John Curl's Blowtorch preamplifier part II - Page 386 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th March 2010, 03:30 PM   #3851
godfrey is offline godfrey  South Africa
diyAudio Member
 
Join Date: Nov 2009
Location: Cape Town
Quote:
Originally Posted by john curl View Post
Cost is not so important, minimum number of series relays is important.
Hi John

It is a pity that it is impractical to use two separate pots (for high range and low range). That would allow only one relay contact to be in circuit at a given time. It would also be easier to use with only 2 switch positions.

I understand the difficulty of having special pot/motor combinations custom-built, but would it not be possible to use two completely separate motorized pots?

Regards - Godfrey
  Reply With Quote
Old 5th March 2010, 03:42 PM   #3852
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Too much hassle, and space, I'm afraid.
  Reply With Quote
Old 5th March 2010, 03:43 PM   #3853
godfrey is offline godfrey  South Africa
diyAudio Member
 
Join Date: Nov 2009
Location: Cape Town
Quote:
Originally Posted by simon7000 View Post
In the case of a 1K pot with an end resistor the resistors should be 988 ohms, 1.91k, 3.75K, 7.39K, 14.3k, 28K and 54.9K.
Hi Simon

The problem with using this kind of approach with a 1k pot is that you end up with about 100 different switch settings.

Just sweeping e.g. from 50k to 60k will involve going through 10 combinations of series resistor. There will be much clattering of relays - not ideal while one is trying to tune by ear!

Cheers - Godfrey
  Reply With Quote
Old 5th March 2010, 07:09 PM   #3854
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Quote:
Originally Posted by godfrey View Post
Hi Simon

The problem with using this kind of approach with a 1k pot is that you end up with about 100 different switch settings.

Just sweeping e.g. from 50k to 60k will involve going through 10 combinations of series resistor. There will be much clattering of relays - not ideal while one is trying to tune by ear!

Cheers - Godfrey
Depending on the complexity of the controller more relays can be used to minimize the number of switches being used as shunts. I don't think the miniature relays being used are as noisy as you expect. Inside a solid case or two they should be well below the problem level.

Somewhere around 15 relays will limit you to mostly 2 switches sometime 3.

Last edited by simon7000; 5th March 2010 at 07:11 PM.
  Reply With Quote
Old 5th March 2010, 10:09 PM   #3855
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by godfrey View Post
Hi Simon

There will be much clattering of relays - not ideal while one is trying to tune by ear!
That's why God invented the reed relay.
__________________
The more you pay for it, the less inclined you are to doubt it.- George Smiley
  Reply With Quote
Old 5th March 2010, 10:12 PM   #3856
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I am blocked once more, lost another one, that would clarify the situation.
  Reply With Quote
Old 7th March 2010, 04:39 AM   #3857
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Well thanks everyone, for your inputs. It might be better to move onward to some other topic that is more general.
  Reply With Quote
Old 7th March 2010, 02:58 PM   #3858
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
John,

I am still measuring resistors and an interesting artifact has shown up in measuring the Vishay bulk metal film resistors. From my preliminary measurements I would characterize these as being a "Warm" sounding resistor.

Have you or any one else have experience with them?
  Reply With Quote
Old 7th March 2010, 03:12 PM   #3859
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Interesting
  Reply With Quote
Old 8th March 2010, 05:32 AM   #3860
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Simon, we will probably use naked Vishays for our project. I don't mind using original Roderstein resistors or Corning Grey resistors, either.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 06:51 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2