Sunday, 29 June 2014

TTSH - ARP 2600 Replica - VCO 1

This is the 4th part of my TTSH (Two thousand six hundred) build.
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 unpopulated rear section of VCO 1

Install the IC headers,  resistors & caps first.

This is the front view of VCO 1



These headers connect the VCO submodules to the motherboard.
I'm installing these on the motherboard as high as as I can to 
provide as much room as possible between the two boards.



Connecting VCO1 to the PSU.

I'm soldering the connections directly to the PSU, though you many wish to use MTA connectors.

The red wire to the base of the resistor is temporary only.
+15V needs to be applied there for testing.

If all is working you should see a square wave from this pad and a saw from the pad above.

The VCO uses fairly inexpensive LM301 op amps which can be found in many vintage ARP 2600s:


This is the pinout:

I might in the future try replacing these with more modern 711's, LF351s or 411s. ???
It's probably not a matter of simply swapping the chips. Maybe the 301's are better left in the VCOs and changed in the filter ??? These 301s are everywhere. They can be found in the VCOs, the filter, the EGs and the VCA.

This modification is just a personal idea and I haven't tested it yet.
I don't recommend any modifications unless you are a qualified technician. 


In Mark Vail's book "Vintage Synthesizers" he discusses the SL19986 describing it as "nothing more than a selected LM-301. He goes on to say that" The reason ARP selected them was for their DC performance. But because they aren't of very high input impedence .... they are not as good as an LF-351,411, or other high-performance op-amps."



Anyway, I'm a bit undecided about changing op-amps. New op-amps may clean the path but I kinda like dirt and noise. Maybe ill keep the old 301's in the end. 





Another ARP guru, Phil Cirocco, has some great info on this website:

 To quote him:
"...The 2600 uses microchip technology in all of its gain stages! The first 2600's .......used hi-fi chips (Teledyne 1339 octal op-amps) with a high slew rate. Although these chips sound great, they were very unreliable and prone to latch up. Around 1972, plagued by failures in the field, ARP was forced to change these chips to a much more reliable type (National Semiconductor LM-301 or SL-1998) The problem is that they slew the wave shape producing a muffled sound. The LM-301 is classified as a general purpose amplifier, and is considered inadequate for audio by present standards. Nearly all the standard production gray-face 2600's use the LM301. This is the main reason why the legendary Blue Marvins sound better!

So I wonder what he replaces the 301's with today ??? 

***********************
Many thanks to "unknown" for his comment re the MC1439
"I've seen picture of 2500 modules where the 301s had been
replaced by MC1439. The PCB looked like it could accommodate
either; the 301, according to the older schematic only used
a cap whereas the 1439 looks like it use series RC for
compensation."

 
Yes it looks like the pinouts for the LM301 & the MC1439 are identical. Ins are on pin 2 & 3. Out on pin 6.
I'll give this a try on one of my next builds.

Thursday, 26 June 2014

TTSH - ARP 2600 Replica - PSU - We have the Power !!!

This is the third part of my TTSH (Two thousand six hundred) build.
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 PCB before population.
 The 12 squares to the left of the DC-DC block is the internal power distribution bus.

 

 I'm using a AUSTEC DC-DC converter.

My walmart PSU is identical to a Buchla PSU.

12┬ÁH Inductor

 Don't forget to cross the beads. Polarity is reversed on the PCB.
A jumper is also needed to the right of the capacitor.
Black is negative, Red positive.

-15V ,0V, +15V

Buchla 250e & 281e - Stage Addressing.

Dueling Buchla 250e and 281e.
Function Generator Vs Function Generator



They work well together.
The top two FGs of the 281e are running independently of each other.
Pulse from the first, CV from the second.


Wednesday, 25 June 2014

Teotihuacan - "birthplace of the gods" - Mexico

Teotihuacan is 48 km northeast of Mexico City
It's the site of many of the most architecturally significant Mesoamerican pyramids in N. America.

 Probably established around 100 BC. It's thought that the city was destroyed around about 550AD

 This is the way up to the peak of the Pyramid of the Sun

 The view from the summit of the Pyramid of the Sun
These are not built of solid stone like the Egyptian pyramids. ... rather, rubble covered with cut stone.

Looking over the Avenue of the Dead
In its heyday, this city came to be the largest and most populated center in the New World.


 This is a view of the Pyramid of the Moon from the Pyramid of the Sun.

This mural of a puma was discovered in 1963. It's part of the Puma Complex" that flanks the Avenue of the Dead.






 From Wikipedia:
Teotihuacanos practiced human sacrifice: human bodies and animal sacrifices have been found during excavations of the pyramids at Teotihuacan. Scholars believe that the people offered human sacrifices as part of a dedication when buildings were expanded or constructed. The victims were probably enemy warriors captured in battle and brought to the city for ritual sacrifice to ensure the city could prosper.[32] Some men were decapitated, some had their hearts removed, others were killed by being hit several times over the head, and some were buried alive.

Buchla Acid Train

Testing out the 222e touch controller.
Very responsive.


The 291r filter and 258v/262v are great acid providers.

Some pics:

 The 222e touch controller

 The 222e module

A 259r
 The 291r filter

The 247v sequential voltage source.

 Verbos' 262v - The Harmonic Oscillator

Buchla 200 case on the left & the 200e case on the right.

Tuesday, 24 June 2014

TTSH - ARP 2600 Replica - 2047-1 VCO submodule

This is the second part of my TTSH (Two thousand six hundred) build.

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 4027-1 was an improved design over the original ARP 4017/4027 VCO's

The TTSH 2047-1 module is pretty straight forward to put together except for
though those pesky SMD caps. They are tiny and one gave me a headache when it decided to fly off my tweezers onto the floor.

This is a packet of six 100n SMD caps viewed against a Australian 20 cent piece.

Pointless trying to find it. A new order from mouser beckons.



Half way there


1k87 Tempco Resistor.

One finished sub module.... two to go.

As a comparison, I'd thought it would be nice to see the TTSH 2047-1 against a original ARP 2047-1 sub module. This is a spare I have left over from a earlier restoration of a vintage 2600.


The original ARP (like the TTSH version) used three of these 2047-1 submodules. The rest of the VCO circuit is on the main PCB.
 The modern TTSH 2047 uses a 3046 IC. The vintage a CA3086 IC



The CA3046 transistor arrays consists of five general purpose silicon NPN transistors. Two of the transistors are internally connected to form a differentially connected pair.

The CA3086 transistor arrays also consists of five general-purpose silicon NPN transistors. We also have two of the transistors internally connected to form a differentially connected pair.
The pin outs of both look the same.The CA3046's probably have closer tolerances
than the older CA3086, however I wonder if CA3086’s can be used (if you can find them)?
 As in the TTSH build the 2N3904 and 2N3906 transistors are pushed together for thermal contact.

The vintage 4027-1 PCB:(It's a work of art).