Buchla 245/ 246 Sequencer

[Robbot]

Forgive my ignorance here but I would be grateful for any help with this please.

I understand that the 245 /246 models have 2 separate (and not electronically related) sections. The left section is a pulser section and the rest is the 5 or 16 knobs and pulse outs of the sequencer section. The Pulser can be patched to the Sequencer section (and vice-versa).

I understand using the CV controllable Pulse Length and Pulse Time functions. But please could someone explain what the "Ref" does? And how it could be usefully used (either for sequencing or as an envelope, which I understand these can be used to create). It is an output.

And what does the "Analog" do? It is an input - black CV banana jack.

I was wondering whether the analog could be used as a reference to increase / decrease the voltages from the 4 rows of sequencer knobs. But it doesn't seem to do this. E.g. If the top row was assigned to Osc pitch, it could move those up a 5th if a the equivalent CV was added into the "Analog" input...

Many thanks.

[thermionicjunky]

That's an analog address input, so the programmed voltages can be used like an arbitrary transfer function.

[Robbot]

Many thanks for your reply.

I'm a bit of a newb when it comes to complicated analogue sequencers. Does this mean that a voltage applied to the "Analog" will make the sequencer arbitrarily move from whatever step it is on to some other step? Even if the sequencer is under pulse control which would otherwise make it move along in a linear fashion (1>2>3>4>5 etc)?

That's an analog address input, so the programmed voltages can be used like an arbitrary transfer function.

[thermionicjunky]

Many thanks for your reply.

I'm a bit of a newb when it comes to complicated analogue sequencers. Does this mean that a voltage applied to the "Analog" will make the sequencer arbitrarily move from whatever step it is on to some other step? Even if the sequencer is under pulse control which would otherwise make it move along in a linear fashion (1>2>3>4>5 etc)?

Generally, address inputs go through some kind of window comparator string, so the control range is split into as many bands as there are steps. Low voltage selects stage 1, a slightly higher voltage selects stage 2, etc. If the pulse input is also used, I would expect the sequencer to advance one step from the position selected by the address input.

[Robbot]

Thanks - sounds very interesting. Will do some experimenting and confirm if it does.

Any idea about the "Ref" output though?

Many thanks for your reply.

I'm a bit of a newb when it comes to complicated analogue sequencers. Does this mean that a voltage applied to the "Analog" will make the sequencer arbitrarily move from whatever step it is on to some other step? Even if the sequencer is under pulse control which would otherwise make it move along in a linear fashion (1>2>3>4>5 etc)?

Generally, address inputs go through some kind of window comparator string, so the control range is split into as many bands as there are steps. Low voltage selects stage 1, a slightly higher voltage selects stage 2, etc. If the pulse input is also used, I would expect the sequencer to advance one step from the position selected by the address input.

[thermionicjunky]

Thanks - sounds very interesting. Will do some experimenting and confirm if it does.

Any idea about the "Ref" output though?

According to the 246 schematic, it's a signal coming from the clock before it reaches the pulse-width comparator.

[Robbot]

Thanks. Perhaps it means 'Reference'?
Any ideas on how it can be used interestingly with the sequencer?

I gather that the sequencer can also be used as a quantizer but I'm still scratching my head a little there :-)

Thanks - sounds very interesting. Will do some experimenting and confirm if it does.

Any idea about the "Ref" output though?

According to the 246 schematic, it's a signal coming from the clock before it reaches the pulse-width comparator.

[thermionicjunky]

Thanks. Perhaps it means 'Reference'?
Any ideas on how it can be used interestingly with the sequencer?

I gather that the sequencer can also be used as a quantizer but I'm still scratching my head a little there :-)

Yeah, I would guess "reference clock"

Patching a CV to the analog input will quantize it to the programmed voltages.

[solaris]

from the brochure:

The Sequential Voltage Source is an analogue memory for storing and retrieving control voltages. It includes an electronically separate pulse generator with voltage controlled period and pulse length (duty cycle).

The Model 246 produces up to 16 programmed voltages at each of four outputs.

The Sequencer employs three methods of selecting stages; pulse advancing, analogue selection, and pulse selection. All can be used simultaneously or in any desired combination.

Pulse advancing is used for generating sequences of control voltages. A pulse derived from the self contained pulser or from an external source advances the sequencer one step. sequencers may be cyclic over a number of stages or may be single shot, beginning and ending on any desired stage. Sequence boundaries are established by switches located between stages.

An analogue select input permits the value of an applied control voltage to determine the activated stage. Higher voltages select higher numbered stages; zero volts enables the pulse advance and pulse select inputs. Analog selection is particularly useful for converting a continuous voltage (from an envelope Generator or detector or a random voltage source) into a series of pre selected values (a 12 tone scale for example). It also enables indirect addressing by another sequencer and facilitates simple (one patchcord) extension of the Model 217 Keyboard's number of programmable outputs to 5.

The sequencer may be employed as a preset controller (a random access memory), with pre selected parameter values recalled by applying a pulse to the input of the desired stage. This pulse selection, used in conjunction with pulse advancing, allows several transient or cyclic sequences (different rhythms, for example) to be simultaneously programmed. A desired program might be initiated by pulses from a keyboard or another sequencer.

Light emitters and pulse outputs are energized as corresponding stages are actuated. The period of the self contained, voltage controlled pulser has a range of .005 to 10 seconds. Pulse width can be varied from 1% to 100% of the period.

[boops]

from the brochure:

The Sequential Voltage Source is an analogue memory for storing and retrieving control voltages. It includes an electronically separate pulse generator with voltage controlled period and pulse length (duty cycle).

The Model 246 produces up to 16 programmed voltages at each of four outputs.

The Sequencer employs three methods of selecting stages; pulse advancing, analogue selection, and pulse selection. All can be used simultaneously or in any desired combination.

Pulse advancing is used for generating sequences of control voltages. A pulse derived from the self contained pulser or from an external source advances the sequencer one step. sequencers may be cyclic over a number of stages or may be single shot, beginning and ending on any desired stage. Sequence boundaries are established by switches located between stages.

An analogue select input permits the value of an applied control voltage to determine the activated stage. Higher voltages select higher numbered stages; zero volts enables the pulse advance and pulse select inputs. Analog selection is particularly useful for converting a continuous voltage (from an envelope Generator or detector or a random voltage source) into a series of pre selected values (a 12 tone scale for example). It also enables indirect addressing by another sequencer and facilitates simple (one patchcord) extension of the Model 217 Keyboard's number of programmable outputs to 5.

The sequencer may be employed as a preset controller (a random access memory), with pre selected parameter values recalled by applying a pulse to the input of the desired stage. This pulse selection, used in conjunction with pulse advancing, allows several transient or cyclic sequences (different rhythms, for example) to be simultaneously programmed. A desired program might be initiated by pulses from a keyboard or another sequencer.

Light emitters and pulse outputs are energized as corresponding stages are actuated. The period of the self contained, voltage controlled pulser has a range of .005 to 10 seconds. Pulse width can be varied from 1% to 100% of the period.

Thanks ..as atm i build 3x 245
Càn be useful indeed

[Robbot]

That's very helpful - thank you all.

from the brochure:

The Sequential Voltage Source is an analogue memory for storing and retrieving control voltages. It includes an electronically separate pulse generator with voltage controlled period and pulse length (duty cycle).

The Model 246 produces up to 16 programmed voltages at each of four outputs.

The Sequencer employs three methods of selecting stages; pulse advancing, analogue selection, and pulse selection. All can be used simultaneously or in any desired combination.

Pulse advancing is used for generating sequences of control voltages. A pulse derived from the self contained pulser or from an external source advances the sequencer one step. sequencers may be cyclic over a number of stages or may be single shot, beginning and ending on any desired stage. Sequence boundaries are established by switches located between stages.

An analogue select input permits the value of an applied control voltage to determine the activated stage. Higher voltages select higher numbered stages; zero volts enables the pulse advance and pulse select inputs. Analog selection is particularly useful for converting a continuous voltage (from an envelope Generator or detector or a random voltage source) into a series of pre selected values (a 12 tone scale for example). It also enables indirect addressing by another sequencer and facilitates simple (one patchcord) extension of the Model 217 Keyboard's number of programmable outputs to 5.

The sequencer may be employed as a preset controller (a random access memory), with pre selected parameter values recalled by applying a pulse to the input of the desired stage. This pulse selection, used in conjunction with pulse advancing, allows several transient or cyclic sequences (different rhythms, for example) to be simultaneously programmed. A desired program might be initiated by pulses from a keyboard or another sequencer.

Light emitters and pulse outputs are energized as corresponding stages are actuated. The period of the self contained, voltage controlled pulser has a range of .005 to 10 seconds. Pulse width can be varied from 1% to 100% of the period.

Thanks ..as atm i build 3x 245
Càn be useful indeed

[lucringeisen]

So how do you send an external clock ? is it via the "ref" input ?

[lucringeisen]

is it actually possible to send an external clock into the 245 ? if yes what is the actual input on the panel ? thanks in advance for the info !

[cygmu]

is it actually possible to send an external clock into the 245 ? if yes what is the actual input on the panel ? thanks in advance for the info !

I see what you did there.

[the bad producer]

[Peake]

The pulser is a clock probably with a sawtooth core, squared for use to advance stages etc. REF is the falling saw output of the Pulser, same phase/frequency as the square, so it can be used as a secondary modulation source. You can use it as a falling slew to control LPGs for example.

Don't forget the pulse inputs along the bottom which allow non-linear stage selection via gates.

[lucringeisen]

is it actually possible to send an external clock into the 245 ? if yes what is the actual input on the panel ? thanks in advance for the info !

I see what you did there.

uff nana YOU did that ))

[lucringeisen]

The pulser is a clock probably with a sawtooth core, squared for use to advance stages etc. REF is the falling saw output of the Pulser, same phase/frequency as the square, so it can be used as a secondary modulation source. You can use it as a falling slew to control LPGs for example.

Don't forget the pulse inputs along the bottom which allow non-linear stage selection via gates.

right of course those inputs at the bottom, thanks man

[Pailo]

Peake is right, mine 245r is a saw

[levelhead3]

sorry for the thread resurrection.

i've got both a 245r and 246r and both exhibit the same problematic behavior - when turning up the control voltage pots, the output voltage maxes out just shy of 3:00 and stay there for the rest of the pot's travel.

it's the same across all four banks and all the stages that i tested, and it's the same on both modules.

i've not found reference to this behavior on any of the build threads, but i can't believe it wouldn't have been remarked on if it was inherent to the pcb design.

can anyone with a 245r or 246r check and see whether the last 1/4 turn of pot rotation does anything?

thanks so much!

[njdoyle]

My 246r behaves similarly. I didn’t build it myself so I don’t know why. I speculate that maybe logorithmic pots were used instead of linear pots but that’s just a guess without much basis.

[Peake]

I built levelhead's 246. The BOM calls for linear pots and I used them. No idea why the odd behaviour.

[cygmu]

Unfortunately this behaviour is inherent to the boards. The original circuit used a 24V power supply to drive the output buffers. The Electric Music Store boards have been redesigned to do without the 24V supply, but not well, and the output transistor saturates, if I remember correctly.

I haven't found an easy fix for this. Essentially you'd need to replace the whole output stage. The replacement could be something very simple but the circuitry is spread over the two PCBs so it is a bit tricky to come up with a simple mod.

[levelhead3]

thank y'all for the quick responses!!

[Peake]

+24V runs to two points in each of the four output sections so modding would mean cutting 8 traces and running +24V via eight wires, or less if the pairs are connected and only one cut per section is required, plus restoring any altered values in those output circuits to original/schematic.

There are +15V to +24V converters but the ones in some Roman BOMs are from Germany and I can't see how to order them delivered to the states, so I've been using this device Todd Sines found. It maxes at 10mV less than the other device and is unregulated. No idea how many mA a 246 requires.

Looking at the schematic on the Magnus page there appears to be two power rails to the individual stages but I can't make out the voltage/text. If it's +24 I imagine every stage would have to have values changed as well as that voltage run to 16 or more points.