1st build, 6V6 Cathode Bias Express/Deluxe

[davesi]

Hi all, long time lurker wishing to give thanks for this invaluable resource in assisting me in successfully completing my first scratch build. Special thanks to rj whom I believe drilled my chasis on a Sunday (following tax day). First heard about Ken through the Tube Amp Book, Volume 3, and all my old Blackface Fenders were never the same. The old big amps and playing out days are pretty much over, and after modding all my little Fenders, I wanted to build my own.

I had the idea of a medium power combo amp that could be played out (occasionally), or at home based on a 6V6 output section. After about a year of reading virtually every related article on this forum, I decided on an Express pre-section mated to a cathode biased output section roughly equivalent to a Deluxe, hence the Express/Deluxe. I relied upon the immense knowledge of this forum to guide me through the adjustments needed to make this work. Primarily I wanted to reduce voltages (Weber PT), and output (Hammond OT) to produce an amp that would go clean to mean. I have never heard a Wreck live. Individually bypassed cathodes (switched individually) worked!

It took a while to complete and I had afriend who is a EE with me the first time it powered up. I don't know whose grin was bigger. It Worked on first try! Attached are a few pics. ? Should I leave the "C" logo? It truly is a "Stealth" amp. Thank you TAG!!!

Deviations/voltages can be provided if anyone is curious.

[davesi]

"C' logo pic previously omitted.

Dave

[Colossal]

Hey Dave,

Killer job man! That is a great looking build. A "Crate" never sounded so good! Your friends will all be asking what Crate model is that??? You were fortunate to have your EE buddy close by for startup. I remember flipping the switch for the first time with shaking fingers and then the relief wash over me when no smoke came out and great tone did! What a great feeling. Enjoy your amp. Now you'll be hopelessly addicted like the rest of us junkies here.

Anybody got a fix?? (smacking arm)

[M Fowler]

Dave,

Great job on your TW amp. That crate cabinet filled with a TW will be a fun thing to fool people with. I hope people ask what model that is and where can I get one. I did that with a Line6 212 combo cabinet with Express amp bolted in.

[jjman]

I used the same approach for my build. I reduced the grid leak resistors on the 6v6 tubes to prevent excessive overdriving of them. They expect a cathodine PI and the LTPI pushes them much harder when cranking. I didn't like them being pushed into crossover distortion when clipping. It resolved the "problem." Now I'm using a dual-100k Larmar type post PIMV which now also functions as the grid leaks @ 100k instead of the standard 200k.

That was the only “issue” from mating the 2 designs for me.

[dcribbs1412]

Nice job davesi
I'm looking at doing a similar build...2 6v6's with deluxe PT and OT

Deviations/voltages can be provided if anyone is curious

wondering about the Individually bypassed cathodes
any info is much appreciated

[Ken Moon]

For those of you who want to try a cathode-biased Express-type amp with 6V6s and Deluxe iron, here's a schematic that might give you some ideas to play around with - there are about 30 of these floating around now, and everyone seems pretty happy.

I spent more than a year tweaking this thing, so I wanted to share the results

I did use a Hammond 276X PT so I could get the center-tapped 5V winding, but if you go with a more "typical" power supply, a normal Deluxe PT would be fine.

Also, I've deleted the MV from the last 10 or so Talons - some like it but most don't.

Remember, though, if you switch to cathode bias on an Express/Deluxe-type amp, you've got to stiffen up the psu a bit, or it'll sound too mushy, and you'll get 'note smearing' on fast playing.

[img808]http://www.moonguitaramps.com/images/ta ... ematic.png[/img]

[davesi]

dcribbs, individual cathode resistors work great! I got the idea here on the forum..courtesy degeezer. I played with vaules a bit and ended up with 500 ohm resistors and 100uf/50v caps. Caps are run to DPDT switch to ground so you can have both connected, one connected or none connected. With none connected, there is an approximate 60% drop in percieved volume with almost identical tone to both connected. With one cap in, you get a little volume drop but a little more sheen (presence). With deluxe iron, I changed dropping string resistors to 8.2K. This gave me 361 VDC on plates and 168VDC pin 6 V1b. Everything else is pretty proportional. These values gave me an idle of about 12.4 watts.

KM's schematic is nearly what I ended up with as well. R7=100K, R11=22K, R22=75K. Kept the 1K screens. I also changed C4 to 47uf and added 15K to V1b, but not sure it is neccessary.

I am in awe of the folks on this forum, and amp building is indeed addictive.

Dave

[dcribbs1412]

Thanks Ken
I have been studying your schem for a while...your Talon seems to be an excellent amp
thanks for sharing your hard work...

Thank you davesi for your time and sharing your findings

I am in awe of the folks on this forum, and amp building is indeed addictive.

I hear you my friend...lots of great knowledge here

[RJ Guitars]

Cool amp, nice job of putting it all together to get what you wanted. Is the output (volume) comparable to a Deluxe?

I'd love to hear some clips when you get the chance.

thanks,

rj

[dcribbs1412]

davesi wrote:

also changed C4 to 47uf

did you mean treble cap C2?
also is the PT endbell and bracket from Weber?
Thanks
D

[davesi]

rj, It's been a while since I had a deluxe around but it is at least as loud...only it sounds bigger. Even with a single 12". Pushes a lot of air.

Thanks dcribbs...I meant C17 to 47uf. C2 is a 130pf polystyrene wired in permanently. Yes the end bells were Weber...their model didn't quite clear leads so I added some spacers.

[FrankSi]

Hey Brother,

Your amp looks great! Nice pictures.

And thanks for letting me play it. It sounded fantastic!

I’m really going to have to think hard about building one now. If I could get Andy’s help, I think it would be a very cool summer project.

Cheers!