Saturday, 16 August 2014

Friday, 15 August 2014

Elektron Rytm & Buchla (Test 1) - Cobramatic & JonDent

Just trialing out the new Elektron Rytm drum machine with some Buchla.

The Rytm is sending midi clock to the Buchla/Euro modulars.
Perfect Swedish precision.


Here are some links to unlisted videos from the night:
Video 1
Video 2
video 3
video 4



Thursday, 14 August 2014

TTSH (ARP 2600 clone) build notes - Pre Amp (DIY)

The Microphone PreAmplifer build of the TTSH synthesizer. 

This is part 11 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synth.
You can see my full build thread HERE

There are two awesome TTSH threads in Muffs.
2600 clone - Two Thousand Six Hundred (TTSH)
and
Two Thousand Six Hundred (TTSH) Project General Build Thread

The DSL-Man site has a very good TTSH thread

And of course the official build thread is here

-------------------------------------------------------------------------------

 The front section of the PCB

The back of the PreAmp PCB

There is no submodule for the Pre-amp.
The schematics of the 2600 indicate the use of a Teledyne 1339 Op Amp (A4). This has been replaced with the LM301 Op Amp in the TTSH.


A little on how it works:
The signal enters via R23 (100k resistor) the gain control and is coupled through C24 (a 0.1uf cap for the ARP 2600 & a 100n cap in the TTSH) to the non inverting input of A4 (133901 teledyne).(pin 3)

The range switch (S1) selects the feedback path for A4.
through either
1. R20 (X10),
2. R20(100k) & R 26(10k) (X100),
3. R20(100k) ,R25(1k), & R 28(100k) to ground (X1000)


The amplified signal then passes through pin 6 of A4 and through R27 (1k) to the output.


------------------------------------------------------

TTSH parts list.
Resistors
  • 100 x 1 (R28)
  • 1k x 2 (R25,27)
  • 10k x 2 (R19,26)
  • 100k x 2 (R24,20)
Capacitors
  • 5p x 1 (C15) --- slightly different from the ARP schemo
  • 50p x 2 (C15,C17)
  • 100n x 1 (C24) ---slightly different from the ARP schemo
  • 10µ x 2 (C13,C14)
Semiconductors and Integrated Circuits
  • LM301 x 1 (A4)
Other
  • 3,5mm jacks x 2
  • 100k audio Potentiometer x 1 (R23)
  • DP3T slide switch x 1 (s1)
  • 11mm M3 standoffs x 5

RESISTORS & Caps.

Install the jacks & 100k pot.

Install the five M3 standoffs
The BOM specifies 11mm. These are 10mm. They seem Ok.

 First test of the fit of the faceplate.
Looks good. Make sure the sliders, pots, jacks are in the right places.

Sit that slider in the correct position. This is a 10mm gap.

Before soldering check that the slider's pins just poke through.:-)


the switch& op-amp are in.

Wow ... it looks great !!!! Everything fits in place like it should. :-)

Tuesday, 12 August 2014

TTSH (ARP 2600 clone) build notes - Ring Modulator (DIY)

The Ring Modulator build of the TTSH synthesizer. 

This is part 10 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synth.
You can see my full build thread HERE

There are two awesome TTSH threads in Muffs.
2600 clone - Two Thousand Six Hundred (TTSH)
and
Two Thousand Six Hundred (TTSH) Project General Build Thread

The DSL-Man site has a very good TTSH thread

And of course the official build thread is here

---------------------------------------------------------------------------------------------------


 There are actually 3 circuits here: the Ring Mod, a envelope follower & a pre-amp.

The TTSH ring modulator uses the ARP 4014 submodule circuitry.
The 4014 was used in both the ARP 2500 & 2600.
The schematics from ARPtech are here

The large white square corresponds to the 4014.


 4014 closeup consisting of two LM301 op-amps and four matched transistor pairs.

The original ARP 2500 & 2600 used matched TZ-581 & TZ-81 trannies.
The TTSH uses their modern counterparts, the 2N3904 & 2N3906
(see the link to the schematic above)

It's sometimes tricky to match transistors. Oakley sound has a Euro clone of the 4014 that use THAT 320P PNP arrays & THAT 300P NPN arrays. It's a neat way to avoid the problem of getting those perfectly matched transistors.



The lower section of the ring modulator. This is the section outside the 4014 sub-module.
There is a mistake in the Cap orientation. The schematic indicates that the top left 10uf capacitor
needs to be rotated so its negative terminal is connected to the cathode of its 10uf pair.

R32 (18K resistor) connects to the anode of c21 (10uF cap)
C20 & C21 should connect via their cathodes
if the original schematics are correct

The inputs of the ARP 2600 & TTSH ring modulator are normalised to VCO 1 & VCO2.
.
Front plate of the TTSH synth
                                                                                 

       This is the corresponding PCB front side.
                                                                                                                                                                                                  
 Resistors,Diodes, Capacitors.

These 2 resistors on the extreme right connect directly to the 4014 module. They are your audio input points when you come to test the ring mod.

Install the trim-pots. (This is a pre-soldering pic. I use blutack to hold the pots in place).

Transistors & ICs are in. Ready to test.


An original 2600.

Monday, 11 August 2014

TTSH (ARP 2600 clone) build notes - VCA (DIY)

The VCA build of the TTSH synthesizer. 

This is part 9 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synth.
You can see my full build thread HERE

There are two awesome TTSH threads in Muffs.
2600 clone - Two Thousand Six Hundred (TTSH)
and
Two Thousand Six Hundred (TTSH) Project General Build Thread

The DSL-Man site has a very good TTSH thread

And of course the official build thread is here



The ARP 2600 used 4010 & 4019 sub-modules in the VCA section.
There were matched transistors (TZ-581 & TZ-81)  and a Op Amp (LM 301) at the output stage.

The TTSH uses the TZ-581 & TZ-81 modern equivalents (2N3904 & 2N3906)
The LM301 is unchanged. :-)
----------------------------------------------------------------------------------

 Front PCB (pre population)

Back face of PCB

 Resistors, Diodes then Caps.

Unmatched transistors.

Matched transistors & the LM301 op-amp

Thursday, 7 August 2014

Transistor Matching.

This page is part of my exploration re transistor matching.
Many synth circuits require matched pairs of transistors... often for differential amplifiers.
There are lots of transistor matching circuits and devices out there.
Many ways...... but the question is which to use. ???

Vbe (base-emitter voltage) matching is the most common type of matching done. It is what is used for matching transistors in an exponential converter for example. It can be done with a circuit like Ian Fritz's, or can be roughly done using the diode setting on a volt meter (Ian's circuit gives a more accurate result).
I like using a Atlas DCA Pro DCA75  




Why choose to measure Vbe ?
Taking a NPN transistor as an example, the main point is that the current passing through the transistor depends on the Vbe, the Ies & the temperature (Vt). This is according to the Ebers-Moll model:
 
Ie = Emitter current
Ies = the reverse saturation current of the base emitter diode.
Vbe = the Base-emitter voltage
Vt = thermal voltage

Ies depends on how the transistor is made and can be different from one transistor to the next.
It also changes with temperature.
The goal of transistor matching is to find pairs or transistors with the same Ies.

It's very difficult to measure Ies, but we can instead measure the Vbe if we pass a known current through the transistor. If we can keep the temperature constant, then matching Vbe is equal to matching Ies.

So the solution (if you are to build a circuit) is to have 3 things:
1. an accurate current source.
2. an accurate multimeter.
3. a constant temperature.

Whether you are using a circuit or the Atlas peak, remember that the temperature of the transistor will effect the measurements. I like to leave the transistors alone for about 5 minutes after handling them
and them carry out the measurements.
------------------------------------

The TTSH build required matched transistors in the filter section.
I matched them via hFE ... not by the usual the Vbe (base-emitter voltage).

I'm hoping I'll get away with it for that instance. However, the TTSH VCA section requires more matched trannies. So it's time I guess to bite the bullet.

Moog has a classic transistor checker schematic (from the mini-moog manual).
Here one current drives another current through the transistors and you need to measure the voltages between the base & emitter. It calls for a +/- 10V supply and needs a really accurate volt meter.

There is a variation of this circuit on DragonflyAlley.com
It uses a +/-15V supply, a 741 op-amp & 3 resistors.

 The Op-amp is a 741. (Pin 6 of the 741 connects to the base of the 3904)

 Here are some pics of the breadboarded circuit. (just for the NPN 3904 trannie).


It seems to work though there is lots of voltage fluctuation
Very temp sensitive.

Ian Fritz also has a transistor matching circuit.
You can download it here.

This is a breadboard of the Fritz transistor matcher.
The crossed resistors need to be matched as closely as possible. I guess a variable trim-pot could also be used to get a closer matching between the resistors.

I kinda like it more than the Moog circuit. It's definitely much simpler using just 3 resistors & a diode.

The voltage on the multimeter is the difference between the two transistors. In an ideal world of perfectly matched resistors & transistors the voltage would be zero.

This particular batch of 3906s seem to vary by 0.5 to 4 millivolts.

For completeness here are a few more links to blogs, websites which discuss transistor matching.
Hopefully you will find this useful.

Muffs has a cool thread for DIY Transistor matching if you finally wish to go down this path..
matching transistors - DIY
 
The famous minimoog tester of Dr. Robert Moog.

MFOS has a great page on how to build transistor matchers.
(MFOS Practical Transistor Matching)

I might try this MFOS matcher later if the earlier attempts aren't successful.

Links
+ Transistor - Basic info
+ JFETS - matching for synthesizers  
+ Muffs
+YATMA Yet Another Transistor Matcher

Wednesday, 6 August 2014

Dad Jokes

1. What does the Eiffel Tower and a tick have in common?
    They are both Paris-Sites (parasites)

2. Why do fathers take an extra pair of socks when they go  golfing?
    Incase they get a hole in one.

3. What did the ocean say to the beach?
    Nothing, it just waved.

4. What did one wall say to the other wall?
    "I'll meet you at the corner.

5. What did the zero say to the eight?
    That belt looks good on you.

6.  What did Baby Corn say to Mama Corn?
     Where's Pop-corn?

7.  Where do you learn to make a banana split?
     Sundae School

8. What has more letters than the alphabet?
    The Post Office

9. How do you get a squirrel to like you?
    Act like a nut

10. Why don't eggs tell jokes?
       They'd crack each other up.

11. Why shouldn't you trust stairs?
       They are always up to something.

12. When shouldn't you trust trees?
       When they look shady.

13. What do you call someone with no body and no nose?
      Nobody knows.

14. Did you hear the rumor about butter?
      Well , I'm not going to spread it.

15. Why couldn't the bicycle stand up by itself?
       It was too tired

16.  What did one hat say to the other?
       Wait here, I'm going on a-head

17. Why was the graveyard crowded?
      People were dying to get in.

17a. Why was the ghost so tired?
        He worked the graveyard shift.

18. What time did the man go to the dentist?
      2.30 (Tooth-hurty)

19. Why didn't the skeleton climb the mountain?
      It didn't have the guts

20. What do you call a snowman throwing a tantrum?
      A melt-down

21. What does a bee use to brush his hair?
       A honey-comb

21a. Why do bees have sticky hair?
        Because they use a honey comb

22. How did the penguin build its house?
     It glued (igloo) it together

23. Why are elevator jokes so good?
       They work on many levels

24. How can you tell if it's a dog-wood tree?
      By the bark

25. Why did the coach go to the bank?
       To get his quarter back

26. How do celebrities stay cool?
      They have many fans.

27.  What did the flowers do when the bride walked down the aisle?
       They Rose

28. Why did the man loose his job at the bank?
      Because he pushed a woman over when she asked him to check her balance.

29. How do you row a boat filled with puppies?
      You bring out the doggie-paddle

30.  Why were the utensils stuck together?
       They were spooning.

31.  What sort of music do chiropractors like?
      Hip-Hop

32.  What do you call a tooth-less bear?
       A gummy bear

33.  Why are spiders so smart?
       They can find everything on the web

34.  What does a house wear?
       Address

35.  What do you call an unpredictable camera?
        A loose cannon

36.  Why shouldn't you write with a broken pencil?
       It's pointless

37.  How do you weigh a millennial ?
       In instagrams

38. What do you call a fat psychic?
      A four-chin teller

39. What did the police officer say to the belly button?
      You're under a vest

40.  What do you call a company run by apes?
       Monkey Business

41. What did the baker say when she won an award?
      It was a piece of cake.

42. What vegetable is kind to everyone?
       The sweet potato

43.  What did the geometry teacher say when the class couldn't work out the problem?
       Lets try a different angle.

44.