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 Forum index » DIY Hardware and Software » YuSynth
Problem with Yusynth Sample an hold
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crashlander42



Joined: Oct 21, 2006
Posts: 292
Location: Orlando, FL (US)

PostPosted: Sat Jun 07, 2008 11:14 am    Post subject: Problem with Yusynth Sample an hold Reply with quote  Mark this post and the followings unread

What would cause the range on my Yusynth sample and hold to become very narrow (if that makes any sense). I built two of these and I'm not getting very wide swing to my signal. I breadboarded one of these a long time ago and it sounded awesome. I just can't figure out what I've done different.

Which part of the sample and hold circuit would effect the range of the output? I thought it might have been a cap I substituted for C6, but I've replaced that with an exact component and it still sounds the same. Any ideas?

Any help would be greatly appreciated.

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crashlander42



Joined: Oct 21, 2006
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Location: Orlando, FL (US)

PostPosted: Sat Jun 07, 2008 11:53 am    Post subject:
Subject description: Ok, maybe more of a problem with the noise source.
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Ok. I used my LFO and ADSR as my sample source and it wobbled away like crazy. My noise source seems to be quite quiet. Now I need to figure out why my noise source is so quiet.
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crashlander42



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PostPosted: Sat Jun 07, 2008 12:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Never mind. Problem solved. When the instructions say to pick the noisiest transistor you should listen. I somehow selected the two quietest transistors I had.
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yusynth



Joined: Nov 24, 2005
Posts: 1233
Location: France

PostPosted: Sat Jun 07, 2008 12:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi

I've just seen your message but it seems you solved it all already Wink
Yes nowadays you have to select the tranny to find the nosiest when 30 years ago one would select the quietest Laughing

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frijitz



Joined: May 04, 2007
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PostPosted: Sat Jun 07, 2008 2:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

crashlander42 wrote:
Never mind. Problem solved. When the instructions say to pick the noisiest transistor you should listen. I somehow selected the two quietest transistors I had.


I need to weigh in, again, on this question. There is a serious (IMO) problem with picking your noisiest transistor. The problem is that the noisier they are, the more popcorn noise they have. I once went through a bag of 50 2N3904's, looking for the ones that gave a flat spectrum at low frequencies. I found only 2 devices that gave a flat, i.e. smooth-sounding, noise spectrum. These both had very low outputs. It's an easy matter to increase the circuit gain to compensate.

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Ian
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yusynth



Joined: Nov 24, 2005
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PostPosted: Sat Jun 07, 2008 2:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes Ian, that's why on the web page of my noise generator-S&H module one can read in the trimming section:
Quote:
The trimming is quite simple, it consists of taking a batch of BC547 transistors and selecting among these one that gives the highest white noise level while being symetrically balanced around 0V level, with the flatest spectrum. In order to do so, it is a good idea to use a transistor socket for Q2, this way one can swap easily the transistors to find the best one. It is a good practice to wait about 1min before checking the noise level and quality of white spectrum in order that Q2 has reached a steady temperature.

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crashlander42



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PostPosted: Sun Jun 08, 2008 12:44 am    Post subject: Reply with quote  Mark this post and the followings unread

err... I don't know if I got the technical details or wording right, but changing the transistors worked. yeay. I win.
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softfin



Joined: Oct 11, 2006
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PostPosted: Sun Jun 08, 2008 8:44 am    Post subject: Reply with quote  Mark this post and the followings unread

I built my Yusynth S&H+noise last winter. I have found the noise source to be a bit on the weak side as well (I used a bc109c transistor). Fortunately I put a socket for the noise transistor so perhaps I should start testing different types of transistors to get stonger and flatter noise.
If anyone has had particularly good results with some specific transistors, please share the knowledge Smile
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frijitz



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PostPosted: Sun Jun 08, 2008 9:20 am    Post subject: Reply with quote  Mark this post and the followings unread

yusson wrote:
Yes Ian, that's why on the web page of my noise generator-S&H module one can read in the trimming section:
Quote:
The trimming is quite simple, it consists of taking a batch of BC547 transistors and selecting among these one that gives the highest white noise level while being symetrically balanced around 0V level, with the flatest spectrum.


Yves -- Thanks for the clarification. I was going by what the other post said, without actually reading your instructions. But I have found that the devices with the flattest spectrum have the weakest output. Do you find this to not be the case with the BC547?

Very Happy

Ian
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Sine



Joined: Sep 10, 2007
Posts: 111
Location: Netherlands

PostPosted: Fri Sep 12, 2008 3:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

I don't know if its type specific, but i have a few metal can 2n2222's and reversed these are the most noisy transistors EVER !
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