Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Login
Joshua Tree kit to upgrade and replace volume control in vintage preamp
Options
View
Go to last post Go to first unread
Previous Topic Next Topic
MarkvsMaximvs  
#1 Posted : Thursday, September 15, 2011 12:58:58 PM(UTC)
MarkvsMaximvs

Rank: Member

Groups: Member
Joined: 1/11/2011(UTC)
Posts: 13
Location: Canada
Hi,

I'm entertaining the idea of upgrading the existing potentiometer-based volume control in a preamp with a discrete attenuator such as the Joshua Tree. The existing volume control is a motor driven potentiometer and I was wondering if that could somehow be leveraged to control the Josua Tree. It's not a 5K linear like the pot that's included in the kit, but could the control board be modified to accommodate the resistive range of the preamp's potentiometer?

Thanks,

-Mark
Back to top

Wanna join the discussion?! Login to your Twisted Pear Audio Support forum accountor Register a new forum account.
Back to top  
Brian Donegan  
#2 Posted : Thursday, September 15, 2011 1:07:03 PM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
the Joshua Tree simply uses the pot as a variable voltage divider, and monitors the voltage coming out of the pot, so it would definitely work as is. The main issue would be that the existing pot (most likely) has a log curve, so you will get very little volume until close to the end of the rotation, where it will ramp up quite quickly.

I suppose this could be accounted for in special firmware, but would take some testing to get it working well.
Back to top
WWW
pinnocchio  
#3 Posted : Thursday, September 15, 2011 1:38:11 PM(UTC)
pinnocchio

Rank: Member

Groups: Member
Joined: 11/3/2010(UTC)
Posts: 169
Canada
Location: Quebec
Brian,

What if he buys a ALPS dual 10K linear motorized pot and parallel both resistors together? That would drop the resistor to ~5K?

Item RK27112MC 10KBx2

Ciao!
Back to top
Brian Donegan  
#4 Posted : Thursday, September 15, 2011 1:43:39 PM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
pinnocchio wrote:
Brian,

What if he buys a ALPS dual 10K linear motorized pot and parallel both resistors together? That would drop the resistor to ~5K?

Item RK27112MC 10KBx2

Ciao!


That won't help much unless it fits in the existing spot. It will certainly work, but the question was how to reuse the existing pot.
Back to top
WWW
Brian Donegan  
#5 Posted : Thursday, September 15, 2011 1:44:51 PM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Incidentally, a 10K pot will work without modification. The pot value will just affect the resolution... the divided voltages will be the same regardless of pot value.
Back to top
WWW
MarkvsMaximvs  
#6 Posted : Thursday, September 15, 2011 3:18:40 PM(UTC)
MarkvsMaximvs

Rank: Member

Groups: Member
Joined: 1/11/2011(UTC)
Posts: 13
Location: Canada
Hi Guys,

Thank you very much for your quick replies. Changing the existing volume pot to a motorized linear did cross my mind. I'd have to measure the available space with accuracy, but I think there should be enough clearance.

Thanks again
Back to top
Rss Feed  Atom Feed
Users browsing this topic
GuestUser (2)
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

Youtube
Copyright © Twisted Pear Audio