Mods for a Dean Markley K-20X - Electronic Circuits Projects Diagrams Free

joecool85 · 21st February 2006, 03:30 PM

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.

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.

**Nigel Goodwin** · 21st February 2006, 04:26 PM

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!.

joecool85 · 21st February 2006, 04:57 PM

How about doing it like they do in the K20B?

**Nigel Goodwin** · 21st February 2006, 06:47 PM

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.

joecool85 · 21st February 2006, 08:12 PM

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?

**Nigel Goodwin** · 22nd February 2006, 09:26 AM

Quote:

Originally Posted by joecool85

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?

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

joecool85 · 22nd February 2006, 12:35 PM

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.

**Nigel Goodwin** · 22nd February 2006, 12:38 PM

Quote:

Originally Posted by joecool85

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.

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!.

joecool85 · 22nd February 2006, 09:28 PM

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?

**Nigel Goodwin** · 22nd February 2006, 10:04 PM

Quote:

Originally Posted by joecool85

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?

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!.

joecool85 · 22nd February 2006, 10:50 PM

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?

**Nigel Goodwin** · 23rd February 2006, 10:46 AM

Quote:

Originally Posted by joecool85

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?

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!.

joecool85 · 23rd February 2006, 12:59 PM

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.

**Nigel Goodwin** · 23rd February 2006, 03:17 PM

Quote:

Originally Posted by joecool85

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.

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.

joecool85 · 23rd February 2006, 03:22 PM

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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21st February 2006, 03:30 PM	(permalink)
joecool85	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. 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. __________________ Life is what you make it.

21st February 2006, 04:26 PM	(permalink)
Nigel Goodwin	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!. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

21st February 2006, 04:57 PM	(permalink)
joecool85	How about doing it like they do in the K20B? __________________ Life is what you make it.

21st February 2006, 06:47 PM	(permalink)
Nigel Goodwin	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. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

21st February 2006, 08:12 PM	(permalink)
joecool85	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? __________________ Life is what you make it.

22nd February 2006, 12:35 PM	(permalink)
joecool85	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. __________________ Life is what you make it.

22nd February 2006, 09:28 PM	(permalink)
joecool85	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? __________________ Life is what you make it.

22nd February 2006, 10:50 PM	(permalink)
joecool85	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? __________________ Life is what you make it.

23rd February 2006, 12:59 PM	(permalink)
joecool85	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. __________________ Life is what you make it.

23rd February 2006, 03:22 PM	(permalink)
joecool85	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 :-) __________________ Life is what you make it.