[Asakurai]

Tempotec V1 has no DAC but has Coaxial Out
Tempotec V1A has DAC, Headphone out, but no Coaxial out
Everything else is same

That's it

 

[madnanny2]

indeed. I still have my Sansa Clip+ (Rockboxed) and it sounds awesome. I have bought two DAPs to "replace it", but they haven't. A FiiO X1 1st generations and a Benjie ( I forget which model).

The Sansa Clip is wonderfully small, lightweight and great sounding. Able to drive headphones to ear-destroying levels.

Such a shame they stopped making it.

right now I'm listening to Baroness with the Sansa Clip and Samson SR850s and it is rock bliss.

i agree i have 2 sansa clips ,had them for years and wouldnt part with them,although i have other daps. still listen to the sansas.my headphones are sennheiser px100

 

[actorlife]

i agree i have 2 sansa clips ,had them for years and wouldnt part with them,although i have other daps. still listen to the sansas.my headphones are sennheiser px100

I wish I still had my Sansa + it died all of a sudden about a year ago and still had battery life. If they ever go back on sale I'm grabbing a couple of them.

 

[anyanylee22]

I have it and a few days ago I wrote some messages about it from here. Totally disappointed with him. I think it was money wasted. On top of that, I tried to get in touch with F.Audio to tell them about the problem and they didn't even answer me.
You can't consider a Hi-Fi source that doesn't have a flat response. Much less if at 20Hz it loses 6dB, which is a real barbarity.
The same problem as the previous DAP I bought, the Ziku HD-10.
If I want less bass, I just have to use more balanced headphones. But if I want more bass, what should I do, use the equalizer, which only dirties the signal?

https://www.head-fi.org/threads/obscure-chinese-daps.720512/page-410#post-15051399

Hi cqtek,

Thanks for your measurements on f.audio XS03. I own it too. I didn't have a scope nearby and I had used Wavecor's Test Tones to test it by ears. Yes, bass band frequency from 20 - 60 is weak. I decided to change the VAS opamps. F.audio told me that two opamps at VAS are configured open loop gain (high voltage gain, no current gain).
Hence I started with FET type opamps (high input impedance). Strangely, I didn't get good result. I had tested OPA2604, LM4562, MUSES02 and HDAM.
Then I went on another direction. I tested BJT opamps OPA1622, AD827 and LME49990. Finally four LME49990 (soldered on two dual opamp conversion broads) give me the best result. Bass band sounds stronger. Overall frequency response is much balanced. LME49990 outputs a good S/N too. I can hear more details from songs.
XS03 analog circuit design is good. It is like a desktop DAC amp (3 stages: differential amp., VAS, output). I like its output stage (4 pairs of push pull power transistors BJT in class A config.). It just needs enhancement in mid stage.

 

[cqtek]

Hi cqtek,

Thanks for your measurements on f.audio XS03. I own it too. I didn't have a scope nearby and I had used Wavecor's Test Tones to test it by ears. Yes, bass band frequency from 20 - 60 is weak. I decided to change the VAS opamps. F.audio told me that two opamps at VAS are configured open loop gain (high voltage gain, no current gain).
Hence I started with FET type opamps (high input impedance). Strangely, I didn't get good result. I had tested OPA2604, LM4562, MUSES02 and HDAM.
Then I went on another direction. I tested BJT opamps OPA1622, AD827 and LME49990. Finally four LME49990 (soldered on two dual opamp conversion broads) give me the best result. Bass band sounds stronger. Overall frequency response is much balanced. LME49990 outputs a good S/N too. I can hear more details from songs.
XS03 analog circuit design is good. It is like a desktop DAC amp (3 stages: differential amp., VAS, output). I like its output stage (4 pairs of push pull power transistors BJT in class A config.). It just needs enhancement in mid stage.

That sounds great, but I think you'll need to weld to incorporate your settings. Could you post a picture of the final result? That would be great.

Thank you very much, I'm excited that he can still take advantage of the XS03.

Postdata:
Well, I've opened the XS03 and the OpAmps are soldered, plus they're practically SMD soldered. You must be very good at doing that...

 

[anyanylee22]

That sounds great, but I think you'll need to weld to incorporate your settings. Could you post a picture of the final result? That would be great.

Thank you very much, I'm excited that he can still take advantage of the XS03.

Postdata:
Well, I've opened the XS03 and the OpAmps are soldered, plus they're practically SMD soldered. You must be very good at doing that...

There are 2 versions of XS03, soldered OPA1612 and empty socket version. I chose the latter one. My soldering was done on the dual chip conversion boards first by hot gun and then insert to the empty sockets.

 

[cqtek]

What bad luck, I couldn't choose the version, the store where I bought it sent me the version with OpAmps soldered on the board without me being able to say anything.

That way, it'll be hard for me to do anything to improve the sound... a pity.

But thanks anyway.

 

[anyanylee22]

 

[anyanylee22]

I like the output stage design (above the battery, 8 BJT power transistors into four push pull class A current amplifier circuits). Output power is big enough to drive my Beyer T1 in balanced mode (the right side port).The four cap. are de-coupling cap. for transistors. There is no coupling cap. to output port (a bit dangerous) but it works fine (smaller attenuation). Also, I like the 2 electronic relays (white) as protection of final stage.

 

[anyanylee22]

FYI, XS03 works better on the balanced port (right side). 8 transistors are in full operation. Driving current is doubled.
But I have to buy a special cable (4 wire 3.5 mm plug to 4 wire XLR) in order to use it.

 

[anyanylee22]

 

[cqtek]

Yes, everything you say is fine, it seems that the circuit is very careful and that the manufacturer has matured the design of the board and its components. But that doesn't give me back 6dB at 20Hz. We're talking about half the voltage between 300Hz and 40Hz. That's also part of a design aimed at boosting details, eliminating bass. That's my idea.
On the other hand, it is praiseworthy an amplification in class A, to eliminate distortion of crossing by zero, but the current demand is much greater, the battery lasts very little, although mine is 4000mAh.
In addition, using a balanced connector of 3.5mm, is unwise, I have not found any adapter of 3.5mm balanced to 3.5mm Audio. A bad choice.

As you can see, the size of the battery is bigger and it's on top of the OpAmp, so I can't do anything about it.

Finally, my experience with OpAmps is that they just amplify, they shouldn't change the frequency response. If changing OpAmps modifies the frequency response, increasing the signal of the low zone, there is something "different" in the circuit...

 

[anyanylee22]

What bad luck, I couldn't choose the version, the store where I bought it sent me the version with OpAmps soldered on the board without me being able to say anything.

That way, it'll be hard for me to do anything to improve the sound... a pity.

But thanks anyway.

No thanks. You are the starting point. Without your measurements, I cannot improve it quickly. There are 3 stages.

Differential amp. and LPF: the operation is simple. No chance it attenuates the low frequency
VAS: problem may be here
Output stage current amp. buffer: BJT is very linear in gain. It should work OK

 

[anyanylee22]

In addition, using a balanced connector of 3.5mm, is unwise, I have not found any adapter of 3.5mm balanced to 3.5mm Audio. A bad choice.

Exactly. This is troublesome. I have spent 20 bucks more on the special cable.

 

[colo13]

anyanylee22, please post a link where do you buy the f audio xs03 with empty socket version.
Thanks.