hifiaf
pfm Member
Hi everyone,
Like many people, to get "balance" on my 32.5, I have to have the balance pot at about 2 o'clock, which for obsessives like me is visually offensive I've also been wondering about the potential sonic advantages of using fixed resistors in place of the balance pot.
I found this brief mention of the mod on Acoustica:
I also found a thread here on pfm in which there is some debate about the number (2? 4?) and value of resistors (@neiljadman recommends 1K2), and whether you'd need to use resistors at all.
We've been discussing this over on Audioflat, and here's what we figure so far.
Here's how we've numbered the 6 pins on the pot (1, 2, and 3 are the row hidden in this photo).
Based on values measured in circuit and on the visible traces in the image below, we figure this is what they all correspond to:
1 and 6 connect to ground (they have continuity in circuit)
3 and 4 are input signal from volume pot
2 and 5 are output from the wiper
Last night I removed the pot from my 32.5 (I'm very proud that I was able to do so non-destructively, a feat of solder-sucking!) When I measure the pot, out of circuit, at the 2 o'clock position that gives me more-or-less balance, I get these values:
Between...
1 and 2: 8k18 (this varies from 18.4R to 9k05 L-R; "centre" is 7k20)
1 and 3: 9k02 (this is fixed)
6 and 5: 6k70 (this varies from 8k70 to 18.4R L-R; "centre" is 7k73)
6 and 4: 8k68 (this is fixed)
So to perfectly replicate the effect of the balance pot in the circuit, @nobeone has suggested on AudioFlat, you would do the following:
8.18k resistor in a standard value 8k2 between 1&2,
9.02k - 8.18k = 840 ohm resistor in a standard value 845R between 2&3
6.7k resistor in a standard value 6k65 or 6k8 between 6&5
8.68k - 6.7k = 1.98k in a standard value 1k96 or 2k between 5&4
...BUT it's a bit confusing to me why I would need so many resistors of different values...
...AND this doesn't correspond to what others have done: using only two resistors, and values around 1K2 (@neiljadman) or 2K6 (Acoustica).
Others have also suggested doing away with resistors entirely and linking directly...
So I'm wondering what others have done, what recommendations you'd make. The goal is not so much to replicate the exact effect of the balance pot as to do away with some of its inefficiencies (and not have to look at it cocked over to 2 o'clock all the time!) while also not messing up the circuit.
Of course it's possible the original issue is not the balance pot but some channel imbalance elsewhere in my system...
Like many people, to get "balance" on my 32.5, I have to have the balance pot at about 2 o'clock, which for obsessives like me is visually offensive I've also been wondering about the potential sonic advantages of using fixed resistors in place of the balance pot.
I found this brief mention of the mod on Acoustica:
remove the balance pot and replace with 2 welwyn rc 55y or any good quality resistors e.g vishay dale cmf55s. Try values around 2k67. Not tried this yet but apparently cleans up the sound a bit.
Thanks to Les Worstenholm
I also found a thread here on pfm in which there is some debate about the number (2? 4?) and value of resistors (@neiljadman recommends 1K2), and whether you'd need to use resistors at all.
We've been discussing this over on Audioflat, and here's what we figure so far.
Here's how we've numbered the 6 pins on the pot (1, 2, and 3 are the row hidden in this photo).
Based on values measured in circuit and on the visible traces in the image below, we figure this is what they all correspond to:
1 and 6 connect to ground (they have continuity in circuit)
3 and 4 are input signal from volume pot
2 and 5 are output from the wiper
Last night I removed the pot from my 32.5 (I'm very proud that I was able to do so non-destructively, a feat of solder-sucking!) When I measure the pot, out of circuit, at the 2 o'clock position that gives me more-or-less balance, I get these values:
Between...
1 and 2: 8k18 (this varies from 18.4R to 9k05 L-R; "centre" is 7k20)
1 and 3: 9k02 (this is fixed)
6 and 5: 6k70 (this varies from 8k70 to 18.4R L-R; "centre" is 7k73)
6 and 4: 8k68 (this is fixed)
So to perfectly replicate the effect of the balance pot in the circuit, @nobeone has suggested on AudioFlat, you would do the following:
8.18k resistor in a standard value 8k2 between 1&2,
9.02k - 8.18k = 840 ohm resistor in a standard value 845R between 2&3
6.7k resistor in a standard value 6k65 or 6k8 between 6&5
8.68k - 6.7k = 1.98k in a standard value 1k96 or 2k between 5&4
...BUT it's a bit confusing to me why I would need so many resistors of different values...
...AND this doesn't correspond to what others have done: using only two resistors, and values around 1K2 (@neiljadman) or 2K6 (Acoustica).
Others have also suggested doing away with resistors entirely and linking directly...
So I'm wondering what others have done, what recommendations you'd make. The goal is not so much to replicate the exact effect of the balance pot as to do away with some of its inefficiencies (and not have to look at it cocked over to 2 o'clock all the time!) while also not messing up the circuit.
Of course it's possible the original issue is not the balance pot but some channel imbalance elsewhere in my system...
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