Channel imbalance [resolved]

ryanred · 1494

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Offline ryanred

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on: June 07, 2016, 06:42:56 PM
Just finished my Crack, everything seems to be within spec but there is an imbalance between the channels. Here are my voltage measurements, A6 and B1 are quite low.

Terminal   Spec      Measured
1              75-90     76.7
2              170         173.8
3              0             0
4              170         173.8
5              75-90      84.8
6              0             0
7              100         101.3
8              0             0
9              100          106.7
10             0             0
11             0             0
12             0             0
13             170         173.5
14             0             0
15             185         194.5
20             0             0
21             206         215.7
                 
A1             90           84.7
A2             0             0
A4             0             0
A5             0             0
A6             90           77.2
A7             0             0
A9             0             0
                 
B1             90           76.8
B2             170         173.7
B3             100         101.1
B4             90           84.9
B5             170         173.7
B6             100         106.4
B7             0             0
B8             0             0

After that, I followed Caucasian Blackplate's suggestions in this thread newbielink:http://bottlehead.com/smf/index.php?topic=7788.15 [nonactive].

Terminal               Measurements
RCA jacks             772mV     772mV
Pot Center Lugs    772mV     772mV
A2 and A7             772mV     772mV
Headphone Jack    5.692V    6.78V
Term1, Term5       8.9V      10.4V
Term6, Term10     4.81V     5.834V

Do I need new tubes, or does something else appear to be wrong?
« Last Edit: June 14, 2016, 07:37:14 AM by Caucasian Blackplate »



Offline fullheadofnothing

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Reply #1 on: June 08, 2016, 07:41:44 AM
The difference in voltage from the manual value is caused by a strong tube. It is nothing to worry about.

The channel imbalance you measure is just over a dB. Most people cannot reliably distinguish a difference that small. It is more likely that you have a potentiometer that isn't perfectly matched at low levels. Install the padding resistors to resolve this, or you could turn down the output of your source which would require you to turn up  the potentiometer on the Crack.

Joshua Harris

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