Komet's Concorde

[hbamp]

Hello,

Anyone here tried to build a KT66 or 6550 Concorde or Express clone. If so what is the result. I want to build one with just a little more clean headroom.

Kind regards,

Henk

[Allynmey]

I saw a Komet 60 with 5881's built by KF this weekend!

[AdmiralB]

I've used KT66s and 6550s (original Tung-Sol) in my clone. It doesn't make the amp stay cleaner any longer, though - the preamp and PI clip well before the power tubes. The maxed-out tone with 6550s is a little tighter.

[hbamp]

I think I'am gonna try the KT66 with 5751 ppreamp tubes and a little bit PI tweaking seems a good option to me.
What do you guys think?

Henk

[Allynmey]

The plate voltage is a little high for a KT-66.

[AdmiralB]

The plate voltage is a little high for a KT-66.

???

The Express is in the low 400V range, is it not? The 60 is around 475V; I've used the Chinese KT66 up to 550V and the Saratovs to 500V with no problems. Unless the Concorde has REALLY high voltage I can't see KT66s being a problem

[hbamp]

Hello,

I found no problems in other KT66 amps with 450V-475V plate voltage.
It's amazing what a good KT66 can do with amps.
I must have a soundclip from one of my express clones somewhere.
I post it as soon I can find it.

[ampdoc1]

I just finished this amp last week. Sounds great, but OMG,...it is loud!

ampdoc

[Fischerman]

That looks sweet! What's that you used for the wires to/from the Fast/Gradual switch (where the Komet uses the coiled wire)? Is that foil of some sort?

[ampdoc1]

Truthfully, I was too lazy to coil a wire, so I used a piece of solder braid. But, I checked the noise level before I terminated the braid to ground, and saw no difference between grounded or ungrounded.

ampdoc

[Fischerman]

Truthfully, I was too lazy to coil a wire, so I used a piece of solder braid.

lol, I chuckled when I read this because...and I'm not saying you do this...I'll be so meticulous to make everything 'look' nice when in the early stages of building but those last couple of wires get thrown in as fast as possible because I'm so close and want to spark this baby up.

[ampdoc1]

Fischer,

Yeah, the same thing happens to me. In this case though, since I used the wrong chassis, the build really can't be considered a "stock" Concorde. I think I did a reasonable neat job, but it wouldn't fool anyone that is familiar with these amps, braid or not!

ampdoc

[tsl602000]

I noticed those two 150k resistors instead of the 220K pair bias splitting resistors.
Forgive my ignorance, but could anyone tell this noob what the difference is?

thanks

[mhuss]

The maximum grid circuit resistance allowed depends on the output tubes being used. EL34s can have up to 500k or more. 6L6 types (like the KT66) want no more than 100k in the grid circuit. I suspect this is why the change was made.

Historical note -- one of the changes Marshall made when forced (by the US importer) to use 6550 tubes for a while in the late 70s was to change the grid resistors from the stock 220k to 150k (the max for the 6550 type).

--mark

[j-po]

I just finished this amp last week. Sounds great, but OMG,...it is loud!

ampdoc

Very niiiiice! Mind sharing what that brown plate resistor is on V2?