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Karl Brake
New member
Can you safely replace the stock KT77 in Diezel amps (mine being a Paul) with EL34s? If you've done it, what's your opinion?
Ventura
Well-known member
100% yes.
Just gotta rebias the tubes after install - make sure you pick up a matched quad whenever going from any tubeset to another. And let the amps settle in to observe drift.
Personally I dig KT77s in my Diezels. I also liked 6550s in a couple setups (but Papa won't like me saying that). The current stock 77s are there because they're solid tubes, sound great, are consistent, and not too expensive to replace when needed / if necessary.
Not raining on yer parade but what goal do you seek in swapping over to EL34?? What amp is in question?? I can see how some may work with EL34 over KT77 - but even before Diezel came stock with 77s, I ended up re-tubing my Diezel with GoldLion KT77s are they're still in them to this day (save for one that's got 6550s
)KT77s sound best to me....highs of a 6L6, grunt of an EL34, low end of an 88 - love em.
Unkle Mo
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Karl Brake
New member
Just curious. I'm a Marshall guy from way back, but am digging the Diezel thing. I have a power tube acting up, need to replace the set...I have sets of matched el34s lying around, so....but I like the punch of the Paul so will stick with the kt77s. Wondered a bit about differences in breakup between the two types. Thanks for your reply.
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Karl Brake
New member
Well, I just put my new JJ KT77's and biased it to 80mA as instructed on the PCB. Sounds great!!! I actually got a note back from Peter Diezel saying that with the Diezel Paul EL34's are fine, since it evidently runs at lower plate voltage than other Diezels. Maybe this is part of the "Vintage" tone?? The bias was sitting at about 65 before, and I think I hear the difference with the slightly warmer bias.
Ventura
Well-known member
That sounds WAY too hot!!!!! Pull back - usually EL34s run optimally at around 32mA each, therefore maximum 70mA per pair.
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Karl Brake
New member
I hear that...but the instructions are clear on the board. I'll ask Peter. Yes, normally, 35 per tube is pretty standard, with Diezel and everyone else, but...it's printed right on the PCB, actually step by step. The Paul is a bit different from other Diezels. I'll ask Peter.
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VESmedic
Well-known member
Pro tip: drop EL34s down in the Herbert to 40-45 per pair on El34s. Better highs, better lows, tighter, less squawk, more punch. I’m surprised no one talks about this more... seriously, give it a shot, no need to run el34s that hot in Amps like this designed to be loud and tight.
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Karl Brake
New member
Interesting! I'll give it a try...I'm very basic when it comes to biasing, I just go with what the manufacturer and my old Marshall factory tech friend told me to do. I'm using a Paul head, which may react differently than the Herbert. I'm waiting to hear from Peter Diezel. He says the Paul is a different animal than the Herbert and D-Moll. Thanks!
Ventura
Well-known member
If it's the PCB as in Printed Circuit Board - often these will indicate maximum thresholds, not "optimum operational range". I can't speak for your particular amp and its related printed circuit board, I only know from my experience of working on a lot of amps, upside-down with biasing and the like, 80mA is fkn hot.
As for the comment above re: EL34 - yep - 25mA was the "hotter side" of those tubes back in the 80s; with many cats bringing them down to 20mA each for a more chunky punch.
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TUBES
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VESmedic
Well-known member
If it's the PCB as in Printed Circuit Board - often these will indicate maximum thresholds, not "optimum operational range". I can't speak for your particular amp and its related printed circuit board, I only know from my experience of working on a lot of amps, upside-down with biasing and the like, 80mA is fkn hot.
As for the comment above re: EL34 - yep - 25mA was the "hotter side" of those tubes back in the 80s; with many cats bringing them down to 20mA each for a more chunky punch.
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TUBES
Wish I would’ve done this so much sooner in my Herbert, unfortunately mine is an older model that doesn’t have external bias points, so it’s much more of a pain to do on the fly unfortunately. To me, running EL34s that hot is the same ridiculousness that people who “bias modded their 5150s to run hotter” and think that sounds better... they don’t, like at all, and are biased cold for a reason. Of course, these aren’t even remotely similar amps, however the same principles apply of course as far as tonal characteristics of a hotter or colder bias. I encourage everyone to Atleast try EL34s in the 40-45 ma range, especially if you have external bias points: it isn’t going to hurt in the least, if anything it’ll be quite the opposite. Especially if you mic up your amp often, the differences will be much more clear under a mic and monitoring in isolation on studio monitors.
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Karl Brake
New member
I'm running kt77s at that setting, short sessions right now until I hear back from the Man. You may notice in the service manual an illustration in what I believe is a VH4 indicating a 60mA per pair setting. Maybe each amp is different. We'll see. No redplating yet, but just playing an hour or two at a time at low volumes for now...
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tonesfoyobones
Well-known member
Exactly! I picked up a Herbie mk1 local and it was loaded with Ruby EL34B-STR's. I've tried 2 other Herberts, one was a mk2 and the newest mk3. In the end they did not do it for me. I dug there features but something was just off for me. I only jumped on my current one because it was close and a good deal. Like I said it had Ruby EL34 BSTR's and sounded huge! Great 3D feel.
I started reading around about it and say that Peter was opposed to the BSTR's because the Herbie because of the screen voltage. He liked the EL34B-HT's better due to being able to handle a higher screen voltage so not wanting to damage my German made beauty I bought a sextet of the Ruby EL34B-HT's. Biased it and gave it a go. Sadly the B-STR'S sounded and felt way better. I was so bummed! Here I finally dug my Herbert ALOT and now it doesn't sound the same as it did with the B'STR's!
Looking back maybe biasing it a little colder would have done it but I sold the sextet of H-STR's and bought a sextet of Gold Lion KT77's and have never looked back! While it's not the same "feeling" as the B'STR'S had it has it's own thing now and I really dig it. Fat, huge, 3D tone with some great velvety middle.
I think that I will retry the H'STR's at some point but with a colder bias setting like VESmedic mentions.
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Karl Brake
New member
I heard back from the Boss, and the Diezel Paul runs at a plate voltage of 420, so, yes, the Paul should run at 80mA per pair. It is a less compressed and looser feeling amp than the Herbert, which works for me, though I really appreciate the Herbert for what it does. It's simply amazing to actually talk with the designer!!! Thanks for the tech tips, I learned a lot!
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VESmedic
Well-known member
Man I really wanna like the gold lion kt77s, but nothing I’ve heard makes me wanna drop the cash for them. I just got some jj kt77s for my Herbert that should be here today, we will see if I like them. But I just couldn’t justify the cash for the gold lions after what I heard. Now the gold lion ecc83 for v1, that’s a different story, those things are phenomenal, huge fan. As well as TAD’s 7025.
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Karl Brake
New member
I wondered about the Gold Lions, too, since I really don't change output tubes that often... even when I'm gigging heavily, maybe every other year, but I am not convinced that there is any reason to pay twice as much for the Gold Lions. If anything, I'd be tempted to try the EL34II's that JJ puts out, I've had really good experience with those in my Marshalls. Preamp tubes seem to be very subjective. I have been guided to always use a JJECC83s in the PI position, since they are so reliable (I have yet to have a JJ go microphonic on me), but I have noticed a bit more aggression, it seems, from Tung-Sol 12AX7's, and tend to use those in the gain slots in my amps. I have had those funk out on me, though. I do like the Tung_Sol EL34B's in my Marshalls, but alot of that was for better bass response...which the Diezel already has. I have rolled expensive NOS preamp tubes in and out, with no sonic difference...I happened to buy an amp with some Hewlett Packard 12ax7's from the early 60's! I sold them. They are renowned primarily for the pure mica they used, which really held up in computers using thousands of tubes 24/7. I really have heard very little magic from any preamp tube. I had a Marshall JVM, and used a 5751 in the V1 position to lower the gain, and that did have a positive effect. Since then I modded one of the JVM's to make it tighter, punchier, and quieter, and picked up a JVM Satriani, that cuts through and is incredible quiet for a high-gain amp. I am liking the purity of the Diezel sound, on all gain levels, and we'll see if it replaces my Satch Marshall when I start playing out again this summer.
Ventura
Well-known member
I went with the GL-KT77s in my 20thA XTC - and they've worked incredibly well in that amp - for ages (they're still in there). I've used them in other amps with not to discernible a difference, basically, not worth the price of a =C=/SED or the like. Lately I've noticed a lot of contemporary manufacturers making some great bottles - way better than 10 years ago. JJ, Svetlana, Tung-Sol, some killer glass out there and price is no longer a direct correlation to "sonic quality" of a tube. The ECC83 are still my preferred preamp bottle, as is the Svetlana 12AX7.
Less hiss & fizz, more guttural punch and grind. Any mic setup will show, gain is NOT your friend when recording unless you want the Beehive Sonata as your final opus.
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VESmedic
Well-known member
For what it’s worth, I just did a ton of shootouts with different kt77s, and EL34s under a mic... for me personally, the EL34s won, ha imagine that! The kt77s were cool, but I honestly liked the gold lion the least, and I’m quite on the fence about the the gold pin 12ax7s they have too... just not great to me personally. the TAD EL34BSTR was the winner to me in my Herbert personally. Punchiest low end by far.
CornNutz
Well-known member
Depends on the plate voltage.