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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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16th Sep 2019, 12:35 pm | #1 |
Retired Dormant Member
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Location: Holmfirth, West Yorkshire, UK
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From a lin to a log
Hi all,
I have just found a 1meg dual pot for my Pye Black Box, the only problem is that they are lin not log. (they should be log) Does any kind member know the best way of changing the law of the pot to approximate the mimic of from lin to log, and if so, the value of caps or resistors across the legs of the pot. Keeping my fingers crossed that some kind member maybe able to assist. Cheers, Ted |
16th Sep 2019, 12:43 pm | #2 |
Heptode
Join Date: Feb 2006
Location: Marlborough, Wiltshire, UK.
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Re: From a lin to a log
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16th Sep 2019, 12:43 pm | #3 |
Dekatron
Join Date: Apr 2011
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Re: From a lin to a log
http://www.learnabout-electronics.or...istors_09a.php
http://www.geofex.com/article_folder...s/potscret.htm Basically a resistor from the wiper to the bottom end (chassis end) of the pot that's of a value that's approx. 1/4 to 1/5th of the pots value. Lawrence. |
16th Sep 2019, 12:53 pm | #4 |
Octode
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Re: From a lin to a log
deleted
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16th Sep 2019, 1:55 pm | #5 |
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Re: From a lin to a log
Hi Ken,
Many thanks for your very kind help, it's very much appreciated. Hi Lawrence, Many thanks to you also Lawrence, it's very kind of you to let me know, so the resistor value should be around 250-300k if I am understand this correctly? Just a thought, will this affect the value of the 1 Meg pot? Sorry to be a bit dim, but just thought I would ask. All help is very much appreciated. All my very kindest regards, Ted |
16th Sep 2019, 2:03 pm | #6 |
Nonode
Join Date: Jan 2010
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Re: From a lin to a log
This is a link to a discussion on here back in 2017 https://www.vintage-radio.net/forum/...d.php?t=142531
Al
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16th Sep 2019, 2:09 pm | #7 |
Heptode
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Re: From a lin to a log
See here
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16th Sep 2019, 2:49 pm | #8 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: From a lin to a log
Quote:
So, in effect you end up with a 212k "log" pot. That will affect the output from the signal source as the volume is advanced, the usual potential divider rules apply...eg: source impedance and load impedance = a potential divider so therefore the lower the load impedance the lower the signal output from the source will be. That's for one section of the control, yours is a dual pot and they are in effect connected together, section A wiper to section B's track according to a schematic I'm looking at. You can but try it and see how it performs. Lawrence. |
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16th Sep 2019, 3:42 pm | #9 |
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Join Date: Aug 2012
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Re: From a lin to a log
Hi Ken, Al, and Stockden,
Many thanks for your very much appreciated kind help, it's very much appreciated. H Lawrence, Wow, many thanks for your very much appreciated kind help and advice. I am now wondering should I use my 500k dual log pot in my Pye Black box, or go for the modified 1 Meg lin to log option. Your thoughts and views would be very much appreciated, in other words, what option would you go for? (I forgot to mention that this is the Black Box volume control.) So sorry to be a pain, but am completely stuck on what to do. All help is very, very much appreciated. All my warmest and kindest regards Ted (Alias Puzzled and stuck.) |
16th Sep 2019, 3:54 pm | #10 | |
Dekatron
Join Date: Apr 2011
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Re: From a lin to a log
Quote:
Lawrence. |
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16th Sep 2019, 4:41 pm | #11 |
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Re: From a lin to a log
Hi Lawrence,
Many thanks for your very kind help, I will take your advice and go for the 500k log pot. Many thanks once again for your very kind help. All my kindest regards Ted. |
16th Sep 2019, 10:44 pm | #12 |
Dekatron
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Re: From a lin to a log
If you have plenty of "spare" volume, a series resistor at the top end of each pot of 220k-470k will improve the bass response with the 500k option.
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17th Sep 2019, 10:28 am | #13 |
Retired Dormant Member
Join Date: Aug 2012
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Re: From a lin to a log
Hi Herald 1360,
Many thanks again for your very kind help, I tried to find my last post with your very helpful advice , but it has been deleted. I will now follow your advice, and fit the 500K log pot with as you advised fitting 470K resistors fitted at the top end of each pot. (Have just ordered some 470K 1% resistors) Many, many thanks once again for all your very much appreciated kind help. All my very best and kindest regards, Ted. |
17th Sep 2019, 3:56 pm | #14 | |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 5,000
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Re: From a lin to a log
Quote:
There was a thread where a kind member offered you a pot free of charge, which you declined as you'd already got fixed up, so the thread got closed. Why not ask that member about that particular pot as it could be what you're looking for to save all this messing about. The thread's here - two pages of it, and the link to it is below, good luck. https://www.vintage-radio.net/forum/...d.php?t=159522 |
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17th Sep 2019, 5:21 pm | #15 |
Dekatron
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Re: From a lin to a log
There was briefly a post by snowman al in this thread, but he deleted it himself.
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17th Sep 2019, 9:31 pm | #16 |
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Re: From a lin to a log
Hi Techman
Many thanks for your message, it's very kind of you to find the thread for me, I did search for my original thread, but couldn't find it. (I'm not the brightest star in the sky) I have taken some very kind advice from forum members, and will replace the pot with a 500K dual log pot with added resistors. I do have a 1meg dual pot, but it is lin. Many thanks once again for all your very kind help. All my very best and kindest regards, Ted |