D-Lite redux - an unintentional manifesto

[kleinm]

Last week, I overhauled my D’Lite that I built this summer. It needed an overhaul for a variety of reasons. I’ve been modifying it non-stop for about 4 or 5 months, and it was starting to show. Most importantly, I was beginning to grow suspect of a few parts.

I figured this would also be a perfect time to change the output transformer. I bought one of Funk's Bludotone 6L6 OTs, and it worked in the chassis perfectly with some careful planning.

I had been planning this rebuild for about 2 months, and as such I’ve been gathering EVERY piece of information I could. What size resistor do guys like on the 6L6 screens? What is the preferred PI plate voltage? Where did Dumble use shielded cable? How did Dumble route and orient his flying leads? If it still needs a treble bleed network, what are the preferred options? I did my homework the best that I could.

The main differences from the “stock” D’Lite and mine are as follows:
- 330pF treble cap (no Mid Boost switching)
- 0.01uF/250k midrange setup
- lowered V1B coupling cap to 0.02uF
- added 0.05uF/10M pre-OD network
- 4k7 NFB resistor off 4 Ohm tap
- 300R choke replacement resistor
- 470R screen grid resistors on 6L6s
- 3k3 swamper resistors on 6L6 (instead of 1k8)
- 220k/150k plate resistors on both V1 and V2 (with corresponding cathode resistors)
- 5uF, 10uF, 5uF, 5uF Ck’s (V1a, V1b, V2a, V2b respectively)
- 120pF bright cap
- 1k/18k/2k2 dropping string (I know it looks odd, but the voltages are just right)
- UF4007 diodes
- Bluesmaster PAB (with different padding resistor)
- 0.001uF cap across Bass pot (not 0.0012uF)
- Swapped Speaker Out and FX loop jacks so the wire routing would be neater and more Dumble-esque than with stock holes
- Different Presence wiring (wasn’t sure how the original worked, replaced with one I could wrap my mind around)
- 150K post-OD2 (replaced 180K)

I previously had the Bluesmaster PI and Presence circuit, but I decided to start with the “standard” Dumble PI in this. I’m still on the fence as to which I like more. The BM is certainly more complex and adds both crazy harmonics and crazy bloom. The “standard” is noticeably smoother and seems to stay more consistent across different volume situations. Each has their strong points….

I also used to have a treble bleed network because the amp was pretty bright, borderline nasal/harsh before. I decided to start without it and take it from there.

When I fired it up the first time, I was simply shocked. My amp NEVER sounded this good before. Its well-balanced, and never harsh. It has great high-end, but isn’t harsh like it could get before. This amp now needs no Band-Aids, which is something the amp had an abundance of before. The only change I plan on doing is making the LNFB switchable on V1B, which is why the empty DPDT is in the rear corner.

I could go on about how excited I am, but the reason I’m posting this is I learned a few things in the process that may help future builders.

In a nutshell: everything adds up.

The amp works as a system. I’ve read this 100 times, but now I know from experience. You will likely not have as good as results if you do something without understanding why and how it could influence the greater circuit. Try to understand the how and why, then get inside the chassis with your iron.

Why did Dumble use shielded only on the OD controls? Why did he run the leads against the chassis? Why did he orient the 12AX7 leads so they ran against each other? Why did he use regular, non-shielded wire all the way from the Master Volume to the Preamp Out for the FX loop? What happens if you increase a 470R screen grid resistor to 1K? How much voltage drop do you REALLY want from the choke replacement resistor? Will x, y, z OT give you what you want?

Sorry for the novel, but I’m extremely excited about this amp.

I owe a great deal to three individuals in particular from this forum that shared ideas and insight with me on this rebuild: dogears, Gil, and Funk. Thanks for the knowledge, pictures, and advice.

Obviously, ups to Norm and Moss for putting the kit out there.

Here are a few pictures. The cabinet is an Avatar 2x12 oval back with Celestion G1265s. I tore off the stock grille cloth and put matching cloth and piping on it. I also used better quality wiring.

[kleinm]

More pictures

[kleinm]

One more....

[mlp-mx6]

Congratulations on building it closer to your "dream" amp! You gonna leave this one alone now? Or is it, "NEXT!!!"?

[mat]

Perfect. I think this is as good looking build as it can get. Also the head and cab looks stunning. Congrats, and thanks for collecting the important info on a single post. I think that will help many of us

[Structo]

Sweet rebuild Kleinm!
I would love to tweak my 44 ( 6L6 ) to what you have.
I'm afraid I'm in the camp of not understanding everything (very well) done there.

What do you think the most important thing you did, that smoothed things out?

Mine seems a bit on the harsh side in OD.
Thanks.

[Funkalicousgroove]

SWEET FRIGGIN BUILD DUDE!!!!!!

[kleinm]

Thanks guys! I may dick around with a few things, but it is certainly "done". I hope to build a BM or HRM next.

As far as taming the harshness, I'd look in a few areas. Look at your lead dress around V1 and V2 and compare to pictures of Dumbles or builds by Brandon or Gil.

The 0.01uF/250k Midrange setup really, really fattens things up, which can influence your perception of the high end. I am a believer in the .01/250k side of things.

Also, the 0.05uf/10M OD entrance is really critical, I think. Lowering the coupler off CL2 to 0.02uF helps remove some bottom end hash.

Lower your choke replacement resistor to something between 300R-350R. 500R caused some goofy things at high volumes. Got a little nasal. If you're running 6L6s, decrease your screen resistors to 470R. I found 1K to be a little compressed and, again, "hashy".

[EDIT - I may be smoking crack on the 470R screen resistor thing. I need to mess with it some more to see what happens.....it could have been placebo. ]

Take a gander at your lead dress around the tonestack and see if your OD wires are running by them. Try to keep them separate. FWIW, Dumble seemed to use shielded wires on the OD gain and level inputs, like you can see on my pictures. You might remove some treble harshness with shielded wires' inherent capacitance.

Finally, I'm really digging the symmetrical plate resistors on V1 and V2. It seems to work REALLY well. I prefer it over 220k/150k & 180k/120k. It'd be hard to put it in words, but the sound is more pleasant to my ears.

[kleinm]

SWEET FRIGGIN BUILD DUDE!!!!!!

Thanks man! Your OT, pictures, and advice certainly helped!

I can't wait to start on the Dumble-ator next!!!!!!!

[Funkalicousgroove]

I can't believe you can hear the difference in 470 ohm and 1K screen resistors!! I can't !!

BTW, I have seen 470, 500, 510, 680, 691, and 1K in 6L6 Dumbles!!

[kleinm]

I can't believe you can hear the difference in 470 ohm and 1K screen resistors!! I can't !!

BTW, I have seen 470, 500, 510, 680, 691, and 1K in 6L6 Dumbles!!

Keep in mind, I could be tripping balls at any given moment. I am totally subject to the placebo effect when I try these things after I read about them!

Wow...that seems to be verification that I may indeed have been tripping balls when I thought that. Oh well. LOL!

Nevermind the n00b.....

[brownnote]

Looks great Mike, are you still running the 100k/110k plate loads on the PI?

Just curious....
Did you have the PI couplers down to .02 before with the BM PI?
Did you try 200K/150K arrangement on V2?

[kleinm]

Looks great Mike, are you still running the 100k/110k plate loads on the PI?

Just curious....
Did you have the PI couplers down to .02 before with the BM PI?
Did you try 200K/150K arrangement on V2?

Thanks!

Yeah, I have 100k/110k on the PI plates.

When I ran the BM PI, I used the full setup including the Presence control. 0.02uF coupling caps, same NFB resistor and long-tail setup, etc. Oh yeah, I had the snubber cap across the plates too. GREAT PI setup IMHO.

I never did try the 200k/150k arrangement. 'Tis nice?

[Funkalicousgroove]

I don't know if it's a placebo, you hear what you hear. Every little thing makes a difference, and if it sounds better to you one way than another run with it man!!!!

I didn't mean that statement to mean that you are not hearing a difference, I was just saying I can't.

The build is beautiful, I think anyone would be proud of that one! It's clean, and from what you say sounds like heaven, ENJOY IT!

Also, it seems it was me who was tripping balls, I went back through my notes, and I was wrong about seeing amps with 510 and 680 ohm screen resistors, they had 500 and 691, not sure where I saw 510 and 680...Whoops!

[kleinm]

True, true. I guess if I dig how it sounds (which I certainly do) I should just roll with it. Thanks for the kind words! I really appreciate them.

Heh, no worries man. The 500 and 691 are still news to me! Makes me wonder if its a part that he just used what he had, or if he "tuned" for whatever desired outcome?