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TTSH Synth - The Human Comparator - VCO 3

July 28, 2014, 9:23 pm
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Finally the third VCO of the TTSH synthesizer.
This is part 6 of my TTSH (Two thousand six hundred) build.
You can see my full build thread HERE


 
The VCO3 section before population (well almost)

Resistors & Diodes first. Then caps, headers, etc.

Install trimpots on the front side of PCB

 

 Almost there. 

This is what the front PCB looks like now.

Now to test for the waveforms.The square first.



And the ramp. Yahoo !!!


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TTSH Synthesizer - Two Thousand Six Hundred - 4012 Filter (DIY)

July 29, 2014, 9:02 pm
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The filter build of the TTSH synthesizer. 
This is part 7 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synth.
You can see my full build thread HERE



I understand this filter is based around the coveted Model 4012 filter, a four-pole low-pass VCF.
The 4012 filter used a design that closely resembled Moog's ladder-filter. This led to a legal dispute between Moog and ARP which forced ARP to design a new filter for their later models.
All the early ARP 2600 (pre 1977) used this filter. It's one of the reasons why the early Blue Marvins,  Grey Meanies, the (pre 1977) 2600s & 2601 v1.0 sounded so good.



 This is the filter sub-module.

The original design uses 8 pairs of matched and thermally coupled TZ-81 and TZ-581 transistor pairs.
There is a Dual FET AD3958, a LM301 Op Amp & temperature compensation via a 1K87 tempco resistor.

The TTSH combines the filter sub-module with the additional main board filter circuitry. 


 To the left (from top to bottom) are marked Ring MOD, VCO1, VCO2, VCO3, Noise, KYBD CV, ADSR, VCO2 (Audio & CV summing).

Post 1976, ARP used the model 4072 filter (which was in turn replaced with the ARP 4075 4-pole 24dB low pass filter in the ARP Odyssey Mark 3, Omni and Quadra).

Some pics of the almost virgin PCB first:

 This is the back of the PCB

And the front section

Resistors & diodes first as usual.

These are Multilayer Ceramic Capacitors MLCC - Leaded 47pF 50V.
The BOM specified 50pF (as does the original 4012 schematic) but the Mouser order number (810-FK28C0G1H470J) shows them as 47pF.
I hope the slight discrepancy won't cause problems.

Caps & headers in.

The original 4012 filter used 8 pairs of matched and thermally coupled TZ-81 and TZ-581 transistor pairs.
The TZ81 was a NPN made by Sprague.The TZ-581 is a PNP trannie

The TZ-81 is now defunct. The TTSH uses the 2N3904. (its modern equivalent).
The TZ-581 is also defunct. The 2N3906 is a modern equivalent.


This is what the PCB looks like before the transistors:

Some of the trannies need to be matched.
First insert the unmatched transistors:

 
 This is a 2N395. It's a dual JFET


2N395 pinout

 Unmatched transistors.

There are lot's of ways to match transistors.
Vbe (base-emitter voltage) Vs Hfe (current gain). ????

And the question of whether its really needed in this case is debatable.
Modern manufacturing tolerances are far tighter than back in the 70s.
I'm buying all my transistors in a single order so they should come from a single manufacturing batch. I guess that matching will only make a difference when your trannies come from several sources.

I'm testing each PCB as I go along & … I'll swap for matched pairs at a later date if I need to.
So far I've not run into any problems, but I found that thermal coupling (thermal compound between the transistors) seems to help.

Anyway, Muffs has a cool thread for DIY Transistor matching if you finally wish to go down this path..
matching transistors - DIY
 
Vbe (base-emitter voltage) matching is the most common type of matching.
Eg: the famous tester of Dr. Robert Moog.
Moog assumed you have a +/-10V supply. He measured the base to emitter voltage.
You need a volt meter capable of reading to 0.001Volts DC.
(Sadly my VC97 meter only does 2 decimal points. ... time for a new one I think)

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

At the moment I'm using a cheap digital multimeter. (Vichy VC97) with a a hFE mode.
(It's useless for Vbe matching).



Matching hFE is really easy to do. First define whether your trannie is NPN or PNP,
 then insert the emitter, base & collector into the appropriate hole.The DMM calculates the hFE for IB (In fractions of a mA I think). The value will be displayed on the LCD.

IB = base current
IC = collector current
hFE = DC current gain = IC / IB
The hFE varies with the current draw, the temperature & the applied voltage ... so I guess if we want to be really precise we should measure this all under the circumstances the transistor will see in its working environment.

These are my 3904s sorted in order of hFE

Same with the 2N3906s

Tempco 1k87 resistor.

The transistor ladder of hFE matched 2N3904s

Trimpots finally.
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Native Instruments Master Class - Pro Sound & Lighting

July 30, 2014, 8:51 pm
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This Native Instruments Master Class was held on the night of Wed the 30th July at Pro Sound & Lighting Studio in Wollongong, Australia.

Thanks to Claude of  Pro Sound & Lighting and Mike from CMI Music & Audio for organizing this event.

 

It was a great chance to trial out some of the latest gear that NI (Native Instruments) had on offer.
I was particularly interested in checking out the new MASCHINE STUDIO& TRAKTOR KONTROL S4




DJ Kuya demoed both the Maschine & the S4.
He is a 3x DMC Victorian Champion, 1x Australian ITF Champion!!
:-)

DJ Kuya explaining the Maschine & Traktor setup

Maschine looks like it's a solid host for VST/AU plug-ins and effects.
It's basically a hardware sequencer that hosts soft synths.

 Machine Mikro

Machine Studio (Pro version). 1 midi in & 3 midi out....so you can drive external synths or drum machines and even sync Maschine to external MIDI clock sources while at the same time being able to assess your arsenal of VSTs, plug ins & soft synths. 

Machine Studio - smaller than the Pro version. I think it would be great for live performance.
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TTSH Synth - Two Thousand Six Hundred - 4020 ADSR (DIY)

August 1, 2014, 2:36 am
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The envelope generator build of the TTSH synthesizer. 
This is part 8 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

And of course the official build thread is here
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The ARP 2600 has two envelope generators: an AR & ADSR.

 The EG section of the TTSH faceplate.

Vintage 2600s use a 4020 submodule in the ADSR section.
The TTSH synth has this built into the main PCB.

These are pics of a vintage 4020 submodule from an old 2600

The large silver circular component is a LM301

 
The TTSH uses the modern version.



Schematics for the vintage 4020. (There might be mistakes here).
Trying to match up the TTSH BOM with the old schematics of the 4020.... they are pretty close.
(I've read there were some (intentional?) errors in the 4020 schematic... might be just a rumor though).

The TTSH BOM of Integrated circuits & semiconductors is:
       1N4148 x 8 (CR1-CR8)
       2N3904 x 1 ???
       2N3906 x 3 (Q1,Q5)
       2N4392 x 1  (Q3)
       2N5172 x 3 (Q2,Q6,Q7,Q8)
       2N5460 x 1 (Q4)
       LM301 x 1 (A1)

 Resistors
  • 120 x 1 (R20)
  • 1k x 1 (R12)
  • 1k5 x 1 (R24)
  • 4k7 x 1 (R15)
  • 9k1 x 1  ??
  • 10k x 2 (R7 & ?)
  • 12k x 1 (R23)
  • 15k x 1 (R5)
  • 22k x 1 (R2)
  • 33k x 1 (R8)
  • 39k x 1
  • 40k2 x 1 (R11)
  • 68k x 2 (R17 - 19)
  • 68k1 x 1 (R13)
  • 100k x 2 (R14 & ?)
  • 120k x 1 (R10)
  • 180k x 2 (R4,R22)
  • 270k x 1 (R1)
  • 470k x 1 (R18)
  • 1M x 2 (R6,R9)
  • 1M2 x 1 (R3)
In the ADSR section, at the input of the LM301 (A1), the resistor going to GND [R7] is 10K in the original schemo. The TTSH uses a 33k instead.


A work of art.


Maybe the envelopes on the 2600 could be improved ???
Without modifications, their maximum Attack, Decay and Release times are short (esp the attack ---> 1.5 seconds on mine). The Decay & Release were about 10 secs. This could be a good place to start future modifications.

Phil Cirocco of Discrete Synthesizer offers EG upgrades to 2600s.
He describes the ADSR in a stock 2600 as "quick".
His upgrade looks cool:

"ADSR: The ADSR is quick in a stock 2600. The 3 position switch we install gives you a x1(factory speed), a x2 and a x3 speed, providing much longer times previously unavailable on a 2600.
AR: Conversely, the AR generator in a 2600 is quite sluggish in certain situations. This mod now includes an upgrade of the AR circuit. In addition to the normal X1 mode, the high quality 3 position switch provides a new high speed mode for sharper attacks, as well as a X2 mode for longer attack and release times."
Anyway, below are pics of the TTSH (envelope section) PCBs before population with most of the components:

 The rear PCB.

The front PCB.

For now, I'll build the EG section to TTSH specs.

Resistors & diodes first as usual.

Caps next. The TTSH schematic uses a 30pF cap here in The AR section.
However the BOM specifies the 33pF cap from Mouser.. 
Hopefully it won't make too much difference.

The  2N5460 is a P-channel JFET.designed primarily for low level audio and general purpose applications with high impedance signal sources. In the TTSH it's used in the AR envelope section. 
It was also used in the early ARP2500 1004 VCO module.

 AR section. Two 1M sliders & the SPST Off(On) Pushbutton Switch.

The 2N4392
N-Channel JFET used in the ADSR section.It's identical to the JFET used on my original 4020 module.




The Decay slider in the ADSR is 100K linear. The rest are 1M Audio.

All components are in. Ready to test.


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Sabah - Malaysia

August 3, 2014, 6:19 am
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Sabah is one of the 13 member states of Malaysia, and is its easternmost state. It is located on the northern portion of the island of Borneo.

It's still very wild which is the reason for my visit (along with the great food).
Malaysia is the country of my birth.
Leave those synths at home and return to nature.


This is a Sabah Longhouse. It's a great way to experience the traditional Malaysian Borneo rainforest lifestyle.

Longhouses represent some of the earliest form of permanent structure in many cultures. Types include the Neolithic long house of Europe, the stone MedievalDartmoor longhouse which also housed livestock.

This is a Rungus longhouse, where each family have their own separate quarters off a common hall.




The start of our hike through the jungle in Borneo. Cool bridge. This place was once the domain of the Iban tribes who once practiced head hunting.











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Arturia Beatstep & Microbrute with a Korg MS 20 mini

August 6, 2014, 4:57 pm
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The Korg mini & Arturia micro are small in name but not in nature.
I have plenty of synths to play with but i keep coming back to these.



Sounds are all from the Korg.. The Arturia Beatstep is sequencing while the Microbrute is providing CV modulation via its patch matrix.

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Transistor Matching.

August 7, 2014, 7:20 pm
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This page is part of my exploration re transistor matching.
There are lots of transistor matching circuits out there.
Many ways but the question is which to use. ???
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.
http://www.dragonflyalley.com/images/TransistorMatching/ianFritz-transmat0011_144.pdf

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.

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

August 11, 2014, 11:29 pm
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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. :-)
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 Front PCB (pre population)

Back face of PCB

 Resistors, Diodes then Caps.

Unmatched transistors.

 
Matched transistors & the LM301 op-amp

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

August 12, 2014, 9:13 pm
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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 these schematics are correct


As you can see from the schematic, 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.

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

August 14, 2014, 11:07 pm
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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.

The ARP 2600 PreAmp schematic

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 ARP 2600 PreAmp schematic

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


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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. :-)

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

August 15, 2014, 3:19 am
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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



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Elektron RTYM meets Analog Four

August 16, 2014, 9:14 am
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These two babies were meant for one another.



 Ambient patch Sat morning.

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MUSEO FRIDA KAHLO

August 17, 2014, 6:49 pm
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The Frida Kahlo Museum (in Spanish it's called the Museo Frida Kahlo) is one of the must sees when you visit Mexico city. It is also known as the Blue House (La Casa Azul) after its cobalt-blue walls. You can find it in the Colonia del Carmen neighborhood of Coyoacán in Mexico City.


 It's a moving tribute to Freda. She was born (1907) & died here.The home is today a museum dedicated her art (& tragic) life. She spent the last 13 years of her life there.

The house is built around a central courtyard with garden space in a French-style.
It gives a good glimpse of how wealthy Mexican bohemian artists and intellectuals lived during the first half of the 20th century.


Freda spent much of her childhood here and this is where she developed her sense of social consciousness. Her connections to the communist party are well documented. During the Mexican Revolution, her mother would open the windows of this house in order to donate supplies to the Zapata army. 

In 1918 she was struck with polio. This left her with one leg shorter than the other. And when she was 18 a tram accident almost killed her. She spent over 2 years in hospital and never totally recovered. This was a very painful period in her life, full of casts and orthopedic devices. It was however a blessing in disguise as in order to pass the time & communicate her anguish & pain she began to paint.




The museum is decorated with lots of Mexican folk art,Kahlo’s own personal art collection, pre-Hispanic art, photographs, postcards and letters.There are also works by José María Velasco, Paul Klee and Diego Rivera (her husband).




This wing was added on by Diego Rivera (volcanic stone and shells).


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TTSH (ARP 2600 clone) build notes - Envelope Follower (DIY)

August 18, 2014, 1:23 am
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The ARP 2600 envelope follower is a really cool module.
The pre-amp is internally wired (normaled) to the envelope follower.
It converts amplitude to voltages.The louder the input signal, the greater the output voltage.
It's a great way of introducing external sounds (like drums) into your TTSH to modulate the filter cutoff for example.

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

This is part 12 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

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


A bit on how this works.
The Envelope Follower is basically a full wave rectifier.
It generates a +ve DC voltage output directly proportional to its input. (a 2V peak to peak = 5V DC).
The rectifier basically consists of A1 & A2 (both LM301s) and two diodes.
The +ve input leaves pin 6 of A1 & passes through CR2(diode),then enters A2 via pin3(non inverting input)
The -ve input passes through the diode CR1, and enters A2 via pin 2 (inverting input)
The rectified signal leaves A2 via pin 6.
The resistors R12,13,14,15 & caps C7,8,9,10 filter the signal.
Finally A3 amplifies the signal.


Pre soldering of components.

Resistors, Diodes, Caps

The LM 301s are in. 

Test then on to the mixer.


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TTSH (ARP 2600 clone) build notes - Mixer & Reverb (DIY)

August 18, 2014, 10:10 pm
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This is part 13 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 Mixer section before components.



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

August 19, 2014, 11:10 pm
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Part 14 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synthesizer.
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 Noise module pre-population


The ARP 2600 used the 4022 submodule to generate noise.
Here is a link to the schematic care of ArpTech
The transistor Q1 (2N5172) acts like a zener diode. The base-emitter junction of any silicon transistor can function as a noise-generating zener diode if its emitter base junction is reversed biased.
The zener produces random noise. The noise is then fed to an amplifier (LM 301)

The official TTSH build states that "a 2N5172 should be selected for maximum noise. But the 2N5172 may be too noisy!... causing clipping and distortion. Any other transistor will probably do. Try a BC547 ??? (Beware the pinout though, the 2N5172 is BCE and not CBE/EBC as most other transistors)".

DSL man suggest using a bc337 instead and/or soldering a 10K resistor to the 1uf cap.


RESISTORS FIRST

Music from Outer Space have a great page devoted to noise generator circuits and they make special mention of the 2N5172 transistor.

Quote:
"These 2N5172 NPN transistors have been tested and selected for their emitter base reverse bias noise. They give greater than 3V peak to peak noise with a non-inverting gain of 100. While testing I observed a wide range of noise levels with > 3V p-p as what I consider the lowest acceptable level. However several of the tested transistors caused clipping at a gain of 100 because they are very noisy. Due to this fact it is often necessary to reduce the gain in the white noise generation section of many MFOS circuits when using one of these selected 2N5172 noise transistors."

Anyway, I'll stick with the 2n5172 for now. I've cut up some female headers to make a socket for the transistor. The original ARP 2600 schematics use a "selected 2N5172". I may have to try out a few 2N5172s before I find one I like.


IC's and transistors installed.

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TTSH (ARP 2600 clone) build notes - Voltage Processors (DIY)

August 20, 2014, 8:22 pm
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I love this section of the ARP 2600. They are not as sexy as the filter or VCOs but still very useful.
Below are some demos using my vintage 2600.


And the lag processor:



It's a awesome module.
Anyway, this is the next part (no.14) of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synthesizer.
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 TTSH rear section of the Voltage processor PCB

 Front section.



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Elektron Analog Rytm & Analog 4 jam - flying

August 21, 2014, 6:30 pm
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You gotta love these two machines. Such an awesome combo.

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TTSH (ARP 2600 clone) build notes - Internal Clock (DIY)

August 21, 2014, 7:01 pm
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Part no.15 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synthesizer.
The Internal clock.

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

Most of the clock circuit occupies the bottom half of the PCB.
In this section there is a sample & hold (on the right) and electronic switch (on the left).


I'm building the clock circuit first.
Here is a little on how it works.

THE internal clock is basically a LFO (square wave).
It's  pulse width is determined by the variable resistor R385 (which is a linear 100K trim)..

The circuit uses the combination of Q45 (2N4870) & C115 (1µ5 x 1 Electrolytic cap) to make a relaxation oscillator. This produces a sawtooth wave which is then converted to a square by
A42 (a LM 301 comparator). It's output is pin 6  -- leads to the diode (CR47).

A relaxation oscillator is a non-linear circuit consisting of a feedback loop containing a switching device - in this case a transistor (Q45) that repetitively charges a capacitor (C115) through a resistance until it reaches a threshold level, then discharges it again. Relaxation oscillators are commonly used in car blinker lights to indicate which way you wish to turn.



This closeup shows the relaxation oscillator (including the 1.5uF cap & the 2n4870 trannie). At the base of the 47k resistor (R384 in the 2600 schematic) is your saw wave test point.

The square wave test point in the centre of pic.
It's at the base of the diode.



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TTSH (ARP 2600 clone) build notes - Sample & Hold (DIY)

August 21, 2014, 10:26 pm
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Part no.16 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synthesizer. 

SAMPLE & HOLD

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
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The ARP 2600 synth used a 4015 sub-module for the sample & hold.


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