Herbert "Crackling" question. Tubes?

[Rob Tahan]

First off, Ive had both my Diezels for years and LOVE them!

Lately my amp has been making crackling noises and i was wondering what you all may suggest. Im thinking power amp tubes? Maybe pre amp.

AND....

If so, which tubes do you all recommend for a really warm brown dark sound? (preamp that is..)
Thanks in advance

 

[Ventura]

I'd go for a complete retube.

Darker sounding pre's?? Tung Sols in my experience.

YMMV,
V.

 

[slyvren]

+1. You just need a tung sol in v1. Thats what Dave Freidman rcommends sometimes. My vh4 is too bright with my guitar unless I use a tungsol in v1. Everything else as per papa's recommendation.

 

[Rob Tahan]

Follow up.
Problem solved. Retubed everything
Tung sol is warm as piss! Love it!!

 

[King Guitar]

perfect.

 

[racerevlon]

I'm having a similar "whooshing" sound problem after putting in all new power tubes (2 x 6L6, 4 x EL34) and putting in Ruby 12AX7AC5 HG+ in V1, V2, V3. Rest are the JJ's that came with it. Seems to be happen after the amp's been on for a while and is hot. I'm thinking I may need to adjust the bias slightly.

EL34's are at 33mA per tube @ 480V PD and 6L6's are at 19mA 470V PD. Are the 6L6's biased too cold? The chart that I have shows good value is 38mA @ 470 PD, but I'm assuming that's per PAIR instead of per TUBE.

Can someone clarify?

 

[Peter Diezel]

Increase the current of the 6L6 to 35mA each tube,
70mA each pair.

 

[racerevlon]

Thank you Sir!!

 

[racerevlon]

Since we're "semi" on-topic, what is the recommended bias for EL34B's in a Herbert and 6550's in a VH4?

 

[King Crimson]

Since we're "semi" on-topic, what is the recommended bias for EL34B's in a Herbert and 6550's in a VH4?

A quick and general overview of the most common tube types for use in the
Herbert:

EL34/6CA7: Aggressive, slender low end, higher total harmonic
distortion…
Recommended bias setting: 30-35mA

5881/6L6: Great tube for clean sounds, good bluesy tones, also has
strong bass and excellent clarity…
Recommended bias setting: 25-35mA

6550: Very loud, very good dynamics, strong low end, amazingly
percussive…
Recommended bias: 40-60mA

KT88/KT100: Similar to 6550, but very punchy with great clarity and
warmth… Expensive…
Recommended bias: 35-50mA

 

[racerevlon]

Ok--I need some real help here. I've just finished re-tubing the power section of my Herbert and setting the bias via a Weber Bias Rite to Papa Diezel's recommended values. I also replaced V1, V2, V3 with brand new Ruby 12AX7AC5 HG+ tubes. It sounded great through my test cab (Crate Blue VooDoo with Mesa V30's, mono, 16 ohm) and I was finally at peace. I moved it back into my music room and connected it to my stock Marshall 1960A (mono, 16 ohm, G12T-75's) and after about 5 minutes of playing on Channel 2+ I started getting the mentioned crackling sound BAD. So bad the amp would completely cut out at times. Problem is, it only happens on Channel 2. Channel 1 and Channel 3 are solid and the problem does not happen--only on Channel 2. I looked up the tech specs on the Diezel web site and it doesn't appear there is any preamp tube that is exclusive to Channel 2. I'm going to put back the preamp tubes I took out to see if maybe one of the new pre tubes is bad, but C'mon... this is getting ridiculous.

Oh, and this only happens when I get up past bedroom levels, like around 8:00-8:30 on the Volume 1 knob. Past bedroom level but not concert volume. Fairly loud.

HELP!!

I finally get this amp sounding exactly like I want, and now this. Please help!!

Thanks in advance...

 

[racerevlon]

Can the mods please remove the "solved" word from the thread title so I can continue to receive assistance?

Thanks!

 

[King Crimson]

I looked up the tech specs on the Diezel web site and it doesn't appear there is any preamp tube that is exclusive to Channel 2. I'm going to put back the preamp tubes I took out to see if maybe one of the new pre tubes is bad, but C'mon... this is getting ridiculous.

Diezel Herbert Preamp Tube Layout:

V1 - All Channels
V2 - Channel 3
V3 - All Channels
V4 - FX Loop Send Driver & Mixer
V5 - FX Loop Return Driver
V6 - Phase Inverter

 

[racerevlon]

Yes, I can read--as noted above, no preamp tube exclusive to Channel 2, the only channel experiencing the problem.

 

[slyvren]

The tubes are usually used as 2 halves so sometimes half is dedicated to a certain channel. Sometimes half works and half doesn't. I'd try to replace ALL of the pre tubes just to make sure. Before that, what we usually do is fire the amp up, and tap the tubes gently with a butter knife with your guitar plugged up and volume up. If you hear it crackle as you tap you've found your problem tube. You also might try cleaning the socket and making sure the tube is seated properly. If that seems ok, then I'd take apart the head and make sure the caps still look ok. I.E. No Yellow goop leaking from them. If not, tech time email Papa.

Good Luck!

-John

 

[King Crimson]

Can the mods please remove the "solved" word from the thread title so I can continue to receive assistance?

Thanks!

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[Ampaddict]

Sounds like a preamp tube. Try replacing em one at a time. I know its hard to reach v1. Been there many times! Diesels are preamp tube eaters!

 

[racerevlon]

Update....

So, I pulled the head back onto the bench and hooked it back up to my test cab. Before powering up, I reseated V1. I played at volume for about 1 hour and the problem never occurred. I'm going to put it back into the music room where the remaining variables will be:

Different speaker cable
Marshall 1960A instead of the Crate Blue VooDoo
Different Mains cord into different physical power strip/outlet
Different guitar lead
Different environment (room) -- It will be sitting back on top of my VH4.

I'm hoping the re-seating of the V1 tube solved the issue, but as weird as this issue is, I'm not getting my hopes up. Will report more when I know more.

Thanks to all for the great support!

Cheers,

 

[racerevlon]

Ok--I put the amp back on top of the VH4 and plugged back into the 1960A. After about 10 minutes of playing, the problem re-surfaces. I need to change the speaker cable and try a different cabinet in that room.

Question: when testing for microphonic preamp (or power amp, for that matter) tubes, what is the condition I'm looking for? When I tap the tube, what sound will it make if it's bad? Static? Crackling? Both? Something else?

Also, if it's a good tube, what should happen when you apply the "tap" test?

I'm seriously confused, but I guess I don't get to be that confused until I swap out the cabinet and the speaker cable in the music room. What baffles me is that the condition is not consistent--only occurs after about 10 minutes, and only on Channel 2. Heat-related? Environmental?

 

[xXxGhotimanxXx]

If it doesn't do it in the music room, I'd look at everything else that is different. If the amp is fine in one place and not fine in another...it's not the amp...it's the place.

J