Sidebar

What are the advantages/disadvantages of different amp topologies?

christoph

christoph

Well-Known Member
Dec 11, 2015
4,689
4,075
825
Principality of Liechtenstein
Hi Guys

Please carry on with your interesting discussion here in this dedicated thread and NOT in the SET-owners thread.

Knock yourselves out.
 
  • Like
Reactions: the sound of Tao
bonzo75

bonzo75

Member Sponsor
Feb 26, 2014
22,646
13,683
2,710
London
  • Haha
  • Like
  • Love
Reactions: Another Johnson, hogen, the sound of Tao and 2 others
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland
christoph said:
Hi Guys

Please carry on with your interesting discussion here in this dedicated thread and NOT in the SET-owners thread.

Knock yourselves out.
Click to expand...
Let's see between all of us in the Switzerland/Liechtenstein area if we can get a bunch of amps together from all different topologies and then on a suitable speaker for all of them, see which have the best subjective sound and then hopefully we find measurements for many of them and see if there is some correlation once we calculate the prediction from one of the metrics? Maybe we can get funding from the Swiss science foundation :D?

I think we have several SET (KR, Ayon, Horning, Silvercore, Amplifon, Line Magnetic, Ukranian amp etc.), a new TriodeFET hybrid (Essentia), a more traditional hybrid(Lamm M1.1), a Class A SS amp or two (Accuphase and Plinius), PP tube both pentode (Not sure) and Class A triode (Nagra 845) etc. Maybe some Class D (anyone?) in there as well. Maybe a Class AB SS amp (Spectral, Plinius in AB mode) or two... about the only thing missing would be likely an OTL...unless you know someone with one?
 
Tangram

Tangram

Well-Known Member
Nov 10, 2022
211
282
70
60
morricab said:
Let's see between all of us in the Switzerland/Liechtenstein area if we can get a bunch of amps together from all different topologies and then on a suitable speaker for all of them, see which have the best subjective sound and then hopefully we find measurements for many of them and see if there is some correlation once we calculate the prediction from one of the metrics? Maybe we can get funding from the Swiss science foundation :D?

I think we have several SET (KR, Ayon, Horning, Silvercore, Amplifon, Line Magnetic, Ukranian amp etc.), a new TriodeFET hybrid (Essentia), a more traditional hybrid(Lamm M1.1), a Class A SS amp or two (Accuphase and Plinius), PP tube both pentode (Not sure) and Class A triode (Nagra 845) etc. Maybe some Class D (anyone?) in there as well. Maybe a Class AB SS amp (Spectral, Plinius in AB mode) or two... about the only thing missing would be likely an OTL...unless you know someone with one?
Click to expand...
Does LTA have any footprint in Europe? I would - selfishly - love to have one of their David Berning-designed OTL amps included in a shootout.
 
Last edited:
Atmasphere

Atmasphere

Industry Expert
May 4, 2010
2,375
1,866
1,760
St. Paul, MN
www.atma-sphere.com
Tangram said:
Does LTA have any footprint in Europe? I would - selfishly - love to have one of their David Berning-designed OTL amps included in a shootout.
Click to expand...
The Berning amplifier isn't an OTL, which does not take away from the brilliance of its design. It has an output transformer but the transformer is air core. Its probably more accurate to call it an RF-coupled audio amplifier. It can be executed in single-ended or PP and any variant thereof.

christoph said:
Hi Guys

Please carry on with your interesting discussion here in this dedicated thread and NOT in the SET-owners thread.

Knock yourselves out.
Click to expand...
'Advantages and disadvantages of amplifier topology' covers a pretty wide spread. Since this is your thread, is it limited to tubes? Just in the world of class D there are a variety of different topologies. So at present this thread from its title might have a lack of focus.
 
  • Like
Reactions: French Fred and Republicoftexas69
S

Salectric

Well-Known Member
Jan 15, 2012
381
501
998
Comparing a number of amps with different topologies can be a lot of fun, but I wouldn’t count on drawing any reliable conclusions about topologies alone.

The sound of an amplifier is affected by so many different factors and the circuit design is just one factor. Different output tubes, different input/driver designs, different operating points, different choices of capacitors, resistors and wire, different input and output connectors, and different types of chassis construction.

There’s nothing wrong with having an amp shootout. It can be lots of fun but conclusions will be limited to the particular amplifiers.
 
Last edited:
  • Like
Reactions: the sound of Tao and Atmasphere
christoph

christoph

Well-Known Member
Dec 11, 2015
4,689
4,075
825
Principality of Liechtenstein
Atmasphere said:
The Berning amplifier isn't an OTL, which does not take away from the brilliance of its design. It has an output transformer but the transformer is air core. Its probably more accurate to call it an RF-coupled audio amplifier. It can be executed in single-ended or PP and any variant thereof.


'Advantages and disadvantages of amplifier topology' covers a pretty wide spread. Since this is your thread, is it limited to tubes? Just in the world of class D there are a variety of different topologies. So at present this thread from its title might have a lack of focus.
Click to expand...
It is not MY thread but I would say ANY topology can be discussed.
 
  • Like
Reactions: French Fred
A

acousticsguru

Well-Known Member
Feb 17, 2014
507
326
373
Hi everyone! I would love to see those spectral analysis measurements of SET vs PP / OTL discussed in the SET owners thread! Says more than words! Thanks!

Greetings from Switzerland, David.
 
  • Like
Reactions: French Fred
Rumpole

Rumpole

Active Member
Aug 26, 2023
102
77
30
63
Colorado, USA
Atmasphere said:
'Advantages and disadvantages of amplifier topology' covers a pretty wide spread. Since this is your thread, is it limited to tubes? Just in the world of class D there are a variety of different topologies. So at present this thread from its title might have a lack of focus.
Click to expand...
I know you have written about this elsewhere, but maybe this would be a good place to describe in more detail your Class D versus you OTL amps? Your web page has nice description of the benefits of OTL but not a lot of detail of your Class D vs OTL I'm also interested in how you would compare the Novacron to your Class D and other OTL amps.
 
  • Like
Reactions: Argonaut
Hear Here

Hear Here

Well-Known Member
Feb 14, 2020
744
460
155
Portsmouth, UK
"Horses for courses"! Some amps just won't work with certain types of speaker and vice versa, so I'm doubtful any conclusions will be reached, even if an example of each amp technology is connected up with its ideal speaker mate. However it might be a fun exercise, although I can't contribute myself, being a few hundred miles from Switzerland.

When I bought my first horn speakers (101 dB) I was advised that its ideal match was an SET valve amp. So I bought a few over the next 17 years (mainly PX-25 and 845 based), plus an OTL and a PP or two. I found the PX-25 the most delightlful with female vocal and small-scale music but the 845 best for full-blooded orchestral, etc.

Then I decided to look for a less "troublesome" ss amp that might offer equally satisfying listening (without trying to mimic SETs) and bought or borrowed a dozen amps of various classes. I ended up with a Purifi Eigentakt- based Class D amp and have recently added a pair of Atma-Sphere Class D amps. Both offer exceptional sound with my latest 107 dB horn speakers and no regrets whatsoever for abandoning valves. They were fun at the time, but times have changed!.
 
Last edited:
  • Like
Reactions: Atmasphere
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland
Hear Here said:
"Horses for courses"! Some amps just won't work with certainly types of speaker and vice versa, so I'm doubtful any conclusions will be reached, even if an example of each amp technology is connected up with its ideal speaker mate. However it might be a fun exercise, although I can't contribute myself, being a few hundred miles from Switzerland.

When I bought my first horn speakers (101 dB) I was advised that its ideal match was an SET valve amp. So I bought a few over the next 17 years (mainly PX-25 and 845 based), plus an OTL and a PP or two. I found the PX-25 the most delightlful with female vocal and small-scale music but the 845 best for full-blooded orchestral, etc.

Then I decided to look for a less "troublesome" ss amp that might offer equally satisfying listening (without trying to mimic SETs) and bought or borrowed a dozen amps of various classes. I ended up with a Purifi Eigentakt- based Class D amp and have recently added a pair of Atma-Sphere Class D amps. Both offer exceptional sound with my latest 107 dB horn speakers and no regrets whatsoever for abandoning valves. They were fun at the time, but times have changed!.
Click to expand...
Glad you like it. I have had some Class D on my horns and...well, no that sound doesn't work for me.
 
Atmasphere

Atmasphere

Industry Expert
May 4, 2010
2,375
1,866
1,760
St. Paul, MN
www.atma-sphere.com
Rumpole said:
I know you have written about this elsewhere, but maybe this would be a good place to describe in more detail your Class D versus you OTL amps? Your web page has nice description of the benefits of OTL but not a lot of detail of your Class D vs OTL I'm also interested in how you would compare the Novacron to your Class D and other OTL amps.
Click to expand...
The Novacron, like our other OTLs, has as its dominant distortion product the 3rd harmonic, with the 2nd at about 2/3rds that level since the balance in the amplifier isn't perfect. Now if you compare to an SET, the SET will have a particularly prominent 2nd with the 3rd quite a bit lower. In the Novacron, the 3rd is at a proportionate level lower than found in SETs. So its a considerably lower distortion amp and it sounds like it too (smoother, more transparent).

The class D has two aspects which cause most of the distortion in the amp: the input encoding scheme and the deadtime in the output section. In our design, both of those non-linearities tend to generate lower ordered harmonics. The 2nd is dominant, followed by the 3rd at about 1/2 that amplitude. So it probably has more in common with the distortion of an SET than our OTLs, but its at a much lower level than either. I've described its distortion spectra in the past as being very much like a really good tube amp.

In a zero feedback tube amp, the sonic signature of the amp is exactly two things: the distortion it makes and the frequency response it has on the speaker with which its being used. The FR varies from speaker to speaker since there is no feedback. Usually the distortion dominates the ear's perception of it since the ear pays particular attention to the tonality it assigns to the distortion (in a manner similar to how harmonics cause the tone colors of musical instruments). So you can see that for an amplifier to sound musical, its vital that it have a benign distortion character.

Our class D does- and has a very nice first Watt. If its not broken in properly (which seems to take about 450 hours or so; customer feedback is pretty consistent in this regard) the Novacron will be slightly more musical, but after break-in it seems to go the other way. The big tell seems to be how the rear of the sound stage is portrayed; people describe the class D as being more 'focused'. The bass is different, owing to the fact that the class D is able to behave as a near perfect voltage source and that interacts quite differently with the low frequency resonance most speakers have as compared to our OTLs (which, like most zero feedback tube amps, tend to act more like a power source (see Paradigms in Amplifier Design for more on this).

The Novacron was one of our best sounding amps when it was on the right speaker. But you can so as well or better (depending on the speaker) with a fully optioned set of MA-1s, which also have more power. FWIW all the Novacrons built in the recent run of a few years back were 'fully optioned' with the same resistors, coupling caps and power supplies as a fully optioned set of MA-1s.
 
  • Like
Reactions: Rumpole
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland
acousticsguru said:
Hi everyone! I would love to see those spectral analysis measurements of SET vs PP / OTL discussed in the SET owners thread! Says more than words! Thanks!

Greetings from Switzerland, David.
Click to expand...
Good luck getting anything that isn’t in the public domain already.
 
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland
Atmasphere said:
The Novacron, like our other OTLs, has as its dominant distortion product the 3rd harmonic, with the 2nd at about 2/3rds that level since the balance in the amplifier isn't perfect. Now if you compare to an SET, the SET will have a particularly prominent 2nd with the 3rd quite a bit lower. In the Novacron, the 3rd is at a proportionate level lower than found in SETs. So its a considerably lower distortion amp and it sounds like it too (smoother, more transparent).

The class D has two aspects which cause most of the distortion in the amp: the input encoding scheme and the deadtime in the output section. In our design, both of those non-linearities tend to generate lower ordered harmonics. The 2nd is dominant, followed by the 3rd at about 1/2 that amplitude. So it probably has more in common with the distortion of an SET than our OTLs, but its at a much lower level than either. I've described its distortion spectra in the past as being very much like a really good tube amp.

In a zero feedback tube amp, the sonic signature of the amp is exactly two things: the distortion it makes and the frequency response it has on the speaker with which its being used. The FR varies from speaker to speaker since there is no feedback. Usually the distortion dominates the ear's perception of it since the ear pays particular attention to the tonality it assigns to the distortion (in a manner similar to how harmonics cause the tone colors of musical instruments). So you can see that for an amplifier to sound musical, its vital that it have a benign distortion character.

Our class D does- and has a very nice first Watt. If its not broken in properly (which seems to take about 450 hours or so; customer feedback is pretty consistent in this regard) the Novacron will be slightly more musical, but after break-in it seems to go the other way. The big tell seems to be how the rear of the sound stage is portrayed; people describe the class D as being more 'focused'. The bass is different, owing to the fact that the class D is able to behave as a near perfect voltage source and that interacts quite differently with the low frequency resonance most speakers have as compared to our OTLs (which, like most zero feedback tube amps, tend to act more like a power source (see Paradigms in Amplifier Design for more on this).

The Novacron was one of our best sounding amps when it was on the right speaker. But you can so as well or better (depending on the speaker) with a fully optioned set of MA-1s, which also have more power. FWIW all the Novacrons built in the recent run of a few years back were 'fully optioned' with the same resistors, coupling caps and power supplies as a fully optioned set of MA-1s.
Click to expand...
Your OTL, while no doubt very transparent (having owned a couple OTLs I never doubted this) , is likely less musical because of it distortion spectrum. Your OTL will also have FR issues on speakers with lower impedance due to high output impedance…unless you use quite a bit of feedback to lower it.
 
Rumpole

Rumpole

Active Member
Aug 26, 2023
102
77
30
63
Colorado, USA
Thanks, Ralph - I really appreciate you sharing your experience and knowledge. Nelson Pass talks about distortion at about 11 minutes into in the interview link below - would you agree about a more pleasing sound with greater 2nd than 3rd order distortion, and also with his finding about differences in a positive vs negative phase for the 2nd order distortion?

if you have dominant second followed by lesser quantity of third and then the other higher order harmonics drop off rapidly, you get a sound that tends to be most pleasing to the listener "
Click to expand...

and

"but we saw to it that it had the negative phase character on that second because we found that that was that was an important element if you have (and this is a common perception, I can't say that everybody experiences the same thing) but a negative phase second harmonic tends to give an apparent expansion to the sound field so that things move out a little deeper and farther. If you go positive phase it kind of moves in and becomes a little more intimate maybe a little more detailed - it's totally any illusion but there it is, and we also found out that most of the customer base liked the negative phase"
Click to expand...

 
  • Like
Reactions: AudioHR and Atmasphere
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland


audioxpress.com

You Can DIY! A 25W OTL Tube Amplifier

More than a decade since the original publication by audioXpress, many readers still actively search for information and share the schematics of this OTL tube project. Tim Mellow's design explores a different output stage using a novel combination of local feedback and current drive in order to...
audioxpress.com audioxpress.com



An older discussion along similar lines…seems overall preference was SET…at least among tube designs.

www.superbestaudiofriends.org

Push Pull vs OTL vs SET (Tube amps)

I'm surprised at the animosity towards a lot of OTL amps. I actually prefer them (when they're designed properly and when using complementary speakers/...
www.superbestaudiofriends.org www.superbestaudiofriends.org
 
  • Like
Reactions: acousticsguru
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland
SoundStage! Measurements - Wyetech Labs Topaz 572B Stereo Amplifier (6/2003) (soundstagenetwork.com)

Lamm ML2.1 monoblock power amplifier Measurements | Stereophile.com

Lamm ML2.2 monoblock power amplifier Measurements | Stereophile.com

Air Tight ATM-211 tube monoblock power amplifier Measurements | Stereophile.com

Air Tight ATM-300R power amplifier Measurements | Stereophile.com

Allnic Audio A-5000 DHT monoblock power amplifier Measurements | Stereophile.com

Audiopax Model Eighty Eight monoblock power amplifier Measurements | Stereophile.com

Bel Canto SET 80 monoblock power amplifier Measurements | Stereophile.com

Cary Audio CAD-805RS monoblock power amplifier Measurements | Stereophile.com
Crap output transformer on this amp...resonance just above 20Khz and big saturation in the bass :(

Cary Audio Design CAD-300SE LX20 monoblock power amplifier Measurements | Stereophile.com

Cary Audio Design CAD-572SE monoblock power amplifier Measurements | Stereophile.com
This one actually sounds pretty nice...I had it a long time ago.

Lamm Industries ML3 Signature monoblock power amplifier Measurements | Stereophile.com

Sophia Electric 91-01 300B monoblock power amplifier Measurements | Stereophile.com

Thöress 300B monoblock power amplifier Measurements | Stereophile.com

Wavac SH-833 monoblock power amplifier Measurements | Stereophile.com

Wavelength Audio Cardinal XS monoblock amplifier Measurements | Stereophile.com

Yamamoto A-08 power amplifier Measurements | Stereophile.com

Audio Note Jinro integrated amplifier Measurements | Stereophile.com

Audio Note Meishu Tonmeister Phono integrated amplifier Measurements | Stereophile.com

Cayin A-300B integrated amplifier Measurements | Stereophile.com

Line Magnetic Audio LM-518IA integrated amplifier Measurements | Stereophile.com

Line Magnetic LM-845IA integrated amplifier Measurements | Stereophile.com

Mastersound 845 Compact integrated amplifier Measurements | Stereophile.com
Some weird transformer behavior

Western Electric Type No.91E integrated amplifier Measurements | Stereophile.com
 
  • Like
Reactions: Amir, acousticsguru, DasguteOhr and 1 other person
DasguteOhr

DasguteOhr

Well-Known Member
Sep 26, 2013
2,445
2,623
645
Germany
morricab said:
SoundStage! Measurements - Wyetech Labs Topaz 572B Stereo Amplifier (6/2003) (soundstagenetwork.com)

Lamm ML2.1 monoblock power amplifier Measurements | Stereophile.com

Lamm ML2.2 monoblock power amplifier Measurements | Stereophile.com

Air Tight ATM-211 tube monoblock power amplifier Measurements | Stereophile.com

Air Tight ATM-300R power amplifier Measurements | Stereophile.com

Allnic Audio A-5000 DHT monoblock power amplifier Measurements | Stereophile.com

Audiopax Model Eighty Eight monoblock power amplifier Measurements | Stereophile.com

Bel Canto SET 80 monoblock power amplifier Measurements | Stereophile.com

Cary Audio CAD-805RS monoblock power amplifier Measurements | Stereophile.com
Crap output transformer on this amp...resonance just above 20Khz and big saturation in the bass :(

Cary Audio Design CAD-300SE LX20 monoblock power amplifier Measurements | Stereophile.com

Cary Audio Design CAD-572SE monoblock power amplifier Measurements | Stereophile.com
This one actually sounds pretty nice...I had it a long time ago.

Lamm Industries ML3 Signature monoblock power amplifier Measurements | Stereophile.com

Sophia Electric 91-01 300B monoblock power amplifier Measurements | Stereophile.com

Thöress 300B monoblock power amplifier Measurements | Stereophile.com

Wavac SH-833 monoblock power amplifier Measurements | Stereophile.com

Wavelength Audio Cardinal XS monoblock amplifier Measurements | Stereophile.com

Yamamoto A-08 power amplifier Measurements | Stereophile.com

Audio Note Jinro integrated amplifier Measurements | Stereophile.com

Audio Note Meishu Tonmeister Phono integrated amplifier Measurements | Stereophile.com

Cayin A-300B integrated amplifier Measurements | Stereophile.com

Line Magnetic Audio LM-518IA integrated amplifier Measurements | Stereophile.com

Line Magnetic LM-845IA integrated amplifier Measurements | Stereophile.com

Mastersound 845 Compact integrated amplifier Measurements | Stereophile.com
Some weird transformer behavior

Western Electric Type No.91E integrated amplifier Measurements | Stereophile.com
Click to expand...
Mastersound problem had nothing to do with opt, first the bypass cap for katode ressistor is to small hence the bass drop in the frequency response(mesurements). The bad square wave behavior comes from the coupling capacitor between 6SN7 and the 845 being too large. This makes the amplifier sluggish. the same with the 300b from that program. If you change that, you won't recognize the amplifier again. how good sound after that promise. Green marked +some little other mods helps to get a really good amp.
Here 300b mod only german sorry

Röhrentechnik: Treiberstufe & Bypass-Kondensator – Seite 3 von 3 – **frihu.com ** - Part 3

Treiberstufe. Der problematische Schaltungsteil in einem Röhrenverstärker. Dabei ist eine gute Treiberstufe keine Raketenwissenschaft. - Part 3
www.frihu.com www.frihu.com
20240130_113518.jpg
 
M

morricab

Well-Known Member
Apr 25, 2014
9,531
5,068
1,228
Switzerland
DasguteOhr said:
Mastersound problem had nothing to do with opt, first the bypass cap for katode ressistor is to small hence the bass drop in the frequency response(mesurements). The bad square wave behavior comes from the coupling capacitor between 6SN7 and the 845 being too large. This makes the amplifier sluggish. the same with the 300b from that program. If you change that, you won't recognize the amplifier again. how good sound after that promise. Green marked +some little other mods helps to get a really good amp.
Here 300b mod only german sorry

Röhrentechnik: Treiberstufe & Bypass-Kondensator – Seite 3 von 3 – **frihu.com ** - Part 3

Treiberstufe. Der problematische Schaltungsteil in einem Röhrenverstärker. Dabei ist eine gute Treiberstufe keine Raketenwissenschaft. - Part 3
www.frihu.com www.frihu.com
View attachment 124422
Click to expand...
Makes you wonder how they made such mistakes as they seem to have some idea how to design an amp...
 
  • Like
Reactions: DasguteOhr
DasguteOhr

DasguteOhr

Well-Known Member
Sep 26, 2013
2,445
2,623
645
Germany
morricab said:
Makes you wonder how they made such mistakes as they seem to have some idea how to design an amp...
Click to expand...
I have nothing against a design if it works, they use the same input+driverstage for the 300b and 845 amp. In the 300b it doesn't work well for the 845 there are better solutions. Everyone hears differently. I don't like both amplifiers.
300b pic 679792f87771f2d3d02ba99d26c92443.jpg
 
Last edited:
You must log in or register to reply here.

Similar threads

bonzo75
Alternative Audio
Replies
13
Views
648
General Audio Forum
bonzo75
bonzo75
M
Audiovector R11 Arreté - downgrade to what?
Replies
1
Views
256
Speakers
DasguteOhr
DasguteOhr
simorag
What are you listening today and WHY – Only one rule, see first post
Replies
62
Views
5K
General Music Discussion Forum
davidavdavid
davidavdavid
FT251
Anyone have experience with the Legacy Audio Wavelet II?
Replies
17
Views
2K
Digital Audio Forum: DAC, Transports, Digital Processing Forum
SCAudiophile
SCAudiophile
P
40+ watts SET
Replies
20
Views
855
Power Amplifiers and Preamplifiers Forum
Kingrex
Kingrex

Members online

Total: 1,158 (members: 46, guests: 1,112)

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

Home Forums Contact us

User Menu

Login
Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing
Top Bottom