CTS custom potmeters

Custom CTS potmeters are now available.

Custom CTS vs standard CTS

Regular standard CTS potmeters are very common used in electric (bass) guitars, and they work just fine, but some people who has used them might have noticed a variation in resistance value and taper curve.

A standard CTS potmeter have a big variation of +/- 20% in the real resistor value as you measure a few potmeters of the same listed value. The new custom CTS potmeters have only a +/- 9% variation. The real value is more close to the listed value.
The custom CTS potmeters also never get a lower resistance than 250k or 500k, and have a custom taper curve that is suitable for both volume and tone control.
Here is a summary:

name use curve value tolerance measured value
CTS 250k audio potmeter volume logarithmic 250k +/- 20% 200k – 300k
CTS 250k linair potmeter tone linair 250k +/- 20% 200k – 300k
CTS 500k audio potmeter volume logarithmic 500k +/- 20% 400k – 600k
CTS 500k linair potmeter tone linair 500k +/- 20% 400k – 600k
CTS 250k custom potmeter volume & tone custom 275k +/- 9% 250 – 300k
CTS 500k custom potmeter volume & tone custom 550k +/- 9% 500 – 600k

What value should you choose?

A potmeter, when turned at volume 100% will cut off a little bit of treble from the sound. If you connect the pickup straight  (without a potmeter) to the output, it will sound a little more bright. The lower the value of the potmeter, the more the treble cutoff will be. A 250k potmeter will cut off more treble than a 500k potmeter.

In general, a 500k potmeter is used with a humbucker and P90 pickup, and a 250k potmeter with a Fender style single coil pickup and most bass guitars.

There is no hard rule, a Jazzmaster has 1M (1000k) potmeters in the lower sound controls. Many strats with a humbucker bridge pickup have still a 250k potmeter.

When your pickup sounds a touch too bright, you could try to change the potmeter to a 250k value.
When the pickup sounds muddy and dull you could try to replace the potmeter by 500k value.

If you have questions feel free to contact me a info@fernsguitars.nl

CTS potmeters can be ordered here:

http://www.fernsguitars.nl/nl/webwinkel/webwinkel.php?cat=42 (Dutch)

http://www.fernsguitars.nl/en/webshop/webshop.php?cat=42 (international)


50’s De-Armond pickups.

DeArmond pickups from the 50’s are considered the sweetest sounding transducers ever made for jazz guitars among many musicians. The pickup came in many variations and sometimes I get them in the workshop for repairs. Most common is the famous “Guitar Mike”.

This Gibson L5 is fit with a model 1000 “Rhythm Chief”. My job was to re-install the pickup permanent on the instrument without the sliding attachment and the volume and tone control. To do so, we decided to drill a bigger hole in the tailpiece to fix a Switchctaft output jack / strapholder combination. The pickup would be fixed on the body with double sided tape. A piece of very sensitive masking tape would protect the guitar finish.


I tested the pickup, fixed the new output jack, removed the controls from the pickup, connected the pickup and…no sound! I called the customer to tell the bad news and we decided to open the pickup – at the customers risk. DeArmond pickups have been made with extremely thin wires and because they are almost 70 years old, the insulation around the wires can be dry and easy to damage. Some pickups just die when you look at them.


After opening the pickup I connected a temporal connector, and the pickup just worked. After closing the pickup – no signal. After a close look and some physical tests ( pressing here and there, moving the cable) it seemed to be a thin wire got disconnected after pressing the side of the pickup. Because the pickup has been waxed (probably not original) we decided to leave the pickup and make the cover a bit wider so it would not clamp the side too much. I made a small piece of brass to slide in the side to keep the cover on the pickup. This worked. After attaching the pickup secure to the Gibson L5 the customer has a semi-permanent fixed system in wich he doesn’t need to be afraid of broken cables, another common problem with older DeArmond pickups.


This operation shows how careful you have to be with the pickup and how sensitive the material is. To rewind the coil is another problem; most pickup builders refuse them as it takes sometimes over 10 tries to make a new one.

Here is a 50’s DeArmond Guitar Mike, I had to replace the cable. When replacing the cable (original 50’s too) the insulation within the cable just came out like powder, making the cable worthless. To replace the cable, you have to careful open the pickup. This one has not been waxed, and makes it possible to re-solder the wires directly to the coil. This is still a tricky job, if you damage them or if you are shakey with the soldering iron it can end up in the trash bin.



Vigier output modification

For all of you people who own a Vigier guitar and get nuts from the output getting loose all the time. For this particulair guitar it is very hard to tighten the jack again. Here is a simple modification.

1. This output is used standard in the guitar. It is a Switchcraft tube jack that can be only tighten from the inside of the guitar. And there, in the electronic cavety there is no space to use standard wrenches or plyers.
If you are not careful you ruin the thread and have to drill out the complete jack.

2. I replace them by a Switchcraft tube jack that is used for acoustic guitars, the ones that are output and strap holder.

3. I remove the strap holder washer and just fit the tube in the guitar. It now can be tighten from the outside with a regular 13mm pipe wrench, although you want to hold it from the inside to not twist and loose your electronic connections.

It might not look THAT pretty; it is very practical, and to connect the cable is really no problem.