something about input of the Bruno UG 30

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ironlung
Posts: 3
Joined: Fri Aug 15, 2008 5:59 pm

something about input of the Bruno UG 30

Post by ironlung »

hello :D
I got a Bruno Underground 30 head with two channels. The input jack of channel I is mounted 3 resistors on it(the photo following). It's not like the Low input of a traditional Hi/Low inputs. The 1M resistor seem redundant, is it? The two 68K resistors just form a voltage divider, right?
Thank you.
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tictac
Posts: 617
Joined: Fri Mar 31, 2006 4:42 am

Re: something about input of the Bruno UG 30

Post by tictac »

those are 680K resistors not 68K.... :oops:
ironlung
Posts: 3
Joined: Fri Aug 15, 2008 5:59 pm

Re: something about input of the Bruno UG 30

Post by ironlung »

tictac wrote:those are 680K resistors not 68K.... :oops:
Sorry, maybe the orange somewhat like yellow, but it's real 68K.
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bcmatt
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Location: Canada

Re: something about input of the Bruno UG 30

Post by bcmatt »

I had to stop and think through this at one point but I don't believe any of the resisters are redundant. If you draw both the hi and lo inputs completely with the way they switch when plugged into one or the other, I think it will be more clear.
The 5E3 is the same way. Look at this schematic.

Plugging into the lo input gives you travelling through a 68k resister with a 68K to ground. Plugging into the hi input gives you travelling though a 68K resister with 1Meg to ground.
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ironlung
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Joined: Fri Aug 15, 2008 5:59 pm

Re: something about input of the Bruno UG 30

Post by ironlung »

bcmatt wrote:I had to stop and think through this at one point but I don't believe any of the resisters are redundant. If you draw both the hi and lo inputs completely with the way they switch when plugged into one or the other, I think it will be more clear.
The 5E3 is the same way. Look at this schematic.

Plugging into the lo input gives you travelling through a 68k resister with a 68K to ground. Plugging into the hi input gives you travelling though a 68K resister with 1Meg to ground.
The amp I got has two channels, each has only one input. The channel I input jack mounted all the 3 resistors. The 5E3 schematic you post is not the same. If the designer wants a Low input, he only needs two 68K resistors to form a voltage divider. Why did he use an additional 1M resistor? Thank you.
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