my amp went in for some service, hum issue. my amp tech is telling me i shiold put in 6550 instead of the 6l.
any thoughts or issues???
any thoughts or issues???
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Fender Super Twin Bass Head
- Thread starter johnk_10
- Start date
- Feb 16, 2008
- 21,240
- 23,636
- Disclosures
- John K Custom Basses
I wouldn't change them to 6550's if I were you.
you just want heavy duty 6L6GC's. I've used Shuguang 6L6GC's (coke bottle shape) and 6L6GCR's with excellent results, and they're both cheap, sound great and are built very rugged.
you just want heavy duty 6L6GC's. I've used Shuguang 6L6GC's (coke bottle shape) and 6L6GCR's with excellent results, and they're both cheap, sound great and are built very rugged.
thanks guys. I had a feeling you would disagree and to be honest i just don't know enough.
he was saying that the 6L6's were being pushed to hard and the 6550 would take it better. but all i remember hearing is that the new 6550 are lousy and everyone with SVT's is always bitching about changing them so soon. my old SVT had GE and they lasted as long as i owned the amp. Same with my 72 V4B and the 7027's.
he was saying that the 6L6's were being pushed to hard and the 6550 would take it better. but all i remember hearing is that the new 6550 are lousy and everyone with SVT's is always bitching about changing them so soon. my old SVT had GE and they lasted as long as i owned the amp. Same with my 72 V4B and the 7027's.
Of course they are run too hard, any MI amp runs the valves "too hard". That is where the power output and "tube sound" come from. There are current production tubes that will survive the service, just maybe not the cheapest ones.
I have no trouble with a "tech" that suggests "You could try", but not you should.
I have no trouble with a "tech" that suggests "You could try", but not you should.
The heater of the 6550 draws a lot more current compared to a 6L6GC (1.6A vs. 0.9A per tube). That could damage the power transformer.
Just saw on on my local 'list for 600 already converted which got me searching this thread. If I didn't think my better half would get upset
So, tried out the Super Twin at practice the other day... and it just couldn't hang. Refurbed, new tubes, etc. I was distorting trying to get to a usable volume.
Now, this was through my Mesa Diesel cabs, which I'm starting to think may be too thirsty for this amp (original EVs). I have a couple of Faitals waiting for boxes; would these be efficient enough for the ST?
I liked the tones I was getting, just wish I could hear them once the band kicks in...
Now, this was through my Mesa Diesel cabs, which I'm starting to think may be too thirsty for this amp (original EVs). I have a couple of Faitals waiting for boxes; would these be efficient enough for the ST?
I liked the tones I was getting, just wish I could hear them once the band kicks in...
you did not give us any info on just how loud the band is. As long as your amp is in reasonably good shape as far as tubes and caps and such, it will put out an honest 180w. OTOH, the ST and Studio Bass amps are just 180/200w and if you are needing huge stage volume, you may be out of luck with the ST. I use my Studio Bass with an LDS 2x15 (Faital loaded) cab and a Berg CN212 (104db) with great results in several working bands, but I do not need the amp to knock down walls as far as total volume goes.
Another consideration is how you are setting the EQ controls. If you are running bass heavy on the tone and rotary EQ sections, you might consider cutting a bit down low and focusing on low mids/mids. That will get more out of the amp.
It already sounds like you know that you will likely get a bit more out of your ST with more efficient cabs, so maybe the Faitals will work better.
it's a great amp for sure, so keep trying
good luck
Band is two guitars (a Deluxe and an Egnater Tweaker), drums, horns. Multiple EQ scenarios. I can barely keep up with the drums (band is a Replacements-y pop band).
- Feb 16, 2008
- 21,240
- 23,636
- Disclosures
- John K Custom Basses
with two K140's mine is more than loud enough, with headroom, and that's playing with a LOUD rock band with no FOH support.
Most probably not the speaker... I have experienced the same distortion problem with my 1975 ST. First check that the distortion footswitch is on the OFF position, boost button pushed to the left, and distortion switch/knob at zero.
I checked and re-checked all the (matching) power and preamp tubes, added a bias adjustment pot and set it up right to 35 mV/35mA, cleaned all tube sockets and pins, swapped all electrolytic caps for new ones, with no result. Finally, I removed (disconnected) the whole distortion section (7 soldering points), cut the wire to the V3B screen and connected it directly through a shielded wire to the output volume pot. I also added a cathode bypass to V3A (same as for V1A, 1500 ohm // with a 1000µF/10V cap replacing the 750µF/3V cap in both V1A and V3A), which my ST version was missing. So, the V3 stage is almost similar to that in the Studio Bass now, and the distortion has reduced significantly, but not totally gone... So, some work is still to be done by a skilled tech this time, before getting access to heaven...
Note that there are at least two different versions of the ST preamp schematics (with the same document number though). One can be easily found on the Internet (a somewhat lousy version). And, only by chance, I found the other one here (see the second picture), and it shows almost exactly how the preamp on my ST is built. Minor differences in mine are: a] an additional diode in // with a 2.2 K ohm resistor after the 500 mH inductance from the V3B cathode bypass, and b] a 150µF/6V cap instead of a 5µF/50V between the 47 K ohm resistor to the V3A screen and the ground. But all these have now been removed with the whole distortion section.
GOOD LUCK -
(Beware of high voltage loaded in the amp, that can kill you, even when disconnected from the mains, and have the work done by a trained tech if you're not sure of what you are doing).
I actually use mine with a 2x15 with jbls. Recently I picked up a single 15 and it has an old EV in it. I almost find it louder than my JBLs. Sounds amazing actually. So it probably isn't the speaker. My EV cab is an 8 ohm and the head is a 4 ohm and even then I'm having no volume issues. Haven't needed to go past 4 yet at any shows yet.
i use mine with either a 4 ohm ev in a MM HD115 cab or a 2 15 ev 4 ohm cab for outdoor shows. It is pretty loud and can approach uncomfortably loud when pushed.
One going fast on Ebay, cheap !
http://www.ebay.com/itm/1976-Fender...039?pt=LH_DefaultDomain_0&hash=item20e83f877f
http://www.ebay.com/itm/1976-Fender...039?pt=LH_DefaultDomain_0&hash=item20e83f877f
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Time to revive this beautiful thread! I just bought a Fender Super Twin yesterday. What an amazing amp!! My other tube amps are a Sunn 200S, Music Man HD One Thirty and a Sound City B120 with a new preamp. I'm pretty sure the Super Twin is going to be my new #1! Thanks to John for starting the thread and letting me in on the secret! And to everyone else for contributing!
I'm about to buy the headcase from Mojotone that has been discussed earlier in the thread. Is that still a good option, or does anyone have other suggestions? When buying from Mojotone, did you guys drill the screw holes yourselves? It seems they will only drill for a Mojotone chassis.
Thanks!!
I'm about to buy the headcase from Mojotone that has been discussed earlier in the thread. Is that still a good option, or does anyone have other suggestions? When buying from Mojotone, did you guys drill the screw holes yourselves? It seems they will only drill for a Mojotone chassis.
Thanks!!
Attachments
Congrats! Assuming you bought the whole amp, it shouldn't be too difficult to properly place the holes in the headcase. The metal chassis straps that Fender uses are pretty forgiving too. If I was doing this, once I located the holes on the head case, I'd probably cut out a small square of tolex where the bolts will go so that the tolex doesn't get snagged and stretched by the drill bit. A No. 1 Xacto knife with a new blade cuts tolex like warm butter.
enjoy the Super Twin. I have been enjoying my Studio Bass (basically the same amp as the Super Twin) for several years now. great sounding (and looking) amp. My amp came in a Mojotone headcase when I bought it, so I can't offer you an answer on the mounting question.
These amps have plenty of power, but if you wish for just a bit more, along with a bit more clean headroom, a good option is retubing with 7581a power tubes. Tung Sol released a true 7581A this year and they work great. The 7581a's are a 6L6 pin compatible power tubes that have a bit higher plate dissipation than the std 6L6. Earlier this year I retubed my Studio Bass with them, and it definitely gave the amp more clean headroom, and a bit different voice overall.
good score Kreken
enjoy!
Thanks guys!
I really appreciate the input! I used the head on three gigs this weekend with my TKS 215 (Swedish cabinet builder) with Faital Pro 15PR400's. Souned superb!! I believe I've found my new favorite amp! Such a fat bottom, but still very tight and distinct. What I've done so far settings wise, is to keep everything pretty much flat, maybe cut back the bass a little bit, master volume pretty much all the way up and adjusting gain to get the stage volume needed.
Thanks for the heads up on the 7581A tubes. When buying power tubes for the ST, do I need all six tubes to be matched, or just buy three matched pairs?
I really appreciate the input! I used the head on three gigs this weekend with my TKS 215 (Swedish cabinet builder) with Faital Pro 15PR400's. Souned superb!! I believe I've found my new favorite amp! Such a fat bottom, but still very tight and distinct. What I've done so far settings wise, is to keep everything pretty much flat, maybe cut back the bass a little bit, master volume pretty much all the way up and adjusting gain to get the stage volume needed.
Thanks for the heads up on the 7581A tubes. When buying power tubes for the ST, do I need all six tubes to be matched, or just buy three matched pairs?
