Why are tube OTL amps so common?
Mar 27, 2013 at 10:49 AM Thread Starter Post #1 of 10

kramer5150

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Something I have always wondered, with high impedance headphones (seemingly) on the decline... why are amp makers still predominantly making high impedance OTL amps?
For every high-Z headphone theres (at least) 5-10 low-Z, and for every ~5 high-Z OTL amps theres one non-OTL?  It seems they are going in opposite directions.
 
Its not cost or availability of capable OTs, effective speaker level PA transformers can be found for as low as $5/ea... and are readily available world wide.
 
???
 
Mar 27, 2013 at 12:56 PM Post #3 of 10

kramer5150

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Quote:
Cheaper to make.  Good output transformers are pricey.

Has it been proven and measured... good $$$ OTs are necessary in headphone amplification?  or is that a snake-oil myth portrayed by the high end transformer manufacturers?
 
Is there even such thing as a high-end output transformer specifically designed for low mili-wattage headphone amplification?
 
Mar 27, 2013 at 1:38 PM Post #4 of 10

hodgjy

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Maybe nothing is proven, but the fact does remain that hand wound transformers take time and money for the person winding them.  That is probably where the cost comes from.
 
Mar 27, 2013 at 1:44 PM Post #5 of 10

hodgjy

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Also, OTL designs are relatively simple.  The tubes are the only active devices in the circuit.  With output transformers, there is another level of complexity.  Plus, I think OTL designs are easier to tube roll a variety of similar tubes, whereas some transformer coupled amps will have less latitude in tube rolling.
 
Mar 27, 2013 at 2:16 PM Post #6 of 10

Greed

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I'd also add, that the headphone market really hasn't changed much. The higher impedance headphones that were around 3 years ago are still widely used. Even though there are a ton of OTL amps, they all will sound different. If you look at people inventories, especially when you climb the headphone scale, you will see HD 800 and Beyerdynamic T1 a lot. Those are said by many to sound there best on OTL amps, I tend to agree.
 
Also, it is easy to design an OTL amp. The schematic is relatively the same amp to amp, the implementation is different, but really it comes down to a lot of companies being cheap and not wanting to change something that already works.
 
Mar 27, 2013 at 8:03 PM Post #7 of 10

Spareribs

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It probably boils down to personal taste and what kind of headphones you are using. I really like OTL amps but for my cup of tea, I love the transformers. From my experience of trying different amps, i have to admit that my personal favorite amps have a good transformer and even a rectifier tube is a must.

That said, a good amp is a good amp and rules can be broken.
 
Mar 27, 2013 at 8:10 PM Post #8 of 10

hodgjy

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I agree.  For a while, I loved my Woo 3 OTL, but my Trafomatic Head One is in a whole other league.
 
Quote:
It probably boils down to personal taste and what kind of headphones you are using. I really like OTL amps but for my cup of tea, I love the transformers. From my experience of trying different amps, i have to admit that my personal favorite amps have a good transformer and even a rectifier tube is a must.

That said, a good amp is a good amp and rules can be broken.

 
Mar 27, 2013 at 9:37 PM Post #9 of 10

GrindingThud

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So, lets consider the Mapletree Ear+: http://hollowstate.netfirms.com/Super2manual.pdf

It's got pretty affordable Hammond 119DA transformers hanging on the output of a cathode follower. For $60, these can be purchased and put in a box with 1/4 jacks in and out and transform almost any OTL amplifier into a nice low impedance load and maintain relatively flat response. I'm working up a set for my WA3 for the fun of it. Good sounding transformers need not be expensive.
 
Mar 27, 2013 at 10:08 PM Post #10 of 10

Dubstep Girl

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