KT-7500 upgrade - now we're talkin'

I just did a recap, opamp replacement and jumpered a few wires on my KT-7500 and I am amazed at the improvement. It's sounding very similar now to my unrestored KT-8300. Bass is stronger and deeper and there is an actual sound stage and depth to the music that was not there before. With the various tuners I've recapped I haven't experienced such as radical transformation before. The improvement in quality is similar to going from a run of the mill MP3 to a CD.

For this initial restore, I stuck to these easy things. I replace the electrolytic caps and kept the current capacitance values. The diodes in the power section were replaced with 11DQ10 Schottkys. The opamp was replaced with the recommended OPA2604. I removed the standoffs at C26, C27, C28, C29 , C30 and jumpered C26-C27 and C28-C29 and removed the wiring to the de-emphasis switch. I replaced the C45, C46 caps (.15 disc type) to .33 polypropylene, .47 was recommended but I don't have those on hand at the moment. I used a mix of caps, Nichicon PW in the power supply and a motley bunch of FG's, KW's and a lonely KT, with some Elna Silmics. The orange Elna's were replaced with Nichicon KL's. I also replaced anything 1uf and below with Panasonic ECQ's or Wima's. The recap did not affect the dial alignment.

There are a bunch of other things that can be done but I am going to put this into the stack and enjoy until I upgrade my KT-8300, and then look into some of the other tricks.

Thanks go to Leesonic for his excellent post and pictures http://www.audiokarma.org/forums/showthread.php?t=457960, and for sharing his parts list with me.

It is paired up with a splendid KA-7100, restoration also inspired by Leesonic, and that is another story.

Pics below.

Looks great. I just got a KT-8300 I'm interested in restomodding. I'm going to file away some nuggets from this and the link you provided.

Nice work. You'll find even more improvement with the negative regulator mod which allows you to lower the dc offset of the opamp to the point you can remove Cb49/Cb50 and jumper them.

dyehardfan said:

Looks great. I just got a KT-8300 I'm interested in restomodding. I'm going to file away some nuggets from this and the link you provided.

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Thanks, when I get to the 8300 I'll post some pictures etc.

hopjohn said:

Nice work. You'll find even more improvement with the negative regulator mod which allows you to lower the dc offset of the opamp to the point you can remove Cb49/Cb50 and jumper them.

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That looks like a nice mod - I checked the web for more info but didn't have any luck - do you have any more info?


A few updates to the original post - I changed the photos up for something a little bigger. Also I forgot to mention I updated the diodes in the power section to 11DQ10 Schottkys.

The tuner was missing it's original feet, it must have been in a rack at some point. I got some cheap rubber stick on feet for now, but if anyone has suggestions for nice replacements for Kenwood gear that would be very much appreciated.

Negative regulator mod.

The information for it is in post #16 of this thread.

You can source feet in lots of places. Here are some I've used in the past that seem to work well.

39cross said:

Thanks go to Leesonic for his excellent post and pictures http://www.audiokarma.org/forums/showthread.php?t=457960, and for sharing his parts list with me.

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Thank you for your kind words. What kind of case do you have on your KT-7500? The one I'm using now has the wooden one, and I hate it.

I'd love to get another KT-8300 and restore that one, but I'm so broke right now it's not funny.

Lee.

hopjohn said:

The information for it is in post #16 of this thread.

You can source feet in lots of places. Here are some I've used in the past that seem to work well.

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I completely forget that I'd read that sometime in the past...thanks!!!

leesonic said:

Thank you for your kind words. What kind of case do you have on your KT-7500? The one I'm using now has the wooden one, and I hate it.

I'd love to get another KT-8300 and restore that one, but I'm so broke right now it's not funny.

Lee.

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My KT-7500 has the standard grey metal case. So does the 8300, but it has a crusty, rusty patina (sounds nicer than it looks). However the insides are clean and rust-free. Maybe those extra case screws kept the inside pristine.

When I get to the 8300 I will be referring to your post(s), they are very, very helpful.

Hope you have a chance to pick up another one soon. I don't get too gushy over most of the equipment I have, but I do love my 8300. And now the 7500 too.

Hi 39Cross et al,
I too about 3 years ago did the full monty FMTUNERINFO mods to my KT7550 including sending out to Bill Ammons for a final full alignment. Very nice and very fun to do.

Fast forward to 2013 and I did the same thing to a newly acquired KT-8300 including Bill Ammons narrow filter mod and MPX board mod with final alignment by Bill. Hands down, the fully modded KT-8300 beats the fully modded KT-7550 and honestly, it's not that close either. Much better sound and better sensitivity. IMHO, do the full mods on your KT-8300 and I don't think you'll be disappointed.

Very nice!

It is good to hear that yours now sounds as good as the KT-8300 after the mod. I just received a KT-8300 for Christmas from my brother (Wolverine) and am about to get around to hearing what it sounds like...I had to change the speaker posts in the KA-8100 that I also received as a present before I made shelf space for the two units.

wjcjr said:

IMHO, do the full mods on your KT-8300 and I don't think you'll be disappointed.

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Thanks for your kind comments. I am very much looking forward to working on the KT-8300, it is my favorite tuner, and I'm sure it will be king of the hill afterwards. There's no doubt it is the better of the two. It is pretty cool how much better the KT-7500 can be made by mere mortals (or at least those who can follow advice).

Bstable said:

It is good to hear that yours now sounds as good as the KT-8300 after the mod

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Well...maybe not quite as good...but it is a lot closer. I hope you enjoy yours, sounds like a killer combo!