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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
utility lfo
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johnnymad



Joined: Apr 28, 2008
Posts: 40
Location: Gonzales, Louisiana

PostPosted: Sun Jul 06, 2008 12:08 pm    Post subject: utility lfo Reply with quote  Mark this post and the followings unread

does anyone have samples of the utility lfo? i've heard great things about it, but i have never actually heard it in action. Question i'm planning to build one as soon as the parts come in the mail. Cool
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numbernone



Joined: Aug 16, 2006
Posts: 477
Location: new york city

PostPosted: Sun Jul 06, 2008 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

JUST DO IT.

I have built 2 of them and LOVE them. Make sure you max them out with the join and swap for the Vari outputs. Also range switching is a MUST, check out Foniks site for a diagram of how to hook it up, I think my first had something around 2 uf for the slow setting, while the second was maybe 4.7uf for GLACIER speed. These are extremely versatile modulators that you will never tire of.
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johnnymad



Joined: Apr 28, 2008
Posts: 40
Location: Gonzales, Louisiana

PostPosted: Sun Jul 06, 2008 8:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbernone wrote:
Also range switching is a MUST, check out Foniks site for a diagram of how to hook it up


thanks. i'll check that mod out.
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Luka



Joined: Jun 29, 2007
Posts: 1002
Location: Melb.

PostPosted: Sun Jul 06, 2008 8:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

good point on the range switch i am about to do that
i might add a rotary switch and give it a good set of range options

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widdly



Joined: Jun 25, 2007
Posts: 265
Location: singapore
G2 patch files: 2

PostPosted: Sun Jul 06, 2008 10:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

I built three of these on a small piece of perf board.

I left off the right hand side of the schematic ( square and variout), so I can't comment on that part.

I think they are too fast if built straight from the schematic. I have a switch to parallel the 47n with a 470n cap. I one of them I added a 2uf bipolar for really slow settings.

Last edited by widdly on Thu Aug 05, 2010 10:13 pm; edited 1 time in total
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johnnymad



Joined: Apr 28, 2008
Posts: 40
Location: Gonzales, Louisiana

PostPosted: Thu Jul 17, 2008 8:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

just finished building it today. Cool it is a SWEET module. i added the range selection mod as suggested, and i'm glad i did. it makes some awesome sounds when using the vari out with the two lfos in different ranges. thanks for the suggestions!!
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creatorlars



Joined: Nov 26, 2007
Posts: 524
Location: Denton, TX
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PostPosted: Fri Jul 25, 2008 10:58 am    Post subject: Reply with quote  Mark this post and the followings unread

I just built mine with join/swap switches and I REALLY love this LFO. Way more flexible than my MFOS VCLFO (of course no PWM or VC -- but I was rarely using those anyway.)
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johnnymad



Joined: Apr 28, 2008
Posts: 40
Location: Gonzales, Louisiana

PostPosted: Fri Jul 25, 2008 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

i thought about building the mfos lfo, but this one seemed to have more to offer. i'm really glad it built it. i may build one of ray's eventually though. the voltage control could come in handy.
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j.dilisio



Joined: May 19, 2009
Posts: 186
Location: baltimore

PostPosted: Tue Aug 11, 2009 6:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm thinking of different ways to do the range mod.
Would It work if I had a large cap (470nf-1uf) and a pot in series with the 47nf?
I imagine the pot would act as a course speed while the speed pot would be more of a fine tune.

Does that make any sense?
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j.dilisio



Joined: May 19, 2009
Posts: 186
Location: baltimore

PostPosted: Tue Aug 11, 2009 7:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, I tried it with a 1uf cap and a 200k pot and it seemed to work just fine.
The pots cover different ranges but neither is really any coarser or finer than the other.
The max time of the 1uf is around 30 secs. It would be nice to have something longer.

Here's what I'm thinking..
Replace the original cap with something smaller like a 1nf and wire a 10uf with a pot in series.
This should give it a really wide range(5mins to very fast).
Then maybe even replace the speed pot on the front panel with this new pot.

Here's a question.. is that 200k pot going to cut it with a 10uf cap or should I increase the resistance?
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otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Sat Aug 15, 2009 12:35 am    Post subject: Reply with quote  Mark this post and the followings unread

j.dilisio wrote:
Ok, I tried it with a 1uf cap and a 200k pot and it seemed to work just fine.
The pots cover different ranges but neither is really any coarser or finer than the other.
The max time of the 1uf is around 30 secs. It would be nice to have something longer.

Here's what I'm thinking..
Replace the original cap with something smaller like a 1nf and wire a 10uf with a pot in series.
This should give it a really wide range(5mins to very fast).
Then maybe even replace the speed pot on the front panel with this new pot.

Here's a question.. is that 200k pot going to cut it with a 10uf cap or should I increase the resistance?


It is a ratio thing. No need to mess with the pot values.

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j.dilisio



Joined: May 19, 2009
Posts: 186
Location: baltimore

PostPosted: Sun Aug 16, 2009 10:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeh, I'm not having much luck with it.

Ken, do you know any way of increasing the range without adding switches between cap values?
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otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Sun Aug 16, 2009 3:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

j.dilisio wrote:
Yeh, I'm not having much luck with it.

Ken, do you know any way of increasing the range without adding switches between cap values?

The range is controlled by the ratio between the 100k pot and the 4k7 in series with it. Increasing the pot, or decreasing the 4k7 will change the range. (yes, I know I said the pot was fine last message.) Reducing the 4k7 too much WILL result in the LFO stalling.

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j.dilisio



Joined: May 19, 2009
Posts: 186
Location: baltimore

PostPosted: Sun Aug 16, 2009 7:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Ken,
I'll try messing with these values and post the results.
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j.dilisio



Joined: May 19, 2009
Posts: 186
Location: baltimore

PostPosted: Wed Aug 19, 2009 7:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

I ended up switching the 4k7's with 1k resistors and leaving the pot as is.
This extends the range so it goes down to about 25 seconds per cycle.

This feels a lot more musical to me than having to switch between ranges.
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TekniK



Joined: Aug 10, 2008
Posts: 1062

PostPosted: Fri Aug 21, 2009 12:29 am    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:
I just built mine with join/swap switches and I REALLY love this LFO. Way more flexible than my MFOS VCLFO (of course no PWM or VC -- but I was rarely using those anyway.)


i still have to build mine,am surprised you prefer this one as the MFOS VCLFO
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creatorlars



Joined: Nov 26, 2007
Posts: 524
Location: Denton, TX
Audio files: 4

PostPosted: Fri Aug 21, 2009 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
i still have to build mine,am surprised you prefer this one as the MFOS VCLFO


obviously there's lots of stuff you can do with a VCLFO, just saying that with the join/swap switches i can get a pretty complex modulation signal from a single module.
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haricots



Joined: Aug 15, 2007
Posts: 33
Location: guelph

PostPosted: Mon Aug 31, 2009 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

I love and use the dual utility LFO all the time however I've always suspected there is something wrong with the join/swap switching on mine. I haven't found a use for this yet because I can only get (slightly) usable modulations when either of the pots are turned to the extreme ends of their rotation. Does this sound like something is wrong or is this how it is supposed to be?

Does anyone have some audio examples of what it should be doing?

Thanks.
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haricots



Joined: Aug 15, 2007
Posts: 33
Location: guelph

PostPosted: Mon Aug 31, 2009 8:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

**crickets**

Ok, I need to replace the two switches. They are DPDT. However switch action confuses me. Should these be simple On-Off switches or not?
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jean-louise



Joined: Apr 27, 2009
Posts: 73
Location: berlin
Audio files: 2

PostPosted: Tue Sep 01, 2009 4:35 am    Post subject: Reply with quote  Mark this post and the followings unread

haricots wrote:
They are DPDT. However switch action confuses me. Should these be simple On-Off switches or not?


On-On i guess
there's a wiring diagram :
http://www.cgs.synth.net/modules/cgs58_lfo.html
jan
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numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Tue Sep 01, 2009 5:58 am    Post subject: Reply with quote  Mark this post and the followings unread

You don't see DPDT as often (as least I don't) in an On-Off setup (which would actually be a DPST). If you need some basics on switches check this site out: http://www.beavisaudio.com/techpages/Switches/ - could help you determine from a wiring diagram or schematic whether an On-On is required or an On-Off would suffice.

haricots wrote:
**crickets**

Ok, I need to replace the two switches. They are DPDT. However switch action confuses me. Should these be simple On-Off switches or not?
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wmonk



Joined: Sep 15, 2008
Posts: 486
Location: Enschede, the Netherlands
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PostPosted: Tue Sep 01, 2009 9:01 am    Post subject: Reply with quote  Mark this post and the followings unread

It chooses between normal mixing, and joining/swapping, so a DPDT is needed. (see wiring diagram on the CGS site).
My problems are the same, should check that one time. I think the problem is that I use the LFO at the power connector side on the right of my panel (LFO2), and the other on the left (LFO1). And on the Bridechamber panel, the one on the LFO on the power connector side is on the right.
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camelneck



Joined: Sep 27, 2008
Posts: 68
Location: KY (USA)

PostPosted: Mon Aug 22, 2011 8:11 am    Post subject: Reply with quote  Mark this post and the followings unread

I just finished wiring and testing my module. However, I'm not sure if it is working properly or not.

I've looked at the saw/tri and pulse outputs of each LFO with an oscilloscope and both LFO's are working properly and the waveshapes look
really good.

The problem I'm having though is with the variable outputs. Let me first say that I chose to wire my module as shown in Ken's first wiring diagram which I "think" is representative of the schematic. (In other words, I added the 2 Mix pots, but I didn't add the swap and join switches.)

Anyway, the schematic says that Variable Output #1 should be a mix of the square and tri waveforms produced by LFO #1 as determined by Mix #1 Pot. Similarly, Variable Output #2 should be a mix of the square and tri waveforms produced by LFO #2 as determined by Mix #2 Pot. Thus, variable output #1 is an output of LFO #1 and is independent of LFO #2 while variable output #2 is an output of LFO #2 and is independent of LFO #1.

However, when I tweak either LFO #2's Frequency and Shape pots it also effects Variable Output #1. Thus, variable output #1 is controlled by both LFOs and is not independent of LFO #2 as shown in the schematic. The same goes for Variable Output #2, which is also effected by the shape and frequency pots of either LFO.

Here is my question:

Is the variable outputs of my LFO module working correctly? (Remember, I haven't added the swap and join switches. I wired it as shown in Ken's first wiring diagram.)

Should Variable Output #1 be controlled exclusively by LFO #1 pots (Shape 1, Frequency 1, and Mix #1) or is it also effected by the LFO #2 pots (Shape 1, Frequency 1, and Mix #1)? (Both sets of pots control Variable Output #2 in a similar manner instead of just the LFO #2 pots.)


If Variable Output #1 suppose to be independent of LFO #2, perhaps I need to add some decoupling capacitors to the TL072. Any other suggestions?

David
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Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Mon Aug 22, 2011 8:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi David,

I think you must have it wired incorrectly. The two LFOs are completely independent if you don't have the join or swap stuff in place. I'd recommend just going through and double checking it all.

If you look at each end of the mix pot, you should see the square at one end, and the triangle at the other. They should both come from the same LFO. If they don't there's a wiring error.

You may also want to double check your power and ground connections. It's possible that maybe the ground is bad or something, but I have a hard time believing the thing would work at all if that were the case.

Gary
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camelneck



Joined: Sep 27, 2008
Posts: 68
Location: KY (USA)

PostPosted: Mon Aug 22, 2011 4:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Mongo1 wrote:

The two LFOs are completely independent if you don't have the join or swap stuff in place. I'd recommend just going through and double checking it all. <snip> You may also want to double check your power and ground connections.


Hi Gary,
That is what I needed to know!

I had already triple checked my wiring and solder connections and was sure that they were good. I had also checked the waveforms on the 2 mix pots as you had suggested although I forgot to mention it in my previous post.

As I mentioned earlier, I felt sure the problem was centered around the TL072 even though I had previously replaced this op amp with a spare and it did not solve the problem. (The only thing I could think of was it may be picking up stray signals from the power rails and this is why I was considering adding decoupling caps.)

I then realized that I hadn't checked to see if the TL072 op amp was being powered properly. Fortunately, I decided to do that next. Although I measured +15V on pin 8 of the TL072, I wasn't measuring the expected -15V on pin 4. Thus, I started to tone out the traces on the PCB to see if I had a bad trace when I discovered that I had completely overlooked that teensy, tiny jumper wire. (I discovered that the purpose of that jumper is to supply pin 4 of TL072 with -15V.)

Once I installed the jumper, the circuit began to work properly. Without the -15V, the TL072 was mixing the 2 variable outputs (or the outputs of its 2 op amps) together.

Thanks for all of your help and suggestions, Gary. I really appreciate it.

David
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