Modification of MHZS CD players - diyAudio
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Old 21st May 2008, 05:33 PM   #1
Koifarm is offline Koifarm  Netherlands
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Default Modification of MHZS CD players

We buy the MHZS players on Ebay for € 200,- ( MHZS 33 ) til € 350,- ( MHZS 88) Incl.shipping and tax.

Click the image to open in full size.
MHZS33

Click the image to open in full size.
MHZS66

Click the image to open in full size.
MHZS88

It is very popular in the Netherlands, Germany and China.

Below I will try to tell how we do the mod’s at a total cost of € 20,-.

We do the following mods:

1 – Remove the opamp and filter( it calls the passive mod)

2 – Bridge and replace capacitors in the audio path.

3 – Higher the anode voltage from 80 to 100V and replace the buffercapacitors.

It all takes a hour of work, and give you much more detail, bigger staging and it is like the curtain is falling down.



1- passive mod.

Click the image to open in full size.

C11 and C12 must be bypassed on the other side of the board and a few other points must be short. See below.

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Connect the yellow points with solder tin.

Then remove the 3k9 resistors and the opamp. See below.

Click the image to open in full size.

These are the light blue parts. And ready is the the passive mod.

It is possible that the output signal is lower then before to correct that you have to replace two resistors a channel see below.

Click the image to open in full size.

Replace the green 33K for 22k/1/4 Watt and replace the 68K for 82K/1 watt and the output signal is higher.

2- Brigde and replace the capacitors in the audio path

Replace C7 and C8( see first picture ) for PIO Capacitors of 0,27 uF or 0,33 uF. Good and cheap brands are Sprague Vitamine or Russian pio k40-2. Replace C13 and C14 ( output capacitors ) for PIO Russian 2 uF (2 x parallel 1 uF) or Neutral MKP between 2,2 uF and 10 uF like Clarity Caps APW. See below.

Click the image to open in full size.

C11 and C12 we already bypassed in the passive mod. So we have just two capacitors a channel.

3 – Higher the anode voltage from 80 to 100V and replace the buffer capacitors.

Click the image to open in full size.

Replace zenerdiode D1 for a 100V/min. 2 Watt type, Replace C1,C2, C3 for 220uF/160V ( Panasonic or so ). We also replace D2,D3,D4,D5 for scottky diode’s like BYW100/200.

Click the image to open in full size.

On the other board you have to replace C4 for 220uF/160V.

This mod is only for the MHZS 33 and 66, the MHZS88 already has a higher anode voltage.

I hope this description is useful for you.

Ronny

Last edited by Koifarm; 14th May 2014 at 07:59 PM.
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Old 23rd May 2008, 01:18 PM   #2
PetrL is offline PetrL  Czech Republic
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An other mod of MHZS player:
http://www.lampizator.eu/LAMPIZATOR/...HZS_CD66F.html

According to the link, the tales on new chip design is marketing bull*hit. Pitty for otherwise probably good players...
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Old 23rd May 2008, 03:16 PM   #3
Koifarm is offline Koifarm  Netherlands
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Quote:
Originally posted by PetrL
An other mod of MHZS player:
http://www.lampizator.eu/LAMPIZATOR/...HZS_CD66F.html

According to the link, the tales on new chip design is marketing bull*hit. Pitty for otherwise probably good players...
you are right, forget all the marketing. For over a year we know already inside the MHZS players is a lot of fake components but al of this *hit sounds great.

The mods i have done are results of the discussions on hififever.



http://www.hififever.com/forum/viewtopic.php?t=952

http://www.hififever.com/forum/viewtopic.php?t=1573
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Old 6th January 2009, 02:47 PM   #4
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I'm planning to start with cd66E soon. Or later. I'm a newbie with cd mods, but rather handy with soldering iron, and I think this unit is a good starting point to study modding a cd. The referred Hififever threads were a bit too much for me to follow, so I post here.

I'm planning to take three steps to evaluate the effect of each separetely, but to take them in different order than what Koifarm showed. I'm in no hurry, and I'm especially interested in output capacitors' effect, since replacing or bypassing them seems like a common mod for many CDPs.
1st:
Replace output capacitors (C13 and C14 in pic). I'm considering Mundorf. You refer to values 2...10uF. More details or experience to share about the value?
2nd:
Up the voltage to 100V. D2...D5 replacement is just to have better diodes, but the originals would do ok as well, right?
3rd:
Getting rid of the op-amp as in 'passive mod'. Change C7 and C8.

All comments welcome.
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Old 6th January 2009, 07:31 PM   #5
Kooka is offline Kooka  Italy
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Sorry, what do you mean with "We buy the MHZS players on Ebay for 200,- ( MHZS 33 ) til 350,- ( MHZS 88) Incl.shipping and tax"?

Prices on eBay are a little higher, actually.
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Old 6th January 2009, 10:02 PM   #6
Koifarm is offline Koifarm  Netherlands
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Quote:
Originally posted by Juuso
I'm planning to start with cd66E soon. Or later. I'm a newbie with cd mods, but rather handy with soldering iron, and I think this unit is a good starting point to study modding a cd. The referred Hififever threads were a bit too much for me to follow, so I post here.

I'm planning to take three steps to evaluate the effect of each separetely, but to take them in different order than what Koifarm showed. I'm in no hurry, and I'm especially interested in output capacitors' effect, since replacing or bypassing them seems like a common mod for many CDPs.
1st:
Replace output capacitors (C13 and C14 in pic). I'm considering Mundorf. You refer to values 2...10uF. More details or experience to share about the value?
2nd:
Up the voltage to 100V. D2...D5 replacement is just to have better diodes, but the originals would do ok as well, right?
3rd:
Getting rid of the op-amp as in 'passive mod'. Change C7 and C8.

All comments welcome.
The value of the output capacitor needs to be 1uf or higher because together with the inputimpedance of the amp it becomes a highpass filter with cut off the subbass. 10uf is standard in the MHZS players.


Quote:
Originally posted by Kooka
Sorry, what do you mean with "We buy the MHZS players on Ebay for 200,- ( MHZS 33 ) til 350,- ( MHZS 88) Incl.shipping and tax"?

Prices on eBay are a little higher, actually.
These prices we paid a year ago. Today the prices are almost 2 times higher. Succes has it price.
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Old 6th January 2009, 10:43 PM   #7
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Thanks for the reply, Koifarm!
The thing is that I don't have the CDP in hand yet: I shall get it from a friend at some point soon.

Quote:
Originally posted by Koifarm
The value of the output capacitor needs to be 1uf or higher because together with the inputimpedance of the amp it becomes a highpass filter with cut off the subbass. 10uf is standard in the MHZS players.
I get the basic idea, but I was mere wondering about getting the value to be on the safe side, i.e. resulting in no filtering independent on the pre-amp input impedance. 10uF is probably a safe choice, since originally designed to have that, but less capacitance might bring in more caps to choose from, and maybe a bit faster transient response.

You suggested using 0.33uF caps for C7 and C8 instead of apparently (haven't checked, since no player in hand) original 0.22uF. Why is that?
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Old 6th January 2009, 11:22 PM   #8
Koifarm is offline Koifarm  Netherlands
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Quote:
Originally posted by Juuso
Thanks for the reply, Koifarm!

You suggested using 0.33uF caps for C7 and C8 instead of apparently (haven't checked, since no player in hand) original 0.22uF. Why is that?
The MHZS 33 has 0.22uf capacitors and the 66 or 88 has 0.47 uf on that position. Every thing higher then 0,22 uf is good. I like to use PIO capacitors in this position. I used Sprague Vitamine Q PIO's with where 0.33 uf.
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Old 7th January 2009, 03:28 PM   #9
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Quote:
Originally posted by Koifarm
The MHZS 33 has 0.22uf capacitors and the 66 or 88 has 0.47 uf on that position. Every thing higher then 0,22 uf is good. I like to use PIO capacitors in this position. I used Sprague Vitamine Q PIO's with where 0.33 uf.
Oh! I had thought that cd33 and cd66 have identical boards; that the only difference is the cd loading mechanism. Well, for C7 and C8 I shall stick with 0,47uF.
Is the schematics, found on HifiFever page, valid for cd66e?
How about other (than C7 and C8) component values; are the resistor values you suggest as replacement, when doing the passive mod, suited for cd66e?
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Old 7th January 2009, 11:21 PM   #10
Koifarm is offline Koifarm  Netherlands
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The schematic and board are the same as the 33 but the 66 has after the tubestage a extra symmetrical outputs. If you use them you can change also the opamps and capacitors in the symmetrical output. If you use the RCA output just leave the symmetrical output as it is.

The 66/88 has other output tubes ( 12ax7 ) so you do not have to change the 68K resistors but only the 33K resistors to 27K. The rest of the passive mod are the same as in the startpost
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