address two