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1J17B Tube VCF eurorack
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3  Next [all]
Author 1J17B Tube VCF eurorack
rvrv
Hi,
So I have hear this :

https://www.youtube.com/watch?v=KhRn9sNCieE&feature=share

the author said it was built from this schematics
http://www.homebuilthardware.com/index.php/projects/sk-tubevcf/

using 1J17B tubes.

Is there someone interested to help me porting this schematics to eurorack +12/-12v?
Jarno
Just give it a try!

Here's another tube vcf using submini tubes, by a fellow Dutchie:
Mean Sucker VCF
daynehacks
Ooooh, that mean sucker looks cool!
vtl5c3
That is one crazy pants take on the lopass gate!

rvrv wrote:
Hi,
So I have hear this :

https://www.youtube.com/watch?v=KhRn9sNCieE&feature=share

the author said it was built from this schematics
http://www.homebuilthardware.com/index.php/projects/sk-tubevcf/

using 1J17B tubes.

Is there someone interested to help me porting this schematics to eurorack +12/-12v?
rvrv
Ha yes that Mean sucker design is also very nice!

I will give it a try as you suggested. It s just a matter of good resistor choice to be sure to power the tube enough from the 12v.
I am just not skilled enough to be sure not to miss something.

Let's order the tube first.
Silver
Hey, I've always been interested in this one as well. I've been working on completing the original Ken Stone VCA (CGS 65) that it's based on for a while.
I can't help with the mods you'll need on the vcf, but it was very simple to mod the CGS 65 to +/-12v.
see here...
http://www.muffwiggler.com/forum/viewtopic.php?p=1415228

other info on that tube vca is here:
http://www.cgs.synth.net/modules/cgs65_vca.html
http://electro-music.com/forum/topic-26469.html
http://www.dragonflyalley.com/synth/constructionCGS65tubeVCA.htm

Hope that helps.
PrimateSynthesis
rvrv wrote:

the author said it was built from this schematics
http://www.homebuilthardware.com/index.php/projects/sk-tubevcf/


I wouldn't use that cathode circuit without a good explanation. I'm guessing its trying to spread the heater current over several resistors. But perhaps someone doesn't understand how to calculate resistors in parallel, or doesn't know that resistors are available in higher power ratings. All those resistors and diodes could be replaced with a single resistor.
LeftyLogic
The tube in that circuit isn't doing anything special whatsoever. You can probably just switch it directly over to 12 volts without much (if any) change in overall sound.

It looks like the diodes in the heater circuit are being used as a crude voltage regulator. Just straight up swapping that entire subcircuit with a dedicated regulator IC would probably work much better.

Seth
rvrv
Thanks all,

Indeed in ken stones original design for the vca http://www.cgs.synth.net/modules/cgs65_vca.html , the parrallel resistors are switched with a 2W 240 ohm to dissipate current for this tube.

The two 1N4148 are also "merely an insurance policy. They are to prevent the heater seeing any more than around 1.5 volts if an incorrect resistor is installed, or a similar mishap occurs."

In the schematics http://www.homebuilthardware.com/index.php/projects/sk-tubevcf/ I guess V6 is for "cut off" (vactrol input amount) and v8 for resonance? I have never worked with vactrols but I was thinking of modding it to add cv for resonance. Maybe this schematics will help I will check http://clsound.com/vcresonantlpg.html
PrimateSynthesis
LeftyLogic wrote:

It looks like the diodes in the heater circuit are being used as a crude voltage regulator. Just straight up swapping that entire subcircuit with a dedicated regulator IC would probably work much better.


Running it off -15V is to increase the potential between the plate and cathode. And the -15V should already be regulated.

rvrv wrote:

Indeed in ken stones original design for the vca http://www.cgs.synth.net/modules/cgs65_vca.html , the parrallel resistors are switched with a 2W 240 ohm to dissipate current for this tube.

The two 1N4148 are also "merely an insurance policy. They are to prevent the heater seeing any more than around 1.5 volts if an incorrect resistor is installed, or a similar mishap occurs."


I think someone is mixing designs. And adding parts (even if it made sense) in case someone builds it with the wrong parts, is just silly. The heater, which is also the cathode, should be seeing negative voltage held by the cathode cap. Then a single resistor can limit the current across the heater. For -15V that would be 1.2K. A power rating of a 1/2W should be fine.
rvrv
thanks a lot.

Primatesynthesis do you still have a cad file of one of your design or ken stone one of the vca? I will try to redraw the vcf from these design with the improvement suggested
Ayab
Jarno wrote:
Just give it a try!

Here's another tube vcf using submini tubes, by a fellow Dutchie:
Mean Sucker VCF


Hi Jarno

The Mean Sucker is a really interesting design (and great name!). I would really like to try this one on 12v. Do you have any tips for me on what might be the right resistor values to change.

*Edit - Realised now I am not scared of schematics that the original design is for 12V! Parts ordered!

Have a great weekend! cool
julian
Im, kind of, surprised that none of these designs make a visual thing out of the tube - i assume they still glow, or not?
Silver
The submini's don't glow I don't think. The CGS65 does put a couple of led's behind the tube, so I made a window to see it in my panel, but the led's are just burning off current and sort of fake a glow.
PrimateSynthesis
rvrv wrote:
thanks a lot.

Primatesynthesis do you still have a cad file of one of your design or ken stone one of the vca? I will try to redraw the vcf from these design with the improvement suggested


I drew this schematic, but it only shows the audio section. Where it reads "BIAS" is an SPDT switch.



You also might want to note that some of the seemingly confused commentary linked above ignores the difference between a TL072 and OP275. Although many different op-amps will work fine, their optimal circuits are slightly different...

The tube does not glow at all.
Ayab
*Edited - I now see that the original schematic is for +12V (and +5V) only the layout is for +15V and can be used with +12V if the correct 1W resistor is used (100r 1 watt for the VCF and 270r 1 watt for the VCA) as per the schematics.
mskala
I'm not sure leaving the diodes out of the cathode circuit is a good idea, even if Ken Stone's description of their purpose is silly, because without them you're depending on the filament to maintain a consistent and predictable resistance.
rvrv
Thanks all.

I have also found that Befaco provided a 15v and 12 v of their tube VCA, below I have corrected the schematics with the resistor values used in their 12v version for the 1J24B tube.

rvrv
not sure how to use all these informations but here
http://www.radiomuseum.org/forum/russian_subminiature_tubes.html?threa d_id=200277#13

are tested operation of the filament between 500 mV to 1.2 V with interesting features on the gain curve obtained for the 1J24b.
rvrv
So the breadboarded version is alive and screaming :

https://www.youtube.com/watch?v=bc2-CRW4JbQ

Still need to adjust a few resistor but the result is already very nice.

Also I am considering adding an extra input to control grid G3 to perform amplitude modulation with audio signals within the pentode. I guess a 10vpp input would need a factor 2 gain to be usefull.

Next step is also adding CV control of the resonance.
basicbasic
Sounds great! I'd be super keen on schematics or even a PCB if you do a run.
rvrv
Thanks,
I will definitely do a pcb run and will post here about it. Although this is my first project so I have a lot to learn on schemactics and pcb design etc... so be very patient smile
LeftyLogic
That sounds fantastic!
basicbasic
rvrv wrote:
Thanks,
I will definitely do a pcb run and will post here about it. Although this is my first project so I have a lot to learn on schemactics and pcb design etc... so be very patient smile


SlayerBadger! w00t SlayerBadger! w00t SlayerBadger! w00t SlayerBadger!
Ayab
Go rvrv!!!

applause
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