First D'Lite done.

[markmalin]

Hi guys. (I also posted this on the hoffman site, for those of you who frequent the hoffman forum.)

Well, I fired up the d'lite chassis I just finished and it's working. My digital camera bit the dust last week, so I can't post photos, but will when I have a camera. I had a couple questions I thought you guys could help with.

1.) It's pretty quiet on the clean setting, but when I switch to OD there's quite a buzz. The fact that I'm playing a Strat doesn't help, as the single coil pickups act like big antennas. If I wave my hand over the chassis to where it buzzes loudest, it's right over the 500pf/220k resistor at pin 7 of V1. I realize that with the OD on, switching in another gain stage is just amplifying the faint buzz that's there already, but is this typical for this amp (i.e. such a difference)?

2.) For the wire that goes from those two components to the volume control I didn't use sheilded cable. The wire is pretty "live", in that tapping it with a chopstick is pretty loud. I guess I've seen this in Fenders I've worked on, but does this seem normal for this amp? I may try shielded cable.

3.) I'm using JJ 6V6's -- where's a good range for bias current? Right now it's dialed to about 35ma.

4.) Regarding that trim pot on the drive circuit, how do I determine where to adjust it to?

Thanks for the help, guys.
Mark.

[ampgeek]

Congrats on the build Mark!

6V6's are happy in the 17 to 20ma range. 6L6 types in the 35'ish ma area.

Happy Holidays,
Dave O.

[Normster]

Yep, drop that bias! That may even help with some of the buzz you're hearing. The wire from the input volume pot to V1b grid should be shielded cable.

[mlp-mx6]

Personal opinion - I've found that I prefer 6V6 tone in the 22-25ma range, usually. Unless the plate voltage is too high, of course. 400V-420V on the plates is okay at that dissipation, especially with JJ 6V6s. Those are some STOUT 6V6s.

[markmalin]

Thanks, guys. Here's an update.

I swapped the tubes around and while playing the OD setting went silent. Did some measuring and V2 (a new JJ 12AX7) had whacky voltages on it, so I swapped in an EH I had laying around and it worked great. Much quieter, too! I put the JJ on the tube tester and both the plate and grid on section one are shorted!

So after playing around some more I noticed I couldn't get the 6V6's to bias. One was always 10 ma different from the other. Did some more measuring and noticed at one point the one that kept reading low, was now drawing twice the current of the other. (again, these are a set of brand new JJ's, matched from CE Dist). So I happend to have a set of old RCA's laying around that were "somewhat matched". These were out of an old radio, most likely (my other hobby). I put those in, they biased nicely and the amp is sounding much better now.

Go figure. This is the second set of JJ power tubes I bought from CE Dist that were bad out of the box. I'm going to call CE and have them exchanged, but it make me wonder if I really want JJ's. Like the way they sound (have them in other amps).

Mark.

PS - my opinion of the amp so far, using a Jensen Alnico speaker I borrowed from another build, is that it takes some getting used to. I'm such a fender guy that I had to play with it a while before I had it dialed in to where I like it. Looking forward to getting a "real" speaker for it, and getting the cabinet done.

[ampgeek]

Sounds like good progress so far. Great to hear!

You know...I have been hesitant to mention this.... thinking that I was just unlucky....but....I have had NOTHING but trouble, right out of the boxes, with 3 pairs of JJ 6V6's in my homegrown D'lite build.

Much like you, I have an old pair of 6V6 pulls (dark glass/coating/whatever the hell that stuff is in there!) that sound marvelous so I know that the platform is OK.

However, so far, I prefer NOS TS 5881's with the Bluesmaster configuration in this build (not to mention I have "acquired" a boat load of them!!) so I won't be going the 6V6 route on this one.

I included a dual bias arrangement in my build. In my mind, a must have if you are playing around with different tubes and tube types.

Merry Christmas and happy amping in the New Year!
Dave O.

[Structo]

Try Bob at www.eurotubes.com for your JJ's.
That's all he sells and he is quite knowledgable about them.
He has even been to the Slovakia factory.

[skyboltone]

I have had NOTHING but trouble, right out of the boxes, with 3 pairs of JJ 6V6's in my homegrown D'lite build.
Dave O.

I'm running about 25% culls on JJ El-84s. The ones that work sound fine but they have (so far) had a disappointing failure rate.

[markmalin]

Sounds like good progress so far. Great to hear!
Much like you, I have an old pair of 6V6 pulls (dark glass/coating/whatever the hell that stuff is in there!) that sound marvelous so I know that the platform is OK.

Yup, those are the ones!

Re the NOS TS 5881's, what other drop in replacements can I use? I have a 25w output transformer, so I don't think I want to run 6L6's, but what are some other options?

I included a dual bias arrangement in my build. In my mind, a must have if you are playing around with different tubes and tube types.
Dave O.

Did you use fixed and cathode bias? If so, I would be really interested in the circuit layout. The amp sounds good, but I miss that 50's Fender cathode bias sustain on the clean settings.

Mark.

[brownnote]

Sounds like good progress so far. Great to hear!
Much like you, I have an old pair of 6V6 pulls (dark glass/coating/whatever the hell that stuff is in there!) that sound marvelous so I know that the platform is OK.

Yup, those are the ones!

Re the NOS TS 5881's, what other drop in replacements can I use? I have a 25w output transformer, so I don't think I want to run 6L6's, but what are some other options?

I included a dual bias arrangement in my build. In my mind, a must have if you are playing around with different tubes and tube types.
Dave O.

Did you use fixed and cathode bias? If so, I would be really interested in the circuit layout. The amp sounds good, but I miss that 50's Fender cathode bias sustain on the clean settings.

Mark.

I think the dual bias he's referring to is 'splitting' the 220K 'bias resistors' into 2 separate trim pots, each with their own tail to ground creating 'separate' fixed bias for each tube.

BTW...You should be getting a good amount of sustain on the clean tones.

You may want to look at lead dress...

[ampgeek]

BNote is correct on the bias arrangement. Separate fixed bias for each tube.

I am using standard BNote D'lite iron and am getting loads of clean sustain. Very 3D sounding. Loving it!

I am still dorking around with the OD side. It sounds very good but I can't seem to keep myself from experimenting.

Dave O.

[markmalin]

I think the dual bias he's referring to is 'splitting' the 220K 'bias resistors' into 2 separate trim pots, each with their own tail to ground creating 'separate' fixed bias for each tube.

BTW...You should be getting a good amount of sustain on the clean tones.

You may want to look at lead dress...

I'll poke around with the lead dress and see. It might just be in my head. I can't compare to my 5E3 because I'm temporarily borrowing the speaker. Thanks for the tips, though.

Mark.

[markmalin]

Hey brownnote,

Just thought I'd let you know, I played with lead dress a little and it's sounding much better. I shortened up the grid wires on V1, as well as shortened up the way the caps/resistors are attached to V1. I removed the Orange Drop 0.047 and replaced it with a Mallory 150 0.047 uf cap I had because it was smaller and allowed me to pack things in better.

After doing this I notice a lot more clean sustain! Thanks for the tips.

Next thing I might try is teh 330 pf brite cap. It's a little harsh right now, but I'll give it time. From some of the posts I've read, it sounds like you have to put in more hours on the amp and then it will get less ice-pick bright on the Bright setting.

Mark.

[dogears]

Try a 120pf bright cap.

The 330pf refers to the treble cap. Not bright cap. Replace the 270pf treble cap with the 330pf size. It will thicken things.

[Structo]

Yes the treble cap is the ceramic one on the right side of the main board where the the treble pot enters.
Bright cap is on the volume pot.