Newbie D'lite question...Dropping string and presence...

[frischmann]

Hi guys,
I've been trying to catch up on my reading here (there really is a ton of information). I'm trying to tweak out my D'lite. I haven't decided if I want to go full out for the RF thing or just make some tweaks.

I decided to try the dumble style presence control. I'm using the Ceriatone layout. (still working on reading schematics). I wired it up and it didn't work at all....I think I need to install a new ground back at the joining point of the .1 cap 24k resistor etc...I'm not sure where.

I also decided to check my voltages while I was there..

V1a 200
v1b 207
v2a202
v2b208
PI 292 and 311

v4 (6l6) 429 and 425
v5(6l6) 425 and 422

the dropping string is
428
420
325
319

I'm using the 1k, 22k, 2k2 set up.
It Think these voltages may be a touch high, especially the PI.
I'd appreciate any suggestions you might have.

[skyboltone]

Stop!

Take the power tubes out and lets have all the cathode voltages too. If you've got a ground missing you'll spot it there.

Did you red plate the 6L6's?

[Structo]

Not sure what you are referring to about the 24K and the .1 uf cap unless it is the PI tail resistor you are talking about.
There isn't a ground there that I know of.

That Ceriatone layout is difficult to read and would be very difficult for a beginner.
Here is the Brown Note layout which is a lot easier to read.
I know the layout is a bit different on the filter supply board but you should see the differences.
So did you build it exactly like the Ceriatone layout with a choke and the FET input?

Here is a layout incorporating a lot of what has been said here.
Try these values before you change a bunch of stuff and have no idea what is what. It's a lot harder to go back when you don't know where to start.
Leave the dropping string alone until you change to these values.
Just by changing the choke resistor (if you are using one) it drops everything down a little.
The only different thing I did was I used 120K/ 110K Rp values on the PI.

I'll attach a couple files.
I used the presence wiring scheme that I show, it seems to allow a good range of adjustment.

[Bob-I]

Sky's right. Be careful of burning up your power tubes.

Double check the grounds on the power tubes as well as the C- voltage on pin 5, it should be in the range of -40 to -50 VDC.

Your preamp voltages seem correct but if you're not getting sound you have something wrong. I like to listen through the preamp stages. Make a "Stethoscope". Get a pair of alligator clips, a .1uF/600V cap and an 1/4" jack. Connect the cap to the HOT lead of the jack then to an alligator clip. Connect the other alligator clip to GROUND of the jack.

Now pull the power tubes leaving only the preamp tubes. Connect a sound source to the input of your amp, I use an mp3 player turned down fairly low. Connect the ground lead of the stethoscope to the chassis, plug the jack into a working amp, again turned down fairly low, and touch the hot alligator clip to test points as follows.

1) The input grid of V1a
2) Plate of V1a, signal should be louder
3) Grid of V1b, tone controls and gain should now work
4) Input grid of each side of the PI
5) Plates of each side of the PI

This will help narrow down where the problem is so you can focus your troubleshooting on that area.

Also, if you can post some detailed pics it'll help.

[Bob-I]

oops, double

[frischmann]

sorry guys,
I think I was a little confusing in my original post. I built the amp using the D'lite layout. The amp sounds really good. I'm using Brown note Iron from the first run of kits. I've been gigging with the amp for about two months with no issues.

I wanted to change the presence to the truer dumble set up as it was suggested that it may be an improvement and was told the ceriatone was closer to the real thing. I tried the config but realized there might be a difference between where the d'lite and ceriatone had that ground set up.

I'm getting sound, really good sound but my attempt at the new presence didn't work. Once I put it back to the stock D'lite circuit, it sounded fine.

The 6l6's are a pair of old RCA black plates. The tubes are at about 37-38ma which is about 16 watts and not red plating at all.

With that said, is there something of disconcerting about those voltages?

Thanks again,
Paul...

BTW,
I may try the stethascope any way.....I've always wanted to try that.

[frischmann]

duh....the 6l6's are showing 425 and 422 on the plates....I didn't read my own post

[Structo]

Today I modded my amp with dual bias adjustment pots.
So now I can run unmatched tubes and not worry about it.

[frischmann]

Hi Tom,
thanks for the responses. As soon as I can straighten out a few other thing to my liking, I'm going to try the bias splitting trick. It sure would be noce to be able to use tubes that are a little far away. I have a set of Syvania STR 387s that would probably sound amazing in here.

About the presence, on the D'lite, coming off the grid of the PI (pin 6) going to a .1 which then joins in with a 6K2 (NFB). I realize there is more termintating here but this is just for reference...... a wire goes to lug one of the presence pot (2K). If I read your schematic correctly, 3905 goes from lug one to ground, 1uf cap goes from lug 2 to ground. lug three is open....correct?

[dimitris]

If I read your schematic correctly, 3905 goes from lug one to ground, 1uf cap goes from lug 2 to ground. lug three is open....correct?

Yes,that's right.

[Structo]

Hi Tom,
thanks for the responses. As soon as I can straighten out a few other thing to my liking, I'm going to try the bias splitting trick. It sure would be noce to be able to use tubes that are a little far away. I have a set of Syvania STR 387s that would probably sound amazing in here.

About the presence, on the D'lite, coming off the grid of the PI (pin 6) going to a .1 which then joins in with a 6K2 (NFB). I realize there is more terminating here but this is just for reference...... a wire goes to lug one of the presence pot (2K). If I read your schematic correctly, 3905 goes from lug one to ground, 1uf cap goes from lug 2 to ground. lug three is open....correct?

Correct, the first leg (CCW) is not connected.

If you want to do the dual bias set up it's kind of hard to find the correct pots for it.
I was lucky enough to find two NTE 25K pots at a local NORVAC store.
They are the short shaft type with top slotted shafts. They have a lock nut that you screw down to lock the shaft in place when done adjusting.

So with the 25K pots I used 15K tail resistors.
Seems to have decent range of adjustment from around 18mv to well over 100mv.
So be sure to back them off before powering up.

You have to split the 220K grid resistors on the board apart so that you can feed each one individually from the pots.

I put the second pot between the existing bias pot and the power tube.
It was a pretty tight fit!
The D'Lite chassis is on the small side and it's easy to run out of real estate fast.

[frischmann]

Presence sucessfully completed.
It's kinda weird sounding (I'm more of a Marshall/Fender guy.)
It seems to roll of just the really high end, infact...it seems really subtle unless you dime it. from about 1:00 to 5:00 you can really hear it add some top end, I really can't hear much of anything from 12:00-down..
at least not like I'm used to.

I did notice it doesn't affect the gain as much as the Normster version..I guess it's not playing with the NF as much...


Just going back to the earlier posts on my dropping string...Are there some numbers in there that concern you guys?

Thanks again for all the help,
This is too cool for words.....

[Structo]

You may want to get V1 down in the 180-190v range and the PI in the 280-300v range.