Well I didn't get on with the Wima 0.068uF cap in the C906 position - it's not bad sounding, but a little too clinical for my liking. All the sounds were there but it lacked any emotion, and front to back soundstaging was non-existant... very 'flat' sounding.
This morning was going through my parts box and found a brand new Jensen copper foil 0.1uF cap, so I decided to install that - overkill I know, but that's DIY isn't it?
Anyway I think this willl turn out to be a 'keeper' - the music sounds so vibrant, so natural that I can't imagine wanting to change it anytime soon. Seems to offer all the detail of the Wima, but with the emotion and excitement of the original 0.1uF electrolytic.
Amazing how one cap position on the board can have so much influence over the sound - it's not like it's directly in the signal path! Strange - still I'm happy with it now... until the next mod
John
This morning was going through my parts box and found a brand new Jensen copper foil 0.1uF cap, so I decided to install that - overkill I know, but that's DIY isn't it?
Anyway I think this willl turn out to be a 'keeper' - the music sounds so vibrant, so natural that I can't imagine wanting to change it anytime soon. Seems to offer all the detail of the Wima, but with the emotion and excitement of the original 0.1uF electrolytic.
Amazing how one cap position on the board can have so much influence over the sound - it's not like it's directly in the signal path! Strange - still I'm happy with it now... until the next mod
John
Who said BG's take weeks to come on song !
Have been using mine as standard with a BNC out (no resistors)
Made it 75ohms last night, not bad, less glare and grain.
Having got my bits from Peter earlier in the week (with the caveat of "you don't neccessarily need them all") I thought I would attack it.
Removed R1 - R5
Substituted, E1, 10uf and E5 47uf for the BG's.
Well, bugger me, how good is that (30 mins on them at present) ! If they get any better then it's a bonus.
Now I've got to tread carefully as to any other substitutions.
Have been using mine as standard with a BNC out (no resistors)
Made it 75ohms last night, not bad, less glare and grain.
Having got my bits from Peter earlier in the week (with the caveat of "you don't neccessarily need them all") I thought I would attack it.
Removed R1 - R5
Substituted, E1, 10uf and E5 47uf for the BG's.
Well, bugger me, how good is that (30 mins on them at present) ! If they get any better then it's a bonus.
Now I've got to tread carefully as to any other substitutions.
I must be tired and confused today. Im having trouble making the PSU that I built behave like it should. I made it using Peters schematic. I used MUR820 diodes because thats what I could get my hand on. Im getting around 40V AC/17.5V DC after the rectifiers and around 16V AC/7.85V DC after the voltage regulator. Im using a center tapped 2x12v EI transformer. Am I supposed to have that much AC at the output? What have I done wrong, because Im pretty sure I did?
lohk said:
You really can't - you need the supporting electronics, the mechanism by itself is worthless. (Except as a spare) I have looked at the cost of the mechanism by itself, and retail it costs roughly half of what the entire boom box would cost you depending on where you are. Factor in the chips, pcb , and the lcd display, and cannibalizing this inexpensive boom box starts to make a lot of economic sense. I know this is not what you wanted to hear.
FWIW it seems that a lot of the performance potential resides in the Sanyo chip set used..
MrMajestic said:
Some cheap multi-meters give erroneous results when set to the ac range in an attempt to measure ac superimposed on dc, while others will actually give you the residual ac riding on the dc you are measuring. Put a small cap (say a couple of uF - if electrolytic observe polarity) in series with one of the meter leads and try the ac measurement again - I bet (hope) you get a different reading.
What brand and model of multi-meter?
A scope would answer this question definitively.
robot said:
This unit does not appear to be suitable as it supports MP3 cd playback which indicates a different chip set is used.
So far the only ones identified with the correct family of chips are the RCEZ31 which is still readily available in Europe and Canada, and the RCEZ32 which is a more complex version available in the USA and possibly elsewhere.
John has added the RCEZ51 to the list, one I have not seen personally, but has been mentioned. There is also a model by Alba that uses a version of this mechanism and the right chips. (See earlier postings for more info.)
johnm said:
Yes, you need a 75 ohm source impedance to drive 75 ohm cable which in turn is terminated into 75 ohms. Properly implemented this will result in the lowest level of reflections.
The output of the LA78601 doesn't really want to see a 75 ohm load directly, because of limitations in the amount of current it can source it should ideally not see a load impedance much below 400 ohms - driving the dac with your current values you will be in the vicinity of 340 ohms which is a bit low but seems to work ok.
The original values I recommended of 392 and 93 ohms actually meet all of the criteria in this regard. (But I think 301/100 is probably ok long term.)
MrMajestic said:
Wow, your trick worked. I put a 10uf cap between the probe and the measuring point and voila, no AC. It started off at the same reading but trickled down to close to zero. Thanks for your help, I will now start looking for a new multimeter
Glad to hear it. An inexpensive Fluke is a good investment as would be any inexpensive good quality scope you could score. (Kikusui, Tektronix, Philips.)
