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Tube VCF on Dutch synth forum
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Funky40



Joined: Sep 24, 2005
Posts: 875
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PostPosted: Thu May 01, 2008 7:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Etaoin wrote:
As the VCA is close in design to the VCF, I modified the PCB to make a VCA one This will take both versions (just replace the transistor by a jumper and leave off the 4k7). Check the schematics to see which component values belong to the version you want.

http://www.casia.org/modular/SF/tubevca.jpg

http://www.casia.org/modular/SF/tubevca.pdf


@Etaoin,

Hi, i have got this Board here etched.
But i see now i would prefer the other one.
I don't understand how to build a Filter out of this one, so i gonna make the VCA.
But there i don't understand all Values. It's not clear for me, sorry:
12K/27K ?
1µF/ 10µF
What to connect exactly with the Jumper ( you use the Yumper for VCA use ? )
merci
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etaoin



Joined: Jun 30, 2005
Posts: 761
Location: Utrecht, NL

PostPosted: Thu May 01, 2008 9:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Funky40 wrote:
I don't understand how to build a Filter out of this one, so i gonna make the VCA.


Indeed, you can't build the filter from this board. I did the VCA version as it was similar enough, but they are not interchangable. The VCF board is at the top of this thread.

Quote:

But there i don't understand all Values. It's not clear for me, sorry:
12K/27K ?
1µF/ 10µF
What to connect exactly with the Jumper ( you use the Yumper for VCA use ? )


Check Jeroen's schematics for those. There are two versions of the VCA. Both can be build on this PCB but component values differ between the two.
http://www.synthforum.nl/forums/showthread.php?t=90425&page=2

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Funky40



Joined: Sep 24, 2005
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PostPosted: Thu May 01, 2008 10:16 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Etaoin.

I see, i missunderstud the phrase: " you can build both".
ahh, ok, i haven't seen this Schematics.
Maybe Jeroen should load them up on his site . Threads are so short living . Wink
Funnywise i built it right = Version 2 VCA.

I have a shortening in the momnet, but it seems not to be on the Board. The DMM shows nothing wrong
I used the first time not DIY cable for 15V stuff.


btw.: i just soldered 4003 Diodes in, i had no 4007 and those were the closest ( from number Rolling Eyes )
looking forward to get it kickin

btw.: It's so simple, nothing on the Board Smile
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Funky40



Joined: Sep 24, 2005
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PostPosted: Fri May 02, 2008 1:37 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, i have 2 Boards running.
VCA 1 + VCA 2, both without Faceplate yet.

1. ) they seem both to have low OutputLevel.
My Doepfer stuff has anyway low voltage on CVs.

how can i adjust Levels ?
A) Outlevel
B) Cv Level
C) how about the input Levels ?
is the electric dog VCA only clean or does one get a distorted Tube sound ?

I have now allready 270R but +15V
one is running with 4003
diodes, one with 1N4148, maybe thats a point too
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6221
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Fri May 02, 2008 3:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow, this is totally tubular! Well, actually it's only partially tubular and partially solid state, heh. My compliments on the whole mini-manufacturing effort you're doing here in this thread. It's like you folks, working together, can go from concept to working product in no time flat!

I'm also working on tubes, but I'm doing a software tube model which I must say is not easy at all! I am kicking myself for jumping into this project but I love to read about the tubes so I guess the effort is worth it. The early models are so full of flaws, but then that's what iteration and improvement is all about. The next model will be better and so on.

So keep on tubing, your work is inspiring to others...

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j.baars



Joined: Jan 11, 2008
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PostPosted: Mon May 05, 2008 4:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi, nice to see a lot of people building the vca and vcf designs of me.
I will put up all the schematics on the electricdog site soon.
there's more to come soon, I am sorting out all the 70's and 80's synth and studio equipment designs of me .
so soon, a complete diy modular synth design, low cost .
( now at the moment i am rebuilding all the stuff to see if its still working, and to add some extra's to it)

some more tube stuff, a tube modulator, a tube 12dB vcf, a tube muly vcf ( voltage controlled multiple vcf to create voice like effects, like a talking synth)

now on the duch synth forum, fhe first peek into stepman, a stepsequencer program.
runs on (free)dos of in a windows dosbox (not fully tested on xp or vista)
soon the completed version with the interface schematic.

regards,
jeroen baars


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Fernando



Joined: Dec 30, 2006
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Location: Barcelona & Emporda, Spain

PostPosted: Tue May 06, 2008 8:40 am    Post subject: Reply with quote  Mark this post and the followings unread

great Jeroen! thanks a lot! looking fwd to all that material for SDIY, specially all the small tube stuff!!!
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q42



Joined: Aug 13, 2008
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Location: Innsbruck/Tyrol/Austria

PostPosted: Wed Aug 13, 2008 6:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi there!

Great project!!!
I just love those pencil-tubes!

I don't have 5672's but i'm going to give it a try
with 1p29b or even 1p24b if the power is too less.

BTW: as also mentioned in the dutch forum (sorry no dutch)
were to put the pot for cutoff???
i know that you can vary the frequency response by
changing the 100p cap but................ Confused

Thanks to j.baars for the great circuit, keep on soldering!!!
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etaoin



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PostPosted: Wed Aug 13, 2008 6:39 am    Post subject: Reply with quote  Mark this post and the followings unread

q42 wrote:
were to put the pot for cutoff???


Just wire it to the appropriate voltage levels and feed it to the cv input.

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q42



Joined: Aug 13, 2008
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PostPosted: Wed Aug 13, 2008 6:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Etaoin!

As my mean sucker-project is still in a early stage
(found it yesterday) and i have to wait 'till some of
the parts arrive, i'll give it a try when i'm in test-phase.

May i bother you again when i'm there Rolling Eyes

Thanks again!!!
(great forum btw.)
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q42



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PostPosted: Wed Aug 13, 2008 2:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

ähh, sh#* sorry, it's of course 1b29b (1sh29b) not 1p29b!

i'll try them 1st at about 24volt, let's see what happens...


cheers to anybody Wink
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q42



Joined: Aug 13, 2008
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PostPosted: Thu Aug 14, 2008 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi guys!

I got a question: when i go up to 28 volt, do i have to change any of the
resistors for the silicium ? (the two 4,7k on C&E on the BC547 up to 10k maybe???)

thank's in advance...
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frequencycentral



Joined: May 25, 2008
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PostPosted: Sat Aug 16, 2008 3:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi, I just recieved four 5672 tubes in the post today - NOS, made in 1958!

I have a question: for the BS107 (MOS)FET in the VCF circuit, can I use any FET or must it be a MOSFET.

Here are the FETs I have in my parts stock:
J201
BF245B
BF245C
2N5457
2N5458
2N5459
2N5461

Can I use any of these? Or must I get some BS107?

Also, must the diodes be 4007? I only have 1N4148, can I use these?

Thanks!

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metasonix



Joined: Dec 28, 2003
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PostPosted: Sat Aug 16, 2008 2:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hello Jeroen!

Nice little filter circuit you have there. My congrats.

You really ought to offer this as a finished product. More tubes are better.
I'd suggest making it a Eurorack (Doepfer compatible) module, as dotcom isn't nearly as popular. You could always offer other panel sizes as options.

Metasonix doesn't use those battery tubes because their filaments are quite fragile, and might not have the long lifetime that indirectly-heated tubes can manage.

I'd love to use submini tubes, as 80% of my problems come directly from the physical size and heat load of regular miniature tubes.
However, I try to use tubes that are easy to get in large quantities, and tube dealers have warned me that subminis in general are getting scarce.

(Some crazy people, mostly dealers in places like Tokyo and Hong Kong, are hoarding them for speculative purposes. NOS subminis (new ones are NOT made anywhere today) are used in quite a few audio devices, mostly condenser microphones but more and more guitar pedals as well.)

But for small-production devices like a synth module, you should have no problems with tube supplies. If you like, I could help you with dealers who have quantities of American submini types.
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Luka



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PostPosted: Sat Aug 16, 2008 9:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

quick questions

i am making a couple of pnp layouts for myself and friends as i just bought a batch of 5672 pentodes. some of my friends are running on 12v supplies. will this be possilble for this module?

other question.. can this module be switched from VCA to VCF like in the buchla LPG. how could i mod the layout to achieve this?

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j.baars



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PostPosted: Fri Sep 05, 2008 8:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,
thanks for the positive reactions.
The MS VCF will be for sale somewhere next year .
available as a module , as a kit and as a complete stand allone filter with an envelopefollower , lfo + AD generator. ( so guitarists can use it as well)

there will be a different version of the MSVCF as well, with some minor ajustments.

also next week ( I think) on my site a ECC83/ 12 AX7 based filter design , just as mean as the mean sucker filter.
www.electricdog.eu

soon much more synth designs.

bye,
jeroen baars
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j.baars



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PostPosted: Fri Sep 12, 2008 5:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

o.k., there's a new (old ) design.
\based on the big people tube 12ax7
posted on www.synthforum.nl + www.electricdog.eu

bye,
jeroen baars
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crashlander42



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PostPosted: Sun Sep 14, 2008 12:06 am    Post subject: Reply with quote  Mark this post and the followings unread

My 275R resistor burnt up. I upped it to 390R, but even that gets real hot. is this normal or did I create a short somewhere? I thought It might be because I'm running off of +/-15 powersupply.

Doesn't quite sound like the examples either. Not as much filteriing (if that makes sense) It sounds more like it's just adding resonance to the original signal and there's still some resonance even with the resonance know turned all the way down.

I didn't build from the PCB. I put it together on breadboard. I probably just screwed something up.

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frequencycentral



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PostPosted: Mon Sep 15, 2008 11:58 am    Post subject: Reply with quote  Mark this post and the followings unread

I just used two 5672 to make a pentode overdrive for guitar. I powered the heater slightly differently. Planning to build the VCF soon.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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frequencycentral



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PostPosted: Mon Sep 15, 2008 1:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

crashlander42 wrote:
My 275R resistor burnt up. I upped it to 390R, but even that gets real hot. is this normal or did I create a short somewhere? I thought It might be because I'm running off of +/-15 powersupply.


According to my calculations that resistor value should be:

15 volt supply: 275 ohm, 1 watt.

12 volt supply: 215 ohm, 1 watt.

The resistor WILL get hot, as that voltage reduction shows as heat - but it needs to be 1 watt, any lower and it will burn out sooner or later.

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crashlander42



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PostPosted: Tue Sep 16, 2008 10:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey! Thanks! That did the trick! It sounds even better AND I'm not worried about it catching fire!

I might just build that distortion. Looks like fun.

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frequencycentral



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PostPosted: Wed Sep 17, 2008 10:41 am    Post subject: Reply with quote  Mark this post and the followings unread

crashlander42 wrote:
Hey! Thanks! That did the trick! It sounds even better AND I'm not worried about it catching fire!

I might just build that distortion. Looks like fun.


Great news!

The calculation for the heaters is as follows:

1. Using a 12 volt supply. 5672 heater is 1.25 volts 50ma

Voltage drop required = 10.75 volts

10.75 / 0.050 = 215 ohm

10.75 x 0.050 = 0.5375 watt

2. Using a 15 volt supply. 5672 heater is 1.25 volts 50ma

Voltage drop required = 13.75 volts

13.75 / 0.050 = 275 ohm

13.75 x 0.050 = 0.6875 watt

It would seem that J. Baars quoted the resistor value for a 15 volt supply, (but not the wattage requirement), but quoted a supply voltage of 12 volts. So the heater voltage will not be correct, this could cause damage to the heater, and the circuit probably won't be operating at it's best.

Also, looking at the 5672 data sheet, pin 1 has the red dot, not pin 5. In practice this is irrelevant if you build the VCF or VCA directly from J.Baars' schematic, as he has the tube pinout reversed too. Be aware though that my 'PentaDriver' schematic has the correct tube pinout.

5672 data sheets:

http://frank.pocnet.net/sheets/127/5/5672.pdf

http://frank.pocnet.net/sheets/030/5/5672.pdf

http://frank.pocnet.net/sheets/138/5/5672.pdf

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j.baars



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PostPosted: Wed Sep 17, 2008 6:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is the reason for the 2 anti-parallel diodes.
I wanted the heather voltage to be 0,7 volts, to put the tube in a ultimate starving setting.
when supplying the heather with 1,25 volts the tube will have a much shorter life and the filter will be different from the original.
not a big deal, but in my design no mistakes are made, everything has its purpose.
the wrong inverted numbering of the pins is extracted from a very old dutch electronics magazine, early 50's, after publishing I noticed, but left it this way, as long the red dot is in its place, everything should be ok.
the purpose of me publishing these schematics is to have fun , building ans using the things.
Not to surge for tiny mistakes, if you follow the schematics, there won't be any.
bye for now.
jeroen baars
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frequencycentral



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PostPosted: Fri Sep 19, 2008 10:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Jeroen, I apologise. I'm not trying to pick fault with your schematic. I just really need to understand a circuit before I build it. That's why I'm looking at it so closely. From what I understand, if you go too far at starving the heater it will cause as much damage to the tube as overheating the filament - this is because you begin stripping the cathode. It will change the tone, but most of the change is due to the reduced emission changing the bias point. I guess I'll just have to try it!

And yes your schematic IS great fun. Thank you for sharing.

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crashlander42



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PostPosted: Fri Sep 19, 2008 5:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

sssoooo..... What value should the 275R resistor be at 15v? I think I'd be able to figure it out I think except that I don't know what the little diode thingi is doing.
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