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Amp Camp Amp Pre-Orders

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#21
Just built and tested the 1.6 kit this weekend. And I am thoroughly impressed!

My speakers seems perfect for this amp. I have klipsch 280Fs. The sound is more pleasant, but at the same time more detailed and punchy, imaging seems more holographic. Everything sounds more real it seems? (Its like I realize some of the hifi hyperbole has merit : )) My room adds quite a lot of dbs, but it is plenty loud, like party loud. Source was straight from airport express analogue out, my old amp is an anthem.

Measurements would be very interesting, it cant all be 2nd order harmonics playing me for a fool?

Makes me want to build a F5 or Aleph J.
 
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Sal1950

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Thread Starter #22
Makes me want to build a F5 or Aleph J
Glad you happy with the results of your labor. As discussed earlier Nelson designed these amps to have that "more pleasant" sound you describe. It's not exactly an accurate amp but purpose tuned for a particular sound.
Enjoy
 
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#23
Glad you happy with the results of your labor. As discussed earlier Nelson designed these amps to have that "more pleasant" sound you describe. It's not exactly an accurate amp but purpose tuned for a particular sound.
Enjoy
Pleasant is one part, but the micro dynamics, reverb decays and all around clarity has to be part of the class A difference in some way?
Its just so much better than my AB amp.
 

solderdude

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#24
Pleasant is one part, but the micro dynamics, reverb decays and all around clarity has to be part of the class A difference in some way?
Its just so much better than my AB amp.
Such assumptions are exactly how many myths are born and continued.
Perhaps your class AB amp is faulty (or has a poorly adjusted idle current) or above mentioned bias might be at play ?
 
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#25
Such assumptions are exactly how many myths are born and continued.
Perhaps your class AB amp is faulty (or has a poorly adjusted idle current) or above mentioned bias might be at play ?
Subjectively it sounds better, and i am searching for the objective reason for it.

It might be that my old amp is a really bad match for my speakers, as it is way too powerful and I usually play it at about nine o'clock. I seem to remember reading that AB can sound worse at lower levels?
And i guess klipsch can be harsh in the toppend without some rolloff/tube grunge..

I built a dac earlier really hoping to hear the NOS difference..but it ended up sounding very similar to my current dac, albeit with the top abit rolled off. As expected from measurements.

The idle current theory looks interesting:

https://www.tnt-audio.com/clinica/bias_e.html

I will check it out!
 

SIY

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#26
Subjectively it sounds better, and i am searching for the objective reason for it.
Most likely: expectation bias, which all humans are prone to. To eliminate that, run an ears-only (i.e., double blind level matched) comparison. If you still can identify the differences, then it's worth plunging into things like idle current issues. If you can't, then you've saved yourself a lot of work.
 

solderdude

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#27
The idle current theory looks interesting:

https://www.tnt-audio.com/clinica/bias_e.html

I will check it out!
Idle current is usually set with small potmeters. In the old days these were 'open' and the spring tension became less. When the amp is designed properly an 'open' wiper would reduce the idle current to 0 mA (safety thing).

This amp isn't rolled off at all.
It just has a bit more lower harmonic distortion due to the simplicity of the design and usage of a FET in the gain stage.
For the lowest frequencies the output resistance may be on the high side of things (output cap)
 
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#28
Most likely: expectation bias, which all humans are prone to. To eliminate that, run an ears-only (i.e., double blind level matched) comparison. If you still can identify the differences, then it's worth plunging into things like idle current issues. If you can't, then you've saved yourself a lot of work.
Way ahead of you:) there is actually a negative(?) idle current of about 20mv on both channels of the old amp. Found only two pots inside, probably for bias as they are close to the transistors. Asked for aservice manual from the producer, lets se how it goes. Aca amp is deadon zero dc.

As for a/b test, not sure how I will be able to do so easily, but it would be fun to try.

It seems you guys feel there should not be a difference? Even though they are very different topologies. Why is that?
 

SIY

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#29
If the distortion and output impedance are moderately low, frequency response is flat, and the amps aren't clipping, it's highly unlikely that you'll be able to hear a difference ears-only. Electronics tend to be audibly neutral unless one box or the other is badly broken.

But there's only one way to find out for sure and that's to run an ears-only (double blind, level matched) comparison.
 

DonH56

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#30
There are a myriad of reasons why there might be a difference, may be hard to nail down which are audible and contributing.

Simplicity of the design has little to do with lower distortion. Simpler designs often have higher distortion.

Single-ended circuits will produce different harmonic (distortion) signatures than balanced circuits.
Single-ended outputs produce different distortion than push-pull outputs.
Tubes, FETs, and BJTs all have fundamentally different distortion characteristics. Also noise characteristics vary among them, as well as sensitivity to mechanical vibration and so forth.
Bias in an AB amp affects the level of crossover distortion among other things.
Feedback and open- versus closed-loop bandwidth can change the response.
Output impedance varies among amplifiers and can change the frequency response when they drive speakers. Depends on the amp and the speakers.
A tiny (<<1 dB) difference in gain will make two amps sound different with the louder generally "better".
Sensitivity to external noise from the power supply or EMI/RFI can change things.
The stability and noise of the power supply rails can impact the performance.

Etc. etc. etc.

All of the above is measurable, BTW, if you've the gear, knowledge, and time.
 

cjfrbw

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#31
This amp project is just Nelson Pass' way of getting people to try something and succeed i.e. put it together and hear sound. It is a way of increasing interest in the 'roll your own' amp building community.
 
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Sal1950

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Thread Starter #32
It seems you guys feel there should not be a difference? Even though they are very different topologies. Why is that?
Just like building a high performance engine, many designers-builders have their favorite path to power.
Do all amp sound the same, of course not.
But if they do sound different, the reasons are measurable and can be explained.
More times than not having to do with how they interact electrically with the source, load or both.
It's been a number of decades since these things were mysterious.
 
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#33
Thanks for the replys!:)

Did a quick REW sweep on both, you can actually see the 2.order distortion on the aca!

They both show about 0.55 total thd, but i guess thats the room adding stuff?

Will try to level match and do a ab, albeit non blind, test.

Is there an amp today with different distortion signatures added by dsp? Or even speaker signatures, as there are some neuman monitors that does that. Would be a cool product to make:) not sure how you would pick up more temporal things though, like compressio and such.
 

solderdude

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#34
most likely the distortion is coming from the microphone (assuming you measured using a mircrophone)
Those types of mics usually have higher 2nd harmonic distortion.

To find out what the amp does you have to loopback the amp's output under load conditions. Beware of the level as tweeters usually don't like this, nor do the ears at higher levels.
 

12B4A

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#35
Just built and tested the 1.6 kit this weekend. And I am thoroughly impressed!

Makes me want to build a F5 or Aleph J.
After building all in question here: the Aleph J is just a more powerful, slightly cleaner ACA but with significantly more Btu radiation. It's also significantly more costly to build an Aleph J with a chassis that'll usually end up 5-7 times heavier than the ACA chassis. It's not something I think is worth it unless 10 more watts would be critical in your system. The F5 is not what you want if you like the ACA results.
 
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#36
After building all in question here: the Aleph J is just a more powerful, slightly cleaner ACA but with significantly more Btu radiation. It's also significantly more costly to build an Aleph J with a chassis that'll usually end up 5-7 times heavier than the ACA chassis. It's not something I think is worth it unless 10 more watts would be critical in your system. The F5 is not what you want if you like the ACA results.
So..maybe a second aca then, for monoblock action. Or..the m2:) decisions decisions.
 

12B4A

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#37
The M2 does look interesting because of the interstage xfmr. I don't have direct experience but it seems the Sony VFET might be more aligned with your goals. Of course, the problem is finding the parts but SS devices with triode curves seem like the right foundation.
 

andreasmaaan

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#38
Thanks for the replys!:)

Did a quick REW sweep on both, you can actually see the 2.order distortion on the aca!

They both show about 0.55 total thd, but i guess thats the room adding stuff?

Will try to level match and do a ab, albeit non blind, test.

Is there an amp today with different distortion signatures added by dsp? Or even speaker signatures, as there are some neuman monitors that does that. Would be a cool product to make:) not sure how you would pick up more temporal things though, like compressio and such.
That 2nd harmonic distortion is most likely produced by the speaker drivers. Speakers are almost always going to add significantly more nonlinear distortion than amplifiers, and this is likely to be mostly 2nd and/or 3rd harmonic (and IMD of course).

DSP can in theory produce exactly the same types of distortion as any analogue circuit, but it's complicated to replicate the exact dynamic distortion properties of a circuit. There are distortion effect plugins widely used in DAWs that seek to replicate particular tube effect units, for example.

Which Neumann speakers are you talking about? Would be interested to see what they're doing there.
 
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#39
That 2nd harmonic distortion is most likely produced by the speaker drivers. Speakers are almost always going to add significantly more nonlinear distortion than amplifiers, and this is likely to be mostly 2nd and/or 3rd harmonic (and IMD of course).

DSP can in theory produce exactly the same types of distortion as any analogue circuit, but it's complicated to replicate the exact dynamic distortion properties of a circuit. There are distortion effect plugins widely used in DAWs that seek to replicate particular tube effect units, for example.

Which Neumann speakers are you talking about? Would be interested to see what they're doing there.
Could have sworn it was neumann, but it was these i was refering to:

https://barefootsound.com/micromain27/

I agree that it seems like a complicated tadk to replicate distortion on all dynamic levels.

Since last post i have gotten some klipsch heresys. And to me the sound is amazing with the aca. I have ordered parts for a F6 based on another heresys owners suggestion. So i guess i am already down the euphonic rabbithole. ;)
 

andreasmaaan

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#40
Could have sworn it was neumann, but it was these i was refering to:

https://barefootsound.com/micromain27/

I agree that it seems like a complicated tadk to replicate distortion on all dynamic levels.

Since last post i have gotten some klipsch heresys. And to me the sound is amazing with the aca. I have ordered parts for a F6 based on another heresys owners suggestion. So i guess i am already down the euphonic rabbithole. ;)
Thanks :)

Interesting idea with those speakers, and yeh they seem to be doing exactly what you say by trying with DSP to emulate the "frequency, phase and transient responses, dynamic compression and even specific distortion components" of classic monitors.

What they won't be able to do is emulate the polar response characteristics of those other speakers. That will be for the most part fixed by the polar responses and relative positions of the drivers (unless there is sophisticated cardioid directivity shaping going on, which I see no evidence of in the published material). However, some control over polar response will be possible through DSP adjustment of the crossover frequencies and filters (again, there seems to be no evidence of this in the published material).
 

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