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Kegger/blueglow kt88 project

My last three or four builds have been with edcors so I want to try something different
For the end bells on my amps in the pic I used raw bells, wire brushed them for texture and finished with poly clearcoat which I find to look great and is a durable finish.

Holes are easy.
Play with this on paper and figure out what geometry you want with your holes
I think the ones around the kt88's are almost optimum considering top plate thickness.
I do all this with simple tools and a cordless drill with unibit tool.
Do you have a sharp unibit tool?
 
santa said:
My last three or four builds have been with edcors so I want to try something different
For the end bells on my amps in the pic I used raw bells, wire brushed them for texture and finished with poly clearcoat which I find to look great and is a durable finish.

Holes are easy.
Play with this on paper and figure out what geometry you want with your holes
I think the ones around the kt88's are almost optimum considering top plate thickness.
I do all this with simple tools and a cordless drill with unibit tool.
Do you have a sharp unibit tool?
Click to expand...

Yep, got the unibit, I also have a drill press and chassis punches for the tube sockets, the meter holes will probably be some type of hole saw. I contacted Hammond to see if I could order primer chassis versus the grey or black powder coated but would have to buy 10 so that's out of the question. I intend to rubber mount the Power transformer with grommets to eliminate any vibration. Overall eliminate some of the errors I made.
 
Biggest difference with the kt120 seems to be filament current and you can run them hotter due to increased plate power rating
Not sure on the kt150 though

Good thing you have the punches, steel chassis are a bit tougher to work.

I too have a selection of punches, what size hole do you need for the meters?
 
I think it would be a waste of money to go with the 120 or 150 without changing to a much beefier power transformer. You need more current, and much higher B+ if you want to reach the potential of either of those tubes. Other than that, the bias may need to be optimized but the rest of the circuit should be fine.
 
JohnT123 said:
I think it would be a waste of money to go with the 120 or 150 without changing to a much beefier power transformer. You need more current, and much higher B+ if you want to reach the potential of either of those tubes. Other than that, the bias may need to be optimized but the rest of the circuit should be fine.
Click to expand...

Thanks John, guess I will stay with the KT88's, I have no issues with the power, just was wondering about something different with the new build, and you say you can't stop tinkering! I am going to build my perfect amp, some here will quibble but what I have is nearly perfect to my ears, my new PS Trans has been shipped and guess that will keep me with the KT88's, I have a new matched set of KT88's coming for this amp. These are pretty sweet tubes. Looks like I would need B+ at 500 + to run these bigger tubes, shoot, I freak out at the 460V B+.

Just thinking.
 
The B+ you'll get from that transformer should be high enough to drive those KT120 tubes fine. I think each tube will need about 1.8 amps of 6.3 volts so you should be OK there also.
 
santa said:
Bill,
Out of curiosity,
What PT are you using for your builds?
What size holes do you need for the meters?
Click to expand...

The meters diameter is 34mm or about 1 5/16, looks like they will protrude into the chassis with wiring hooked up about 1 1/4 inch.
 
JohnT123 said:
The B+ you'll get from that transformer should be high enough to drive those KT120 tubes fine. I think each tube will need about 1.8 amps of 6.3 volts so you should be OK there also.
Click to expand...

Thanks John, always appreciate your insight, I have been looking online and some say the tubes are interchangeable, not sure if that's the case, do I need to re calculate the bias/led setup?

The KT120's look a little different, I have a matched set of KT88's Gold Lion coming, may just use those.

Mounting the PS Transformer I am using grommets with a stainless steel tubes cut at the correct length to somewhat isolate the transformer on the chassis, just several of the upgrades I plan for this build. Someone here said they look at the compromises after a build, I just want it as near perfect as I can do, guess nothing is perfect.
 
Heffa said:
View attachment 1459825
I used this one, found in the instructions of a VU kit from diy-tubes.com.
The schematic itself is a variant of several others I found when searching online, so not sure where it originates from.
Anyway, this one is available freely in the instructions to diy-tubes.com's kit, so I hope it's ok for me to upload it here.
Click to expand...

Where in the amp are you connecting the audio in? Also when looking at the manual they talk about reversing a couple of the diodes.
 
Ruidoso Bill said:
Where in the amp are you connecting the audio in? Also when looking at the manual they talk about reversing a couple of the diodes.
Click to expand...
I have tested it connected directly over the input signal, and it seems to be working ok. Didn't test it together with the amp yet though, so don't know if it impacts the sound in some way.
I am about to take a trip to Tenerife, Spain so won't be able to test more for another week or two.
 
santa said:
Bill,
I have a sharp 34.6 mm punch that I will gladly loan you if needed.
Also have a 43 mm if that helps get er done.

Glen
Click to expand...

Very Generous Glen for the offer, I went ahead and found a 1 5/16 greenlee on the bay pretty cheap with free shipping, I am hoping to back mount the meters, maybe a little trimming with a dremmel. I wish I could find some of the vinyl split trim tubing rather than painting.

Thanks again for the offer!
 
Last edited:
Heffa said:
I have tested it connected directly over the input signal, and it seems to be working ok. Didn't test it together with the amp yet though, so don't know if it impacts the sound in some way.
I am about to take a trip to Tenerife, Spain so won't be able to test more for another week or two.
Click to expand...

I picked these up Meters and no schematic or instructions, need to do some research. Enjoy your trip!
 
Ruidoso Bill said:
Thanks John, always appreciate your insight, I have been looking online and some say the tubes are interchangeable, not sure if that's the case, do I need to re calculate the bias/led setup?

The KT120's look a little different, I have a matched set of KT88's Gold Lion coming, may just use those.

Mounting the PS Transformer I am using grommets with a stainless steel tubes cut at the correct length to somewhat isolate the transformer on the chassis, just several of the upgrades I plan for this build. Someone here said they look at the compromises after a build, I just want it as near perfect as I can do, guess nothing is perfect.
Click to expand...

I don't think you have to do anything to the bias of the driver tube but it's always possible that the cathode bias resistor on the output tubes will have to be altered. Your transformer looks to provide more B+ than the original circuit design so you'll want to check the plate dissipation at idle and make sure it's in the ballpark. I've been putting many different output tubes in my build and haven't changed the 500 ohm bias resistor. Too lazy to do all the measurements with each change. I'd love it if I could find a big wire wound rheostat that would allow me to dial in each tube. Maybe a fixed bias scheme on the next version.
 
JohnT123 said:
I don't think you have to do anything to the bias of the driver tube but it's always possible that the cathode bias resistor on the output tubes will have to be altered. Your transformer looks to provide more B+ than the original circuit design so you'll want to check the plate dissipation at idle and make sure it's in the ballpark. I've been putting many different output tubes in my build and haven't changed the 500 ohm bias resistor. Too lazy to do all the measurements with each change. I'd love it if I could find a big wire wound rheostat that would allow me to dial in each tube. Maybe a fixed bias scheme on the next version.
Click to expand...

Tried my new tubes matched KT88's in the current amp, sounds great, need to put it on the scope, I swear it's putting out a tad more power and both tubes glow the same, before I do the new build take a look at this, SRB02 "Stu" sent this to me: http://audiokarma.org/forums/index.php?threads/kt120-150-se-ul-build.734130/

I'm thinking more the KT88's & KT120's, if the 120's are optimized what would you think another watt?
 
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