Bosoz pot, linear or log?

gchrist · 16th March 2008, 07:05 PM

I have constructed the Bosoz preamplifier for some time now but I am wondering if I made a mistake on the pot selected. I have selected a quad pot that is linear. Is this correct or should I have selected a logarithmic one?
I have read the original artical but this is not explained. From the data sheet of the original part suggested by Mr. Pass a linear pot was selected but on the net log is the choice for audio. Am I understanding something wrong?
I have started to look into this because I feel that the preamp does not have enough gain to run my final amp as needed.

Thank you
George Christofilopoulos

gchrist · 17th March 2008, 02:48 PM

I think this a rather simple question. So many of you have built the bosoz. Can someone please point me in the correct direction?

Thanks

stefanobilliani · 17th March 2008, 02:59 PM

I think Linear should do pretty good . You just try and see if youre satisfied with it .

For the gain... look at the article and find about . It can be selected for high figures . The distorsion of the circuit varies as well with it .

WithTarragon · 17th March 2008, 03:04 PM

For audio you want to use a log taper not a linear taper.

I am not sure what Z you have on your pot, but it is possible to use a second resistor with a linear pot and approximate a log taper.

Do a search on "Fake Law" pot or go to the ESP website (Elliot).

-Tom

Babowana · 17th March 2008, 04:17 PM

I think with log.
When the pot is log, my ears feel linear.

noisefree · 17th March 2008, 05:35 PM

The original parts from the article are all linear types (for input, output and gain).
But it is better to use logarithmic ones as for the reason Babowana has mentioned also for P5.
For the gain I use an 11 position switch to switch in discret resistor values to get 2dB steps from 0dB to 20dB.

Dirk

jupiterjune · 18th March 2008, 12:55 AM

Sorry to jump in so late.

I used the stock linear pot on the output. What I found was that, for an amp with high gain ( ie A75), it was very difficult to adjust at low listening levels. The tiniest increment of rotation would make the output louder than desired.

A stepped attenuator works great, as noisefree mentioned.

JJ

stefanobilliani · 30th March 2008, 03:54 PM

I am having very nice results with double ( stereo )slide log pots .
They are way better than the rotatives , and if you buy lets say... 5 of them , you may have the chance to find one that has very good match of resistance between channels . They offer good precision between channels at low levels and very good control .

They are cheap , they endure and are easy to implement .

16th March 2008, 07:05 PM	#1
gchrist diyAudio Member Join Date: Mar 2002 Location: Athens Greece	Bosoz pot, linear or log? I have constructed the Bosoz preamplifier for some time now but I am wondering if I made a mistake on the pot selected. I have selected a quad pot that is linear. Is this correct or should I have selected a logarithmic one? I have read the original artical but this is not explained. From the data sheet of the original part suggested by Mr. Pass a linear pot was selected but on the net log is the choice for audio. Am I understanding something wrong? I have started to look into this because I feel that the preamp does not have enough gain to run my final amp as needed. Thank you George Christofilopoulos

17th March 2008, 03:04 PM	#4
WithTarragon diyAudio Member Join Date: Jun 2007	Fake Law For audio you want to use a log taper not a linear taper. I am not sure what Z you have on your pot, but it is possible to use a second resistor with a linear pot and approximate a log taper. Do a search on "Fake Law" pot or go to the ESP website (Elliot). -Tom

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17th March 2008, 02:48 PM	#2
gchrist diyAudio Member Join Date: Mar 2002 Location: Athens Greece	I think this a rather simple question. So many of you have built the bosoz. Can someone please point me in the correct direction? Thanks

17th March 2008, 02:59 PM	#3
stefanobilliani diyAudio Member Join Date: Jun 2002 Location: Italy	I think Linear should do pretty good . You just try and see if youre satisfied with it . For the gain... look at the article and find about . It can be selected for high figures . The distorsion of the circuit varies as well with it .

17th March 2008, 04:17 PM	#5
Babowana Formerly "jh6you". R.I.P. Join Date: Jul 2006	I think with log. When the pot is log, my ears feel linear.

17th March 2008, 05:35 PM	#6
noisefree diyAudio Member Join Date: Jun 2007	The original parts from the article are all linear types (for input, output and gain). But it is better to use logarithmic ones as for the reason Babowana has mentioned also for P5. For the gain I use an 11 position switch to switch in discret resistor values to get 2dB steps from 0dB to 20dB. Dirk

18th March 2008, 12:55 AM	#7
jupiterjune diyAudio Member Join Date: Nov 2006	Sorry to jump in so late. I used the stock linear pot on the output. What I found was that, for an amp with high gain ( ie A75), it was very difficult to adjust at low listening levels. The tiniest increment of rotation would make the output louder than desired. A stepped attenuator works great, as noisefree mentioned. JJ

30th March 2008, 03:54 PM	#8
stefanobilliani diyAudio Member Join Date: Jun 2002 Location: Italy	I am having very nice results with double ( stereo )slide log pots . They are way better than the rotatives , and if you buy lets say... 5 of them , you may have the chance to find one that has very good match of resistance between channels . They offer good precision between channels at low levels and very good control . They are cheap , they endure and are easy to implement .

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