I just tried plugging my CD player (Technics SL-PG100, modified) *directly* to my DOZh, for the first time, and it makes a strange crackling noise (almost like clipping) with strong signals... i measured them and were well below the maximum input signal of the amp - "something's weird at the input" i thought, so i checked on Google and found out that this line of players have an output impedance of 1kohm (???). Is this normal? The amp works perfectly with any other audio source i've tried (Sony CDP, CDROM, tape decks, etc).
1k seemed pretty high to me, so i thought it MIGHT had something to do. I spent a couple of afternoons doing various mods to it; it has the DAC practically integrated to the transport and both digital and analog signals are then picked by a separate board. For the analog path there's an opamp gain stage (where i did most of the mods) and a discrete buffer. I didn't even bother to check it, i mean, if there's a buffer it can definitely supply a couple of mA. I was thinking of bypassing the buffer but now i'm not quite sure... I don't think the mods i did have much to do with this issue either (improved psu, bypassing caps, changing electrolytics and bipolars for plastic caps where possible, higher values for coupling caps, etc).
PS: The Technics works fine with my dad's amp. As a matter of fact, it's quite a sweet sounding deck.
PS: The Technics works fine with my dad's amp. As a matter of fact, it's quite a sweet sounding deck.
The DOZh that you speak of, that is the DOZ headphone amp is it not? If so you've got a pretty high input impedance, around 100k I do believe, so if a CD player cannot suply enough current to drive a 100k load there is a problem I would say. That buffer wouldn't be there if it couldn't drive such a load, because then it would be rather useless.
I'm guessing there is another problem here.
I'm guessing there is another problem here.
Yes, yes and yes. The Doz for headphones has an input sensitivity of 1vp-p; the deck spits about 2vp-p, but with the volume control (a 100k log pot) the signal during these noises is arround 0,6 - 0,7v (p-p).
I'll reopen the deck tonight and play with it some more, to see if i can figure this one out...
I'll reopen the deck tonight and play with it some more, to see if i can figure this one out...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.