Topping EHA-5

[spritzer]

Well this just arrived and as is our fashion, it has not been plugged in at all before I rip it apart.  I'm having some camera issues (bloody Lightroom) so not as many as I'd like. Now first off why this belongs on a trashpile... here is the output:

It's a pain to get a camera to focus between the transformers so I ended up grabbing the phone.  Those are the ballast resistors, two 1M units in series and one 3M3 unit, all in 1206 package so likely 150V rated.  Yeah no... just no, this is not good enough!!  It gets worse though...  It's a shit angle but here is how the transformers connect to the output socket:

Now do you notice any parts on this PCB except connectors?  Nope, neither do I... there is no protection on the output at all.  No 5K1 output resistors nor the clamp circuit found on all later Stax adapter boxes.  This thing will kill your headphones when pushed hard enough and there is nothing to protect the user if something goes wrong.  Yup, pure class here... zero fucks given. 

Some other random pics, main amp runs off a +/-15V supply and the PSU brick is 15V/2A. 

Preamp presumably and the whole thing looks to be AC coupled through those electrolytic caps so that will not sound good at all.  

I see no other reason for those caps to be there so yeah, who does something like this.  At least the volume pot is 4 gangs so the thing is fully balanced. 

Conclusion, without even plugging it in, this is a pile of crap and should not be used by anybody.  The small changes to make this secure and sound good cost next to nothing but nobody cares.  Best avoided unless you want to have a special talk to the manufacturer of your headphones as to why there are holes in the diaphragms... 

Now if I have time, I'm going to fully strip this thing down and design a PCB for the Stax socket which adds full protection and a clamp circuit.  Fix the input caps and other issues that I find and this might a semi good 400$ amp.  Personally I'd take a Stax SRM-313 over this pile of crap. 

Edited April 19, 2023 by spritzer
Fucking typo's....

[spritzer]

So, I listened to it (as next step it to fully rip it apart) and in my regular test rig which is a Teac UD-503 dac driven over USB.  Output set to 0dB on the DAC (no attenuation and no gain either), balanced inputs and I had to use the high gain function and volume control at 2-3pm on the dial.  I could listen at full volume level, not something I'd recommend but yeah, this thing is just fucked.  This is with SR-207's (my go to test headphones) so anything more power hungry will suffer even more. 

Now how does this sound... well mushy and very peaky.  The midrange has this haze to it and the treble is very... alive.  Bass is exaggerated but not always so, it kinda comes and goes as this thing struggles to get any output.  Sound-staging is also pretty terrible so I find it hard to recommend this over the Stax SRM-252S. 

I also put it on a Kill-a-watt and at full output it draws 7.5W from the wall.  That's not a whole lot of power there... 

[spritzer]

Jest before I stopped playing with it last night I took some measurements, I fed it a 10kHz squarewave, 1Vpp from a function gen and while it was a pain to get a good ground in there, we are not dealing with high speed signals either.  Here is the input to the amp:

Nice enough squarewave but here is the output of the amp, set to my usual listening level:

This was one leg of the output of the transformer, here is the other:

Yeah....  this isn't great, is it?  Might be the worst I've ever seen but I naturally forgot to measure the primary of the transformers and I've already started to rip the unit apart.  I may do that later.   

[Timb5881]

Interesting write up Spritzer.  When you have time, tell us what changes Topping should make.

[spritzer]

Throw it out and start again?  I mean this truly terrible stuff but I stripped it down yesterday and yeah... I can see why Topping has a reputation for failing a lot as this was probably soldered by people not being paid a whole lot.  Some joints have barely any solder on them and there is flux everywhere. 

The transformers are clearly styled after the Stax SRD-7 units (down to the color of the wires) but who knows how they are actually wound.  It is quite tricky and expensive to wind a really low capacitance transformer. 

The back of the Stax socket board and yup, straight links to the socket from the bias and the transformers. 

Look how dirty this thing is, it is covered in muck. 

Sorry for the shit pictures, I didn't want to drag out a better camera for this.  This is not good... 

Here is what I'm doing to my own unit as I ripped off the Stax connector PCB:

This simple board just adds some high voltage resistors to the bias line, adds output protection resistors (also HV units) and zeners to clamp the output so it can never go over 1150Vppss.  The board is designed to go on the smaller pins of the socket so this could be fitted to the amp with the original board in place if the connectors are just cut off. 

[guzziguy]

On 4/19/2023 at 10:44 PM, spritzer said:

Jest before I stopped playing with it last night I took some measurements, I fed it a 10kHz squarewave, 1Vpp from a function gen and while it was a pain to get a good ground in there, we are not dealing with high speed signals either.  Here is the input to the amp:

Nice enough squarewave but here is the output of the amp, set to my usual listening level:

This was one leg of the output of the transformer, here is the other:

Yeah....  this isn't great, is it?  Might be the worst I've ever seen but I naturally forgot to measure the primary of the transformers and I've already started to rip the unit apart.  I may do that later.   

Built-in vibrato?

[spritzer]

Hehe, maybe they can market it like that? 

[kevin gilmore]

and yet the audio precision actually reports .0008 % thd at 1khz. so much for that being worth anything.

sure looks like about 10 volts per microsecond slew rate. pretty grim at higher voltage levels.

winding transformers correctly really is not that hard. too bad the lundhal transformers won't fit inside the box. 

hmm, there is that size thing again. (usa_love)

what really gets me is the really poor soldering job, probably there is a significant failure rate of topping products in the field.

And yet led lit sails that makes you think there are tubes inside.

my guess is that the koss box sounds better than this, for roughly the same price.

quoting from someone who knows how to actually make transformers like this..

quote

In a transformer winding, inter-turn capacitance is generally negligible compared to inter-layer capacitance.

We can approximate the winding self-capacitance within a small factor by considering only the capacitance between winding layers, approximating the layer to a conductor sheet.

The highest capacitance arrangement is when each layer is wound in opposite directions, so left to right on the first, right to left on the next. That's because the first turn of the first layer is opposite the last turn of the next layer, so there's twice the voltage per layer between those turns. As the energy stored in the self-capacitance goes as the square of the voltage, this more than offsets the lower voltage difference at the other side of the windings.

A lower capacitance can be obtained by winding each layer in the same direction, returning between layers, so left to right, then left to right again. The voltage between layers is now uniform at the per layer voltage.

end quote

transformers made this way have to be partially done by hand. no winding machine currently available does this. its why esl63 replacement transformers are $500 each.

 

 

Edited April 21, 2023 by kevin gilmore

[aokman]

Thanks for the teardown as I was going to order one of these just to mess around with but I'm now glad I kept working on building my own Lundahl converter now...

The hilarious part about this I power my Lundahl converter with a Topping LA90 which is a stunning desk amplifier and If you open the chassis, you could actually fit 2 Lundahl transformers in there I reckon... This unit seems to use some LA90 parts...

[spritzer]

Those two parts in the middle are just the copper standoffs and the other look like connectors to something below the board. 

I'm not sure about that amp though, just look at those output inductors trying to stabilize the circuit and are those modules similar to the ones used in the Gainclone?  Not very discrete then...

[aokman]

I just copied an existing picture, wasn’t highlighting anything.

The new version is a discrete design, the older one used ICs which I have. Dunno but its been heavily tested on ASR and performs very well. The build quality certainly impressed me and was ideal for a desk setup so I don’t need a massive power amp…

[spritzer]

Thanks to the wonder of modern PCB manufacturing, this showed up yesterday:

I bought the boards fully assembled as I'm lazy and I hate SMD soldering so I just had to add the connectors.  To make it a single sided load (so the assembly would be much cheaper) the board had to be a bit wider than the stock board so one of the transformers had to be moved around 10mm. 

Just remove one screw and slide it to one side.  Drill a new hole and it is done. 

Now the EHA-5 still sounds like shit but it is at least safe for the end user. 

[Pars]

On 4/22/2023 at 5:24 AM, aokman said:

I just copied an existing picture, wasn’t highlighting anything.

The new version is a discrete design, the older one used ICs which I have. Dunno but its been heavily tested on ASR and performs very well. The build quality certainly impressed me and was ideal for a desk setup so I don’t need a massive power amp…

Oh god, ASR. I can't stand that site. Known Topping shill as well.

[spritzer]

ASR is the Scientology of audio... it has Science in the name but that's about it.  For me it is just the polar opposite of SBAF, same drivel though and makes Head-fi look good. 

[aokman]

20 hours ago, Pars said:

Oh god, ASR. I can't stand that site. Known Topping shill as well.

Everyone is a shill for something… Topping does have some good products and the LA90 is highly regarded by most aside from its limited power.

I cannot speak for the EHA5 as it seems much cheaper build with sheet metal but still following this. I guess my only criticism is why are you focusing on the output side of the OTs exclusively rather than looking at the topology as a whole and if the unit already has protection on the low voltage side like the LA90 does?

You may be trying to fix a problem that doesn’t exist.

I must say it is definitely confusing why they would choose an electrostatic amp at a cheap price point rather than doing it at a price point similar to their higher end gear…

[spritzer]

That doesn't make any sense, why would protection on the low voltage side matter?  How can the low voltage side know of a short or anything like that on the other side of the transformer short of a basic overload?  There is nothing that connects the two, except the transformer.  There are no large relays on the amplifier side to turn off the output in the event of something bad happening so I very much doubt there is any protection at all.  Certainly not on the main, large PCB.  Another factor are the large impedance swings of electrostatics which will mimic a dead short at times. 

The build quality is terrible, it's better than the Monoprice or Drop Cavalli units but yeah, these will not last for long. 

The main thing though is this sounds absolutely horrid.  I had a SRM-1 Mk2 and a SRM-252S I needed to test yesterday so I connected them all together to the same source and matched the output voltage of them.  The difference in sound quality is rather stark, even driving a set of SR-207's (so very light load) the Stax units walk all over it.  The EHA-5 sounds just like the squarewave, it is under immense strain so very bright and broken sound. 

[aokman]

5 hours ago, spritzer said:

That doesn't make any sense, why would protection on the low voltage side matter?  How can the low voltage side know of a short or anything like that on the other side of the transformer short of a basic overload?  There is nothing that connects the two, except the transformer.  There are no large relays on the amplifier side to turn off the output in the event of something bad happening so I very much doubt there is any protection at all.  Certainly not on the main, large PCB.  Another factor are the large impedance swings of electrostatics which will mimic a dead short at times. 

The build quality is terrible, it's better than the Monoprice or Drop Cavalli units but yeah, these will not last for long. 

The main thing though is this sounds absolutely horrid.  I had a SRM-1 Mk2 and a SRM-252S I needed to test yesterday so I connected them all together to the same source and matched the output voltage of them.  The difference in sound quality is rather stark, even driving a set of SR-207's (so very light load) the Stax units walk all over it.  The EHA-5 sounds just like the squarewave, it is under immense strain so very bright and broken sound. 

I’m confused… there is at least 6 Omron relays in your pictures and probably more protection inside the NCFA modules.

Im just pointing out that claiming this unit has no protection seems highly unlikely as many things can be mitigated upstream where voltages are lower and you can implement thermal / current protection.

I look forward to hearing one sometime anyway and hear how bad or good it is but there are reviews already out there comparing it to a blue hawaii with the corina that are more favourable so I'm unsure where these stark differences are coming from…

[Pirx]

41 minutes ago, aokman said:

I’m confused… there is at least 6 Omron relays in your pictures and probably more protection inside the NCFA modules.

Omron relays you are talking about are small ones designed for small signals, small voltages, small currents.

They are there for many reasons but protection delicate electrostatic drivers from overloading ...

[aokman]

1 hour ago, Pirx said:

Omron relays you are talking about are small ones designed for small signals, small voltages, small currents.

They are there for many reasons but protection delicate electrostatic drivers from overloading ...

Size has very little meaning… They can be used to shut down earlier driver stages in the amplifier that are lower current, crowbar the outputs just before the OTs or used to drive large switching transistors that can handle far more current.

My point is, without context and knowing the entire amplifier topology, we cannot make claims on this. I agree it is nice to have overload protection right at the output but since the amplifier modules ultimately deliver that power, it can be tackled elsewhere also with active feedback and monitoring.

I understand the hate for China products but this seems like to create a very jaded and aggressive attitude towards any product.

To be clear I don’t have a horse in this race lol, EHA5 doesn’t interest me, but I prefer to keep an open mind as to why design decisions are made…

[eggil]

I  wonder why the guy from audiosciencereview is such a big fan of Topping 🙄

[Timb5881]

33 minutes ago, eggil said:

I  wonder why the guy from audiosciencereview is such a big fan of Topping 🙄

Based on measurements only, and Topping products usually measure very well.

[Kung]

5 hours ago, Timb5881 said:

Based on measurements only, and Topping products usually measure very well.

Yep, ASR's evaluation is just based entirely on measurements...

My source told me that topping has also designed a discrete component version of electrostatic amp to drive estats directly, ap show that its specs far exceed any known electrostatic amps, and it will be on the market sometime in the future. . .🤷‍♂️

[spritzer]

7 hours ago, aokman said:

Size has very little meaning… They can be used to shut down earlier driver stages in the amplifier that are lower current, crowbar the outputs just before the OTs or used to drive large switching transistors that can handle far more current.

My point is, without context and knowing the entire amplifier topology, we cannot make claims on this. I agree it is nice to have overload protection right at the output but since the amplifier modules ultimately deliver that power, it can be tackled elsewhere also with active feedback and monitoring.

I understand the hate for China products but this seems like to create a very jaded and aggressive attitude towards any product.

To be clear I don’t have a horse in this race lol, EHA5 doesn’t interest me, but I prefer to keep an open mind as to why design decisions are made…

We do know the entire amp topology and those relays are to switch signals, nothing else.  You can accuse me of hating Chinese products but yet I buy everything I can from China to test out... weird that...  I have every electrostatic amp or headphones I can get from China.  It can't be that you are just a retarded Topping fanboy, is it?  Have you tried this thing or even measured it? 

I just wonder what anybody at Topping was thinking about when designing this thing, how was a roughly 1W+1W amp supposed to drive electrostatics?  I mean they could have put in a simple Class D unit (while not ideal) with far more power and get a better result.  You only need to understand the basics with regards to electrostatics to know you just need more power for them to behave. 

16 minutes ago, Kung said:

Yep, ASR's evaluation is just based entirely on measurements...

My source told me that topping has also designed a discrete component version of electrostatic amp to drive estats directly, ap show that its specs far exceed any known electrostatic amps, and it will be on the market sometime in the future. . .🤷‍♂️

Now that is far more interesting though I'll have to call into question any specs they publish... or even think they can reach.  The parts are available to make a fully discrete amp with excellent specs, hell it is possible to make it all SMD if you can figure out the heatsinking issues. 

Also reading ASR's evaluation of R2R dacs just hurts my brain.  There is so much stupidity there it is simply painful...

[whitefang]

On 4/30/2023 at 4:40 PM, aokman said:

Size has very little meaning… They can be used to shut down earlier driver stages in the amplifier that are lower current, crowbar the outputs just before the OTs or used to drive large switching transistors that can handle far more current.

My point is, without context and knowing the entire amplifier topology, we cannot make claims on this. I agree it is nice to have overload protection right at the output but since the amplifier modules ultimately deliver that power, it can be tackled elsewhere also with active feedback and monitoring.

I understand the hate for China products but this seems like to create a very jaded and aggressive attitude towards any product.

To be clear I don’t have a horse in this race lol, EHA5 doesn’t interest me, but I prefer to keep an open mind as to why design decisions are made…

 

Right, buying the amp, opening it up, knowing the topology, measuring it and listening to it is not enough, one should go to Topping factory and interview the actual person who assemble that particular amp.

Be open-minded, the dirty solder, the square wave output and even the disconnected connector might have profound reasons we do not know of.😀

Those could be the "secret sauce" of Topping's world-class measurement performance, Topping engineers are top of the world, they must know what they are doing.

[thebrunx]

Topping wants to take over hifi audio, monopoly style.