|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
160.62.7.250
In Reply to: RE: OTL vs SET posted by saki70 on January 11, 2015 at 13:48:31
First, I have owned a couple of different OTL models: Silvaweld OTL refernce monoblocks (4 x 6C33C per mono) and a Transcendent Sound Beast. I have also owned a fair number of SETs: KR Audio VA350i, JJ 322, Cary CAD-572se, NAT Symbiosis SE and had friends with several others that I have heard at length.
A really good SET will have tight clean bass but it still won't sound like solid state bass, or even the bass of a single ended transistor output design (like my NAT). Harmonically, well within its power envelope, it will also be very transparent and sometimes even slightly lean...at least compared to those SETs with compromised iron. Highs will often be a bit soft(ish) as compared to just about any amp with feedback and/or push pull designs and this is regardless of how extended the bandwidth of the output iron is from my experience. If the amp is using a solid state power supply it will be a bit leaner and perhaps faster sounding than one with a tube power supply.
Palpability and 3d imaging as well as soundstage depth will be world class.
A really good OTL will have SHOCKING transparency...something that I have yet to hear with even the best SETs and of a wholly different quality from SS such that all SS sounds grainy and opaque by comparison. Dynamics also are quite lively. Imaging and soundstaging is right up there with the top SETs. Where they fall down, IMO is often in tonal balance and overall coherence. They tend to sound leaner than most SETs and, IMO, than real life. I think this has to do in many cases with the use of negative feedback (My OTLs used around 10db of negative feedback). Not using output iron probably also impacts this.
Those OTLs that don't use negative feedback are somewhat warmer in character but still have that amazing transparency.
Bass (for a circlotron design) is somewhere between SS and SET bass. It is drier and tighter but still not SS sounding. For other types the bass on normal speakers has issues and could contribute to the lean sound.
Where my OTLs fell down ultimately was in coherence...nothing beats a really good SET, IMO, for seamlessness and "continuousness" (to use a classic HP descriptor). A single ended OTL might do it but it seems that they need too much negative feedback or dozens of tubes to be a viable solution.
There is one company, a Cyprus one called Aries Cerat, that makes a zero feedback, single ended OTL, that is massive and with a large number of output tubes...I am dying to hear it.
My NAT is the closest so far that I have heard to marrying the concept of SET and OTL because it is a direct coupled single ended hybrid with ONE big MOSFET on the output per channel. It has NEARLY the transparency of an OTL and NEARLY the tonal character of a top SET but with a SS like bass. It does not quite get there as the ultimate amplifier. After a couple hours of playing it does get pretty hallucinogenic and very close to the ideal, IMO, but not quite. A MOSFET just has not got the same character as a power triode and you can hear that.
Follow Ups:
Hi, Good to have you aboard, but any comment on how an amplifier sounds, particularly an SET or OTL should be qualified by speaker-specificity, and the subjectivity of the opinion as well. That said, there's nothing particularly jarring about what you wrote, except huge amounts of NFB in a SET OTL? I am not familiar with any SET OTL amplifier, personally, but if such a design "needs" large amounts of NFB to drive a speaker properly, then the design itself would be questionable in my mind. Like maybe it's not a good idea at all to marry an SET with an OTL. A shotgun wedding at best.
When do we talk about too much negative feedback?
In his post he says that SET OTLs "need" large amounts of NFB. I am not sure why that would be the case, except to reduce apparent output Z, but it is not a desirable property of an amplifier design, IMO.
Very nice post, Morricab. Thanks.
I have found that to properly benefit from the wonderful transparency of the OTL—in my case, a pair of Atma-Sphere Silver Edition MA-1’s—I must pay attention to the smallest parts of my overall system. The amps are at the penultimate end of a long chain of segments and interfaces, any one of which—or in combination—can affect the sound markedly. Thus I would no longer be sure enough of my ground to say that an OTL or SE amp is thus or so per se.
When I first hooked up my amps to my current speakers (GR Research LS-9’s with servo subs) I was mildly disappointed. I had heard the 9’s at RMAF driven by conventional amps (Dodds) in a carefully set up system, and they sounded terrific. I believe I have gone well beyond that sound now, but here’s what it took:
1. New internal wiring (Marigo)
2. Removing a sleeve I had put on a segment of the Marigo’s and separating the wires
3. Different series/parallel wiring scheme to optimize impedance
4. Different solder on the new wiring (Stop that! I heard someone giggling.)
5. A change to the crossover (because of the new wiring scheme)
6. Different IC’s (my silver ones were now too bright)
7. Replacing the 6SN-7 input tubes
I and several experienced observer friends heard a difference with every one of these changes. Whereas before the changes an especially picky (annoying, really) audio buddy politely declined my offers for a listening session, now he comes over often and brings others.
Placebo effect? Maybe. I did believe going in that the Marigo would make a substantial difference, and it did. But the difference was immediately obvious to other observers as well. As to the predicted effects of some of the other changes, well skepticism reigned supreme until the changes were made.
I suspect that the same attention to detail is necessary to make SE’s really sing in a real world system.
What’s next? Maybe some further tweaks: fuses, room mods, vibration control? The point is, the OTL’s let me hear what’s going on to an unprecedented degree compared to what I had before. Benefit or curse? You tell me.
What is it? Copper or silver or silver-plated copper? Stranded or solid core? LItz or not? Round or ribbon in cross-section?
Thanks.
Lew,
Pure copper, 18ga, round in cross-section,600 individual (lacquered, I believe)strands.
Ron Hedrich is easy to talk to; why not give him a call?
Contact Us
Call Ron Hedrich at (360) 835-9239
Our Address :
Marigo Audio Lab
32711 SE 16th St., Washougal, WA 98671 USA
map
Tel: (360) 835 – 9239
Fax: (360) 835 – 9249
Thanks, Chuck.
I use a Marigo power cord on my preamplifier, but that wire would be very difficult to use as chassis wire (for me, anyway). It's murder to strip off all the enamel insulation in order to make a good solder joint. I have a solder pot for that, but it's not really a cure for the aggravation. Anyway, I am happy with narrow gauge solid core silver (for chassis wire). In my speakers I use 6 or 8 parallel insulated strands of 19ga Cardas silver wire on the treble and parallel strands of enameled copper transformer wire on the bass. (Only because the silver is so darned expensive.)
Having owned double digit OTL and SET amps, from low power to high power versions of each, I can assure you that the sound of neither type of amp can be stereotyped. There are some lean, some neutral, and some fat versions of each. There are dynamic and less than dynamic versions of each. Some of each are very sensitive to speaker load and some of each seem relatively insensitive to speaker load. I've heard a 2 watt OTL sound more powerful into an easy load than a 100 watt OTL. I've heard 20 watt versions of 2 different SET amps using the same tubes into the same speaker with one sounding very powerful, tight, and dynamic and the other sounding weak and strained.
No specs will allow you to figure this out without trying, and no manufacturers' claims will allow you to figure this out. You need to hear the combinations somewhere or try them yourself.
Sound like the Symo wire that Krells KSA 100 class A Amp was wired with. I used in the 90s to run my Apogee Duettas, the late Jason Bloom used on his Apogees.
Vary,Vary hard to tin!
http://www.6moons.com/audioreviews/gma4/sidebar.jpg
Not so hard to tin if you use a solder pot. It takes several steps: 1) debraid the sleeve to about one inch; 2)cut and cauterize the end of the braid; 3) dip the end into the solder pot. Rewiring my speakers required 200 such operations. As I said, a royal PITA--well worth it, though.
Most don't have a Pot laying around,I never like the sound of the Symo!
Only difference I see is the cloth type covering that can make all the difference in the sound.
Wire is tuff,you like Vanilla I like chocolate.
But thanks for the info on Marigo Audio Lab.
Looks like Mr Bloom at Apogge was on to some thing with the Symo wire in the 1990s.
I'm using four Silver Edition MA-1's to drive my Dali MegaLines. Ralph's gear/circuits will readily respond to variants of 6SN7. I'm also using an MP-1. I wish all my sources were 1/2" master tapes :-)
Vbr,
Sam
Oh boy, me too! I had a great collection of tapes, but nearly all deteriorated to the point that they were unusable (Ampex Grand Master back-coated). Sure was great while it lasted. I love vinyl, but a great tape setup was truly magic. Sigh!
Oh, what a bummer! :-(
Baking couldn't resurrect them?
Vbr,
Sam
Might've, but you get to a certain point of disgust . . .
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: