Topping EHA-5

[spritzer]

Yeah, that's my recommendation as well.  A SRM-1 Mk2, SRM-3, SRM-313 all walk over this thing.  Sure the older ones need some new electrolytics at this point but it's a much better sounding system. 

L300's are also not as good as the x07 series was but quick mod, remove the stupid screen inside the earpads, remove the earpads and take out the 4 screws.  Swap the back panels between left and right and fix them back into place so they are reversed from where they were before.  Helps clear up the imaging of them. 

[kevin gilmore]

in other news, significant amounts of topping la90discretes are overheating and burning up.

the eha5 is based in part of the la90d. so expect those to be burning up soon.

[skullguise]

As members of my tribe would say....Oy fuckin' vey....!

[justin]

On 6/15/2023 at 3:35 PM, kevin gilmore said:

in other news, significant amounts of topping la90discretes are overheating and burning up.

the eha5 is based in part of the la90d. so expect those to be burning up soon.

soon or already have

[kevin gilmore]

only 2 with dead bias supplys that i am aware of. both died in less than 1 hour.

 

Edited June 17, 2023 by kevin gilmore

[spritzer]

Perhaps we should design replacement modules for people...

[kevin gilmore]

add on external module. much better idea. don't want to void the warranty.

[Timb5881]

Yes the older Stax amps do offer a way into the Stax world.  But be weary that many have parts that are no longer available.  I have a

On 6/15/2023 at 12:04 PM, spritzer said:

Yeah, that's my recommendation as well.  A SRM-1 Mk2, SRM-3, SRM-313 all walk over this thing.  Sure the older ones need some new electrolytics at this point but it's a much better sounding system. 

L300's are also not as good as the x07 series was but quick mod, remove the stupid screen inside the earpads, remove the earpads and take out the 4 screws.  Swap the back panels between left and right and fix them back into place so they are reversed from where they were before.  Helps clear up the imaging of them. 

Buyer beware on older Stax amps.  Many have parts that are no longer available.  I have a SRM 1/ MK2 that I tried to refurbish but some of the transistors are not to be found at any price.   I know the Stax SRM1 is loaded with obsolete discontinued parts.     If you were to look at this point of view, Topping at least has modern and available parts.  Design wise the topping is iffy at best.

Maybe Birger and Mr Gilmore can give us a list of Stax amps that have replacement parts issues so others can make better informed decisions.

[spritzer]

Maybe a very old SRM-1 Mk2 has some obsolete parts but the rest can all be replaced either directly or by substituting close parts.  Anything after that can also easily be fixed.  Now how long we will have HV TO220 parts is not clear but I've lost count of how many SRM-1 Mk2's I've fixed over the years and none were a complete write-off. 

[kevin gilmore]

1 hour ago, Timb5881 said:

   If you were to look at this point of view, Topping at least has modern and available parts.  Design wise the topping is iffy at best.

absolutely not. topping has potted modules including the bias module that are not available as spare parts. topping has a custom switching supply that may not easily be substituted. every one of these is likely to be dead in less than 5 years.

where 40 year old stax amps continue to function even though all the silicon is obsolete.

topping is flavor of the month throw away garbage.

[justin]

3 hours ago, Timb5881 said:

Yes the older Stax amps do offer a way into the Stax world.  But be weary that many have parts that are no longer available.  I have a

Buyer beware on older Stax amps.  Many have parts that are no longer available.  I have a SRM 1/ MK2 that I tried to refurbish but some of the transistors are not to be found at any price.   I know the Stax SRM1 is loaded with obsolete discontinued parts.     If you were to look at this point of view, Topping at least has modern and available parts.  Design wise the topping is iffy at best.

Maybe Birger and Mr Gilmore can give us a list of Stax amps that have replacement parts issues so others can make better informed decisions.

I bet I have the parts. they are probably available through head-case 

Edited June 21, 2023 by justin

[luvdunhill]

Obsolete parts are better than obfuscated parts.

[Timb5881]

6 hours ago, luvdunhill said:

Obsolete parts are better than obfuscated parts.

I was looking for 2SB832 four of them 

[spritzer]

That's actually a SRM-1, not a Mk2 unit.  It seems Stax just had a bunch left over so they stuck them in a Mk2 chassis.  These amps are less than 1% of all SRM-1 Mk2's so yeah, not a true representation of them. 

Still the 2SA1968/1967 would work there attached to a heatsink.   Edit:  Given the rail voltages, a 600V part might even work there or a 700V one. 

Edited June 22, 2023 by spritzer

[Timb5881]

Thanks Spritzer.  I know I asked you if there were subs for those transistors.

[Timb5881]

So if I use them as. A sub.  Is this a plug and play transistor or do I need to mod something.

[spritzer]

Completely different package so you need to match the pinout but that should be it.  Could be some freak oscillation though to look out for. 

Still this wouldn't be worth it as real 2SA1968's are probably 50$ each now for low quantities and most for sale are fakes.  I can't remember the rail voltages on those amps but if it is +/-300V, then a 700Vpnp would work.  There are none in current production but they can be found. 

[Timb5881]

I am glad you told me that, I would not want to buy bogus transistors.   So with that in n mind, I will continue to use my SRD-7 Pro and my SRM 212, and save up for a better amp.

[simmconn]

Both the 2SA1967 and the lessor 2SA1831 can still be had for less than $1 a piece, if you know where to look. They have the same B-C-E pin order so should be a drop-in replacement for the B832 (please don't take my word for it, verify yourself!). But I agree with you, it'd be better to save up for a better amp.

On the Topping/transformer topic, I know people don't like the SRD-7SB because the transformers are taxed to provide the bias. Has anyone compared the SRD-7 and SRD-7SB with the bias circuit disconnected? I mean, does the additional bias tap on the SRD-7SB transformers hurt the performance even if not used?

[spritzer]

In reality the bias harvest a negligible amount of energy from the audio signal so the effect is pretty small.  My main issue is with the cross talk it will generate as Stax always placed the bias supply (or the transformer on the later versions) between the channels to maximize the potential available.  Well that plus the extra inductance of the second transformer is bound to have some effect. 

That all being said, I'd really pick this over having the mains effective rigged directly to my head which is the case for all of the mains units.  Couple that to 40-50 year old diodes, caps and carbon resistors and it is a scary thing. 

As for the Topping, I've been thinking about what to do with it.  It's main issue is the crap amp and bias supply so that could be fixed.  Retrofit the small bias supply Kerry designed for the portable amp project (200V boost battery charge chip fed into a voltage tripler) and change the amp boards for some Class D design.  I've been using Icepower for over a decade to run my transformer boxes so something like that. 

[Timb5881]

46 minutes ago, spritzer said:

In reality the bias harvest a negligible amount of energy from the audio signal so the effect is pretty small.  My main issue is with the cross talk it will generate as Stax always placed the bias supply (or the transformer on the later versions) between the channels to maximize the potential available.  Well that plus the extra inductance of the second transformer is bound to have some effect. 

That all being said, I'd really pick this over having the mains effective rigged directly to my head which is the case for all of the mains units.  Couple that to 40-50 year old diodes, caps and carbon resistors and it is a scary thing. 

As for the Topping, I've been thinking about what to do with it.  It's main issue is the crap amp and bias supply so that could be fixed.  Retrofit the small bias supply Kerry designed for the portable amp project (200V boost battery charge chip fed into a voltage tripler) and change the amp boards for some Class D design.  I've been using Icepower for over a decade to run my transformer boxes so something like that. 

I would love for you to do a write up the D amps.   I use one of 3 amps with mine.  The Golden Tube SE40, the Aragon 8008, and a Carry Rocket 88 are my usual suspects for amplifying headphones.  I do have a few other amps that I could use but they need repair.

[lupoal]

On 6/15/2023 at 8:04 PM, spritzer said:

....

L300's are also not as good as the x07 series was but quick mod, remove the stupid screen inside the earpads, remove the earpads and take out the 4 screws.  Swap the back panels between left and right and fix them back into place so they are reversed from where they were before.  Helps clear up the imaging of them. 

Hi,
were could I find deteiled procedure to do that?
I have the 300 Limited, does this mod apply to my version too?

(sorry for the small OT 😬)

[spritzer]

That's really all the procedure for this.  I never tried it on the L300 LE's but the labels on the earcups might be an issue.  I just never use mine but I might test it out. 

[lupoal]

ok, thks

[bobkatz]

I bought the Topping and got it this week, with hopes it could be a second or extra Stat amp. I was even planning on doing a "bargain stat amp" feature at my new journalistic home "Positive Feedback", where you can find my review of the Audeze CRBNs, for example. Anway, I'm not going to publish, I don't like to publish reviews of bad gear 😞

What a disappointment this amp turned out to be. My disappointment came in stages. The first stage was an optimistic listen: "Hey, not too bad". At that time I was listening to some simple classical and folk arrangements: with solo voices and guitar, the weaknesses of the Topping circuit are not immediately obvious. But as soon as I played more complex music, full orchestra, rock band, you name it. Where it starts to get real harsh, bloated, lose dimension is with complex music, full orchestra, rock band, you name it. The more I listened, the more I started to hate this amp. 

I WILL BET THAT THERE ARE MEASUREMENTS THAT WILL REVEAL THIS AMP'S WEAKNESSES. You just have to know how to find out where the bodies are buried. I did find some that clearly show its weaknesses. Attached below. Frequency response (with a 100 pf load), Output level just before clipping, THD at various frequencies at normal levels and just before clipping (spectrum and %), IMD (19-20 kHz) (spectrum and %). The one thing I should have measured is a special multitone signal I use, I bet that would show where the bodies are buried, and tell us why the amp falls totally flat the more complex the music you put into it. But I'm so disenheartened and disappointed by the sound of it that I don't have the energy to bring it back to the test bench. 

I like to display an amplifier's measurements in equivalent SPL, based on Stax 007 and CRBN nominal sensitivity of 100 volts RMS = nominally 100 dB SPL. It helps bring a real-world perspective to amplifier measurements. 

Topping Factory spec for max is 700 volts RMS (I suppose the factory took this a cat's hair below clipping and only at 1 kHz). I measured maximum output at 1 dB below clipping at 630 volts RMS at 1 kHz, equivalent to 116 dB SPL. But When performing the 20 Hz THD test, the amp's DC protection circuit kicked in and the most I could get out of it at 20 Hz with a continuous sine wave was the equivalent of 105 dB SPL, 177 volts RMS before the amp shut down. So the lower the frequency, the worst the amp's headroom for transients. Plus, the THD at low frequencies is pretty bad, the transformer saturates very strongly.

To see where the skeletons are buried in this amp, take a look at my measurements. The measurements to really study is a comparison of the Mjolnir KGSS HV Carbon and the Topping at nominally 90 dB equivalent SPL of IMD 19-20 kHz 1:1 ratio. I think that lurking in that measurement is at least one of the reasons why the Topping sounds so harsh and the Mjolnir sounds so pure. The primary difference tone at 1 kHz in the spectrum does not tell the story. Notice the high frequency side bands near the 19-20 kHz that begin to reveal to us the Topping's nonlinearities. There's more in the attachments. I'm sorry that I didn't do the multitone, I will some day, when I get around to it, and I'm sure it will reveal the skeleton underneath the "golden glow" of this amp. 
 

The date in the Fluke scope pictures is wrong... it's actually yesterday, 7/28/23. I have to fix the date in my Fluke Scope. Every time the battery dies, it loses the date 😞

 

Edited July 28, 2023 by bobkatz
PDFs do not show here, so I changed those to PNG