Steve, I do think it surprising that no one has other than you. Especially since from the beginning, everybody was eager to try all new ideas.Maybe people just reached a kind of saturation after all the time. It would be ironic if your cicuit was just the ultimate touch and no one ever knew but you! I for one fully intend to try it when I send my player to Rowmeister the next time. Brent where are you???
Yes, 4.34v across R507. Also measured the pins from Q502. The pin that feeds R507 was, of course 4.34v and the others were at 4.9v and 5v.
Looking at the schematic the pin with 4.9 is right, the others are not.
Is this the problem ? (he asks hopefully)
By the way, how is the proud owner of the pink soldering iron doing. Still providing joy, smiles and sleepless nights?
Steve
The little one is doing fine, she doesn't know how to solder yet, but she's now taking her first small steps, very cute
. Oh, and she's got two more teeth on the way. The sleepless nights are almost gone, depending on when she get's her last evening-bottle, she makes it through the night more often.Back to electronics...
Looks like the DC setting for Q502 is off. There's 0.66V (5V - 4.34V) between base and emitter, which is basically a diode internally, so that's good. Q502 is probably not broken. But the base should be around 3.4V instead of 5V, so what's causing it? If Q501 is not conducting properly, the base of Q502 is pulled to 5V by R506. So, next step is to measure the voltages at the pins of Q501
.Regards,
Ray
Well, it helps that I design my own boards, which makes it all much easier. I started with under board parts modifications, and the improvement was easily noticeable and real. And I just went from there. But that's just me.
Eventually someone else will get around to it.
I did measure Q501 and got 5v from middle pin, nothing from the outer pins.Looks like the DC setting for Q502 is off. There's 0.66V (5V - 4.34V) between base and emitter, which is basically a diode internally, so that's good. Q502 is probably not broken. But the base should be around 3.4V instead of 5V, so what's causing it? If Q501 is not conducting properly, the base of Q502 is pulled to 5V by R506. So, next step is to measure the voltages at the pins of Q501
Regards,
Ray
I'm away for a week now so I'll catch upon return.
Thanks again, Steve
I'm planning to do, I have all the bits. The board from Steve is a bit big to fit in the space that I have so I may have to do an underboard fitting on the original dos boards.
Just trying to find out how to add the bits under the board. I saw a mail from Steve which described how the additional transistor and resistor fit but it didn't mention if any traces have to be cut/lifted - maybe it's simpler than I thought.
Pete
That's not right... Looks like there's something wrong with the DC setting of Q501 too. It could be the ribbon cable, the DC level for Q501 comes from the RF amp that's on the board under the mech. They are DC coupled, so if the ribbon has a bad contact, the whole chain is pulled to a wrong setting.
C U in one week!
Regards,
Ray
IIRC, indeed no trace cutting is involved. Now that i'm looking at both schematics: if you swap T1 and T2 that are in there now for the PNP part, you already have that section connected. All you have to do is lift the base of the PNP before you solder it, to break the connection to the filter, and fit the original transistor (or FET) and the 6k8 resistor in between. Seems it's easier to fit them on the top-side then.
Regards,
Ray
Last edited:
Here's some refreshment history on the CFP-DOS.
This is not my circuit by any means, though at present it is my board design and implementation of the circuit.
The DOS is Ray's. The CFP modification to the long tailed pair was suggested to me by Hugh Dean (Aksa here on diyaudio). Ray did some simulations on it and I implemented everything in an under the board modification, with excellent results. The current sink was suggested to me by someone else, and I also incorporated this into the board.
What the CFP does!
The standard LTP circuit will have a fairly large voltage swing, depending on the input voltages. In my 8260 the DSD mode voltage is 5.4v, or +2.7v and -2.7v, for a huge swing. In PCM mode the voltage is 3.3v, for a +1.6v to -1.6v swing, still quite large. The CFP will stabilize this. The effect of the large voltage swings is signal compression. The effect of the stabilized voltage swings is signal uncompression, with music expansion into the room and vastly increased bass response. These two effects were immediately apparent to me upon first listenings to the CFP modified DOS. The results were the same whether I played rbcd or sacd.
Most of the folks with my board have 63's or 67's. I have no real way of knowing the end results of the CFP-DOS in those players. However, I assume they have operating voltages of 3.3v and the resultant large voltage swings, so the results should bear similarity to my own.
Steve
This is not my circuit by any means, though at present it is my board design and implementation of the circuit.
The DOS is Ray's. The CFP modification to the long tailed pair was suggested to me by Hugh Dean (Aksa here on diyaudio). Ray did some simulations on it and I implemented everything in an under the board modification, with excellent results. The current sink was suggested to me by someone else, and I also incorporated this into the board.
What the CFP does!
The standard LTP circuit will have a fairly large voltage swing, depending on the input voltages. In my 8260 the DSD mode voltage is 5.4v, or +2.7v and -2.7v, for a huge swing. In PCM mode the voltage is 3.3v, for a +1.6v to -1.6v swing, still quite large. The CFP will stabilize this. The effect of the large voltage swings is signal compression. The effect of the stabilized voltage swings is signal uncompression, with music expansion into the room and vastly increased bass response. These two effects were immediately apparent to me upon first listenings to the CFP modified DOS. The results were the same whether I played rbcd or sacd.
Most of the folks with my board have 63's or 67's. I have no real way of knowing the end results of the CFP-DOS in those players. However, I assume they have operating voltages of 3.3v and the resultant large voltage swings, so the results should bear similarity to my own.
Steve
That's not right... Looks like there's something wrong with the DC setting of Q501 too. It could be the ribbon cable, the DC level for Q501 comes from the RF amp that's on the board under the mech. They are DC coupled, so if the ribbon has a bad contact, the whole chain is pulled to a wrong setting.
C U in one week!
Regards,
Ray
OOPS, Should the ribbon cable be plugged in when checking Voltages?
If so, all the others too?
Steve