OTL amp owners

KeithR · Nov 15, 2017

Ron Resnick said:
I think needing to increase speaker impedance would be covered by 2) speaker incompatibility.

I was not aware OTLs are often lacking in bass. I certainly did not have that feeling with Danny's Einsteins driving Alexxes.

The third harmonic point is an excellent one and, in fact, Ralph said this himself. But no OPT tube amplifier I have ever heard approaches the clarity of the OTL I have heard. Why do you think it is not the OPT? Maybe it is the OPT supplemented by the second harmonic distortion of the SET?

If not the OPT to what do you attribute that incredible crystalline transparency of the OTL?

Some say SET is the most transparent, others say OPTs screw them up. The reverse is true with OTLs - because you are forgetting how the tube circuit without the OPT is designed (paralleled tubes through more of a Class B stage). And they are threat to oscillate, run tubes hard, and blow up. There are negatives just like any other amp design.

Sean Casey at Zu makes an "OTL friendly" version of his speakers - at 32 ohms.

As far as Danny's system, what other amps did you compare with? I've heard Einstein vs Dart in his old house.

Ron Resnick · Nov 15, 2017

Mike Lavigne said:
no transformer in the signal path = more transparency. but also = impending explosive tendencies and challenges in authoritative grip. so the better sounding (most refined) OTL's require speaker to match amp. not fit amp to preferred (already purchased) speaker. relatively authoritative OTL's exist......but are maybe not the most magically sounding ones.

so Ron, you need to fall in love with an amp and buy it, then find a speaker to match......not the other way around. unless you go with very easily driven speaker choices.

Yes; if the first imperative is OTL, then the speaker must be found to match the amplifier. I agree.

jeff1225 · Nov 15, 2017

User211 said:
I think the Einstein OTL amps sounds relatively normal with my brief exposure to them with their own speakers at Munich.

I have only ever heard Atma-Sphere amps once driving horns at Munich. I was freaked out it sounded so weird. The sound floated out with consummate ease and no bite whatsoever. Huge 3D soundstage type of presentation. Obviously seriously coloured.

I posted a video on YouTube of the Atma-Sphere set up a while back. Might post it later.

What speakers were used?

Ron Resnick · Nov 15, 2017

morricab said:
An OTL will not need bass in your system and a flat impedance ribbon will make an OTL relatively unstressed...same for a SET.

Ralph agrees with you. He is familiar with the BG ribbon driver and is sanguine about using his OTLs to drive it. He even suggested the MA-1 is sufficient, but he did not disagree with my "excess" power for musical ease and headroom preference.

Ron Resnick · Nov 15, 2017

KeithR said:
Some say SET is the most transparent, others say OPTs screw them up. The reverse is true with OTLs - because you are forgetting how the tube circuit without the OPT is designed (paralleled tubes through more of a Class B stage). And they are threat to oscillate, run tubes hard, and blow up. There are negatives just like any other amp design.

As far as Danny's system, what other amps did you compare with? I've heard Einstein vs Dart in his old house.

I understand.

No amp comparison at Danny's. But the crystalline clarity of the amplifier was, I think, unmistakable in an absolute sense. (Don't gag, Kedar!

)

Ron Resnick · Nov 15, 2017

morricab said:
While it is true that SOME transformer coupled amps have sufficient iron, I would argue that most do not in order to be truly transparent. Once you clean that up a good SET sounds closer to a good OTL than to a "normal" SET or push/pull tube amp.

Which transformer-coupled SET amps do you believe have sufficient iron to transcend the transformer limitation and be truly transparent, and be competitive on that attribute with OTLs?

awsmone · Nov 15, 2017

Hi Ron

My friend built big 300 b amps with massive tango opts, incredibly spooky transparent

Also recently heard the new Silbatone which was equally transparent

These cost much more than an otl as good opt are really expensive

The others which I heard are good are Cat monos with silver transformers..

KeithR · Nov 15, 2017

Ron Resnick said:
No amp comparison at Danny's. But the crystalline clarity of the amplifier was, I think, unmistakable in an absolute sense. (Don't gag, Kedar! )

I think there are transparent amps of all topologies - and tubes all sound different (be it OTL or SET or ??). What's more "transparent" - a 45-based or a 300B SET (or a NAT Magma!)? Can anyone really answer that kind of question? Dartzeel is P/P SS - isn't that supposed to be the least transparent kind of amplifier to some around here? Think MikeL agrees with that statement?

Ironically, you were listening to a class A/B push/pull KT150 amp at my house. Which has outperformed all SETs and a pair of Class A p/p tube monos in my listening room (well to me, and on my speakers). Morricab would be terrified

Actually my Devores might be decent OTL candidates (8ohm nominal, 7.5ohm minimal). My 101db/6ohm Zus were not - as even told me by Sean Casey himself.

I guess my opinion is - the most transparent amp will be the one best suited for the speakers as the speaker/amplifier interface is so critical to the overall sonic picture.

bonzo75 · Nov 15, 2017

KeithR said:
I guess my opinion is - the most transparent amp will be the one best suited for the speakers as the speaker/amplifier interface is so critical to the overall sonic picture.

This is true, but it is also true that certain amps are not transparent even if they match. They might be excellent on respective speakers yet be colored and not transparent.

morricab · Nov 15, 2017

Ron Resnick said:
Ralph agrees with you. He is familiar with the BG ribbon driver and is sanguine about using his OTLs to drive it. He even suggested the MA-1 is sufficient, but he did not disagree with my "excess" power for musical ease and headroom preference.

I have a pair of BG planar drivers (they are not really ribbons as they are Push/pull design that is tensioned on all sides...a true ribbon is only fixed at the ends and is relatively loose) in a DIY hybrid design that works full active. I drove it very well with a pair of 30 watt KR Audio VA350is many years ago crossed with an Accuphase F25 active xover. That worked beautifully as I also had KR on the bass. Sensitivity was around 87db with a flat 4 ohm on the planar. It was capable of quite high SPL without sounding stressed. Pretty neat...I may set them up again someday...

BGs will work fine with SET or OTL.

morricab · Nov 15, 2017

Ron Resnick said:
Which transformer-coupled SET amps do you believe have sufficient iron to transcend the transformer limitation and be truly transparent, and be competitive on that attribute with OTLs?

Well, we can talk about this privately, since I don't want to discuss my brand too much in a public forum. Suffice to say, that I have heard one or two SETs that get VERY close to that bracing and breathtaking feeling a good OTL delivers. It is not just transparency but perceived dynamics too, micro and macro. The SET did better with "feel" and coherence, particularly in top to bottom tonal consistency. Personally, I think a SET OTL could be the ideal amplifier. However, I only know of two companies that make them; Aries Cerat (for an all-out assault on the concept) and Transcendent Sound, which offers a 4 watt kit (or 12 watt monos) for a bit over $1000. I am really tempted to buy and build the kit to play on my 96db Foxtex based Decware HDT speakers...just to see what it is all about. The Collatio II from AC makes like 20 or 25 watts, which is fine for me but the 1200 watts of heat and 120Kg are not fine...but that is Stavros...no half measures.

KeithR · Nov 15, 2017

bonzo75 said:
This is true, but it is also true that certain amps are not transparent even if they match. They might be excellent on respective speakers yet be colored and not transparent.

You raise a good point. Probably better to say I think its more likely to be transparent if the speaker/amp interface is correct.

Ron Resnick · Nov 15, 2017

Thank you, Brad. But there still is the very important matter of integration with the bass tower amplifier.

Yes, please sent me a PM or email!

bonzo75 · Nov 28, 2017

Does anyone own OTL on horns?

microstrip · Nov 28, 2017

bonzo75 said:
Does anyone own OTL on horns?

Usually horns have very high efficiency, and due to the topology of the output stage, OTLs have in general higher residual hum than transformer coupled tube amplifiers. So I can imagine that most of the time it will not be an easy matching.

microstrip · Nov 28, 2017

morricab said:
Well, we can talk about this privately, since I don't want to discuss my brand too much in a public forum. Suffice to say, that I have heard one or two SETs that get VERY close to that bracing and breathtaking feeling a good OTL delivers. It is not just transparency but perceived dynamics too, micro and macro. The SET did better with "feel" and coherence, particularly in top to bottom tonal consistency. Personally, I think a SET OTL could be the ideal amplifier. However, I only know of two companies that make them; Aries Cerat (for an all-out assault on the concept) and Transcendent Sound, which offers a 4 watt kit (or 12 watt monos) for a bit over $1000. I am really tempted to buy and build the kit to play on my 96db Foxtex based Decware HDT speakers...just to see what it is all about. The Collatio II from AC makes like 20 or 25 watts, which is fine for me but the 1200 watts of heat and 120Kg are not fine...but that is Stavros...no half measures.

Considering that Ron only needs an amplifier for the middle/treble panel, that will not deliver bass, a SET/OTL can be easily designed, as it can be capacitor coupled - or perhaps the panel crossover includes a series capacitor at the input and DC is not an issue in this amplifier (although this can be a dangerous game!

).

Do you know what is the output topology of the Aries Cerat SET/OTL?

Aries Cerat · Nov 29, 2017

microstrip said:
Considering that Ron only needs an amplifier for the middle/treble panel, that will not deliver bass, a SET/OTL can be easily designed, as it can be capacitor coupled - or perhaps the panel crossover includes a series capacitor at the input and DC is not an issue in this amplifier (although this can be a dangerous game! ).

Do you know what is the output topology of the Aries Cerat SET/OTL?

Hello microstrip

The Collatio SE OTL uses two banks of 20 triode 6C19p tubes.
Can be configured in stereo mode (20W) or mono ( 80W).

Each bank is biased at 2.6A (adjustable) , 5.2A total.

The two banks are DC coupled to a 814DHT that is used as a driver.

Each of the output tube banks is loaded with three(six in total) chokes in parallel (acting as a single choke) ,AC coupled to the output with a custom capacitor(enough capacitance to have low enough -3db) ,with 1mohm ESR, and 15.000A max surge.That said, the capacitor is virtually a wire in AC,but can protect the speaker even if the tubes decide to do their own nasty trades.

Best
Stavros

bonzo75 · Nov 30, 2017

Joule http://sigsound.com/classic-product-info/joule-electra-info-page/

Ron Resnick · Dec 3, 2017

Thank you, Stavros, for posting here! The Collatio II truly is a unique design! Congratulations on this accomplishment!

Who has actually heard the Collatio II?

The main question for me is: does the Collatio II manifest that leanness or absence of richness (which I readily stipulate may be a sonically inaccurate byproduct of output transformers) which I and many others hear from most OTL amplifiers?

Aries Cerat · Dec 6, 2017

Ron Resnick said:
Thank you, Stavros, for posting here! The Collatio II truly is a unique design! Congratulations on this accomplishment!

Who has actually heard the Collatio II?

The main question for me is: does the Collatio II manifest that leanness or absence of richness (which I readily stipulate may be a sonically inaccurate byproduct of output transformers) which I and many others hear from most OTL amplifiers?

Hello Ron
Thank you for the compliments.
Happy to be among the company here at WBF.

I do tend to agree with you on the basis that ,at least to the OTL models i have heard,there is a certain leanness or absence of richness to say it better in OTL sound in general.

I have to state in front that the Collatio is a current amplifier,and not a voltage amplifier which is the norm.The majority of speaker drivers(dynamic drivers usually) will not like that. There is a certain niche of speaker drivers/technology which like and prefer to be driven by current amplifiers.Compression drivers are one of them.Some ribbons(usually transformer coupled,like the ones we use),some very low Q dynamic drivers as well do like current amplifiers.

In other words the Collatio is not designed to be an all around amplifier,but specifically designed to drive a certain category of speakers.

That said,i can say that the Collatio does not present the normal OTL sound traits.You may attribute this to being SE (the distortion spectrum is vastly different),the fact that is a current amplifier,or that carries a lot of iron in the signal path(being choke loaded parafeed) ,or even having a big DHT as driver tube.Any of these design choices could deviate the sound of Collatio from the normal OTL sound,but i cannot separate the effect that each of these parameter have, on the end result.

In any case it does not sound like a lean amplifier ,but at the same time it is not an amplifier we would recommend to speakers which would not be happy with current drive.And the majority of commercial speakers are just that .

Cheers
Stavros

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