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RE: OTL vs SET

Posted by groovy.guru (A) on January 12, 2015 at 12:20:02

In Reply to: OTL vs SET posted by saki70 on January 11, 2015 at 13:48:31:

I have both SET and OTL amps. Speaker matching is very important to get the best out of either type of amp. I just bought a pair of Coincident Frankenstein DHT 300b monoblock amps, and I have owned a Joule Electra VZN-80 Musicwood OTL stereo amplifier for the past 7 years. I’m not sure if they meet your definition of average, but here’s my two cents.

Right now, my SET monoblock amps are more analytical, and my OTL amp is more musical, which is the opposite of the stereotypes of these two types of amps. My Franks only have 30 hours on them right now. As they break in, I have heard the bass and treble ripen up; they are definitely moving more towards the musical camp, and I suspect they will end up being my favorite of the two topologies.

Here is my summary of how they sound (bearing in mind that with the Franks, this is my first impression before full break-in):


SUMMARY OF SET (8 watts/ch 300b)


Definitely clearer than my OTL, this is very easy to discern

More transparent

Better dynamics, sounds can jump out and startle you

Better low level detail, better “blackness” and “air”

Better harmonic overtones; i.e. when a guitar note is played, I can better hear the nuances after the initial sound of the note

Very good coherency from the bass to mids to treble; nothing unduly stands out or is missing.

Surprising amount of tight, weighty bass with good tone for 8 watts a channel

Mechanically very quiet

Runs relatively cool, does not heat up my room

In a nutshell (based on 30 hours of break-in): Sounds more like I am hearing everything that is on the recording




SUMMARY of OTL (80 watts/ch 6c33c)


Fuller, more ripe tone across the entire spectrum (more meat on the bones)

Fatter, weightier, and more pleasant bass

Excellent cymbals, very natural and extended without sounding harsh

Voices are more full and less edgy, and voices project more out of the middle of the soundstage

Sounds other than voices are more blended, with less air and blackness between sounds

I have to try harder with my OTL to hear the same sounds that I hear with my 300b amp

Hotter than Hades!

6c33c tubes are getting hard to find

The variac because of its large toroidal transformer has a low level hum (a common issue with Joules)

My OTL requires careful placement in relationship to my other components; it does not like being near my preamp or some of my other components (it will start buzzing through the speakers!)

Other than the variac, once it is placed away from my other components (I use a configuration with the amp between the speakers, the rest of my system on the side wall), the Joule OTL is surprisingly quiet for an amp with 8 large output tubes

In a nutshell: The best thing about my OTL is that I often imagine I am at the performance.


Hope this helps!

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