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  #1  
Old 17th July 2016, 10:28 PM
Kyron Kyron is offline
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Smile Wiring a Volume control to KaT 6550

Sorry, I think I posted this in the wrong section previously!
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Hi there,
I'm already eager to get playing with my newly acquired KaT6550 amplifier (thanks again, Gary); I would like to install a volume control POT.

I'm not looking for information on chassis/front panel modification, but just a KiT 6550 wiring diagram and/or POT specifications.

Any other useful advice is greatly appreciated,

Thanks in advance,

Kyron
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  #2  
Old 18th July 2016, 08:12 AM
bob orbell bob orbell is online now
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Default Re: Wiring a Volume control to KaT 6550

Hi Kyron, how about a cheap passive Pre? BOB
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Old 19th July 2016, 08:34 PM
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Phil Y Phil Y is offline
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Default Re: Wiring a Volume control to KaT 6550

Hi Kyron,

Are you sure you only want 1input ? If so, then a 50K "Alps blue" pot mounted in the front panel would be fine. My preference would be to build a passive pre as BOB suggests. It will then cope with most of what you might want to do in the future.

Phil.
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  #4  
Old 19th July 2016, 11:17 PM
Kyron Kyron is offline
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Default Re: Wiring a Volume control to KaT 6550

Hi all,
Thanks for the responses.

I am planning to use this amp in my studio; for this purpose, it only requires the one input.
My KEL84 will provide my multiple source needs for now.

Phil,
I'd like to wire the pot outboard, into a separate box; perhaps a hammond 1590a/b style enclosure, or fancier EMC shielded equivalent- This would suit the studio application well
What are your thoughts on this?
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Old 20th July 2016, 02:59 PM
Richard Richard is offline
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Default Re: Wiring a Volume control to KaT 6550

Hi Kyron,

I ran a CDp and Tuner into my power amps for a long time via a "passive pre" or "pot in the box" volume control and selector switch.

You'll find various opinions on how well they work but ideally they need low output impedance sources such as solid state tuners, CDp, etc (<1K) and high input impedance power amps such as valve amps (>100K) with a suitable value pot usually 50K or 100K. Connect with short low capacitance interconnects and the results can be very good indeed. Get it wrong and they can sound weak and insipid.

(If a low input impedance power amp is used, such as the 20K of many ss amps, a 10K pot with ss source may still be fine.)

What source will you use?

Here is a drawing and my first effort in Maplin 6" x 4" x 2" box. It looks basic but worked very well indeed using ss sources into a 100K Panasonic pot and 1M valve power amps via low cap cable.

Wiring is enameled "solder through" magnet wire from Maplin, very easy to use.
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File Type: jpg potin.jpg (39.5 KB, 28 views)
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Old 20th July 2016, 03:03 PM
Richard Richard is offline
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Default Re: Wiring a Volume control to KaT 6550

I later tidied it up by turning the box around and fitting a perspex plate, rubber feet, and stick on weights inside to stop it moving around!

I also changed the standard wired pot to a shunt wired pot working against a fixed resistor.
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Old 21st July 2016, 12:11 AM
Kyron Kyron is offline
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Thumbs up Re: Wiring a Volume control to KaT 6550

Thanks for the advice Richard.
After some further discussion with Phil Y tonight, I've got a good idea of what I need now.
My TC Electronics 24d Audio Interface has a 100ohm lineout impedance (let's refer to this as 'source' impedance); after studying the KaT 6550 schematic/BOM, I believe that the input impedance is 100kohm.
I am now of the opinion that a Pot with a 'mid-point' impedance value, that is between the source and input impedances, would be of preference here.
The Pot I am intending to use is an Alps (Blu) 50kx2 (not 100% sure of part number yet; conflicting info online).

I intend to mount the chosen Pot into a diecast enclosure, and wire to neutrik RCA sockets etc.

Thank you for your help so far, and please feel free to correct any of the above
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Old 21st July 2016, 01:55 AM
Richard Richard is offline
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Default Re: Wiring a Volume control to KaT 6550

That sounds fine
RS have the pot as 236-9604
Kat6550 is line sensitive 500mV so have you tried the 24D line op straight into Kat using the output level on the front of 24D?
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Old 21st July 2016, 08:56 AM
Kyron Kyron is offline
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Default Re: Wiring a Volume control to KaT 6550

I didn't really think of using the 24d's output control...

I could give it a try; are there any risks associated with this? Or any pros/cons to not using the 'pot box' and just using the 24d output?
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  #10  
Old 21st July 2016, 10:04 AM
Richard Richard is offline
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Default Re: Wiring a Volume control to KaT 6550

Pros and cons,

I suppose there's a chance the line stage may not be stable into high impedance. It will be expecting a 20K load in its solid state world but Kat's 100K should not do any harm if you start low and turn it up gently. You can easily change Kat's 100K resistors for 20Ks later if you wanted to use it that way long term. Signal-wise that would be the minimalist set up and I personally would try it if only to see what levels I had to play with and if a pot later might be useful.

With a passive pre volume control inline you'd be hooked up the same way with the source output level first set on the 24D. The volume pot inline appears parallel to Kat 100K input so a 50K pot would drop Kat input to around 35K, or you could use a 20K pot. Interconnects and pot positioning may have an influence. Integrated into the amp with very short connections the vol pot and amp input appears as one load. Set the other end on long interconnects though and the pot may influence source impedance and vary as volume level is set. That said, short interconnects will probably show little difference.
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