Thanks Robert8,
I will do some searching this evening and see if I can find a unit that will work with the B1. I had planned on pick up a Freya+ and decided to give the B1 a try. I am very pleased, the Freya may have to wait. Thanks again for all you help I very much appreciate it.
Oliver2112
I will do some searching this evening and see if I can find a unit that will work with the B1. I had planned on pick up a Freya+ and decided to give the B1 a try. I am very pleased, the Freya may have to wait. Thanks again for all you help I very much appreciate it.
Oliver2112
Good evening all,
Thanks again for all your help yesterday concerning my left/right imbalance output question. To recap, with the volume at zero as I increase volume the left speaker will begin to play while the right speaker has no sound. as I increase volume the right speaker will begin to play; however, there is a noticeable difference in output. It is annoying to say the least. Several members suggested a better potentiometer or a stepped attenuator.
While looking for options to replace the stock potentiometer, I decided to measure the resistance of the output for of the left and right channel. Here were the values
1.2 ohms left channel
1.8 ohms right channel
I am newbie, is this variance normal for the left and right channel and does this indicate the problem I am experiencing is caused by the potentiometer?
All values for T1 through T8 are in spec.
Thanks again, Oliver2112
Thanks again for all your help yesterday concerning my left/right imbalance output question. To recap, with the volume at zero as I increase volume the left speaker will begin to play while the right speaker has no sound. as I increase volume the right speaker will begin to play; however, there is a noticeable difference in output. It is annoying to say the least. Several members suggested a better potentiometer or a stepped attenuator.
While looking for options to replace the stock potentiometer, I decided to measure the resistance of the output for of the left and right channel. Here were the values
1.2 ohms left channel
1.8 ohms right channel
I am newbie, is this variance normal for the left and right channel and does this indicate the problem I am experiencing is caused by the potentiometer?
All values for T1 through T8 are in spec.
Thanks again, Oliver2112
I've seen specs for the RK27 that the tolerance is +/- 20%, but no tracking tolerance between gangs seems to be quoted. 20% of 1.5 ohms is 1.2 on the low end, and 1.8 of the high end. So it might be within tolerance but not clear what is the minimum resistance spec.
Thanks for the reply Halauhula,
I am going to replace the potentiometer, not sure with what just yet. As I mentioned, the difference in channel output is annoying.
Thanks again, Oliver2112
I am going to replace the potentiometer, not sure with what just yet. As I mentioned, the difference in channel output is annoying.
Thanks again, Oliver2112
As a stop gap, you could take some measurements over the range of your pot and choose a value of resistance to put in series to balance it out. It kind of depends on how linear the deviation from channel to channel is and where it is most irritating.
There also some inexpensive stepped attenuators on ebay, but you might find a reputable seller by searching on the forum.
There also some inexpensive stepped attenuators on ebay, but you might find a reputable seller by searching on the forum.
Love the idea of measurements to try and sort it out. Nothing below requires a reply. It might just be some fun for you.
Note - What you're describing could be due to the 'channel matching' of the pot as previously described. It happens. I'd still travel down the road of replacing it and/or altering a few things with some guidance. If you're going to go to the trouble of changing out the pot, you're going to have to desolder/resolder some wiring, and you likely won't be able to use the cool PCB for the Alps pot. So, maybe have some fun before you do that. Since you went to the trouble of taking some measurements, maybe take a few more... Who knows, you may save yourself the trouble of replacing the pot. Better yet, if you replace the pot, and it works; you'll have "before" and "after" measurements to show you what "good" and "bad" look like.
When you say you measured "the resistance of the output" - Did you measure it with a hand-held DMM? If so, where precisely were the probes, and how was your DMM set? Where was the volume knob set (since you're concerned about difference in volume at low levels)?
It might be fun to see if you can answer your own question re: "is this variance normal for the left and right channel and does this indicate the problem I am experiencing is caused by the potentiometer."
With the unit turned off and nothing connected to the inputs or outputs...
With the probes exactly where they were before for your previous measurements...
Start with the volume 'all the way down', and take measurements
Move the volume knob to roughly 'half way', and take measurements
Turn it 'all the way up', and take measurements
Do more measurements at various points if you like
Note the differences in the measurements. No need to report them here or answer. Did they change? Was it in a fixed ratio? Was one channel always precisely the same value greater than the other?
Those answers might help you to think through whether or not that particular measurement indicates anything related to your particular issue and/or if your measurement of the "output" was what you intended.
Viewing the wiring diagram in the build guide (the schematic does not show the 'volume pot') ... is the pot at the input or output?
If you were looking for a difference in resistance (due to the pot) between channels that could affect the volume at low levels, where and how might you measure that?
It might be useful to know (but perhaps unrelated) that at least one of my hand-held DMMs has pretty poor accuracy below 5 ohms => I would not trust that my measurements of 1.2 and 1.8 ohms were "really" different by that amount if I used that meter. It may also be fun and maybe even more useful to know that at the "lowest volumes" the resistance => signal attenuation is the highest.
Thought example - With a 10k pot... would the resistance in line with the input signal be closer to 10k ohms or 0 ohms for the "lowest" volume?
Have fun!
Maybe there's a thought or two in there that might provide some help. I can't be certain of your outcomes, but I doubt you'll harm yourself or your gear by having a bit of fun and taking a few more measurements.... again with it off and nothing else connected. 🙂
Note - What you're describing could be due to the 'channel matching' of the pot as previously described. It happens. I'd still travel down the road of replacing it and/or altering a few things with some guidance. If you're going to go to the trouble of changing out the pot, you're going to have to desolder/resolder some wiring, and you likely won't be able to use the cool PCB for the Alps pot. So, maybe have some fun before you do that. Since you went to the trouble of taking some measurements, maybe take a few more... Who knows, you may save yourself the trouble of replacing the pot. Better yet, if you replace the pot, and it works; you'll have "before" and "after" measurements to show you what "good" and "bad" look like.
When you say you measured "the resistance of the output" - Did you measure it with a hand-held DMM? If so, where precisely were the probes, and how was your DMM set? Where was the volume knob set (since you're concerned about difference in volume at low levels)?
It might be fun to see if you can answer your own question re: "is this variance normal for the left and right channel and does this indicate the problem I am experiencing is caused by the potentiometer."
With the unit turned off and nothing connected to the inputs or outputs...
With the probes exactly where they were before for your previous measurements...
Start with the volume 'all the way down', and take measurements
Move the volume knob to roughly 'half way', and take measurements
Turn it 'all the way up', and take measurements
Do more measurements at various points if you like
Note the differences in the measurements. No need to report them here or answer. Did they change? Was it in a fixed ratio? Was one channel always precisely the same value greater than the other?
Those answers might help you to think through whether or not that particular measurement indicates anything related to your particular issue and/or if your measurement of the "output" was what you intended.
Viewing the wiring diagram in the build guide (the schematic does not show the 'volume pot') ... is the pot at the input or output?
If you were looking for a difference in resistance (due to the pot) between channels that could affect the volume at low levels, where and how might you measure that?
It might be useful to know (but perhaps unrelated) that at least one of my hand-held DMMs has pretty poor accuracy below 5 ohms => I would not trust that my measurements of 1.2 and 1.8 ohms were "really" different by that amount if I used that meter. It may also be fun and maybe even more useful to know that at the "lowest volumes" the resistance => signal attenuation is the highest.
Thought example - With a 10k pot... would the resistance in line with the input signal be closer to 10k ohms or 0 ohms for the "lowest" volume?
Have fun!
Maybe there's a thought or two in there that might provide some help. I can't be certain of your outcomes, but I doubt you'll harm yourself or your gear by having a bit of fun and taking a few more measurements.... again with it off and nothing else connected. 🙂
Problem solved. At low volume levels the difference in resistance between the left and right channel is about 50 percent. At much higher volume levels the differential between the left and right channels is approximately 5 percent. I increased the volume of the B1 well beyond normal listing levels and controlled the output to the B1 with the computer. Magically, both speakers produce sound at the same time, so this is definitely a potentiometer problem. Thanks again for all your help diagnosing the problem.
Oliver2112
Oliver2112
Good morning ItsAllnMyHead,
I posted the above info before I read your post. To diagnose the problem, I did what described. Checked resistance at low and high volume levels and found at low volume levels the percent difference between the left and right channel was much greater than at high volume levels. Then set the B1 at a volume level well beyond normal listing levels and controlled the output to the B1 with my computer. Both speakers produced sound at the same time. I will be replacing the pot ASAP.
Thanks again for all your help, Oliver 2112
I posted the above info before I read your post. To diagnose the problem, I did what described. Checked resistance at low and high volume levels and found at low volume levels the percent difference between the left and right channel was much greater than at high volume levels. Then set the B1 at a volume level well beyond normal listing levels and controlled the output to the B1 with my computer. Both speakers produced sound at the same time. I will be replacing the pot ASAP.
Thanks again for all your help, Oliver 2112
Hello everyone,
I have a question on the power supply voltage for this preamp. I wonder if I can use a LiFePO4 battery instead of AC. The actual measured voltage of the battery is between 26 and 27 Volts depending on the charge. The preamp is specified for 24 Volts and my build works fine with the AC adapter. However my question is if I can apply 27 Volts instead and if any circuitry changes are needed before doing this. Sorry if this question has been asked before. I would appreciate any insights, links, or experiences you can share.
Thank you,
Alex
I have a question on the power supply voltage for this preamp. I wonder if I can use a LiFePO4 battery instead of AC. The actual measured voltage of the battery is between 26 and 27 Volts depending on the charge. The preamp is specified for 24 Volts and my build works fine with the AC adapter. However my question is if I can apply 27 Volts instead and if any circuitry changes are needed before doing this. Sorry if this question has been asked before. I would appreciate any insights, links, or experiences you can share.
Thank you,
Alex
you can use 27V instead of 24V
just re-set working points (with trimpots) and that's it
you can even increase 10R input resistor (first on rail) to decrease initial current rush to caps, simply because you have battery, hefty current source comparing to measly AC adapter
33R or so; 1W or more
just re-set working points (with trimpots) and that's it
you can even increase 10R input resistor (first on rail) to decrease initial current rush to caps, simply because you have battery, hefty current source comparing to measly AC adapter
33R or so; 1W or more
Hi all, I messed up one of the B1 Korg toggle switches, can someone give me a part number, hopefully I can get a replacement in he UK. Thanks.
Is It a good move to use a very powerfull powerbank at 24v (fluctuate Between 24v and 24.6v) or nothing substitute a good lps?
I could as well use the stock smps with po89 filter, but not sure which option Is the best Between the 3
I could as well use the stock smps with po89 filter, but not sure which option Is the best Between the 3
I tried several SMPS (more or less powerfull and low ripple ones) and "big regulated linear PS" and prefered the the std SMPS + filter combo in my set up.
IMHO once you add Mark's filter the differences between (good to excellent) SMPS vanishes, and the SMPS+Mark's filter+upgraded PS caps on the board makes such a good PS that I stopped worried about that section
All IME and just me
Claude
IMHO once you add Mark's filter the differences between (good to excellent) SMPS vanishes, and the SMPS+Mark's filter+upgraded PS caps on the board makes such a good PS that I stopped worried about that section
All IME and just me
Claude
Quick question about using a stepped attenuator. I have the A3 attenuator from Glassware on a Korg Nutube. I had it on hand so decided to use it.
only problem is that the attenuator at the lowest volume is too high going into my amp camp. I also had this issue on my BA3 preamp which is why I removed it.
I read a view people mentioning I can add a resistor for each channel between the switch and my attenuator.
Is this correct and how do I determine the value?
Or, could I change the value of the very first resistors for each channel on the A3?
only problem is that the attenuator at the lowest volume is too high going into my amp camp. I also had this issue on my BA3 preamp which is why I removed it.
I read a view people mentioning I can add a resistor for each channel between the switch and my attenuator.
Is this correct and how do I determine the value?
Or, could I change the value of the very first resistors for each channel on the A3?