Reducing the Wattage of my Trem-O-Verb?
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YellowJacket
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Yes,
Step 1. pull either the outside pair or the inside pair of power tubes. (6L6s / EL-34s)
Step 2. If you use the tube rectifier, pull one of the two rectifier tubes.
Step 3. The impedance of the amp changes with the two missing tubes. Rather than matching an 8 ohm speaker jack to the 8 ohm speaker output on the amp, you should now plug the 8 ohm speaker jack into the 4 ohm speaker output on the amp. Basically, the impedance is halved with the amp only running two power tubes.
**note** if you switch the power band to 'spongy' you'll get roughly 35watts instead of 50. The downside is that the punch and thump just isn't there anymore on this mode.
Step 1. pull either the outside pair or the inside pair of power tubes. (6L6s / EL-34s)
Step 2. If you use the tube rectifier, pull one of the two rectifier tubes.
Step 3. The impedance of the amp changes with the two missing tubes. Rather than matching an 8 ohm speaker jack to the 8 ohm speaker output on the amp, you should now plug the 8 ohm speaker jack into the 4 ohm speaker output on the amp. Basically, the impedance is halved with the amp only running two power tubes.
**note** if you switch the power band to 'spongy' you'll get roughly 35watts instead of 50. The downside is that the punch and thump just isn't there anymore on this mode.
GuitarGuy503
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When I was a DSL50 Owner (and a member of the Marshall Forums) someone asked the same question in regards to the DSL100 and supposedly a few people ruined their amps as a result of doing this. Personally, I'd call Mesa and run the question by them before I did anything. Better safe than sorry....
The part about switching which impedance jack you plug into should take care of any matching issues which is the biggest concern with pulling tubes. You can do this without much concern for damaging the amp as long as you take the impedance into consideration.
YellowJacket
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GuitarGuy503 said:
Worry not, this mode of operation was actually discussed in the original owners manual for the 2 channel dual rectifier. And you are right, the Marshalls can't handle being operated this way so your word of caution is a wise one, given your experience.
Another point of trivia: Marshalls apparently cook yellow jacket tube converters while mesas are fine with him. Apparently the lower plate voltage required to run 6L6s doesn't run the tube converters as hot.
94Tremoverb
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Anyone who damaged a DSL100 by running it on two tubes was doing it wrong - there is absolutely no difference between them and any other 4-tube 100W amp in this respect. Most likely, they either didn't reset the impedance, or did but got it the wrong way round. (And these amps *are* much more sensitive to impedance mismatches than Mesas.)
There is actually a TSL100 (same power section) at a studio that I work for which I permanently converted into a TSL50 after it burned a couple of big holes in the PCB (while running as a 100) and made it impossible to repair one of the tube sockets. So I removed two, reconnected the OT for the correct impedances - leaving the outside of the amp stock, so you still plug a 16-ohm cab into the "16 ohm" jack, although internally this is now the 8-ohm connection - and it's been totally reliable ever since. Why should it not be? All that's changed is that it's producing half the power and so the transformers and power supply components are under less stress.
It's also untrue that Yellowjackets won't work reliably in them. The plate voltage is just under 500V, the same as most other EL34 or 6L6 amps - and the same as a Mesa set to bold/diode mode. If there have been any fried I would again suspect user error.
There is actually a TSL100 (same power section) at a studio that I work for which I permanently converted into a TSL50 after it burned a couple of big holes in the PCB (while running as a 100) and made it impossible to repair one of the tube sockets. So I removed two, reconnected the OT for the correct impedances - leaving the outside of the amp stock, so you still plug a 16-ohm cab into the "16 ohm" jack, although internally this is now the 8-ohm connection - and it's been totally reliable ever since. Why should it not be? All that's changed is that it's producing half the power and so the transformers and power supply components are under less stress.
It's also untrue that Yellowjackets won't work reliably in them. The plate voltage is just under 500V, the same as most other EL34 or 6L6 amps - and the same as a Mesa set to bold/diode mode. If there have been any fried I would again suspect user error.
YellowJacket
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I ain't arguing with this, makes sense to me!
Ya, guys were whining over on a Marshall forum about cooking YellowJackets but I have not had any trouble with mine and they have to be at LEAST 8 years old now. I use them A LOT! I also ran a TSL100 for a show I played with only two power tubes. I always am sure to change how I connect speaker leads to accommodate the change in impedance. I didn't have any problems except for more awesome tone!
Out of curiosity, how much $$$$s is it for the JCM2000 heads used? I see lots of guys in Toronto listing them for $1000 - $1200 when I figure they're worth more on the lines of $600 - $700. While I like the tone of the DSL 50 I'd rather have the reliability of a Boogie.
Ya, guys were whining over on a Marshall forum about cooking YellowJackets but I have not had any trouble with mine and they have to be at LEAST 8 years old now. I use them A LOT! I also ran a TSL100 for a show I played with only two power tubes. I always am sure to change how I connect speaker leads to accommodate the change in impedance. I didn't have any problems except for more awesome tone!
Out of curiosity, how much $$$$s is it for the JCM2000 heads used? I see lots of guys in Toronto listing them for $1000 - $1200 when I figure they're worth more on the lines of $600 - $700. While I like the tone of the DSL 50 I'd rather have the reliability of a Boogie.
94Tremoverb
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I don't know about prices in North America - where Marshalls are more expensive relatively than they are here in the UK, and Mesas a *lot* cheaper (they're stupidly expensive here) - but in my opinion, if you compare build quality and features, a modern Marshall should be about half to two thirds the cost of a Mesa for the same power and similar feature set (eg TSL compared to 3-channel Dual Rectifier).
Just out of interest, do you reset your impedance when running Yellowjackets? I know THD say not to (or don't mention it) but in fact for correct matching you should, since EL84s have around double the impedance of 6L6/EL34s - so again, if running a full set of four in a 4-tube amp you need to run the speaker from the jack for half the impedance, and if running only two, ideally you need to be running a 16-ohm cab from the 4-ohm jack.
I also wonder if this could be frying Yellowjackets in these Marshalls, if it's not done - there's one little detail in the DSL/TSL schematic that makes me think there is a problem with high-voltage surges, which they 'band-aided' by adding a cap where there should be no need for one... and if the amp was running at the wrong impedance as well, this may be increased and could potentially damage something. I've seen a few where the cap (rated at 1KV) has failed, implying that the voltage spike must have been even higher, and that could probably fry a Yellowjacket.
Just out of interest, do you reset your impedance when running Yellowjackets? I know THD say not to (or don't mention it) but in fact for correct matching you should, since EL84s have around double the impedance of 6L6/EL34s - so again, if running a full set of four in a 4-tube amp you need to run the speaker from the jack for half the impedance, and if running only two, ideally you need to be running a 16-ohm cab from the 4-ohm jack.
I also wonder if this could be frying Yellowjackets in these Marshalls, if it's not done - there's one little detail in the DSL/TSL schematic that makes me think there is a problem with high-voltage surges, which they 'band-aided' by adding a cap where there should be no need for one... and if the amp was running at the wrong impedance as well, this may be increased and could potentially damage something. I've seen a few where the cap (rated at 1KV) has failed, implying that the voltage spike must have been even higher, and that could probably fry a Yellowjacket.
YellowJacket
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Weird. I was resetting the impedance for the yellowjackets but I don't think I was doing that properly. I was running from the 4 ohm output to an 8 ohm cab. I've been running these things for 8 years and I've had no trouble with them yet.
94Tremoverb
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That's correct for four Yellowjackets and only one impedance step out for two, which is how they're 'meant' to be, so nothing to worry about. It's just not quite the theoretical best match.YellowJacket said:
OK, getting things back on track... ;-) I pulled 2 out of 4 power tubes and one of the rec tubes, switched speaker conection and the amps sound AMAZING!!! I can get the tubes much hotter with less volume and I'm VERY happy. Even now at 50Ws they're STILL super loud and definatly louder than any stage mix I've had to content with... :shock: :lol:
