Amplifier Output Impedance - Erin's Gear Synergy Video

[PGansz]

Erin offers a great discussion and video showing results of different tube amps compared to solid state, as well as the Wiim Amp's impedance affecting speaker output. Excellent explanation of perceived and real gear synergy with poorly designed amplifiers.

 

[sgent]

I learned so much from this. I never really considered output impedance before, and obviously it matters.

 

[IngMishael]

Erin offers a great discussion and video showing results of different tube amps compared to solid state, as well as the Wiim Amp's impedance affecting speaker output. Excellent explanation of perceived and real gear synergy with poorly designed amplifiers.

Nice to see some educating of the masses (I know people will be quick with the, "this is not new" comments but why do we want to gatekeep informing people with science even if it's just the first layer)

This is how to get people who are skeptical onboard with rigorous testing

 

[tengiz]

What happened to good old damping factor?

 

[IngMishael]

What happened to good old damping factor?

It is related

 

[tengiz]

It is related

Right, that's what I meant. The power amps specs used to include it.

 

[digitalfrost]

Benchmark has a nice page about this topic https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor

And they have an excel(lent) calculator linked at the bottom.

 

[Matias]

Archimago posted this before but Erin's video has much more details.

SUMMER MUSINGS: No... Not all amplifiers sound the same (but many do! ;-).

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

 

[PGansz]

Nice to see some educating of the masses (I know people will be quick with the, "this is not new" comments but why do we want to gatekeep informing people with science even if it's just the first layer)

This is how to get people who are skeptical onboard with rigorous testing

Precisely. Not everyone is interested in being an electrical engineer to make smart purchases and enjoy a top notch system. Content like this reduces snake oil effectiveness and continues to press audio companies ability to spread fake specs or bogus descriptions of products.

 

[Karmacoma]

Gear synergy is only a thing with bad or undersized gear. We always knew tube amps had a bad damping factor, making the bass sound rounded and not dry, on the other hand we always knew that was one of the advantages of class D amps. I learned nothing with this video and I find the title a bit misleading. Love Erin's work and expertise otherwise though. Once again, if you're looking for gear synergy there's something wrong with your gear.

 

[PristineSound]

Erin just drop a video on how amplifiers can sound different. The title is very click bait.

Basically he compared two tube amps and DB ABX them and then explained how it can sound different.

I'm not sure if I'm allowed to link that video or not, so I won't. In fact, I think my previous post on this topic got removed, not sure why.

My take is that, it's nothing ground breaking. The amp's frequency response isn't load invariant. Which leads me to say that having an amp that's load and frequency invariant is probably more important than SINAD.

Your thoughts on this topic?

 

[Matt_Holland]

I watched it last night. It’s a good video for those looking to get a more scientific understanding of audio and signal transmission. He uses a very extreme example, as you say, where he was able to 100% reliably tell a tube amp with 2ohm output impedance from a transistor amp with negligible output impedance. He usefully shows is the effect on frequency response of different amplifier output impedances into his usual complex test loads.

The video won’t satisfy audiophile concerns of why two amps with load tolerant performance sound different to them.

I’d like Erin to do a follow up video where he compares a few good amps using his ABX setup.

 

[PristineSound]

I watched it last night. It’s a good video for those looking to get a more scientific understanding of audio and signal transmission. He uses a very extreme example, as you say, where he was able to 100% reliably tell a tube amp with 2ohm output impedance from a transistor amp with negligible output impedance. He usefully shows is the effect on frequency response of different amplifier output impedances into his usual complex test loads.

The video won’t satisfy audiophile concerns of why two amps with load tolerant performance sound different to them.

I’d like Erin to do a follow up video where he compares a few good amps using his ABX setup.

I recalled him doing a video some time back where he ABX two solid state amps and he was not able to tell the difference.

I wonder the percentage difference between solid state amp are load variant vs load invariant.

 

[Matt_Holland]

I recalled him doing a video some time back where he ABX two solid state amps and he was not able to tell the difference.

I wonder the percentage difference between solid state amp are load variant vs load invariant.

You’re right he did.

My opinion is that amp SQ differences are mostly bias driven, due to load intolerance, or where distortion at power limits become audible.

 

[pinger]

Tube amps can sound different. Solid State nope

 

[Matias]

Gear synergy is only a thing with bad or undersized gear. We always knew tube amps had a bad damping factor, making the bass sound rounded and not dry, on the other hand we always knew that was one of the advantages of class D amps. I learned nothing with this video and I find the title a bit misleading. Love Erin's work and expertise otherwise though. Once again, if you're looking for gear synergy there's something wrong with your gear.

While personally I agree, I try to see things from other perspectives.

For us analytical minds, it is natural to understand graphs, determine cause and consequence, and solve the issue (tonal balance) at the cause (speaker with flat frequency response, amp with low output impedance).

But for sensitive minds, all these concepts and graphs are tiring, and they "trust their ears" (flawed as sighted listening tests are, we know), or what their friends and dealers told them it is a successful match of amp + speaker. It solves the issue (tonal balance) in another way (mix and matching).

To us analytical minds this endless trial and error method is a crazy waste of time. To sensitive minds it is called the audiophile hobby, an excuse to call friends over and test this amp or that speaker combination over a beer or two.

To me it is just two sides of the coin aka human nature.

 

[Chris A]

Excellent explanation of perceived and real gear synergy with poorly designed amplifiers.

One of the most common pictures of "audiophile" setups includes a single single-ended triode (SET) amplifier mono-amping loudspeakers (either small direct radiating loudspeakers or large horn-loaded designs of much higher efficiency). Also absent from these pictures is any hint of digital PEQ capabilities to rebalance the amplitude and phase response in-room.

SETs are tube-type amplifiers that typically do not have negative feedback to lower their output impedance (because they don't have enough forward loop gain to sustain effective negative feedback). There are also tube-type amplifiers that do have negative feedback and sufficient output transformer capacity. The problem amplifiers highlighted here are generally not the push-pull tube amplifiers having sufficient amounts of negative feedback to lower their output impedance--and this should be noted (...not that I would own any of them).

So when you read that the SETs bring "magic" to the table in so-called hi-fi setups, it's now obvious that it's really the unknowing owners that are using one type of high-output impedance amplifier non-linearity (the subject of this thread) to cover other loudspeaker and room-reflection-induced nonlinearities--without the owners taking the time to acoustically measure what is occurring. This should be one of the takeaways from this thread, IMO.

What's not discussed here is another effect of using high output impedance amplifiers to drive very efficient loudspeakers in relatively small listening rooms--the reverberation effect. This, of course, is not on the recording, but added to the "second room" acoustics--your listening room. I strongly believe that this is the "magic" that one gets from using amplifiers of high output impedance: more low-level reverberation induced from in-room acoustic reflections (less than -40 dB SPL...and mostly at lower frequencies).

Chris

 

[WillBrink]

Does it tell us a well made SS amp should have a linear output impedance and why they're often preferred?

 

[Chris A]

Does it tell us a well made SS amp should have a linear output impedance and why they're often preferred?

If that was directed at my response, then my answer is clearly "yes", linear output impedance that is generally below 0.1 Ohm--or conversely, much greater than 8 ohm--like the First Watt F1 and F1J transconductance amplifiers.

 

[Chris A]

See https://www.audiosciencereview.com/...put-impedance-erins-gear-synergy-video.64457/

This thread looks to be duplicating that thread--which was started yesterday.