Service Manual or Schematic for a tube overdrive mod please

slowtrain · Post by **slowtrain** » Sun Sep 14, 2014 9:04 am

Hi, I've read that the overdrive on the output tube of the King Korg isn't very good, and I'd like to take a look at the schematic or service manual to see if I can figure out a mod to make it better. I used to build tube guitar amps, and I modified my Hammond M3 preamp extensively, so I think I can figure out a good mod for it. A look inside would be good too if anyone has any pics or a link to a youtube video. If I figure something out, I'll post it here. Thanks, -Jim.

SanderXpander · Post by **SanderXpander** » Sun Sep 14, 2014 9:16 am

Maybe it would be good to try one first and see what you think?

slowtrain · Post by **slowtrain** » Sun Sep 14, 2014 10:11 am

I'd like to have the service manual either way, and I like a lot of overdrive. I like to modify tube circuits, so I think I'll figure out the mod. It will be easy to incorporate a true bypass, so it'll have an option to be completely stock.

SanderXpander · Post by **SanderXpander** » Sun Sep 14, 2014 11:20 am

Ok, well I don't dislike the one on mine but many people expect guitar amp style overdrive and as I'm sure you know a single 12AX7 tube mounted "preamp style" isn't really the same thing as a guitar amp with multiple pre and power tubes and a speaker.

slowtrain · Post by **slowtrain** » Sun Sep 14, 2014 11:48 am

True, but if I understand the circuit correctly, the tube is at the end, where there should be line level signal available. Which should be more than enough to overdrive any 12a_7 tube into complete saturation, and with a pot, it could have anywhere from compression/soft clipping to aysymmetrical clipping in between. I'm not familiar with the circuit though, so I'd like to get a schematic and service manual to work with.

slowtrain · Post by **slowtrain** » Sun Sep 14, 2014 10:03 pm

Nevermind. Apparently the service manuals are only for authorized service centers. Thanks anyway, -Jim

SanderXpander · Post by **SanderXpander** » Sun Sep 14, 2014 10:13 pm

Nevertheless, it's a standard 12AX7 and as far as I know there is an analog connection going in and coming out. Can't be hard to mod if you're so inclined. Just not sure I see the point.

slowtrain · Post by **slowtrain** » Sun Sep 14, 2014 10:23 pm

I just like to tinker with tube circuits. It's a hobby.

jimknopf · Post by **jimknopf** » Sun Sep 14, 2014 10:40 pm

The tube is one to the best working parts of the Kingkorg, and I ask myself what and where you read questionable things about it.

It does exactly what you expect: deliver saturation up to slight overdrive in one mode and crunchy warm overdrive in the second mode.

I guess it's the very last problem you should ever have with a KK, after programming all your own sounds, due to the limited offer of available presets, and doing that within limitations like only one available filter curve for both sound shaping and modulation etc..

slowtrain · Post by **slowtrain** » Sun Sep 14, 2014 11:13 pm

slowtrain wrote:I just like to tinker with tube circuits. It's a hobby.

CowboyNQ · Post by **CowboyNQ** » Sun Sep 28, 2014 2:45 am

I have to endorse jimknopf's comment here. The tube on the KK is fantastic. I can promise you it works brilliantly.

slowtrain · Post by **slowtrain** » Sun Sep 28, 2014 4:22 am

Thanks for the input everyone. I've been watching a lot of demos on youtube, and I have to admit, it does sound really good. I'm sure it will be the next keyboard I buy. I doubt I'll end up messing with the tube circuit. It would be nice to have a service manual though. It's hard to believe those aren't available to the consumer. You can get service manuals for cars from the manufacturer. It seems like they're keeping that information proprietary in order to make people get their boards serviced at Korg service centers when many people would be able to do their own service. The service manual links were removed from the Kronos board. Hammond made their service manuals and schematics available for their organs. So far, this is my only problem with Korg though. I really like the Kronos. Although, integration with 64 bit DAWs should be available by now, so I guess that's two problems

It costs $299 to upgrade the editor to the pro version from Sound Quest to get it to work with a 64 bit DAW. I'm on a laptop that's a few years old; was bottom of the line when it was new, and it's 64 bit.

jhulk · Post by **jhulk** » Fri Oct 03, 2014 6:05 pm

no service manual is available to the public until the end of life has been reached and where korg are no longer responsible for the care of the instrument then it is allowed to be sold to the public

and korg service centers do get them but while they are still a warranted product they keep the manuals for there service staff and registered service centers

kkorgian · Post by **kkorgian** » Tue Nov 25, 2014 12:43 pm

Agreed the Tube is a bit wimpy, im a guitarist.

Would of still liked the easy option of going to 11, though i fully appreciate that most keyboardists will only use a little to fill out and gritty up the sound. Guitar on the vocoder input perhaps ?

Circuit benders are go...maybe possible to drop in a replacement valve with different ratings !