Need help with a Vintage Kustom amp. (K250-1)

Discussion in 'Amps and Cabs [BG]' started by _derubermensch, Jul 27, 2019.

  1. _derubermensch


    Jul 27, 2019
    Related Photos

    Hey all, yesterday I was lucky enough to aquire a Kustom 250 bass head for 100$. Now the only problem is that I am having a hard time wrapping my head around a few of its features, and was wondering if any of you lovely people might have some of the answers I've been looking for.

    1: The amplifier has two channels, with 2 inputs a channel. What on earth are these meant to accomplish over just having 1 input with a channel selector switch?

    2: The first channel has a 'Selectone' knob that can be put on settings 1, 2 and 3. After playing around with it, the sound gets thinner the higher up I go. Is there a name for this "Effect"?

    3: Beside the settings for the two channels, there is a toggle button that says 'Polarity'. I couldn't tell any difference between sounds when it was toggled on/off. What is its intended purpose?

    4: Moving to the back panel now, there are a few inputs/outputs I have questions about. There is a 6.3mm jack that is labelled 'To Module Input'. What is the intended purpose of this?

    5: A 6.3mm jack labelled 'To Tape Record' I have never seen a tape recorder with a 6.3mm input jack?

    6: And finally, the speaker output. It claims to have an output of '3-4 ohm'. What type of speaker uses 3 ohm?

    Any help with any of these questions would be greatly appreciated!
  2. buldog5151bass

    buldog5151bass Kibble, milkbones, and P Basses. And redheads.

    Oct 22, 2003
    In the not so good old days, not everything was properly grounded. If the power cord isn't three prong, replace it. Shocks are not fun.
  3. _derubermensch


    Jul 27, 2019
    Don't worry, I was fortunate enough to get a head with a 3 prong cord. Speaking of the cord, I live overseas and just realized that I should probably ask: Will it work just as well if I use an adapter?
  4. Wasnex


    Dec 25, 2011
    Here's a webpage you may find useful: Welcome to VintageKustom.Com!

    They have a web board but the interface is pretty clunky. There are also schematics in the technical section.

    1. The idea is you can play two instruments at the same time. When this amp was made, it was not unusual to play an instrument and run a high Z mic into your amp so you could sing. The two input jacks are set with different sensitivities.
    2. I originally thought Selectone might be a variable HPF, but according to this page, it changes the frequency centers of the tone controls. Welcome to VintageKustom.Com! Open the link ad in the frames on the left click Literature and then click Kasino. Next open the link with the girl on the cover and there is graphic that shows what Selectone does. Click the link with the graphic with two shades of brown and white hill tops.
    3. I believe the polarity is related to the power supply. In the old days amps had two prong plugs that were not polarized. In other words you could plug them in both ways. The polarity switch changes which side of the AC line a small capacitor is connected too. If you amp still has a two prong plug, send it to a shop because it is dangerous. It's likely they will clip the polarity cap out so the switch will not do anything.
    4. I found one webpage that suggest this is for connecting powered "slave" cabs. Repairing Kustom Amps ยป K250-1 bass head In other words, it's basically a "slave" out.
    5. That's why they make adapters.
    6. I recommend treating the amp as 4 ohms minimum. I went through the web board a few months back and the company claimed the amp would support lower impedance but the design is not well heatsinked. FYI Kustom offered cabs with three 15s. 8/3=2.7ohms.