O.T.L. Amplifiers

Bioman · « **on:** 24 Jan 2020, 02:27 pm »

Anyone here a current or former user of OTL designs. They have intrigued me since the time years ago I heard an NYSL offering at a friend's stereo store and was blown away by the crystalline quality of the highs. What do you like and dislike about them, and if you had them but moved on, why?

ketcham · « **Reply #1 on:** 24 Jan 2020, 06:49 pm »

I have owned tubed gear for almost two decades now. I transitioned to OTL/OCL design preamp and was impressed by the clarity. This transition solidified the importance of the preamp and when implemented well is amazing but most often can be a significant bottleneck to the signal path. That said, I believe implementation is key. This particular design has both balanced and unbalanced outputs. To become balanced in a internal unbalanced circuit design, a quality transformer is added and in this application the magic disappears. I replaced my cables from balanced to unbalanced for this reason.

Some traditional point to point wiring with output transformers are also sublime, especially vintage transformers typically age well. I have listened to a handful of OTL/OCL manufacturers and I enjoyed all of them, each with their own qualities. Since there are so many variable with each of our systems, it is best to audition gear before purchasing.

Bioman · « **Reply #2 on:** 24 Jan 2020, 10:35 pm »

Quote from: ketcham on 24 Jan 2020, 06:49 pm

Since there are so many variable with each of our systems, it is best to audition gear before purchasing.

Agreed, although there seem to be fewer and fewer bricks and mortar in which to do so. There is an Atma-Sphere dealer in Texas, may give that a shot.

FullRangeMan · « **Reply #3 on:** 24 Jan 2020, 10:45 pm »

One can always order an amp to a well reputed builder, in this case the only OTL interesting IMO are the Tim Mellow 25W with two inexpensive 6C33 p/c, the parts count are minimal.

leftside · « **Reply #4 on:** 25 Jan 2020, 04:48 am »

I had a custom OTL amp built, but it's not exactly minimal...
https://www.head-fi.org/threads/1101-audio-custom-crafted-headphone-amps.919425/

borism · « **Reply #5 on:** 25 Jan 2020, 01:45 pm »

Bioman, I have an Atma-Sphere S30 OTL and with the right speakers it's a wonderful combination. My AudioKinesis Jazz Modules don't dip below 8 ohms and were voiced with the A-S amplifier. As a comparison, with the McIntosh MC275 the same system sounded good but with the A-S it became much more vivid and three dimensional, as if the performers are present in the room.
I also use a Bottlehead 2A3 SET which in comparison sounds a little more delicate but with 4W/ch does not have the drive or can play as loudly.

Bioman · « **Reply #6 on:** 25 Jan 2020, 03:20 pm »

Quote from: borism on 25 Jan 2020, 01:45 pm

Bioman,
I also use a Bottlehead 2A3 SET which in comparison sounds a little more delicate but with 4W/ch does not have the drive or can play as loudly.

I am a bit leary of SET for the lower power reason you mention. My experience has been having a degree of reserve seems to make a difference in dynamic peaks such as in orchestral crescendos; which is a fair amount of what I listen to.

jsm71 · « **Reply #7 on:** 25 Jan 2020, 03:52 pm »

I have owned a couple of traditional tube amps, those that deploy the typical iron core wound transformers. They can be nice but those transformers cloud the sound a bit and chop off both lows and highs.

I use a different type of OTL tube amp, designed by David Berning, built by Linear Tube Audio. His design is difficult to explain quickly but he uses a different type of transformer, not the sound robbing iron core types. I bought the ZOTL40 amp, which is driving JansZen hybid ESL speakers with ease.

The Berning design's sound is very similar to quality OTL amps but with advantages:
1. The ZOTL40 amp weighs only 15 pounds
2. Tubes last from 10 to 20 years
3. Very little heat is generated.
4. Impedance matching is way more liberal for speakers

Worth a look if you are interested in great tube sound.

https://www.lineartubeaudio.com/products/zotl-40-reference-amplifier

Bioman · « **Reply #8 on:** 30 Jan 2020, 01:23 am »

Anyone look at these. "OTL Amplifier Stereo Pair 20 Watts w/8 Ohm Load, New Quality Parts & AssemblyIntriguing" sold by "raelectron". He is in Arizona if I recall correctly and builds one of these every few months and puts them up for sale on Ebay. Apparently based on a design found in a magazine. He has a fair amount of five stars associated with the sale of these as I look back through his feedback history. Not sure if I could get by with 20 watts; tempting though. Has anyone listened to one? The last one just sold for under $400 a pair. Don't see how could make and sell them for that little.

FullRangeMan · « **Reply #9 on:** 30 Jan 2020, 01:35 am »

Could we see this announcement?

Bioman · « **Reply #10 on:** 30 Jan 2020, 02:18 pm »

Hope this does not violate forum policy. Here are two GIF's

Bioman · « **Reply #11 on:** 30 Jan 2020, 02:20 pm »

PS, don't know this guy; so no idea if this is legit.

FullRangeMan · « **Reply #12 on:** 30 Jan 2020, 06:18 pm »

Description said its based on Futterman, Tim Mellow and Dickie/Macovski what may be a unstable mix, I could not locate this ad, seems sold, as he does no accept returns better you pass this unsual amp.

OzarkTom · « **Reply #13 on:** 31 Jan 2020, 05:15 am »

Was $10,000 a pair back in the 80's, crazy man Harvey Rosenberg showed up with the NYAL Futterman OTL1's and Quad 63's at the CES show in Chicago. Everyone that walked in his room was looking for the sub woofers. Bass and dynamics was incredible.

I know OP is looking for something much cheaper.

Steve · « **Reply #14 on:** 6 Mar 2020, 03:31 pm »

I, personally, designed and built my own test OTL amplifier. It used 20 horizontal output tubes, 10 per channel.
Maximum power output in triode mode was 200 watts/channel. Frequency response was calculated to be
approximately -3db at 1.3 mhz. Unfortunately, idle power consumption was 850 watts, so I only used it in winter.
The sound was absolutely amazing.

However, over the years I have been able to create a perfectly accuracy/naturalness PP tube type monoblock amplifier (with current speaker technology). Slightly better sonics with much less wattage drain. It is possible to create such amplifiers, and preamplifiers and phono stages. But careful design and matching components is necessary.
Caveat: I am retired, so not manufacturing.

cheers
steve

FullRangeMan · « **Reply #15 on:** 6 Mar 2020, 09:16 pm »

Do you have some photos Steve?

Dieterle Tool · « **Reply #16 on:** 7 Mar 2020, 12:05 am »

I have a modified Bernng ZH-270, weighing in at 5 lbs, it is the most musically satisfying amp I have. With its feedback adjustment, to match damping factor, it is suitable for a verity of speakers and packs a powerful punch for 70 watts. Highly recommended.

-Dieter

walkern · « **Reply #17 on:** 7 Mar 2020, 01:02 am »

Transcendent Sound has been offering OTL amp kits for quite a number of years. Lots of options depending on your power requirements and how deep your pockets are. I've never heard any of his amps, but I built a Grounded Grid preamp and thought it was pretty amazing. Here's the website for more info:https://www.transcendentsound.com/products-.html

FullRangeMan · « **Reply #18 on:** 7 Mar 2020, 01:53 am »

The Transcendent OTL kits are not cheap just for a set of parts, the assemblage work, adjustments and testings are not for everyone.

dB Cooper · « **Reply #19 on:** 7 Mar 2020, 02:14 am »

OTLs are not cheap in general