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 Forum index » DIY Hardware and Software » Thomas Henry designs
Thomas Henry Strikes Again
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State Machine
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PostPosted: Sun May 27, 2007 11:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
also liked the definition from the urban dictionary, which states that a gnat's ass is about one tenth of a skosh (which is equal to approximately one nudge of the dial, amounting to something much less than a pussy hair).


Thats f---ing funny man !!!!! Very Happy Very Happy

Thanks for the laughs guys !

Bill
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Coriolis



Joined: Apr 11, 2005
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Location: Stilling, Denmark

PostPosted: Sun May 27, 2007 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ahem:
One question - I've got 1k tempco's but no 2k. If I want to use those, I'll have to use a 50K resistor instead of 100k on the 1v/oct input, right?
But what about the other inputs? Will it matter? Would I have to halve both the pot- and series resistor values (say, on the "coarse" input - R35, R28 and R44 will be 50k, 50k and 1M1 respectively). Or what? What happens if I don't?
Man, I've got 2sa768's, 1000pf polystyrene caps, a couple 3080's...
I'm building one of these! Very Happy

C
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Scott Stites
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PostPosted: Mon May 28, 2007 12:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey Coriolis,

Y'know, I never know the answer to this one. Thomas? Bill? Fonik? Anyone?

If the 1K doesn't work, maybe I can help get you set up with a 2K tempco.

Cheers,
Scott

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richardc64



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PostPosted: Mon May 28, 2007 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Coriolis wrote:
Ahem:
But what about the other inputs? Will it matter? Would I have to halve both the pot- and series resistor values (say, on the "coarse" input - R35, R28 and R44 will be 50k, 50k and 1M1 respectively). Or what? What happens if I don't?
C


I'm pretty sure that if you don't change the series resistor(s) the associated input will give half the range it would with a 2k tempco. The Coarse control would provide, say, a 2 octave range instead of 4 or whatever, the Fine contol would be very fine, an lfo or envelope on the Exp FM would provide half as much frequency sweep.

The pot values do not matter much -- they act as voltage dividers. They affect the loading on the circuit driving them and the low impedance output of opamps provides plenty of drive. I wouldn't use lower than 20k or so in a system, though, just to be safe.
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andrewF



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PostPosted: Mon May 28, 2007 4:46 am    Post subject: Reply with quote  Mark this post and the followings unread

i had the same question when building the SN-voice, can't remember who (it will be somewhere on the SN-voice thread) said putting two 1k tempcos in series, gives you 2k and the temp comp rating doesn't change, the message finished with - trust me!
Anyway i did.
as far as my worn out tin ears can tell its fine.
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State Machine
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PostPosted: Mon May 28, 2007 8:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Ahem:
One question - I've got 1k tempco's but no 2k. If I want to use those, I'll have to use a 50K resistor instead of 100k on the 1v/oct input, right?
But what about the other inputs? Will it matter? Would I have to halve both the pot- and series resistor values (say, on the "coarse" input - R35, R28 and R44 will be 50k, 50k and 1M1 respectively). Or what? What happens if I don't?


If you want the circuit to behave exactly as it did with the 2K TEMPCO feedback resistor when using the 1K unit, you will need to half all the input resistors (R26,R27,R28,R44,R46) that go to the op-amplifiers summing junctions. The pots can remain the same values.


Bill
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Coriolis



Joined: Apr 11, 2005
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PostPosted: Mon May 28, 2007 10:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the advice, people! Cool
I think I'm going to use 50k (49.9k) resistors then. I've got a bunch of 1k 3000ppm tempco's, but if I use two at a time, they'll be used up pretty fast...
Great that I don't have to use different pots - I have loads of the 100k variety from futurlec!
Great to be learning!

C
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Thomas Henry



Joined: Mar 25, 2007
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PostPosted: Wed May 30, 2007 10:31 pm    Post subject: Re: Thomas Henry Strikes Again
Subject description: Another very cool VCO by the Man from Mankato
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Scott Stites wrote:
From way up north, Mankato way, land of a thousand lakes...


Ahem...as our license plates proudly proclaim: Land of Ten Thousand Lakes.

Hey Scott, can I interest you in a VCO which is perfectly in tune over one octave?

Thomas Henry
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Coriolis



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PostPosted: Fri Jun 01, 2007 5:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I believe the "single" thousand lakes land is Finland...

C
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Scott Stites
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PostPosted: Fri Jun 01, 2007 6:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Any state that can wriggle out of a Jesse "The Body" Ventura headlock has got my respect, no matter how many lakes it's got! Very Happy

Now, if Kansas had just one natural lake, I'd be surprised......

We've got cow ponds. Does that count?

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