What do OTL and transformer-coupled mean?

[sacd lover]

Quote:

Originally Posted by slwiser /img/forum/go_quote.gif For a start would you consider either the Lavry DA10 or Apogee miniDAC for both have these switching power supplies. We will go up from here.

The Lavry and Apogee are principally dacs not amps. Would these qualify as high end designs .... not to me. The Lavry is average sounding at best from the times I have used the unit. In no way does the Lavry compare to the better amps I have hear regularly. I have no experience with the Apogee.


A switched-mode power supply, switching-mode power supply or SMPS, is an electronic power supply unit (PSU) that incorporates a switching regulator. While a linear regulator uses a transistor biased in its active region to specify an output voltage, an SMPS actively switches a transistor between full saturation and full cutoff at a high rate. The resulting rectangular waveform is then passed through a low-pass filter (typically an inductor and capacitor) to achieve an approximated output voltage. Advantages of this method include smaller size, better power efficiency, and lower heat generation. Disadvantages include the fact that SMPSs are generally more complex than linear supplies, generate high-frequency electrical noise that may need to be carefully suppressed, and have a characteristic ripple voltage at the switching frequency.

Radio frequency interference — The current in SMPSs is switched on and off sharply, and contains a large proportion of high frequency spectral components. Long wires between the components may reduce the high frequency filter efficiency provided by the capacitors at the inlet and outlet. This high-frequency current can generate undesirable electromagnetic interference. EMI filters and RF shielding are needed to reduce the disruptive interference. Linear PSUs generally do not produce interference, and are used to supply power where radio interference must not occur.

 

[slwiser]

Quote:

Originally Posted by sacd lover /img/forum/go_quote.gif The Lavry and Apogee are principally dacs not amps. Would these qualify as high end designs .... not to me. The Lavry is average sounding at best from the times I have used the unit. In no way does the Lavry compare to the better amps I have hear regularly. I have no experience with the Apogee.

Does this qualify as a power amp for you?

http://www.norh.com/products/leamp2/bg.html

 

[slwiser]

We can also talk about this one:

http://www.linn.co.uk/music_systems_klimax_500_solo

or this one:

http://www.stereotimes.com/amp031803.shtml

 

[spritzer]

SMPS belong in crappy consumer goods and the sad fact that many "high-end" companies use them doesn't make them good, just goes to show how those companies have completely missed the point. It does bolster sales in all kinds of power filters because people think they need to clean the power that goes into the SMPS units but not the other way around. It's often asked why we didn't need power filters until now and the simple thing is that we are surrounded by noisy PSU's and they are messing with the power.

 

[slwiser]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif SMPS belong in crappy consumer goods and the sad fact that many "high-end" companies use them doesn't make them good, just goes to show how those companies have completely missed the point. It does bolster sales in all kinds of power filters because people think they need to clean the power that goes into the SMPS units but not the other way around. It's often asked why we didn't need power filters until now and the simple thing is that we are surrounded by noisy PSU's and they are messing with the power.

The main point is that they are supposed to be noisy, right. That is what the person above suggested in response to my bringing up the ZOTL design as transformer less. Isn't that the basis of your "crappy" moniker?

All of David Bernings power amps use his ZOTL design and that is very quiet, very low noise. Therefore, any suggestion that this design is crappy is simply ill-advised and archaic at best. I would not suggest that the Linn products are simply consumer grade either and they are certainly not crappy. Nor are the products from Halcro crappy..

Enough said since reality need not apply to this discussion.

Don't get wrong. I am not the one saying either one is bad....I have one with and one without...both are quiet. I enjoy my HA-02 right now more than my ZOTL but they both sound closer than they probably should being so different. It is all in the design and implementation.

 

[ChickenGod]

Lately, my friends have been saying OTL a lot.

I heard it is supposed to be a guy bowing or something

Sacred Pizza --> /_\ OTL <--- Guy bowing

 

[jinp6301]

LOL that IS a guy bowing!

 

[sacd lover]

Quote:

Originally Posted by slwiser /img/forum/go_quote.gif Does this qualify as a power amp for you? http://www.norh.com/products/leamp2/bg.html

I have read about many switching power supply power amps. This is a headphone forum .... I was asking about high end headamps.

Regardless, a switching power supply IS noisy. The best you can do is take extensive measures to quiet a switching power supply or isolate the switching power supply outside the chassis and signal path .... when you could simply build a quiet linear supply to begin with. You wont hear megahertz noise but the noise will pollute the audio circuits and compromise the ultimate quality of the product in question.

I use a switching power supply for the heaters of my 12 volt amps. But, the power supply is outside the amp chassis, isolated from the signal path and several feet away from any audio circuitry.

 

[jcx]

I actually believe switched mode power supplies are capable of great performance with careful design/implementation they can be included in audiophile grade equipment without apology

But that is not the general perception, particularly among tube amp aficionados which explains my amusement when they embrace the Berning circuit as a valid “OTL” amp approach

The switched mode conversion of the tube high V output swing to low V audio, preserving the “tube sound” mystique without adding distortion in the modulation/synchronous rectification is considerably more difficult than doing a good job in a switched mode power supply putting out DC

Then assuming the impedance conversion was a success you really should be filtering the switching frequency artifacts – interposing a high order passive filter in the audio path, I don’t see how to do that without inductors employing notoriously nonlinear (again in many audiophile's opion) magnetic materials

More amusement may be derived from the likelihood that the modulation drive circuitry consumes more power than the headphones receive from the tube and the Si semiconductor area involved also likely exceeds that of many solid state amps

 

[Hellenback]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif There is a difference, but it's not as great as you might expect. No doubt though, OTL mode is more romantic sounding - it's the "tubier" sound for sure.

Skylab, with all your ear time with so many different amps, the fact that you have kept the ASLabs says something to me. What impels you to keep this amp and not the Aria and /or many other amps that you have had. I am a one amp guy due to finances and am worn out from searching the forums for a good mate for the 650s. I love their sound and want an amp that best compliments it rather than exaggerating it. As they are very warm cans to begin with, if you had only $400 would you buy the ASLabs over any other amp for the same money or would you stick with solid state for the 650s? Just your opinion, I know!

 

[Skylab]

Well, the ASL is just a great sounding amp. There are a zillion tube rolling options available, and it's cool to have both OTL and transformer mode available.

And did I mention how great it sounds?

 

[wower]

Well this thread went sideways... That sound you hear is the conversation passing right over my head..

 

[jp11801]

Quote:

Originally Posted by slwiser /img/forum/go_quote.gif I agree completely about the Yamamoto HA-02 being very nice transformer coupled even thought, years ago, when we started with transformers and before low noise ones they were always noisy. Some transformers are still have to much noise today but generally they are not used in high end audio.

what are you talking about old iron is some of the most sought after iron out there? NOS tangos go for bucks when Headfi first started many companies might have used cheap transformers but a well made transformer from 20 years ago will sound great. Can you explain or provide an example of when this "new low transformer" technology was made available and who v=created it?

 

[ChickenGod]

Quote:

Originally Posted by jinp6301 /img/forum/go_quote.gif LOL that IS a guy bowing!

Told ya so

 

[cotdt]

Yeah switching power supplies are the worst. The squeezebox comes with one. it is terrible. i replaced it with an S11 and it is such a noticeable difference.

OTL tube amps in general have built-in bass and treble boost, but the output impedance is often quite high so the bass can sound loose. The output transformer gives a smoother response curve. Most transformers that come with transformer-coupled amps are really cheap, though. They cost literally $5 each. Good transformers cost upwards of $400 each. Needless to say, these OPT tube amps are not representative of the transparency of a good OPT tube amp, so often the OTL tube amp would sound better. But with good output transformers, the OPT tube amp should have a technical advantage over OTL tube amp, if you care about such things.

a lot of tubes don't work well without an output transformer, in fact all the bass gets cut off unless the tubes are paralleled or some fancy design is used. the tubes that do work without a transformer, still tend to sound different once a transformer is used. it's a matter of preference as to what kind of sound one prefers. it's hard to generalize the differences since all the tubes sound different.