[schubert]

I'm building a line-level Ripper to use with a Cornet2.  I thought about replacing the Panasonic pot with something better (25K PEC carbon pots and a resistor to make up the 50K), then it occurred to me that I could feed the variable output of my Pass B-1 buffer linestage (which has those PEC pots) to the Ripper and control the levels from there.  If that's the case, I wondered if the buffer stage of the Ripper is necessary - or can I bypass it?  How about running the B-1 output right into C23?  If I can do that would R22 and R23 be necessary?  Anyone that knows more about circuit design than me (most of you no doubt) have any ideas?

[poty]

I'm building a line-level Ripper to use with a Cornet2.

How are you going to use the Ripper? As an ADC after the Cornet 2? Then you can easily cut the entire Analog part of the Ripper.

I could feed the variable output of my Pass B-1 buffer linestage (which has those PEC pots) to the Ripper and control the levels from there.

Yes, it is possible.

... if the buffer stage of the Ripper is necessary - or can I bypass it?  How about running the B-1 output right into C23?  If I can do that would R22 and R23 be necessary?

As I stated before - you could connect your B-1 directly to ADC left/right  of the digital part of the Ripper. Then the whole Analog part of the Ripper will be cut out.

[schubert]

Thanks, poty - I'll probably try it both ways.  In an email jh said essentially the same thing, but he suggested adding a series resistance for safety, so I'll put a resistor in the C23 spot and connect it directly to the RCA in.  This will also allow me to adjust channel levels independently (since the B-1 has a separate volume control for each channel), which is necessary with some source material.

[schubert]

My bufferless ripper is up and running.  It works well with the Pass B-1 as the buffer.  I put in 100 ohms series resistance before the DAC in the C23 position (I left C23 out since the B1 has output capacitors).  I haven't listened to the results yet - I'll post when I do.

[schubert]

Sound quality is very good, except that I'm getting a high-pitched whine in all my transfers.  Analysis with audacity shows peaks at 1000Hz and multiples thereof up to 12K Hz.  I suspect I might have the Ripper too close to the computer.  Anyone have any ideas?

[schubert]

I've found the source of the whine - it's an interaction between the Ripper and the buffer.  I get the same whine with two different buffers (the B-1 and a tube buffer), whether or not there is any input or even power to the buffer - just if it's connected.    No other changes make a difference, including shielding.

I'd like to try to salvage this setup before I give up and go with the stock arrangement.  Currently the input to the ripper ADC is through a 100 ohm resistor only.  Would there be any benefit to adding C23 (which goes right before the ADC), R22 and R23 (resistors from the buffer input to ground), or any combination of these? Anyone have any ideas?

[poty]

I've found the source of the whine - it's an interaction between the Ripper and the buffer.  I get the same whine with two different buffers (the B-1 and a tube buffer), whether or not there is any input or even power to the buffer - just if it's connected.    No other changes make a difference, including shielding.

I think in that case you should check cables or what you use for connecting the buffer to the ADC. Maybe there is something similar in the buffers? Power supply or something else (including the distance to nearest noise sources)? Try to connect just cables, connect something else (instead of buffers) - CD, Radio, MP3 player...
I'd also check capacitors in the Ripper in the PS, maybe joints.

[schubert]

The cables don't matter - I've used two different pairs of different construction and length, and each time the whine disappears if the B-1 output is switched from the ripper to something else, even though the ripper is still physically connected.  The effect is the same whether the buffer is powered or not.  Shielding has no effect, so it's coming in through a cable somewhere.  To tell the truth I think it's coming from the computer, that is, being connected to the buffer circuitry allows it to act as a receiver for noise from the computer.  (In fact jh in the instructions mentions the possibility of feedback from the S/PDIF input, but that was with the Bugle parts in place, and I don't have those in my Ripper.)  As far as I can tell there are no other noise sources in the area (except the computer, which is about four feet away).

How would I check the PS capacitors? What would I look for?

[poty]

Please answer the following questions:

The cables don't matter - I've used two different pairs... and each time the whine disappears if the B-1 output is switched from the ripper to something else, even though the ripper is still physically connected. The effect is the same whether the buffer is powered or not.

Do you have proper ground connection of power supply for computer, Ripper and buffer?
Can you point to the schemes of the buffers you use?

Shielding has no effect, so it's coming in through a cable somewhere..

No way. You've mentioned that even if the Ripper is physically connected to the buffer, but the buffer switched to the other output, the whine disappear. So the cable is not the problem point. I insist that you should try to connect something battery-powered instead of a buffer. Just to eliminate ground loops through the power connector, or no ground on the power connector.

To tell the truth I think it's coming from the computer, that is, being connected to the buffer circuitry allows it to act as a receiver for noise from the computer.

It is possible if the buffer is powered on. But you have the noise regardless of the power. Then it should be inside buffer or inside Ripper.
I think you should try to disconnect all cables and record no signal. If you have the noise in the silence then you have problem with the Ripper.

How would I check the PS capacitors? What would I look for?

It is possible that there is some leakage of the digital frequencies to the input of the ADC. You should check all those filter capacitors for proper grounding (soldering problems?) all power voltages. And the grounding of the chassis too. Maybe you should check for gound loops with ADC input connectors.

[schubert]

Thanks for your answer, poty.

Do you have proper ground connection of power supply for computer, Ripper and buffer?
Can you point to the schemes of the buffers you use?

Everything uses three prong power plugs, if that's what you mean.  I'm afraid I don't know what you mean by buffer schemes - sorry about my ignorance.

I insist that you should try to connect something battery-powered instead of a buffer. Just to eliminate ground loops through the power connector, or no ground on the power connector.

This is a good idea - I'll try it with a battery-powered cassette deck I have.

I think you should try to disconnect all cables and record no signal. If you have the noise in the silence then you have problem with the Ripper.

I did this, and there was no whine.

It is possible that there is some leakage of the digital frequencies to the input of the ADC. You should check all those filter capacitors for proper grounding (soldering problems?) all power voltages. And the grounding of the chassis too. Maybe you should check for gound loops with ADC input connectors.

I'll try this - I can at least reflow the solder joints.  I'm not sure how to check for ground loops.

Again, thanks for your help.  If you think of anything else I'm all ears.

[schubert]

For those interested, I rebuilt this ripper as a stock line level unit, and it sounds better that it did without the buffer - lesson learned.