| Classic Kustom PA Head with Lo-Z Jacks? [message #13869] |
Sat, 05 June 2010 00:57  |
Huskerbay
Messages: 8
Registered: April 2010
Location: Nebraska
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Junior Member |
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Early Kustom PA heads only had 1/4" high-impedance (hi-z) inputs, which limits their use with today's common low-impedance (lo-z) mics.
Chunky impedance converters at the end of each lo-z mic cord would work... but would also look tacky and be prone to breakage.
To keep the classic Kustom faceplate in tact, I'd consider adding XLR-3, lo-z jacks to the BACK panel of the PA head.
I welcome any input on these questions:
Q1) Is there enough space inside a Kustom 200 PA head (or similar vintage) to fit four, rear-facing, XLR-3 input jacks?
Q2) Would a simpler/better solution be to replace the original front panel 1/4" hi-z jacks with combo XLR +TRS 1/4" jacks on the front?
Q3) Is this strictly an "expert level" (professional amp tech) modification?
Q4) Would most amp techs charge as much as the PA head is worth to do this kind of mod?
Q5) Has anyone ever done a mod like this to a vintage Kustom PA?
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| Re: Classic Kustom PA Head with Lo-Z Jacks? [message #13870 is a reply to message #13869] |
Sat, 05 June 2010 08:34  |
pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi
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Senior Member |
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Huskerbay, You pose some interesting questions on converting a K200-5 PA to accept the Lo-z mic inputs. It would be much easier to do this to a K300 PA since it has dual 1/4" inputs. Space would not be a problem. I'm not a service tech, but some things to consider, space on the rear of the amp, you could use the area above the reverb footswitch jack to mount the four XLR chassis mount jacks. You would have to mount the four matching transformers somewhere inside the amp. I'd also be careful as to the location, mounting audio signals near the power transformer section might inject unwanted noise. Since the four 1/4" HI-z input jacks are short to ground type when not being used you would have to disconnect the shorting part of the 1/4" jack. Wire the Hi-z side of the transformer to each 1/4" jack, this would allow the use of either Lo-z Mic's from the back panel or HI-z mics, guitars, keys, etc. on the front panel. Removing the shorting part of the jacks, you would want to keep the volume control at zero on channels not being used to keep down noise.
The downside to doing this is, the cost of transformers, jacks, and labor. You really cut down the resale value. The PA heads bring on average between 125 and 200 depending on color and condition of the covering and working condition and if it's A or B model. I haven't priced a matching transformer lately, but @15.00 each you've added another 60.00 to the original cost of the PA and will loose at least that much and more if you ever want to sell the PA. I know I'd pass on buying one that's been converted.
To add the XLR feature, I'd make up a chassis box with the XLR jacks and transformers and run a mini 4 line 1/4" snake out the mic channel inputs. You don't alter the PA head, the 4 jack XLR box can be used on any future PA heads.
I hate using the long matching transformers, super long by the time you plug the mic cable to them and they are easily broken leaving the 1/4" plug inside the amp. I make up 2' audio patch cables, 1/4" female at one end, and 1/4" male at the other end. Using these takes the strain off the matching transformer at the 1/4" end and saves them from breakage.
You may want to consider adding a pre-amp out and power amp input jacks on the back. This gives you the option of using a PA as normal, and gives the option of inserting a echo, or graphic EQ between the channels and power amp. You could bybass the 4 mic channels and use a external PA Mixer that has the Lo-z mic inputs, more channels and effects to the internal power amp of the kustom. It also gives you the option of using the power amp as a slave amp to drive a pair of monitor speakers.
It's a simple conversion, two Switchcraft 12A 1/4 switching jacks, wire the switch tab of each jack together. Cut the blue wire that goes to the power amp, and wire each end of the cut wires to the tip side of each jack. It is a normal feed through until you use the plugs to route the signal to an external device, and feed it back to the power amp.
pleat
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| Re: Classic Kustom PA Head with Lo-Z Jacks? [message #13871 is a reply to message #13870] |
Sat, 05 June 2010 12:48 |
Huskerbay
Messages: 8
Registered: April 2010
Location: Nebraska
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Junior Member |
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Pleat:
Your idea of keeping the original Kustom PA hi-z jacks "as is" and creating a separate "impedance converter" box with a "mini-snake" makes great sense.
Thanks very much for this and your other mod suggestions!
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