Altmann Tera Player - Page 82  

Shuffling is supposedly "RANDOM" but it's all dependent on your music. You need a nice selection of files in every place to get the best randomness. Like some music files in root with a few artist folders, in each artist folder some music files and some album folders and then some music files in those folders. I find when I make a playlist like that I get the best results.

Quote:

Originally Posted by tds101 

No worries my friend. I'm curious because it's a player that I'm interested in BECAUSE it's great at shuffling. The excellent sq is what I'm wanting verification of.

Yes, we know. Read over the last few pages, people are running into difficulties and then apparently fall off the face of the earth for a few days and then completely ignore what they were doing. I don't have the proper sound card to be able to get good results out of anything, so I am refraining from participating in doing such calculations. Apparently one of the problems is the mono test signal....needs to be stereo. I think that's as far as people got to getting it to work.

Quote:

Originally Posted by skamp 

Geez, it's not that hard.

RMAA:

• generate "Test Signal" WAV file
• calibrate volume and gain by playing a sine wave at 0 dBFS
• play "Test Signal" WAV file and record the output
• load the recording in RMAA
• repeat as above, but with headphones attached via a splitter cable

Output impedance:

• play and record a 1 kHz sine wave at 0 dBFS, note the RMS value (RMS1) of the recording ('sox file.wav -n stat -rms' => "Scaled by rms:")
• same as above, but with headphones of a known impedance attached via a splitter cable, note the RMS value (RMS2) of the recording
• output impedance = (headphone impedance * (RMS1 - RMS2)) / RMS2
• adjust for the input impedance of the recording device: output impedance = 1 / (1 / output impedance - 1 / input impedance)

The fact that we know that we need stereo means we figured that problem out. Please read the last few pages and see what they were saying. I pass over it as I don't particularly care much about getting it tested. 

Quote:

Originally Posted by skamp 

• launch Audacity
• Menu "Tracks" => "Add New" => "Stereo Track"
• Menu "Generate" => "Tone": "Waveform" = "sine", "Frequency (Hz)" = 1000, "Amplitude (0-1)" = 1, "Duration" = 00h01m00.000s

Done.

Here are some measurements of my Attraction DAC, done years ago by Dick van der Merwe - a Dutch Hifi specialist:

http://thehbproject.com/files/img/fotos/testen/Altman_BYOB_Attraction_DAC/Altman_Atrracktion_DAC_Metingen.gif

http://thehbproject.com/nl/testen/74/5/Altmann-BYOB-Attraction-DAC---Het-Meetrapport

http://thehbproject.com/nl/testen/74/0/Altmann-BYOB-Attraction-DAC

I personally do not do any measurements during the design my audio devices. In a way, I just fiddle with the components until I get what I want to hear.

The Tera-Player's DAC, I/V and output section are very similar to that the Attraction DAC. It can be considered a shrink-copy with some adjustments due to size- and power supply limitations.

In that respect, I think it would be rather optimistic to expect anything better than what is shown in the links above.

Charles :)

Thanks for that. There is still a difference here in that their is an additional output stage. If you knew the output impedance and value of (if there is) an output coupling cap would help. I know you'll get grief over the high frequency roll and to be honest it looks a bit much but I do understand the importance of voicing and trade off of evils. The other side of that coin is finding a better solution but that's always open for another to try. People can spend as they see fit and I'm happy to see that you're quite up front about your device.

I few years back, I knew a fellow that had one of your single ended single output device solid state power amps with a spiral 12v battery. I wondered if a bypass cap on the battery would help. Most didn't but there was a high quality 10,000mf one that seem to time up nicely and speed things up while still cohesive. Is this something that you would frown upon or welcome?

Quote:

Originally Posted by skamp 


As NwAvGuy would say, you design by ear! A lot can go wrong that way, because human ears are nowhere near as precise or reliable as electronic gear, and also because your hearing and / or your perception and tastes can be more or less different from your customers'.
 

The ear is the customer  so designing by ear - if you can - is the only way to satisfy the customer.

I would agree, that not everybody is good at designing by ear. 

Output impedance of the Tera-Player has been adjusted for best sound on Koss PP, I think that was that expected ?

SuperDuper and TeraMega outputs feature slightly different impedance, that makes them sound different. I personally prefer the output with the higher impedance (most of the time), but that is a matter of taste ...

Please don't order so much, need spare time ...

Quote:

Originally Posted by goodvibes 

Thanks for that. There is still a difference here in that their is an additional output stage. If you knew the output impedance and value of (if there is) an output coupling cap would help. I know you'll get grief over the high frequency roll and to be honest it looks a bit much but I do understand the importance of voicing and trade off of evils. The other side of that coin is finding a better solution but that's always open for another to try. People can spend as they see fit and I'm happy to see that you're quite up front about your device.

 

I few years back, I knew a fellow that had one of your single ended single output device solid state power amps with a spiral 12v battery. I wondered if a bypass cap on the battery would help. Most didn't but there was a high quality 10,000mf one that seem to time up nicely and speed things up while still cohesive. Is this something that you would frown upon or welcome?

Hi goodvibes, 

great to hear that you know the BYOB amp, mine is playing right now here :)

Yes, some did bypass the battery with something, some changed the power cable, I never did. 

Some removed the small pot and changed the coupling caps, I hate to see this. In most of the cases they were trying to compensate something that was wrong in their system by fiddling with the best component that they had at all -> the BYOB. Mine is still original for 10 years now, and I still make them exactly the same way as I did in 2003.

Charles :)

As Charles has stated in the past (or maybe it was others that said something to this effect), their have been many well regarded lines of products with the PortaPro's being used to tune them. This does not mean other headphones can't pair nicely, but this is the reference standard to which they were tuned to by the creator. Is that really such a big deal that a model gone unchanged for decades is not worthy of usage to tune something? Just because the price isnt grand doesnt mean it's not worthy of tuning something so great.

Quote:

Originally Posted by skamp 

Why don't you give an exact figure? Also, you designed the TP to work well with one specific pair of headphones? What about other headphones, with wildly different characteristics?

Quote:

Originally Posted by skamp 


Why don't you give an exact figure? Also, you designed the TP to work well with one specific pair of headphones? What about other headphones, with wildly different characteristics?

I do it like Rolls-Royce did back then: The power is 'sufficient'.  

You will figure out the number anyway.

Had to choose one headphone. You cannot design the best if you mess up with many different headphones. You need a reference standard.

I found it in the Koss PP - by accident. In 2010 a friend came over to my lab with the Koss. At that time the Tera-Player project was lying on ice. There was already Hifiman and I was using a Sansa Clip, which I liked much better than my ipod.

Okay, then my friend gave me his Porta-Pro and I ran and grabbed my Tera prototype. I immediately realized the potential and started over working on the Tera. In summer 2011 I felt something was wrong in the sound of the Koss PP. I was listening about 10 hours a day for 2 weeks in order to establish final voicing and the sound was not right. I went into a big electronics store with my prototype and tested about 30 headphones, they were all crap in comparison to the Koss. Then I remembered that there was a modification on the internet: The Kramer mod. I decided to do that and this made everything absolutely right. Now I had the sound. The rest is history.

Charles :)

Quote:

Originally Posted by Chucky-X 

Hi goodvibes, 

 

great to hear that you know the BYOB amp, mine is playing right now here :)

Yes, some did bypass the battery with something, some changed the power cable, I never did. 

Some removed the small pot and changed the coupling caps, I hate to see this. In most of the cases they were trying to compensate something that was wrong in their system by fiddling with the best component that they had at all -> the BYOB. Mine is still original for 10 years now, and I still make them exactly the same way as I did in 2003.

 

Charles :)

Like I said, one worked and others sort of unvoiced it. I understand that it would go wrong more than right. Just curious as to your take on that which isn't really a mod since it's outboard of your device. I do tend to find battery power a bit laggy at times but then SS supplies have their own issues. I agree that changing the voice of something designed by same is questionable. In that case, there are always other options.

Quote:

Originally Posted by skamp 


If someone finally decides / manages to do the measurements.

The Koss Porta Pros are 60Ω, but their impedance nearly triples at around 70 Hz:

A proper output impedance for those would be (60/8) 7.5Ω, but that would be too high for many IEMs (and I really can't tell if 7.5Ω is the actual output impedance of the TP to begin with, since you're being so mysterious about it).

Hi Skamp, 

your estimate is not bad at all :)