Mods for a Dean Markley K-20X

Ok, I have a Dean Markley amp that I just love. But I want to mod it. First, a line out. This is the lineout I've come up with so far. Everything else on the schematic is original.

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So far I've added two 1/4" jacks to the back of the amp. One for power from the amp, and one to go to the internal speaker. I'll be adding the lineout also.

As far as other mods, I was thinking of swapping out the 2200uF/25v power supply caps with 6800uF/25v caps. I think it would give me more punch on the low end, acting like a stiffening cap along with the filtering it would do anyway. Think that would help or should I go larger?

btw, its a 15wRMS amplifier.

I would suggest you don't connect the line out socket directly like that, it will load the existing signal and make it quieter. Either add a series resistor (which will make the line output signal smaller), or (preferably) add a buffer to feed the line out.

As for the power supply caps, I doubt you would hear any difference?, but it won't do any harm, and it's 'technically' an improvement!.

How about doing it like they do in the K20B?

**broken link removed**

That's fine, it's an attenuator off the speaker output - the power amplifier acts as a buffer, and the attenuator isolates it as well.

Cool, I'll do it that way then. Would it have an adverse effect if I only used the line out and the speaker was disconnected?

joecool85 said:

Cool, I'll do it that way then. Would it have an adverse effect if I only used the line out and the speaker was disconnected?

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No, it would be fine - it's only valve amps that don't like O/C loads.

Thanks, thats what I thought.

One more question. I'd like to set it up with a footswitch to switch between the clean and OD channels. Right now, as you can tell in the schematic, it uses a DPDT to switch between channels...is there a way to set it up so that when I plug in a footswitch pedal (which I would make) I can remotely change channels on it? A lot of amps have that, and its really nice.

joecool85 said:

Thanks, thats what I thought.

One more question. I'd like to set it up with a footswitch to switch between the clean and OD channels. Right now, as you can tell in the schematic, it uses a DPDT to switch between channels...is there a way to set it up so that when I plug in a footswitch pedal (which I would make) I can remotely change channels on it? A lot of amps have that, and its really nice.

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Replace the switch with a relay, and use the footswitch to switch the relay. Some footswitches are latching, some are momentary contact, a latching one would make it much easier!.

Yeah, shortly after I posted that, I figured out the relay thing lol.

Will the 1k resistor to ground off the positive on the line out bother the load of the amp? I mean, its rated for 4-8 ohms, wouldn't that effectively give it a 1k load?

joecool85 said:

Yeah, shortly after I posted that, I figured out the relay thing lol.

Will the 1k resistor to ground off the positive on the line out bother the load of the amp? I mean, its rated for 4-8 ohms, wouldn't that effectively give it a 1k load?

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Actually it will give an 11K load (as the 10K is in series with it), however this will reduce depending what you plug in to the line out - but can never drop below 10K.

It's no problem whatsoever!.

But the TDA2030 in the amp puts out 8watts at 8 ohms and 14watts at 4ohms...wouldn't it put out next to nothing at that much resistance?

joecool85 said:

But the TDA2030 in the amp puts out 8watts at 8 ohms and 14watts at 4ohms...wouldn't it put out next to nothing at that much resistance?

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It will put out VOLTAGE! - which is what you want for a line output signal - it's not supposed to provide power to feed a speaker!.

But it taps the + on the speaker out...what I'm getting at is wouldn't it kill the amount of wattage going to the speaker? I know the line out doesn't need tons of power lol.

joecool85 said:

But it taps the + on the speaker out...what I'm getting at is wouldn't it kill the amount of wattage going to the speaker? I know the line out doesn't need tons of power lol.

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No, it's taking no power from the speaker at all, it will take a tiny amount more from the amp - but this is far too small to make any difference.

Good. Thanks for all the replies Nigel. It seems you are one of the only people on here that likes to respond to my questions

joecool85 said:

Good. Thanks for all the replies Nigel. It seems you are one of the only people on here that likes to respond to my questions

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Generally people will only join in if there's something to say, or have a different slant on an answer - but this is a very simple thread, and the answers are obvious. Presumably no one disagrees with me? :lol: yet!.

I'm also heavily involved in music with my 15 year old daughter, who regularly plays in a rock band called InBetween - next gig on Saturday as part of 'FebFest' a three day rock festival in Chesterfield.

She's bass player (a VERY! good bass player), and co-lead singer, she'll also be playing keyboards on some songs as they get more tracks together. They've currently got about 7 songs of their own, and about 7 covers.

So our house is full of musical gear :lol:

Amplifiers alone:

400+400W Behringer PA mixer/amp
120W Behringer bass combo
60W Fender keyboard combo (usually used for guitar)
300+300W slave amp
300W old mixer amp
120W old mixer amp
Bass practice combo
Two guitar practice combos

Instruments include:

Yamahe digital piano
5 string bass
4 string bass
Acoustic 4 string bass
Acoustic guitar
Two electric guitars
Flute
Two Yamaha keyboards
Two Casio keyboards

So far I've resisted buying a drum kit! - although she's currently drumming and singing 'Hey Jude' in music class at school.

Wow, thats cool. Right now I have two guitars, a Hamer strat knock off, and a Lyon LG-4. I love the Lyon, any guitar with dual humbuckers is my thing As far as amps I have a couple 1/2w little gem amps that I've built, a dean markley K-20X 15w amp, and I'm building a 50w chip amp to use as a power amp to hook to the lineout on my K-20X. Hooked to that will be a Dean Markley K-110XT cab. I have to say, Dean Markley equiptment is really my thing lol.

Well, I did it and worked the values to get it sounding right. I'm using a 1k resistor from the + speaker to the + on the lineout, and then a 270ohm resistor from + lineout to ground. It works great.

I lined it out to a Fender 30w SideKick bass amp I was fixing for my brother, sounds so sweet

Dean Markley K-20X

Greetings one and all! Cool web site! I am new to this site, but have been messing around with electronics for years. Thus I would say I'm an inexperienced tinker.
But, I digress, I am looking for a schematic for a Dean Markley K-20X amp, as well as any info on cheep mods to the power output of this amp.
I need between 50 and 100 watts, as a stage monitor for a Kurzweil SP76. Have to be able to hear keyboards on stage, (2-lead gituars w/100+ watts) and yes, I intend to make a cab with a good 12" spk. to handle the output. Anybody out there got any suggestions/help? Thanks

Nigel Goodwin said:

Generally people will only join in if there's something to say, or have a different slant on an answer -

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but it's a solid state amp; no tubes?

at my house we have:

my daughter:
Marshall amp & Fender Squier "Strat" guitar

me:
Cerwin Vega C30 cabinet
Promaster cabinet (stacks atop the CV cabinet)
Kustom 100w PA/mixer head
McIntosh MC60 tube amp
RAMSA 150w system amp
Electro Voice mics.
RCA ribbon mic (for vocal recordings)
JBL stage monitors
Univox practice amp
Yamaha keyboard
2 lap dulcimers
12-string acoustic
1963 original Fender Strat (not a reissue)