Kenwood Basic c2 balance adjustment pot

[jnygrgrs]

Yep. In essence it's a headphone version of the Output jacks on the back.. I could've piggy-backed onto those for an easier solution but of course this is cleaner.

For what it's worth, I used the C2 to replace a Art DJ 2 Pre phono preamp and a Liquid Spark headphone amp (also serving as speaker preamp). As a speaker preamp and phono preamp the C2 is a great upgrade. I hooked up an RCA switcher to listen to the Liquid Spark and C2 headphone jacks back and forth from the same DAC source (on a couple of pairs of headphones) and could not tell any difference whatsoever. So good work against this well-regarded modern headphone amp.

 

[vsat88]

I have owned a good few preamps and so far I always go back to the fully restored C2. There is a lot of work involved in building one right but there reward.....

 

[dave99]

Sorry, lost track of this thread. Glad everyone found this balance pot useful. Still one of the better preamps around when everything works

 

[dane79]

DRM audio came out with a replacement pretty recently, always exciting to see what he's making

 

[vsat88]

Damn ! I will have to call Dan and see how he sneaked that past me.

 

[dave99]

DRM audio came out with a replacement pretty recently, always exciting to see what he's making

Excellent, I have a C2 where the loudness switch doesn’t latch. This would be perfect. Thanks.

 

[vsat88]

Guaranteed to bolt up solder in and work perfectly 1st time if Dan sells it. Not affiliated but I know him and I have bought enough from him to know how good his stuff is.

 

[dave99]

Guaranteed to bolt up solder in and work perfectly 1st time if Dan sells it. Not affiliated but I know him and I have bought enough from him to know how good his stuff is.

Yes great products from him. I just ordered 2 of them. That’ll fix my loudness that doesn’t latch on one and fix up both balance pots.

 

[vsat88]

Yep, they are very good preamplifiers both the C1 and C2. Anything but basic. I no longer run one went with all USA made gear. Running a Forté F 44 and a Aragon 28K MKII now but I still have 2 C2's and a C1. Never know right ?

 

[dave99]

Thanks. Does anyone have any idea what available part might work as a headphone volume replacement? Or perhaps a way I could bypass the pot? It's fine if that pot is always maxed since the main volume knob always affects the headphone volume... I guess all that is lost is varying the volume of the headphones while the speakers are in use, but I've no need for doing that.

The service manual calls for a 50K pot. Mouser https://www.mouser.com/ProductDetail/652-PTR902-2020FA503 fits and works, and it even clicks off. The following needs to be done;

1. The pot has 2 locator legs on the bottom rear. Clip those off.
2. The pot is longer than the original so C46 and R63 needs to be moved to the other side of the board. Make sure you maintain the correct polarity for the cap. Make sure the legs of the cap and resistor don’t extend past flush as the pot will hit the legs and not fit flush.
3. This now clears enough space to mount and solder the new volume pot flush on the board.
4. Since the Bournes pot is keyed differently, the notch on the volume knob will be at the 1 o’clock position when off. Exactly 180 degrees out from the original.

edit; need to add to leave the cap legs a bit long as you need to bend the cap over to give enough clearance so it doesn’t hit the power switch when the headphone amp board is reinstalled.

 

[jnygrgrs]

Have bypassed the pot for now (looking at bottom of board with the 6 pot pins at the bottom right, jumpered the first two of each row together). This will work for my use. The main volume knob is always in play here. I tested some low and high-power headphones and both play well, getting very loud without distorting (don't really have to ever go above 12:00 on the knob) so I don't think any resistors are needed.

Following up on this while I'm here. I eventually replaced the little headphone board with DRM Audio's recently introduced replacement and that works great. It's a much improved socket too for what it's worth!

 

[vsat88]

The repair you did was just alright I mean. Must have missed that one somehow. Good show. And look at Dan. He has made up a phono board and I had no idea about that one either. Moved to all USA built equipment a while back and have not been paying attention. I better keep my eyes cracked open!

 

[jnygrgrs]

Yeah I was fine without an independent headphone volume... but added on the part when I finally needed a balance pot replacement. Well worth doing. Picked up a cap kit too, why not. Will need it eventually. Wish me luck with that lol

 

[vsat88]

You won't have no trouble installing that cap kit! I could easily place an order with Digikey or Mouser for all the caps I need for a C 1 or 2 but I use Dan's service for everything Kenwood Basic. He is an awesome guy and his prices are good too.

 

[EC1]

sorry to bring back this old post, ordered the balance pot replacement per @dave99, FA204/200k and FB104/100k just to see which might work better. However the parts I received are somewhat different from Dave post.
the 200k shaft length is actually almost identical to the original. 15mm excluding the thread. The 100k is actually 10mm long, 5 mm short of the original.
the 200k center is actually not the center, that is why Dave and @ricki unit needs to be turned to 9.5 balance point. I installed that 200k and the result comes out exact the same as theirs.
the 100k center is actually the center point. So i took the 200k off and install the 100k one with no idea what will happen with the lower resistance one. It turned out working the same with only the knob is now in flat position for center balance point. See pic.
I cant tell anything difference sound quality wise. Don’t have good trained ears.
I also measure all resistance of these 3 pots at different rot position with the original pot is not working condition (no sound from right channel). Not sure do these make anything sense and forgive my lousy handwriting.
Just want to share.

 

[Artopsy]

Don't know how I missed DRMaudio. great resource. i think my C2 has a bad headphone pot or board so
and my M1A has bad speaker terminals

 

[Artopsy]

Here's my story
I purchased an M1A a while back to scavenge for parts to fix my 880SD. The M1A is repairable but I had no preamp. recently I acquired a C2 with a bunch of other stuff I have started selling off. The C2 looks really clean inside happily. I have no way to test it till my M1A is fixed. I have tried a couple things; The tape outs work well. The head phones though are really weak on the the left channel I imagine a headphone board from DRM will fix that.
My question; Is it a general rule that the headphone amp and the pre amp outs are quite separated? meaning, just because the headphones don't work right, doesn't mean the preamp outs have any issues, especially since the tape outs are clean audio.

 

[rickl]

My question; Is it a general rule that the headphone amp and the pre amp outs are quite separated? meaning, just because the headphones don't work right, doesn't mean the preamp outs have any issues, especially since the tape outs are clean audio.

The headphone signal splits off the preamp output (IC2) and runs through the level pot to an opamp to the headphone jack. Schematics are on hifiengine and akdatabase.

My guess cleaning the headphone level might fix your headphone problem. I don't recall using my headphone jack but the pre works great.

I bet you will enjoy your M1A/C2 combo.

 

[Artopsy]

The headphone signal splits off the preamp output (IC2) and runs through the level pot to an opamp to the headphone jack. Schematics are on hifiengine and akdatabase.

My guess cleaning the headphone level might fix your headphone problem. I don't recall using my headphone jack but the pre works great.

I bet you will enjoy your M1A/C2 combo.

The schematic appears (not that I'm great at understanding schematics) to show the headphone amp is isolated pretty much from the rest of the system.
The headphones go up and down in volume using the headphone pot.
Balancing to about 95% will balance the headphones, using the main balance pot. So I'm hoping the issue is isolated in the headphone amp board.

 

[Artopsy]

With Daniel being retired I decided I had one option to fix the balance pot. To open up an original balance pot even with the warnings of how fiddly it is in there. Well I just finished one balance pot using this as reference https://audiokarma.org/forums/index.php?threads/kenwood-basic-c2-restoration.730787/post-9905847 it works !!
It is not so difficult. 5x jewelers loupe, a dremel, a couple toothpicks, a teeny tiny screwdriver, some JB weld and patience.
Just a note to add to the reference above. I am not sure you need to secure the case pins. all they really do is secure the alps product plate. the e clip hold the everything together well. Time will tell on this idea. two headphone volume pots and another balance pot to go.