Changing the tube

[Narfig]

Can you change the tube in the SV-1? Will it make any difference at all?

I hoped it was as easy as taking the window off and swapping it out, but it seems to be soldered to the socket. I suppose the "Valve Reactor" tech is not suppose to wear out tubes. My issue is that a 12ax7 has WAAAAY to much gain/distortion for my keyboard-centric purposes. I have a nice 5751M that I would like to swap it for. Will this reduce the gain (and hopefully the noise)?

Thanks!

[Akos Janca]

As a new owner I have similar questions. No problems with the sound at all, just would like to know. I couldn't find an answer on the forum. Do you have experience or any info?

I heard somebody has replaced the original tube with another one (same type) made by Marshall - and the sound got even better. What do you think?

Thanks,

Akos

[oy5t3h]

It is certainly possible to change the tube in an SV-1. It requires disassembly of the body of the machine, though - it can't be done simply by removing the window. Korg don't see it as a user-replaceable item. A starved-plate design runs the tube quite cool, and it should last many years before it wears out.

Let us know how it goes!

[teddyc1]

It is certainly possible to change the tube in an SV-1. It requires disassembly of the body of the machine, though - it can't be done simply by removing the window. Korg don't see it as a user-replaceable item. A starved-plate design runs the tube quite cool, and it should last many years before it wears out.

Let us know how it goes!

If anyone has changed the tube, we'd like to know how to do it and what are the results in sound. javascript:emoticon(':soundsgood')

[boris_keys]

It is certainly possible to change the tube in an SV-1. It requires disassembly of the body of the machine, though - it can't be done simply by removing the window. Korg don't see it as a user-replaceable item. A starved-plate design runs the tube quite cool, and it should last many years before it wears out.

Let us know how it goes!

If anyone has changed the tube, we'd like to know how to do it and what are the results in sound. javascript:emoticon(':soundsgood')

I just swapped the tube in my SV-1BK 73-key.

I only had this thing for like a year and a half and the stock tube blew at a gig. No sound with amp modeling on (interestingly, the key click and mechanical noises still came through, since those bypass the valve circuit), but the board played fine with amp modeling turned off.

I had a Mesa 12AX7 kicking around my studio, so I went for it.
Opening the board took some doing, you have to unscrew all the screws on the bottom to be able to move the action around and lift it out of the board. Be very gentle and careful with this, as to not damage the ribbon connecting the action to the logic board. I ended up just disconnecting it. After that, just remove the screws on the glass cover covering the tube, and then two screws on the inside that attach the tube circuit to white tube casing. Replace the tube and adjust the trim on the tube circuit. Carefully put everything back together in reverse order.

After plugging it in, I found that the Mesa tube is noticeably edgier and grittier than the stock tube (as I kind of expected). For me this is a plus, as I play in bands that often times require more aggressive, almost synth-like EP sounds.

Overall, this is a very do-able fix. Korg advises against doing it yourself for good reason, as there are multiple circuits and mechanisms that are exposed and can be damaged if you don't go about it very carefully and slowly.

Also it obviously voids your warranty so if your board is still under warranty, it may behoove you to go that route than DIY.

I'll play out with this thing for a few months and report back as to how it holds up.

[teddyc1]

Boris,

Thanks for your detailed post.
As for "Adjust the trim on the tube," do you mean power up the SV-1 while disassembled, listen to its audio, engage the amp circuit and keybed, and adjust until it sounds good?

Thanks for an already good post.

[boris_keys]

Boris,

Thanks for your detailed post.
As for "Adjust the trim on the tube," do you mean power up the SV-1 while disassembled, listen to it's audio, engage the amp circuit and keybed, and adjust until it sounds good!

Thanks for an already good post.

Thanks glad I could be a guinea pig on this one.

You are correct. There's a small pot on the valve circuit board that can be adjusted with a small screwdriver. I basically adjusted it until the gain difference between the tube sound and non-tube sound was about the same as on the original tube. There's also a friendly sticker on the back of the tube casing reminding you to do that. Be very careful powering the board up while opened, so as not to short anything out.
Let me know if you have any other questions

Thanks

[bluebossa]

So I bought a Korg SV1 a few weeks ago... great keyboard.

In short the amp section didn't work, everything else was fine.
I bought a Valve from eBay UK - £15 Electro Harmonix and yesterday replaced it

- so first off it is possible to change and you can do it yourself.

The process involves 20 screws underneath, carefully moving the keybed while not disconnecting the ribbon cable - then taking the valve holder out with screws on top and underneath - it then slots in and you re-assemble.

For sure it's a painful process and not for the fainthearted nor those still in Warranty - but mine was well past this and so I wanted to get that great part of this machine up and running again.

Result - It worked fine, played it and Amp modelling and distortion sounded great again.

However! - I left the unit on for a couple of hours and pop, it went again!!


So I'm still left wanting advice from this forum - any ideas?

I did notice a label on the holder saying - "when replacing valve - please ensure you re-trim the trimmer" or words to that effect.

As of course with no manual I didn't know what this was I didn't trim or retrim anything? Is this some form of voltage drive setting which then blew my new valve, or something else?

Any ideas from Korg experts welcomed.
What other step should I follow if I get another £15 valve and try again?

Thanks in advance.
Jonathan

[Geitin]

I have a 1.5 year old SV1 and I began experiencing problems this week that indicate a problem with the tube. When amp modeling is turned on, I now hear only the RX noise layer, although sometimes the full sound comes through again. I also notice a smell coming from the tube area, but I don't really see anything noticably wrong with the tube itself (although I'm no expert on tubes).

I'll probably have it replaced, but I was wondering if anyone knew whether there are certain conditions (e.g. temperature or humidity) that might shorten the lifespan of such tubes? 1.5 years seems abnormally short.