I got yo big ol' Ultra Linear right here.

[matt h]

If that's what a UL-run Sunns sound like, I'd say "UL for guitar sucks" is officially myth-busted.

It doesn't surprise me that someone would say to un-UL most guitar amps that have it. Same reason as before: most guitar amps with UL didn't really design around UL. or rather, design starting from UL. Additionally, there's the issue that UL doesn't sound like "pentode mode with gnfb." It's different. Not better, not worse- different. If you're trying to make an amp sound like classic fenmarvoxsons, like the super-famous *insert iconic fixed-biased gnfb" of the mid to late 60s... yeah, UL isn't a good starting point for that.

It really wasn't until the last what, decade or so? that (small) manufacturers started caring about tone at the expense of power out.

UL was, historically, implemented as a way to get more clean power out. As guitarists, that's rarely the best recipe for tone. I still don't think that precludes using UL, just don't drop it into a circuit that wasn't designed to sound good with UL.

That Sunn amp clip sounds killer. If that's with UL, and the Sunn power sections were Dynaco circuits... I'm not surprised. It started with a great sounding power amplifier with UL as a starting point-- not an afterthought.

[LeftyStrat]

First off, let's face it, Jimi listened to whatever he was playing, and could probably find a way to make solid state sound good.

But the clean sustainy thing sounds quite nice to me. Guys freak out over the SSS thing, but the clips of over the rainbow, pretty close to Hendrix playing an SSS.

[matt h]

I'm not really gonna touch the guitarists that followed hendrix bashing, but I will say that channeling some Jimi isn't the same as being nothing more than a copy. Eminem uses a lot of iambic pentameter, but that hardly means he's a nothing more than a Dr. Seuss copy... y'know? Shakespeare made it famous, but he didn't invent it either.


All that being said, Lefty, you did nail one really important thing: Hendrix (probably?) listened to what the amp had to offer and milked it for what it did well. That's really the mark of being an excellent electric guitarist... it's a whole dynamic system


And while this is thread derailment galore, I can see Hendrix digging the shit out of Mark Knopfler (who doesn't, to my ear, overlap with him a bit stylistically). I can hear him covering the sweet buttjebus out of "Sultans of Swing" and "Fade to Black" (the dire straits song of that name, not Metallica's or Nina Gordon's)

Mark Knopfler also comes to mind as another player who's had a very varied amplifier history and worked the amp. (if you've ever read/heard his spiel on volume pedals...)

Different tools do different things, uh, differently. BB King and Dimebag Darrell used SS amps with great results. Go figure- from the cleanest to the dirtiest solid state amps have wiped the floor with tubes. Some modeling amps have been used and sounded excellent (I'm thinking of the current trend in modern backlines of fancy modelers and cabinet simulators straight into house PAs). Now it's not enough to use analog sand, but digital is even kicking ass? yikes.

It's funny that now, in this day and age, with so much more acceptable and legit, there's still so much prejudice about.... oh, right, UL. Sorry, almost turned this into social commentary. haha

But yeah, UL can do a lot more than just a clean-sounding-amp. It just means your power amp will hang together longer and pass whatever it is that your pre and PI are sending it.

Even when someone puts in a UL/pentode switch in an amp, it's not really a fair comparison... why not? Two things come to mind: power supply nodes and adjusting drive voltage. Our ears almost always hear "louder=better", and most of the time, UL isn't going to be as loud with the same sized signal coming in. (assuming "pentode" mode doesn't also have some kind of nfb at the same proportion to what the UL had coming in, possibly via cathode)

I challenge someone to build a pp UL amp, cathode bias, play with the screen resistor values to taste, moderately filtered (but with beefed up "plate" tap since it's really a plate AND screen connection...) with a tube recto with an AC30ish circuit hanging out in front of it, with a tweaked PI bias and tail resistors. I think around here you guys call something a "Rockster"/octal Rocket variant? Start there and optimize that for UL operation and I doubt it'd disappoint.

No surprise, it's not going to sound like the very-high-voltage UL-and-too-much-gnfb fenders. I also suspect it'd sound different from a Rt66 and probably spank it. I doubt it'd have much, if any, common ground with the SSS.

[Reeltarded]

omg Matt. You be Vidal and I will be Buckley. Ready?

UL sucks.

Your turn. lmao

I do not like it on guitar. i did not use it in my car. I cannot stand this thing "UL" and if you can then go to Hell!

bitch fight!!

[matt h]

naww, iggerants is blitz.

[Reeltarded]

Nanananana I know you are but what am I?

Yeah! Come back on that! Oh yeah! I rocked you!!

[vibratoking]

Many of you will hate me for saying this, but Trower, Marino, and SRV, are just pale copies of Hendrix, but we love them because it is all we have.

I don't hate you for speaking the truth.

[stephenl]

I built a RT66 a couple of years ago, i liked it....didn't really love it. It had a nice clean tone but was a "one trick pony", not very versatile as an instrument. I modded the amp many times into several different incarnations but ended up gutting it. I still have the OT, its basically a 50watt, 6.8k, 43% UL taps.

Someone on one of the other forums suggested something called E-linear - using the the screen taps to feed the anodes of a LTPI. I've been meaning to try it but haven't got around to it yet.

Does anyone have any idea how much feedback the screen taps would supply in comparison to a typical feedback loop from the OT secondary?

[martin manning]

Does anyone have any idea how much feedback the screen taps would supply in comparison to a typical feedback loop from the OT secondary?

Voltage ratio from primary to secondary is the square root of the impedance ratio so at the 8-ohm tap (8/6k8)^0.5=0.0343, vs. UL tap's 0.43. So 12.5 times as much.

[teemuk]

FYI, the 43% is a value which Hafler and Keroes picked for least distortion in a KT88 tube. See, there's a very narrow range where distortion of the amplifier will drop tremendously, below that of triode mode, while power efficiency is only slightly decreased, basically matching that of a pentode.

But this value is different for different tubes, although somewhat in the same ballpark. EL34's and EL84, for example, are quite happy with the same value. However, for 6V6 tubes the corresponding value is actually 20%. The important point is that % of tapping must be tuned for the specific output tube and better yet, tweaked to optimum using a distortion analyser. Using 6V6 tubes with 43% tapping doesn't even give an accurate representation of real ultra linear operation. There's a thin line where "UL" is really UL or where it's just distributed loading.

Merlin, that "Valve Wizard" guy summarized it excellently in one of his posts at ampage forum:

The optimum taping point depends on the tube type. For KT66 it comes out around 43%, whereas for 6V6 it is about 20% (IIRC). There is no analytical way to calculate the optimum percentage- you actually have to try out several options and make the distortion measurements for the tube type you want (unless someone has already done it).

Remember, there is a difference between ultra-linear and distributed load.
Distributed load just means supplying the screen grid from a tapping point on the OT. In general, the more you move towards the anode, the more the distortion and power falls, until you reach triode mode.
BUT! somewhere between full pentode and full triode there is a sudden null or valley in the total distortion, and there is also a small *rise* in power too. This optimum point is what is called ultra-linear, and you can probably appreciate why the tapping percentage would depend on the design of the tube, since it involves feedback and distortion nulling, and each tube type is different.

In practice most people are happy with whatever tapping point is available on the transformers they can get hold of. Few people have the time, money and equipment needed to find the optimum. They usually settle for "anything is better than full pentode" (I'm talking about hifi here, of course).

For example, the 135W Fenders may look like they operate in UL but if you measure the specs you will find out their distortion figures were not improved nor was the output power increased from plain pentode mode. As far as I know, the 12% tap in Fenders was merely a cheap way to utilise distributed loading scheme in getting rid of an expensive choke. But UL it isn't.

[stephenl]

Does anyone have any idea how much feedback the screen taps would supply in comparison to a typical feedback loop from the OT secondary?

Voltage ratio from primary to secondary is the square root of the impedance ratio so at the 8-ohm tap (8/6k8)^0.5=0.0343, vs. UL tap's 0.43. So 12.5 times as much.

So would the fb be attenuated through the plate resistor using it as mentioned?

[C Moore]

I see from some of your guys posts that Impedance comes into play with a UL.
Would a a conjunctive filter have any better or worse application with a UL out tranny.?
Thank You

[teemuk]

"Conjunctive filter" is just a RC Zobel filter to compensate increasing inductance of a loudspeaker. I don't see why it would be any different in UL vs. no UL.

[C Moore]

Thanks...do not know enough to know...
Mike Zaite uses them on a few of his models...he is one of the few (I think) guitar amp builders that also likes to use a UL OT...so I got to wondering if there was any correlation.
Thanks Again

[LeftyStrat]

Thanks...do not know enough to know...
Mike Zaite uses them on a few of his models...he is one of the few (I think) guitar amp builders that also likes to use a UL OT...so I got to wondering if there was any correlation.
Thanks Again

The Route 66 uses UL. The amp is beautiful in it's simplicity. EF86, unique tonestack (at least to me, I haven't found anything similar), 12ax7 PI, and the UL KT66's. Seems to be a platform to let the EF86 shine. Mike knows his shit.

Teemuk, interesting info. I have a few original A470 transformers laying around. Might have to try one with KT88's.

Glad to see this thread revived.