Starting a D'Lite

[angelodp]

Your amp is coming along great. Here is a shot of my amp w/ relays. I have been adding various features for a while now. I have the mid-boost as well as the PAB, OD and bright ( two bright caps ). I also have put in the LNFB network switch, a rear panel OD trimmer, and I am about to put in the PI trimmer and the midcap tripcap switch. Have fun it is a great amp.

[IMG:768:576]http://i260.photobucket.com/albums/ii9/ ... G_1584.jpg[/img]

[Structo]

Ange, that is way too neat looking!
You need to melt another 1/2 pound of solder in that thing to give it the worn look!

[dreric]

Ange

nice build! is that a brown note? Also, where did you get the nifty relay boards? Please excuse my ignorance but what is a NFBL?

Eric

[brewdude]

I think he is referring to the local negative feedback (LNFB) in V1b.

[angelodp]

Yes LNFB, my bad. The boards are from Ampdoc. Not too sure if he still has them. he was around for quite while.

a

[dreric]

I try and keep my "duh" questions to a minimum but here's one that I don't know how to figure out the answer to.

I'm using an output transformer with two primary's and I want to make sure that I hook them up to the right tubes, so:

1 = 6600 ohms ..................... 2 x 6l6?

2 = 5200 ohms ..................... 2 x 6V6

If I'm right then I guessed right!

More importantly how do you find this info out? What resistance do specific tubes want to see on the primary from the output trannies? Does this change if to are using 4 tube versus 2?

Thanks as always

Eric

[brewdude]

My Brown Note D'Lite 22/33 came with a dual primary OT.
8k for a pair of 6v6's, or 4k for a pair of 6l6's.
My understanding is that for four tubes you would want half of the impedance as for two tubes.

[ChrisM]

My Brown Note D'Lite 22/33 came with a dual primary OT.
8k for a pair of 6v6's, or 4k for a pair of 6l6's.
My understanding is that for four tubes you would want half of the impedance as for two tubes.

Yep, you got it!

Dreric 5K2 might be a bit high for a pair of 6L6's. I know there is some variance but I am not sure how much. I am sure it would work, you might not get that "Dumble tone" with the difference in impedance though.

[Structo]

Dreric,

I ended up using an OT for the Fender Prosonic on my D' Lite.
It is a 50 watt OT that is almost the size of the PT.
I believe it is 4200 primary impedance.
http://angela.com/fenderprosonicoutputtransformer.aspx

Not sure if you have seen this but Duncan made a small program that you can look up the tube specs in.
It's called the Tube Data Sheet Locator.

Tubes have a spec called Zout or impedance out.
This is published as a property of each tube.

http://www.duncanamps.com/tdslpe/

[IcemanB52]

Tom is spot on! If you do the math and draw the load line for a pair of 6L6's, 4200 Ohms works great. If you want to dig a little deeper into this, there is a good discussion at http://www.freewebs.com/valvewizard/index.html. The two articles on Power amps are pretty good.

[Structo]

That link seems to be broken.

Here is what I use:

http://www.valvewizard.co.uk/

[dreric]

Progress........not perfection

Got the rectifier, filter and relay boards more or less in. Still confused by the output tranny impedance thing and what type of shielded wire to use keeps me up at night.

It's like playing with candy!

eric

[bigmik]

looking good deric chassis looks sturdy, are you going to use gromets on the transformer wires running through the chassis?

[heisthl]

I just modified an amp (Torres Super Texan - Don't ask) that had a Hammond 1650H - 6600 ohm driving 2 6L6 - it was awful - a transformer swap to get to 4200 was much better. It also had the Hammond power transformer (cant remember the number now) but it was 175 ma 350-0 - 350 and under load you could see all the voltages drop dramatically a swap to some similar Heyboer Iron was much better. I am not a Hammond fan, but back to the topic - stay as close to 4200 as you can.

[Structo]

Just a FYI,
The 22M resistors on the local feedback are a bit difficult to source in smaller sizes but you can use 1/4w ones there with no problem.
What you have there will work though.