I hate to say it, but now I think maybe I like my amp in ultralinear mode versus triode
It's a Cary V-12; it features a dozen EL34s and each pair has a switch in between them that configures that pair to either triode or ultralinear. In full triode Cary listed in the specs that it makes 50 wpc and in full ultralinear 100 wpc. For most of the twenty three years that I have owned this amp I have always felt that I preferred triode except for the occasions that I wanted to full out blast (it has literally been many years since I've felt the need to full out blast).
However, today I experimented with a couple of things in my system, and after listening to the same "Jazz Essentials" (compilation) red book CD a couple of times all the way through, the next thing I experimented with was switching to full ultralinear.
Maybe there was more "PRaT"? (Which is a term I am still not sure that I completely grasp.) Maybe . . . but what I do feel I noted for sure was that the imaging (particularly the imaging in the center) had more weight (meatier?) and was presented more forward, which I actually like.
I put a few more hours in (one more time with Jazz Essentials, Holly Cole/It Happened One Night, Dave's True Story/Sex Without Bodies, selected tracks from Rebecca Pigeon/The Raven and Once Blue/self titled and Norah Jones/Feels Like Home) after switching to ultralinear. (No booze during this session, just coffee.) The jury is still out on this, but I do have some CDs in mind that I want to listen to over the next few days as I continue to evaluate.
@dogearedaudio"...anyone with a technical understanding of tube amplifiers (and I’m barely on the periphery of that circle) will shudder at the idea of a "one-size-fits-all" amplifier. ;-)".
To your point, while you can run different output tubes in many of DH’s creations, stemming from his former life with Cary Audio, and recent times creating Inspire, like the early years of Cary V12, V12R, or SLA-70 @immatthewjis referencing periodically - his amps were/are designed and listened to with a very particular output tube in mind. in the case of the V12/R. It’s the classic EL34 tube, paired with particular transformers and input/driver tubes that make for an interesting blend an sound.
Today, If you splurge and buy one of Dennis’ small and more recent 300B amps, you buy it with the new re-issues WE300B tubes, and you pay a bit extra for it and that’s how the designer likes it and wants it to be. Only comes with these tubes.
Falling on my own sword, my existing mono amps were designed with specific power transformers and plate voltage (650v) and such to run TungSol KT150 output tubes in their optimum operating window. With my speakers, I enjoy both sets but also really like how KT120s sound in these amps. Go figure, lol. :)
FWIW, Gary Dodd, shortly before he died in 2015, was contracted by a very rich person who heard his "Blue Monster" amps:
to build the "best sounding amplifier possible; even better than the Blue Monsters." What he came up with was monoblocks with 4 KT77 output tubes run in OPTIMIZED ultralinear mode with 2 6BL7 input tubes; custom would massive power supply and output trannies, huge inductors on both input and output stages, 700 volts on the plates and Dueland CAST coupling caps. He died before finishing the amps. 6 years later, his great friend and talented tube audio builder, Charlie Cocci, completed the two amps. Charlie, who has been building tube amps for at least 50 years, stated "These are not only the best soundfing amps I've ever built, they're the best sounding amps I've ever heard...and I've heard a lot of amps!"
FWIW.
Those amps are in my living room. The Dodd Audio Balanced Power Supply that is shown in the 2nd photo powering the Blue Monsters now powers the amps in my living room.
I'm a very lucky person. Confirmation bias confession? I don't think so, I think I just agree with Charlie.
"Zero" feedback? Really? I’ve looked at the CAD-280SA V12 manual online and it doesn’t mention feedback, but perhaps that's a different model. Hard to imagine they use NO feedback. Maybe not global feedback, which encompasses the output transformer. Internal feedback can be used to good effect, but no feedback at all is hard to imagine.
Oh sure, there are amps that will work well with different output tubes, and "non-optimized" can offer some interesting sound signatures. Like I said, nothing wrong with that. ;-)
Apologies if this came up earlier in the discussion...Do you guys re-bias and adjust for volume difference when you change between UL and triode? UL plays notably louder at the same volume setting than triode on my amps, and I'm assuming others too.
"Zero" feedback? Really? I’ve looked at the CAD-280SA V12 manual online and it doesn’t mention feedback, but perhaps that's a different model. Hard to imagine they use NO feedback.
@dogearedaudio, there should be a page labeled "SPECIFICATIONS" that interestingly is not numbered, but it looks like it would be page 5. (I say looks like, because the pages are starting to come loose in that particular manual.) Anyway, dimensions are listed. next weight is mentioned, next circuit type is mentioned, and then, under circuit type, it lists "FEED BACK: Zero".
And I am not arguing with anything you say, as I truly have a limited understanding of most of this, but just telling you what the "CAD-280SA V12 OPERATING MANUAL" that came with my amp says.
Apologies if this came up earlier in the discussion...Do you guys re-bias and adjust for volume difference when you change between UL and triode? UL plays notably louder at the same volume setting than triode on my amps, and I’m assuming others too.
@knotscott, the owner’s manual says nothing about needing to adjust the bias when switching from triode to UL or vice versa, and I have checked the bias after I made this last switch and there was no noticeable swing in the bias.
As far adjusting the volume when moving from triode to UL, I would have expected that myself, but it seems as if I am mostly leaving the knob on my SLP05 where it was. Maybe turning it just a hair down, but if so, only a hair or so. Not much at all. Mainly what I noticed was a change in "the body" of the sound. (or maybe the "shape of the sound" or maybe the "location of the sound." I am bad with terminology.) The gain on that preamp when using the balance ins and outs (and that’s all I have used so far, but I am thinking about experimenting with that also) seems pretty high to me, and with most CDs or SACDs it is about 9 oclock give or take a hair.
@dogearedaudio, coming back to the feedback, and again not arguing with you, but almost at the bottom of page 4, the page I believe should be just before the un-numbered specifications page, there is a header "OVERVIEW AND CLOSING THOUGHTS" and under that header Mr. Had had written that, "The V12 is in reality four single-ended amplifiers operating without any form of feedback."
@dogearedaudio"Zero" feedback? Really? I’ve looked at the CAD-280SA V12 manual online and it doesn’t mention feedback, but perhaps that’s a different model. Hard to imagine they use NO feedback. Maybe not global feedback, which encompasses the output transformer. Internal feedback can be used to good effect, but no feedback at all is hard to imagine.
Re-checking my own prior Cary amps on this and there are several I can account for that followed Dennis’ vision for "absolute zero-feedback designs", and talk some here about "low- and zero-negative-feedback triode circuitry " and how it "tended to generate the sound he preferred—to his ears" unquote.
Some of the older Steroephile articles in the early to mid 2000s challenge and mention this too;
On some search engines you can look for these words and hyphenated phrase +Cary +"zero-feedback" and different amps will pop up references this about some times.
To @xenolith, agree, yes, you are fortunate to own those very unique and interesting big blue amplifiers from Gary and Charlie. I love one-off boutique custom builds like this with audio, cars, and motorcycles. Great story how they got finished. Very cool, and Thank You for sharing the info and photos. Happy listening.
A single-ended amp like the 805 or his Inspires, sure, I can see no global feedback. But a 100wpc push-pull ultralinear amp without feedback seems like a stretch, in terms of achieving good bandwidth and a decent damping factor. But anything's possible. He's a very clever designer.
A single-ended amp like the 805 or his Inspires, sure, I can see no global feedback. But a 100wpc push-pull ultralinear amp without feedback seems like a stretch, in terms of achieving good bandwidth and a decent damping factor. But anything's possible. He's a very clever designer.
As far as the CAD-805RS, what Cary lists on their site under specs for feedback is "0 to 10 dB continuously variable control."
Ralph makes a very good point about the percentage of screen taps and their relationship to the effectiveness of UL operation. In an earlier post I referred to the original "Musician's Amplifier," the first iteration of the the British Williamson amplifier proposed by Sarser and Sprinkle. It employed tubes and transformers more readily available on the American market. In 1952, when Hafler and Keroes published the first "ultralinear" Williamson, Sarser and Sprinkle noticed that the output transformer they chose for the "Musician's Amplifier," the Peerless S-265-Q, had primary taps that could act as 50% loads for the screens. They urged hobbyists to convert their "Musician's Amplifiers" to "ultralinear" operation by some simple changes to the circuit.
In fact, while the 50% taps of the Peerless transformer are not *ideal*, they actually brought the output tubes just a hair closer to true triode operation while doubling the power output. Having built this amp myself, I can tell you that the result, despite its flaws, is quite beautiful.
@atmasphere, I am not arguing with what anyone is saying; I have stated before that I am illiterate on these subjects. I was simply directly quoting from the owners manual that came with my amp when I bought it. Although he didn't write it that way, is it possible that what i quoted was meant to only be applied to triode operation?
I am not arguing with what anyone is saying; I have stated before that I am illiterate on these subjects. I was simply directly quoting from the owners manual that came with my amp when I bought it. Although he didn't write it that way, is it possible that what i quoted was meant to only be applied to triode operation?
@immatthewjI was commenting more in the fact that the manual was either poorly written or misleading. I doubt the 'triode only' thing since it is a UL design. The best interpretation is there's no global feedback. But there certainly is local feedback.
I was commenting more in the fact that the manual was either poorly written or misleading.
@atmasphere, that could be; this subject is over my head so I will not offer an opinion.. As far as the UL design, Mr. Had does state at least a couple of times in that manual how much he likes triode. He even refers to himself as "a triode crazed audiophile" in that manual and at one point goes on to say that this amp "sounds better" when operated in triode.
Many years ago I had a tube amp w/8 EL34s that I had the mfr mod to allow each power tube to be triode/ultralinear switchable (Roger Mojeski's RM-9). The speakers were Vandersteen's then TOTL, the Vandersteen-4s.
I greatly preferred triode mode with both TT and digital sources (especially with digital sources). Triode mode pushed the inherent musicality and realism of those big Vandy's as far it they went. I never felt the urge to use ultranlinear. What's more, I didn't need to: the internal subs of the speakers were powered by a separate amp, a 200 wpc SS amp.
I wonder if the output transformer of amplifier with the triode/UL option is optimized equally for both modes, or if the default is to design for best operation in UL, then simply switch the screens to pair with the plates of the output tubes (usually via a resistor)? Theoretically, doubling power gets you 3 db of headroom, but if the linearity of the output transformer isn't consistent across both modes the perceived sonic difference may be greater. And to your point, the choice of music plays a role in which mode sounds better. I've got that same pleasant quandary with speakers and two systems in one room.
I wonder if the output transformer of amplifier with the triode/UL option is optimized equally for both modes, or if the default is to design for best operation in UL, then simply switch the screens to pair with the plates of the output tubes (usually via a resistor)?
@pickindougTo do it properly, the output transformer would have to have taps for triode operation since the optimal plate to plate load for a power pentode wired in triode is a lower impedance than that used for UL operation. That could make the transformer a lot more expensive and the switching a bit more complex.
@atmasphere Yes, that's the issue with engineering options like triode vs UL. Based on all the OPT I've used, designed around, etc, a UL OPT will require a certain NFB characteristic for best performance. Using the same level of NFB when the UL taps are lifted may not be the optimal level for the reasons NFB is used. Marketing loves to have perceived needs to sell to.
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