B1 with Korg Triode

rmpfyf

Member
2015-12-27 6:28 am
Hi all,

I have a question for the DIY gurus here.

As noted in this thread I had built a second Korg B1 Nutube and gifted it my brother. After a faux-pas with a resistor purchase screw up, and some help from Ben Mah, I can say the unit is working fabulously.

Now I need some advice on a possible add-on L-R balance pot modification to the Korg in order to help my brother out. He has a slight hearing loss in his left ear. He audiologist determined that he has about a 25 db difference of hearing loss starting just above 10-kHz between his left and right ear.

What this translates too is that he needs to now position himself slightly closer to the left speaker to maintain true stereo. With his prior preamp he just simply adjusted the balance to favor the left channel ever so slightly. This was very convenient and helped tremendously with his hearing impairment. He doesn't really have the capability to rearrange the current listening environment (it's shared and not a dedicated sound room) because of the way the furniture in the room is setup.

So I was thinking that it would make more sense to add a balance pot to the unit, but would like to seek some guidance on the feasibility or pitfalls of adding such a modification.

Please let me know what you guys think.

Kind Regards,
If there's a digital source involved - particularly something with a PC at some stage - creating a response curve for him upstream of it all is a good way. You're possibly after EQ - not just balance.
 

rmpfyf

Member
2015-12-27 6:28 am
Keen to thank @pitbul in particular for helping to get mine running at a good level. It's unexpected, I throught it'd be noisier and more of a plaything than a serious device. @Nelson Pass is correct in his notes; a little here or there is good (IMO it's not best used when distorting the signal as much as possible).

Not going to build this one out with last-word parts - what's in the kit is already pretty good and I think the ultimate potential is greater with my DCB1 (though this thing is a lot of fun!) - will do what a few other have done and try get a little more detail out of it with bypass caps. I'm out of Pana ECQPs so I've some Wima FKPs on the way to play with (I'm sure it's possible to spend more and e.g. replace the kit Nichicon's with some poly audiophile caps, but I don't think the gains are going to be 'huge' relative to other pre designs). Maybe a CLC filter after the wall wart too. Let's see.
 
You might want to try two separate volume controls, one for left and one for right.

Thanks Elwood. That's an interesting possibility and would be quite simple and cheap to initiate with the quality Alps volume pot. This is in the hunt.
see https://eu.mouser.com/c/?q=balance potentiometer

take 100K

if you can't manage with datasheet how to wire it, just say
Hi Zen, As mentioned in my reply to Elwood I like the idea of using the good quality Alps volume potentiometer. Do you think using the cheaper Digi-key balance pots would be on par with the Alps volume pots?

If there's a digital source involved - particularly something with a PC at some stage - creating a response curve for him upstream of it all is a good way. You're possibly after EQ - not just balance.
Yes, rmpfyf a digital source is being used for one of the inputs and that is a source from a PC using "Foobar2000" and a DAC. Foobar2000 has a component download that is used in the Active DSP which allows for a digital balance control.

The issue of not being able to shift the balance arises with the other input which has a Project Audio stand alone phono stage connected to it. It has no balance control. His previous system (Anthem Pre-2L) setup had a balance control, but no phono stage.
 

Ixnay

Member
2020-07-16 2:39 am
Just jumping in here about a balance control possibility. Remember when they stacked volume controls in a way that there were two knobs, one on top of the other? And there was sometimes a detent to keep them together as they were turned up or down. Since they were mechanically separate one or the other could be rotated, thereby adjusting the balance. Don't see them anymore, or maybe I just don't know where to look.
 
......

Hi Zen, As mentioned in my reply to Elwood I like the idea of using the good quality Alps volume potentiometer. Do you think using the cheaper Digi-key balance pots would be on par with the Alps volume pots?


........
well, they can be wired in common way (wiper to downstream signal, one end to GND, other end to signal source) or as variable resistor in series with signal , prior to your ALPS

routing signal through wiper-track contact is inevitable

maybe you can try finding blue ALPS balance pot

or use one blue ALPS per channel, in dual pot arrangement
 

rmpfyf

Member
2015-12-27 6:28 am
Yes, rmpfyf a digital source is being used for one of the inputs and that is a source from a PC using "Foobar2000" and a DAC. Foobar2000 has a component download that is used in the Active DSP which allows for a digital balance control.

The issue of not being able to shift the balance arises with the other input which has a Project Audio stand alone phono stage connected to it. It has no balance control. His previous system (Anthem Pre-2L) setup had a balance control, but no phono stage.

Ah. You could be super cheeky, get a good ADC happening and route the phono into the PC as an input :)

That asides a dual mono control seems the way to go, though it sounds as though EQ is required. Generating an inverse EQ curve pair for him would be fun for an afternoon and a microphone, though you could well get there. I've done something similar for a family member with hearing issues.
 
Search function is your friend... I would advise 2 mono pots to adjust volume, that will give you best sound while being adjustable as you fancy. Need though to be adjusted every time you adjust the volume, obviously.

Tocos makes some very nice mono pots, very affordable and excellent quality. Again, seacrh function is your friend...

Happy new year

Claude

EDIT: ah, didn't see Papa's reply, who was faster... and does that on some of his units! That's the idea I tried to describe.
 
well, they can be wired in common way (wiper to downstream signal, one end to GND, other end to signal source) or as variable resistor in series with signal , prior to your ALPS

routing signal through wiper-track contact is inevitable

maybe you can try finding blue ALPS balance pot

or use one blue ALPS per channel, in dual pot arrangement
Hi Zen, would this blue dual unit Alps pot you are talking about? The RK27112A00AK from Mouser?

I believe this is what is currently supplied in the DIY Store Korg B1 kit and I'm pretty sure that's the one I purchased from Digi-key to complete my brothers Korg.

So I would just need to get another one and the RK27 Breakout PCB and rearrange either the L-in or R-in off the Korg PCB to the proper solder points (say A-in and Com) on RK27 PCB?

https://www.mouser.com/ProductDetai...MIo4fVjIr61AIVk0oNCh3x1QkVEAQYASABEgI2wPD_BwE
 
Search function is your friend... I would advise 2 mono pots to adjust volume, that will give you best sound while being adjustable as you fancy. Need though to be adjusted every time you adjust the volume, obviously.

Tocos makes some very nice mono pots, very affordable and excellent quality. Again, seacrh function is your friend...

Happy new year

Claude

EDIT: ah, didn't see Papa's reply, who was faster... and does that on some of his units! That's the idea I tried to describe.
Claude, wouldn't just using one half of two Alps RK27 accomplish the same thing?
 
Ah. You could be super cheeky, get a good ADC happening and route the phono into the PC as an input :)

That asides a dual mono control seems the way to go, though it sounds as though EQ is required. Generating an inverse EQ curve pair for him would be fun for an afternoon and a microphone, though you could well get there. I've done something similar for a family member with hearing issues.
Yes, unfortunately hearing issues are going to affect us all sooner or later, sad to say.
 

pitbul

Member
2011-07-29 9:34 am
@Benjisan
What you will have to do is marking on front side to position the pots to the right value (or whatever you call).
I think that this volume stereo pot is intended for volume regulation. If you think that you will adjust level by your ear you destroy somebody's musical performance.
Not all music have equal level on L & R channel. With stereo pot you adjust divided value by single turn. Don't care about absolute value of the pots, they will divide signal pretty close.
 
you're underestimating human cognitive capacity in context of differentiation

same as was the case with some FM tuners of Yore ( Quad FM3 as best known one) which had two bulbs working in unison to show center tuning - it is centered when they're equally lit - your brain is good enough to discern slight difference in loudness between two sources close to each other - your speakers actually

just matter of getting used on routine ; especially useful when using pots in lower range, where many even expensive ones are showing worsening of tracking between channels/sections

I have years of work in Radio production - panorama pots and balance pots are piece of cake to use, for whatever you need them, and ears are better than VU or Peak meters, for that sort of task