Review and Measurements of Topping DX7s DAC and Headphone Amp

[Grave]

The general rule of thumb is that you want output impedance to be 1/8 of the transducer's impedance, so 20 ohm is in the right ballpark. For some reason, the DIY Audio Heaven review recommends an output impedance of 10 or less. I'm not sure if Solderdude actually tested anything other than 0.2 and 120 ohm, but he's very friendly and you can contact him on http://diyah.boards.net to ask (or maybe even start by searching the boards).

Yeah I know that.

 

[Ayreonaut]

I wonder if the 20 ohm balanced output would affect the 150 ohm HD 660 S? How do you do this calculation?

Gv=20*log([Zmax(Zmin+Zout)]/[Zmin(Zmax+Zout)])

where

Gv is voltage gain in dB
Zmax is headphone maximum impedance
Zmin is headphone minimum impedance
Zout is amplifier output impedance

Somebody correct me if I'm wrong.

 

[Grave]

HD 660 S

20*log((400(150+20))/(150(400+20)))=0.66 dB

HD 650

20* log((500(300+20))/(300(500+20)))=0.22 dB

This is fine I think. As long as the difference is <1 dB.

 

[Ayreonaut]

If you want the DX7s for the balanced output, don;t forget that the output impedance is around 20 ohms.

The HD 660 S would still be fine.

 

[Ayreonaut]

Sennheiser's own $$$ HDV... headphone amps have output impedances specified as "min. 16 ohm" for both the balanced and unbalanced outputs.

 

[Ayreonaut]

I'm still very interested in seeing the DX7s amp section compared to the A30.

 

[Edelweiss]

Sennheiser's own $$$ HDV... headphone amps have output impedances specified as "min. 16 ohm" for both the balanced and unbalanced outputs.

Looking into the manual you will find something like 42 Ohms, which is at the threshold of audibility for the 800 line it is designed for and slightly rises the otherwise somewhat thin bass of the original HD 800. There are barely any people that will use a $2399 amp for a $499 headphone.

 

[mi-fu]

Actually i'm quite interested in why Sennheiser made their headphone amp with such a high output impedance.

 

[andreasmaaan]

Looking into the manual you will find something like 42 Ohms, which is at the threshold of audibility for the 800 line it is designed for and slightly rises the otherwise somewhat thin bass of the original HD 800. There are barely any people that will use a $2399 amp for a $499 headphone.

Could you point us to where you saw this 42 Ohm figure? I had a look at the manual and could only find the "minimum 16 Ohm" figure, which I took (hopefully) to be a reference to the input impedance of the headphones rather than the output impedance of the amp...

 

[Grave]

Probably because Sennheiser is batshit recently. Their 10+ year old headphones models are the best since they mostly make treble boosted headphones now.

 

[Dana reed]

Finding this amp to work really well with the new LCD2 Fazor headphones I got. I'm not really hearing any difference in frequency response between the single ended and balanced outputs on the DX7s even though their impedance is only 70 Ohm. Since their impedance is so flat vs frequency, I guess 10 Ohm vs 20 Ohm output impedance doesn't matter much.

Still want to compare this 10 Ohm output with the Magni 3 driving some Grados, which have a pretty big impedance hump at 70 Hz
The graph below shows 0.2 Ohm vs 120 has a pretty big hump, but I guess it would be much less at 10 Ohm

https://diyaudioheaven.files.wordpress.com/2017/10/120-gs2000.png?w=614

 

[Darwin]

It's back on Massdrop. $359 There sure are a lot of people reporting dead units of this and the D50.
https://www.massdrop.com/buy/topping-dx7s/reviews#reviews

 

[rdodev]

It's back on Massdrop. $359 There sure are a lot of people reporting dead units of this and the D50.
https://www.massdrop.com/buy/topping-dx7s/reviews#reviews

QC and warranty service is the main thing that's holding me back from buying either of these two DACs.

 

[Veri]

It's back on Massdrop. $359 There sure are a lot of people reporting dead units of this and the D50.
https://www.massdrop.com/buy/topping-dx7s/reviews#reviews

Am I crazy or am I not seeing "all" these dead units in the reviews?

 

[Grave]

Since you don't know anything nobody cares what you think. Ignore.

I know plenty about computers.

My PC:

Intel i7-8700K CPU
Zotac GTX 1080 Ti GPU
G.Skill 16 GB DDR4 3200 MHz RAM
Samsung 960 Evo 450 GB SSD
Dell 1080p/60 monitor

I joined the drop for this DAC/amp since the price keeps going down. It is only $360 now.

 

[Deleted member 3718]

It's back on Massdrop. $359 There sure are a lot of people reporting dead units of this and the D50.
https://www.massdrop.com/buy/topping-dx7s/reviews#reviews

I'm strongly considering joining this but the lack of warranty is concerning.

Am I crazy or am I not seeing "all" these dead units in the reviews?

There aren't plenty but there are a handful if you look enough. Here's one for the DX7s for example:

"NO WARRANTY AFTER 30 DAYS:

Mine stopped working after about 60 days.

See email from Massdrop below.

Hilary L. (Massdrop Community Support) Aug 26, 3:28 PM PDT
Hi Ben,
Thanks for reaching out to Massdrop Community Support, this is Hilary and I am happy to help you today! I am very sorry for my delayed response. I'm sorry to hear your having problems with your Topping.
It looks like this didn't have an included warranty. For products that do not have an included manufacturer's warranty, members have 30 days from the date of delivery to report an issue. For products that include a manufacturer's warranty, members must report an issue within the stated warranty period.
After reviewing your transaction, it appears that the time-frame for reporting an issue has passed, which means we are not able to provide a replacement or facilitate a return.
Thank you for your understanding of this policy. If we can help you with anything else in the future, please contact us.
Best Regards,Hilary"


And another for the D50:

"Great DAC, Great sound. Competes head-to-head with DACs 5-10x the price in terms of sound quality.

Problem: It died 5 months after receiving it. No warranty from either Massdrop or Topping.

The problem is in the power supply chain. It now wants to draw way too much current no matter what supply I try.

Disappointing. Next time I will not purchase from Massdrop without a warranty."

 

[Sal1950]

I'm strongly considering joining this but the lack of warranty is concerning.

I've never dealt with Massdrop, is this the standard deal with them, only a 30 day warranty?

 

[jsmiller58]

I've never dealt with Massdrop, is this the standard deal with them, only a 30 day warranty?

Some items have std manufacturers warranty and that will be stated on the drop page. If no standard warranty, then there is 30 day warranty provided by Massdrop. You have to check for each drop as they are different for different products

 

[amirm]

Interesting. That may be the discount they receive from manufacturer for not having to offer a warranty.

 

[amirm]

Mine stopped working after about 60 days.

Would be interesting to see what failed in it. Are you interested in sending it to me for a look? If you are in US, should only cost $20 or so.