JW001
Active Member
Dynamic range is a property of the signal, not the amplifier. If anything, negative feedback increases DR by improving the amp linearity.
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3e audio A7/A7 Mono Amplifier Review
- Thread starter amirm
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Thank you, @peng, the concern with the Linton 85s is the EPDR, not so much the Impedance, especially where it dips below 2R (75-125Hz), small range but there is alot of music content in this small range, isn't there? Why, to clarify, Impedance, in this case, does not tell the whole story as the speakers phase angle changes with frequency. EPDR combines both the Impedance and Phase angle into a single (real) resistance value. As such, the low EPDR indicates a challenging load and corresponds to a very low resistive Load (<2R) for the amplifyer, doesn't it?Just curious, why would you be concerned? The speakers are rated 6 ohms, 3.5 ohms minimum. The Sansui is not even rated for 4 ohm speakers but it should be fine with the Linton 85 as long as you don't push them to the limit, so if the Sansui amp has been doing fine for you, then the A7Se with the 48 V 10A PS should do even much better in terms of current delivery capability. The Sansui amp would like run warm because of the phase angle in the 65-180 Hz range so overall I would predict the little 3eA7e would be a better amp to use with the Linton 85.
You will enjoy the setup, and if you find it sounds not as good as the Sansui, then try to do blind listening comparison and the difference would likely disappear.
Wharfedale Linton 85th Anniversary Speaker Review
Wharfedale Linton 85th Anniversary Reviewwww.erinsaudiocorner.com
View attachment 500060
Although as you mention, if the Sansui AU-D7 is driveing them without issue then the 3eA7se (most likely/hopefully) also will. The 48V/10A SMPS will/would provide/assist with extra current availablety, wouldn't it, especially with volume/power?
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That is a popular misconception, the EPDR does not affect the current delivery calculations. You must already know Ohm's law, that is Current = Voltage/|
|impedance| is the absolute value that is not affected by the phase angle. The phase angle affects the power dissipation split between the load impedance, i.e. the speaker and the output device. As phase angle increases, more power would be dissipated in the output devices so the amplifier will heat up more. Stereophile started this EPDR thing that tried to figure out a way to allow for the potentially excessive heat dissipation in the output devices that could damage them and/or cause stability issue. In doing so, their method would deflate the impedance so as to inflate the current, but in reality the current does not increase, so that much lower EPDR of the Linton 85 does not mean the current would actually double when it dips from 4 ohm to 2 ohm, it will be the same, but the output devices will have to dissipate much more heat. To conclude, it would be a "more challenging load" as you put it because of the low EPDR value, but not in terms of the current that I thought you were concerned about, it is more about heat dissipation in the amp, and that isn't much of an issue for those class D amps but very much so for class AB amps.
As other experts posted before class D amps are not as affected by EPDR like class AB amps. So, there is nothing to worry, you will love that little amp.
The 3eA7se will do a better, and easier job, compared to the Sansui, that seems like an excellent amp, just can't compare with the modern 3eA7 and that's on paper only. In reality you will likely not hear a difference if you do blind listening tests.
I don't like the way I explained it in my post so let me use a numerical example that hopefully could help clarify my point.
Take a look at the 90 Hz point on the Erin's graph, we can see the following numbers:
Actual impedance absolute value = about 4.5 ohms
Phase angle = about -40 degrees
EPDR = 1.7 ohms
I don't know how Erin measured/plotted the EPDR curve, but he might just use a formula to calculate it (Stereophile, iirc, did published a formula they used at one point at least) Edit: he likely just use REW to measure it, but I am guessing, will have to ask him.
Now let's say we play a 90 Hz sine wave, and applied 50 V to a test load of 1.7 ohms, the calculated current would be = 50/1.7 = 29.4 A.
Reality is, you won't get 29.4 A, because the actual measured impedance at that same point was 4.5 ohms, the the actual current = 50/4.5 = 11.11A.
The reason EPDR is still useful (though often confused many..) is that the 29.4 A based on the 1.7 ohm EPDR actually would more or less represent the heat dissipation in the amplifier (internally/output stage devices) whereas the 11.11 A actual current would not. The reason is, the way power amplifier work is such that when the phase angle increases (leading or lagging) more heat will get dissipated in the amplifier and less heat will be dissipated in the load itself.
In other words, the 29.4 A calculated using the much deflated value, namely the EPDR, represents an equivalency in terms of heat dissipation, but not in terms of resulting in actual higher current demand.
Also, as I mentioned, others who know much more about class D amps than me, had mentioned that class D amps typically are less prone to low EPDR.
PS: It appears that REW can actually measure, or more precisely compute EPDR since 2020, and that may be how Erin did it.
www.avnirvana.com
Take a look at the 90 Hz point on the Erin's graph, we can see the following numbers:
Actual impedance absolute value = about 4.5 ohms
Phase angle = about -40 degrees
EPDR = 1.7 ohms
I don't know how Erin measured/plotted the EPDR curve, but he might just use a formula to calculate it (Stereophile, iirc, did published a formula they used at one point at least) Edit: he likely just use REW to measure it, but I am guessing, will have to ask him.
Now let's say we play a 90 Hz sine wave, and applied 50 V to a test load of 1.7 ohms, the calculated current would be = 50/1.7 = 29.4 A.
Reality is, you won't get 29.4 A, because the actual measured impedance at that same point was 4.5 ohms, the the actual current = 50/4.5 = 11.11A.
The reason EPDR is still useful (though often confused many..) is that the 29.4 A based on the 1.7 ohm EPDR actually would more or less represent the heat dissipation in the amplifier (internally/output stage devices) whereas the 11.11 A actual current would not. The reason is, the way power amplifier work is such that when the phase angle increases (leading or lagging) more heat will get dissipated in the amplifier and less heat will be dissipated in the load itself.
In other words, the 29.4 A calculated using the much deflated value, namely the EPDR, represents an equivalency in terms of heat dissipation, but not in terms of resulting in actual higher current demand.
Also, as I mentioned, others who know much more about class D amps than me, had mentioned that class D amps typically are less prone to low EPDR.
PS: It appears that REW can actually measure, or more precisely compute EPDR since 2020, and that may be how Erin did it.
Equivalent peak dissipation resistance, EPDR
Back in 2007 Keith Howard proposed a measure he called Equivalent peak dissipation resistance, EPDR, to reflect the way the phase angle of a speaker load increases the peak power dissipation in the output transistors of a power amplifier beyond what might be expected from the load modulus. The...
www.avnirvana.com
No, no, no. A million times no.
I have my A7 monos driving my KEF R3 Meta that are rated at 4 ohms and dive easily to 3 ohms. That setup sounds superb.
Roland68
Major Contributor
The A7 monoblocks are designed for 2 ohms, just like the A7. The A7se are only designed for 4 ohms.
TurtlePaul
Major Contributor
EPDR is a fictional number that assumes a class B rail-to-rail amp. That is a fictional device but the calculation is a decently representative worst case scenario for class AB amps as they are basically class B at high power.
Class D amps don’t have EPDR at all. At high phase angles they have power supply pumping. Think of it like regenerative braking in an electric vehicle. When the output transistor is on it bridges the supply to the load and doesn’t care which way the current flows. If you have enough power supply capacitance then the power being fed back by the load can be stored and used again.
The problem with class D is when power supply pumping causes the power rail voltages to increase. Too high of a rail voltage can damage the amp. Also, if the power rail varies too much then the amp needs ample power supply rejection so it isn’t fed back into the amp as distortion. In addition to the obvious efficiency gains, many class D amps use switching power supplies because they can regulate the voltage both upwards and downwards while traditional linear PSUs only can increase the voltage which doesn’t counteract pumping.
Long story short - for Class D amps like the 3e A7 you can look at the speaker impedance and ignore EPDR.
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Thanks for chiming in, would you say that even if such class D amps use linear power supplies, example: some of ATI's, EDPR would still be not quite relevant because the amplifier section itself still runs in switching mode.
EDPR is still not relevant as long as the PSU caps can absorb the pumping. Given that the pumping will be spread spectrum (matching the music), I doubt it would be a big issue. If it were an issue, then I'd expect the amp to shutdown on over voltage, rather than be damaged.
And we don't see that happening. So I don't think we need to worry about it as a real world issue.
I am going to try and sell my Fosi V3s and purchase the 3e A7 Mono, but on Amazon there don't seem to be an option to get the 52V/10 A (edit: actually 9 A) A PS, how did others get that upgrade? I am sure the include 5 A PS is more than I need but I just prefer the 10 9 A one for no reasons.
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I saw it on AliExpress. The A7 can be purchased as a set with a 5V power supply. It can also be bought without a power supply, and a 10V power supply can be purchased separately.I am going to try and sell my Fosi V3s and purchase the 3e A7 Mono, but on Amazon there don't seem to be an option to get the 52V/10A (edit: actually 9 A) A PS, how did others get that upgrade? I am sure the include 5 A PS is more than I need but I just prefer the109 A one for no reasons.
I also don't think I need two mono but on Amazon.ca, they have the mono on 10% discount for quantity of 2 or more, so two Mono costs only about CAD 22 more and you get two 5 A PS instead of 1, seems like a better value.
AliExpress costs much more than from Amazon's. Found one with the AIYIMA brand on Amazon that should work: https://www.amazon.ca/gp/product/B0D48JNKD2/ref=ox_sc_act_title_1?, but Amazon does not sell an A7 Mono that doesn't include the 5 A supply. Wonder why they just don't seem to want to include the 9/10 A supply with those amps, I guess its the shipping cost as the 10 A ones are obviously heavier and larger so might cost too much for them to ship.
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Fosi sell theirs on their website for the same price but free shipping, saves $8
Thanks, if I do that, I still has to figure what to do with the two 48 V 5 A PS that will be included with the A7 Mono. I guess take a hit and sell them on eBay for cheap. I already have a couple of those for my Fosi V3 amps too. It just never make technical sense to me for them to include 5 A supplies with the A7 Mono, even worse for the A7 stereo. I just sent a PM to 3 e enquiring about the possibility to order directly from them (like Fosi does) but I am not hopefully that they would reply.
Roland68
Major Contributor
Why do you want to use a different power supply than the 48V/5A one for the A7 Mono?
The A7 Mono is essentially half an A7 and therefore only requires half the power. The 48V/5A power supply is perfectly adequate for the A7 Mono to reach its full power output. This is also why the A7 Mono isn't available with 10A power supplies; it would be completely pointless.
Furthermore, switching power supplies only operate optimally above a certain load. A 10A power supply for an A7 Mono would likely be far from reaching that load.
If you're powering both A7 Mono amplifiers with a single power supply, you could just use a regular A7, because one of the purposes of mono amplifiers is complete separation and the elimination of mutual interference. Using a single power supply also affects channel separation, perhaps not significantly, but measurably.
I wanted 2 10a for my V3 mono just because (got them with the 10a and splitter). I ended up with a second 5a because it was on sale and “good enough”. It made sense to me at the time, still does since I moved them to easier speakers to drive. For those with the 10a and splitter your 2 5a supplies might be appealing. I didn’t find anything “wrong” with the splitter but hated the layout of the cords and the filter being needed (and adding another connection point) as well. I’d think you could unload them easily, but that’s just my opinion obviously. I’d gladly swap you a 10a for a 5 but I don’t think we’re close enough geographically for it to make sense?
Right, I am in the GTA area, so basically Toronto in terms of calculating shipping costs. Also, technically speaking if you already have the 10 A splitter, you should keep it because it has better current capability for real world use when two channels don't always peak at the same time to the same magnitude. That's assuming the 10 A splitter is an external one, as that would likely mean the PS is a single transformer/bridge rectifier so it actually has the 10 A rating instead of 2 X 5 A. All these, like lots of other things, likely mean nothing in terms of audibly better SQ.
but it sounds good in theory.The more I read about the A7 the more I like it so I decided not to wait and pulled the trigger for two Monos. If I really want to buy 2 52 V/9A or 48 V/10A I will just sell the 48 V 5A PS on eBay, I think it won't be hard to sell them as the 48 V 5 A units seems have enough demands.
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