Checking MDAC caps

[hc25036]

All credit to IAG. My MDAC has been repaired and fully serviced for carriage costs only.

 

[Dark Energy]

I wonder what capacitor they replaced them with?

 

[hc25036]

I'm not going to look!

 

[Lancastrian]

This is the same problem which beset some of the Pink Triangle Ordinal DAC's. Mine was so bad that PT just replaced the unit under warranty. It seems during production a lower temperature rated capacitor was substituted instead of the 105 degree type. This could be the case with the MDAC's.

Ian

 

[sq225917]

You replaced film caps with mica caps. Then you replaced melfs with dales. What are you going to next replace the organic polymer caps with old, used electrolytic?

 

[e53]

You replaced film caps with mica caps. Then you replaced melfs with dales. What are you going to next replace the organic polymer caps with old, used electrolytic?

All organic polymer caps and other electrolytic are new. Not Lelon.
I will not change all the electrolytic caps to an organic polymer.

I think that due to the peculiarities of circuitry, organic polymer caps will not always be better than ordinary high-quality electrolytic. A little about this at # 30.

In addition, Black Gate NX (very low noise) is used for the shunt direct U3, U4, U5, U6 - stabilizers for the generator and ESS9018.

Best Regards

 

[e53]

It is not always possible to directly replace conventional electrolytic caps with organic polymer (low ESR) caps. Possible non-obvious problems. For example:
http://www.acoustica.org.uk/t/3pin_reg_notes3.html

 

[Morph3R]

After this, one of the first stages of tweaks, the DAC became noticeably better than stock:

- Replacement of all RXY Lelon cap's;

In Audio replacement of :

- 24 cap's 4700uF 16V with Panasonic FK;
- all MELF with Dale resistors. (Here's the next stage) Top wiev.
https://www.dropbox.com/s/260lhgg6n44vg45/Dale_Mica top MB audio.JPG?dl=0
- some more changes, which were subsequently modified;

In PSU Board, a little bit more:
External power 5 rails clean DC is a very good and correct engineering solution.
But, after tweaks, because of the lack of advantage in SQ (IMHO), and for other reasons, I use a regular PSU.

- replacement 5 Lelon capacitors on the Panasonic FC (my preferences and on the totality of the characteristics) such as http://uk.farnell.com/panasonic-ele...c1e472/cap-alu-elec-4700uf-25v-rad/dp/9692231 ? MER = sy-me-pd-mi-alte.

- replaced all rectifying diodes S2J on diode Schottky. Digital PSU diodes are located between C4 and C5.

IMHO. A noticeable increase in SQ is due to Schottky diodes.

Due to the increased rectified voltage, the heating of the radiators U58, U59, U61, U62 and especially U60 (Digital PSU stabilizer) will slightly increase. Therefore, it is better not to put on the M-DAC other devices that make ventilation difficult

Hi e53,

can you please provide us exact specs and quantity of the components you were using for this tweak?

Thanks

 

[e53]

Hi e53,

can you please provide us with exact spec and quantity of the components you were using for this tweak?

Thanks

The scheme has been amended. In addition, deliberately used some less powerful parts than before. Including Schottky rectifier diodes. A number of precautions have been taken, up to the drilling of additional ventilation holes in the case. Therefore, I can not recommend my specification for repeating tweaks.

For example:
At my own risk, I applied resistors of less dissipated power. MELF (0204) 1/2W - VISHAY/DALE (1206) 1/4W. (Ask John W about it.)
Headphones do not use. M-DAC works more than a year.

Very good result with not expensive series VISHAY CRCW (1/4W).
Such as here: http://www.mouser.ch/_/?Keyword=CRCW12061K00FKEA
Series CRCW-HP 0,75W - did not try.

Even better, but much more expensive, the VISHAY / Dale RCWP series (1/4W)
Such as here:http://www.mouser.ch/ProductDetail/...b8OZphbjlby5YAcxdbIuDfCDR5hoCOaHH2wMF7EiE/w==

A typo should be 24 cap's 4700uF 16V with Panasonic FR (EEU-FR1C472L)
http://www.mouser.ch/ProductDetail/...dgrAKksAIw0N9wBcc7mUu7o/O2JvvJ6Pfl5cjWYtuHg==

Best regards

 

[Morph3R]

Thanks for the answer e53.

At what positions did you substitute original with Vishay resistors?

 

[e53]

Thanks for the answer e53.

At what positions did you substitute original with Vishay resistors?

At all positions MELF. Denominations as in the original. Without R3, 6, 27, 29 - are shorted (here and below - one channel). Also in all channels.

SQ. The quality of the other capacitors is not less important than the resistors.
My choice, Silver Mica, MultiCap RTX.
Additionally, 0.1uF between the bases of the output transistors Q15, Q16.
C8 - 180pF, C9 - removed. Oscilloscope control.
I do not think that this is important - the solder Wako Tech SR-4.

This is just my experience on my M-DAC, not a recommendation for repetition!! Any repetition is your risk!

Best Regards