|
Home | Forums | Rules | Articles | diyAudio Store | Blogs | Gallery | Wiki | Register | Donations | FAQ | Calendar | Mark Forums Read |
Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc. |
|
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 |
![]() |
|
Thread Tools |
![]() |
#21 | |
diyAudio Member
Join Date: Feb 2004
|
Quote:
|
|
![]() |
![]() |
#22 |
diyAudio Member
|
What are the most sound quality solution for a potentiometer as 'Passive PreAmp' ?
Did anyone comapre some solutions ? There are : 1. Potentiometer like ALPS (motorized) 2. Relay based Attenuator with resistor array 3. IC based volume control It should be possible to remote control the volume, so i exclude the switch based solution which is near to relay based solution (?) Thanks, regards Marcus |
![]() |
![]() |
#23 |
diyAudio Member
|
|
![]() |
![]() |
#24 |
diyAudio Member
Join Date: Apr 2011
|
That doesn't really make any sense. But, have you tried a buffer before or after the volume control? That might localize the problem.
|
![]() |
![]() |
#25 | |
diyAudio Member
Join Date: May 2011
Location: Little Rock
|
Quote:
All good fortune, Chris |
|
![]() |
![]() |
#26 |
R.I.P.
Join Date: Jul 2004
Location: Scottish Borders
|
No.
The source sees the vol pot resistance in parallel with a variable impedance. When the vol pot is set to minimum output the parallel impedance is effectively infinite and the source sees only the vol pot resistance. When the vol pot is set to maximum output the source sees the vol pot resistance in parallel to the input impedance of the receiver after the vol pot. eg. a 10k vol pot a 100k receiver with and RF filter of 47pF and a cable of 300pF and etc... At minimum output the source sees the 10k. at maximum output the source sees 10k||100k||47pF||300pF and the source must be capable of driving this impedance adequately.
__________________
regards Andrew T. |
![]() |
![]() |
#27 |
R.I.P.
Join Date: May 2007
|
Not if the pot is wired back to front, as is sometimes done by newbies or those who prefer 'innovation' to sound engineering.
|
![]() |
![]() |
#28 |
diyAudio Member
Join Date: Aug 2014
|
This is a good post.
What about when the potentiometer is integrated in a stereo amp? Is there such thing as having a wrong value or using too high of a potentiometer resistance? The problem of a low pass filter forming from cable capacitance seems completely avoided. So why wouldn't I want to use a 50k or 100k potentiometer for volume control? |
![]() |
![]() |
#29 | |
diyAudio Member
Join Date: Apr 2011
|
Quote:
A 50k pot has at most a 12.5k output resistance, so you'd want at least 5 or 10 times that for the line stage's input impedance. Also, internal wiring, or the line amp's input capacitance, may require something more like a 10k pot to preserve bandwidth. Last edited by rayma; 7th May 2015 at 03:13 PM. |
|
![]() |
![]() |
#30 |
Account disabled at member's request
Join Date: Jun 2010
Location: UK
|
Its all depends on,
How much series resistance there is with different settings of the volume control..at full volume low series resistance / at low volume higher series resistance..thats not taking into account the drive of a cable if its remote or the lack of a cable if its intergrated..so from the point of an integrated amp the drive required after the control is different to at a remote distance. miller capacitance and series resistance..is another issue. Another is the current available for drive is divided at the pot. So with a higher value pot you get more series resistance at low volumes, however at higher settings the dividing resistance is higher to ground. (as usual its a trade off) So you are asking for a linear device with varying parameters of real life conditions. (You are changing the circuit and expecting the same behaviour in all positions). ie even expecting a passive to be plugged into other amps and work the same.. how audible that will be is another issue. Then there is the loading effect of the value of the pot on the driving stage (input device) and if there is a cable before the pot (connection from device to passive) or if its on the output stage of the source before the cable. So you want maximum drive for the cable..unless its integrated. Trouble is you have an input cable and / or output cable (with a passive pre). ie a load on the drive stage with a cable load and a divider driving into an output cable plus input load(amp). Regards M. Gregg Last edited by M Gregg; 2nd June 2015 at 09:00 AM. |
![]() |
![]() |
Thread Tools | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
"...the best preamplifier ever made" says Mr. David Price, Hi-Fi- World | tiefbassuebertr | Analog Line Level | 78 | 5th January 2018 12:17 AM |
KIT - "FlatBT" audiophile grade LINE preamplifier | boraomega | Swap Meet | 10 | 4th January 2018 04:16 PM |
DIY "ribbon controller" slide potentiometer-please help with blueprints! | VvvvvV | Instruments and Amps | 4 | 21st January 2007 09:51 AM |
WTB: stereo potentiometer ALPS "black beauty" or... | kasra | Swap Meet | 8 | 10th October 2002 06:54 PM |
Suggestions on a preamplifier project with a "A/V processor loop" option | Spyhunter | Solid State | 6 | 8th November 2001 10:31 AM |
New To Site? | Need Help? |