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Prism Orpheus connecting to Project Debut Carbon

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Hi there


I have been using Prism Orpheus as a 'DAC', using it to play the music files from my computer. I am however want to use it to play LPs as well. I planned to buy Project Debut Carbon, with its stock Ortofon MM cartridge. I must admit, however, I am not a technical person in any sense. I bought Prism Orpheus just because I like its sound and knew it could be used as a phono amp (for playing Lps and digitializing LPs). I didn't know very much about instrument, line, and XLR inputs ...


Just wonder if anyone here could teach me how to make Prism Orpheus serve as a phono amp without blowing up the MM cartridge (since Prism Orpheus, if using mic inputs for the turntable, could send a Phantom Power to the cartridge - this is what my friend told me) and of course, I hope Orpheus could sound right.


After studying the manual and some limited posts about connecting turntable to Orpheus, I got several questions (I have attached several photos with info related to how Orpheus works with phono amp, at the end of this message):


1. If I use Carbon’s MM cartridge (specs in the attached pic at the bottom), do I still need to add the extra resistance loading in the connection?


2. I guess there may be two kinds of possible connections made between Orpheus and the turntable (I may be wrong, so please help me here):


A. RCA to Jack (plug into the front panel, analog input 1, 2). In this case, do I still need to worry about accidentally switch on the phantom power of analogue in? In the manual it writes: “Instrument inputs 1&2: two 6.3mm mono jack sockets, auto-select to analog inputs 1&2 when plugged”. I wonder if the control panel of Orpheus will automatically detect that it’s not a mic and disable its phantom power.


B. RCA to XLR (plug into the rear panel, analog input 1, 2) The manual writes: “Mic/line input combos 1-4: XLR for microphones, with 10dB to 65dB finely-adjustable gain and switchable phantom power”. So if I use it this way, I may have the danger of switching on accidentally the phantom power and blow up my Cartridge?


3. If A is the better option – I guess I am using instrument input level? Will it match the MM Cartridge of Carbon’s MM cartridge which has a 47kOhm load impedance? I ask this since the ‘vinyl section’ of the manual explains something I can’t understand: “Since most magnetic cartridges require a higher input impedance than that of the Orpheus microphone preamplifier input, it is usually best to connect a vinyl deck to the instrument inputs using a pair of phono-to-mono-jack cables. The instrument gain controls can then be set to an appropriate level for the particular cartridge. The 1MR input impedance of the instrument inputs will work satisfactorily with most magnetic phono cartridges (which are 'moving magnet' types), but with some cartridges, improved frequency response and noise levels can be achieved by fitting the cartridge's required load resistance (usually 22kR or 47kR) across the instrument input terminals; this is best achieved by soldering it inside the jack. Moving coil cartridges have a lower output level and require a lower preamplifier input impedance. These are best connected to Orpheus' mic inputs, or may require a dedicated preamplifier”. What I can’t understand is the 22kR and 47kR thing. I can’t connect these figures to the spec of the cartridge. Does the Cartridge match Orpheus? (I don’t plan to use MC at this stage).


4. So if everything is all right, I should use


1) a custom-made pair of RCA to 6.3mm MONO JACK cable, that is, 2 RCA, 2 JACK, each of which handle one channel of signal?


2) are there this kind of ‘stock cables’ selling at shops? I googled and are the pair shown here is the kind I need?



3) If I need to custom-made one, what issues must I note and tell the cable man to tackle them? I asked since I read something like this at the forum: “This makes connecting a turntable to an interface a challenge. The RCA connectors and single ended leads to the balanced inputs of the mic preamps. If the tonearm is rewired with a real balanced connection, ground to armtube and +/- from cartridge the mic pres will most likely be quiet enough. But then the arm will only work with a phono with XLR, DIN, or other 3 pin connectors. There is a great reason why microphones are ALWAYS connected with 3 pin balanced connections. Noise rejection. I have been rewiring my tonearms and using 3 pin locking DIN connectors for 20 years. Fought hum issues with tube phono stages and hum magnets, or step up transformers. Swapping to balanced leads into the hum magnet helped. Then balanced into the phono stage with it doing the Balanced to SE conversion.”. I really don’t know what it is saying … I just thought, well, I could ask a cable man to make a pair of RCA-mono-Jack cable just like the way the cable man makes speaker cable terminations. If there is additional issue, could you shed light on this?


4) The final thing is the ground. Orpheus writes: “Most vinyl decks have a ground wire separate from the audio connectors. Connection of this wire for lowest hum is often a matter of trial and error. Ideally this should be connected to Orpheus' analogue signal ground (the outer of the instrument input jacks, or pin 1 of the mic input XLRs). Since no dedicated terminal exists on Orpheus, it is usually easiest to connect the wire to the outer of one of the deck's unbalanced output connectors. In some situations, a direct connection to local mains ground may work better.” What do they mean by “connect the wire to the outer of one of the deck's unbalanced output connectors”? My turntable ground wire is often a U-shape metal. Do they mean I find some way to fix it to the ‘outer’ of the RCA cables connected to the turntable to get the ground connection? Even if it is so, I can’t figure out how I could ‘fix’ this connection! The ground end is not designed to be firmly attached to the RCA connectors in any way …

Sorry for this long post … I am really a non-professional, so I will be very grateful if you could offer your professional help here. Thanks in advance!


Prism Orpheus info related to phono amp application

Vinly Deck Official Explanation.jpg

Front Panel.jpg

Rear Panel 1.jpg

Rear Panel 2.jpg

Input selector.jpg


Project Debut Carbon specification:

0 Technical Specification Project Debut Carbon .JPG

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Hey man,

Firstly don't worry yourself as to potentially 'blowing up' your cart.... !!

You need to intentionally select the phantom power 'button' in the Orpheus control panel application for each channel, and if you're confident enough to cue up a record without fear of destroying your vinyl and/or needle, you're already 99% sorted ;-)


Secondly each cartridge will have a varying sonics based on the interaction with the load presented to it, that and personal preference will determine whether or not you need to experiment with further loading (which you can easily do by simply soldering a 20 cent resistor across the pins of the rca or jack socket).


Initially I would suggest you try using the front inputs as you noted, and if hum is an issue because the TT ground is independently wired (some have their ground also wired to one of the channel shields of the rca's which inherently grounds the TT to the preamps chassis), a simply way of connecting your spade type ground wire to the Orpheus chassis is to buy a single jack plug or rca plug and just either solder or connect it with an alligator (crocodile ?) clip cable to the shield which is the outer part of the jack or rca plug which you can then plug into any vacant socket on the Orpheus making the required grounding connection to its chassis.


Depending whether your TT has captive rca outputs or a female rca output block you will want to choose the most direct connection to the Orpheus, i.e: least amount of additional joins/adaptors or superfluous cable. As such a pair of simple, cheap solid one piece 1/4" - RCA adaptors may be another ideal option to consider.


Regarding balanced connection, which a cartridge inherently is... One can potentially benefit greatly from using the mic inputs, but this arrangement would likely be even better suited to an MC cartridge (and I can attest from experience that the Orpheus performs exceptionally well as an MC preamp when connected in this manner).

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I think you found all the relevant bits, you just have to combine them.


Ground connection. Some turntable /preamplifier combos are quite happy without the ground connection. Play the turntable through the Orpheus without the ground connection and listen for hum. If there is anything noticable, run a small wire from the connector on the back of the Pro-ject to a suitable ground point somewhere in your equipment. It does not have to be the Orpheus. My own turntable is currently quieter without the ground.


Signal connection. You use two identical mono interconnects (called TS to RCA), like the ones shown in your picture, to connect the cartridge to the Orpheus. For a MM cartridge you will need a higher impedance input, that means you need to use the instrument input. The line level inputs have not enough sensitivity, the microphone inputs too low impedance. The phantom voltage supply is symmetric with regard to pins 2 and 3 of the connector, which means there is no voltage across the signal lines. Accidentially applying phantom power would lift your cartridge to 48V relative to ground, but no current would flow through the coils.


Impedance matching. That might be a bit more complicated. You cannot use the microphone input, because the coil inductance together with the input impedance would form a low pass filter, effective from probably 1 kHz. The impedance of the instrument input is better, but essentially too high. Here it's the effect of the parallel capacitance of the cable which will attenuate the highest frequencies. You need something in the middle between a few Ohm and 1 MOhm. I ran a simulation with the available electrical parameters (DC resistance 1.3 kOhm, inductance 700 mH, 120 pF overall capacitance) and arrived at 70-120 kOhm for input termination. You should apply this as a small metal film resistor accross the terminals of the jack plug (not the other side).

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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Thanks Coolhand and iago. My PC crashed and I am working hard on rebuilding it so sorry for my late reply.


The ground connection advice is excellent and clear. Will do that.


I think Project Debut Carbon espirit don't have balanced output ... let me check.


Signal path - I guess I'll use RCA to TS/TRS (that will avoid triggering phantom power) as instrument input. Actually could I use TRS jack in unbalanced mode to plug in the front panel (which seem to me a TS jack for input only)? Any issues I need to know about using TRS in unbalanced mode as far as noise and hum is concerned? I asked since the cable shop which I trust and helps me do cables only have TRS ...


(additional question: I'd also like to connect my cassette deck to Prism Orpheus for future digitalization of tapes). Again, I will use RCA to TRS jack for the analog input in the rear. Since the cables will be unbalanced, so I guess I have the same question as above)


Regarding impedance, I guess I'll try direct connection without resistor first. If I need to play around, I guess I prefer buying something like this: What's a $8500 Cartridge Doing In a Place Like This? The $399 ifi iPhono Phono Preamplifier | Analog Planet

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If the TRS to RCA connectors are mono, they should be OK. Tip and ring connection should join at the RCA sleeve connector, like displayed here. Avoid TRS to RCA Stereo connectors, they are intended for headphone jacks. You can use the same cable for connecting your tape deck, this time using the high level inputs (5-8, I think).


Before you invest additional money in a phono pre-amplifier, order a MC pickup with your turntable. The Ortofon MC Rondo Red was a very nice system and may still be available. The successor is the Quintet Series, but I have not heard them yet. The Quintet Red has a very moderate price uplift to the 2M Red. MC pickups are less critical regarding termination. You would connect them to the microphone inputs this time.


Edit: The Pro-ject has RCA out connectors.

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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Thanks for your Ortofon suggestion. I will look into that. The thing is I can't buy Project Debut Carbon separately from its stock cartridge ... maybe reselling it is an option.


Regarding your photo, why the TRS input is marked with 'BALANCED OUTPUT ONLY"? The RCA output and the wire arrangement here is definitely unbalanced ...

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Some dealers are open to rebuild requests, especially when they increase revenue ;-)


The picture says "balanced input only" on the TRS side; the input jack on the PrismSound expects balanced signals over this connection type. The RCA side is labeled "unbalanced output" which is correct with regard to the connector geometry (conductors are unbalanced in regard to ground potential). The picture is trying to convey the message that a cable built like this is directional. Actually the signal itself is symmetric to ground initially, due to the generator functionality of the pickup coils. Internal wiring (that is what CoolHand hinted at in his post) might pull one end to ground. Actually, in modern players I doubt it will be implemented like this.


I hope I have not completely perplexed you. I have no doubt that a cable wired like the one in the picture will work between turntable and Orpheus.

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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Another item is either software or a phono stage. I like to do RIAA with software.


2012 Mac Mini, i5 - 2.5 GHz, 16 GB RAM. SSD,  PM/PV software, Focusrite Clarett 4Pre 4 channel interface. Daysequerra M4.0X Broadcast monitor., My_Ref Evolution rev a , Klipsch La Scala II, Blue Sky Sub 12

Clarett used as ADC for vinyl rips.

Corning Optical Thunderbolt cable used to connect computer to 4Pre. Dac fed by iFi iPower and Noise Trapper isolation transformer. 

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Just to add to your information overload ... the details on Channel D (Pure Vinyl) website may be of help...


Channel D - Online Store powered by Kagi


CHANNEL D - Support - Getting Started with Computer Audio





...in my opinion / experience...

While I agree "Everything may matter" working out what actually affects the sound is a trickier thing.

And I agree "Trust your ears" but equally don't allow them to fool you - trust them with a bit of skepticism.

keep your mind open... But mind your brain doesn't fall out.

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Hi iago, thanks for your clear expalantion. I have asked the cable 'lady' (yes, not a guy!) to make the RCA-TRS cable for me today. With newly bought turntable and nitty gritty cleaning machine, I hope to use my Orpheus to bring the vinyl music back. One primary motive of re-engaging myself to vinyls is the CDs have been produced with very compressed sound. Ironically CDs should have more dynamic range than LPs, sadly it turns out the complete opposite because of the loudness war.


Audio_ELF , thanks for the page, very interesting articles.


Panelhead - Orpheus has internal RIAA, which many reviews said it's very good. But it's no harm trying very good software, especially if I am to play some older LPs, which requires different RIAA filters which Orpheus doesn't have.


Will post the result when everything is ready and hopefully shine!

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iago, nightmare sound from Project carbon turntable ... I custom-made a pair of RCA-TRS cables with the following instruction given to the cable-lady: http://home.comcast.net/~zenkai-audio/gndtss/dwg/rca_trs.gif.


I didn't see the making process but she did demonstrated through meters that the connection seems to be correct (the signal ends of the RCAs, for example, could allow current to pass through to the tip ends of the TRS but not the ring and sleeve ends).


I connect the cables from the turnable to the instrument inputs of Orpheus' front. Without soldering tools available, I connect the ground 'manually' (and minimally) just to see the effects of grounding. I connected tightly one end of the ground wire to the TT and then hold the other end the ground wire to various outer jacks of different gears to see if there are hums or noises. The method is very brutal and primitive - the other end of the ground wire is in spade type so I could only let the wire just 'touching' those different jacks, which includes the SPDIF jack of Orpheus and my poweramp's RCA inputs (I used Balanced inputs for my poweramp now so leaving the RCAs available). The result is:


With our without touching those jacks, there is a very loud, consistent noise. I don't know if it's called hum.

Link to the noise:




1. The sound is always there, regardless of switching on or off the turntable, playing or not playing music.

2. Turning up the gain or volume result in louder noise.

3. Unplugging the RCA-TRS cable of course give me peace again.


ONE piece of extra info - I used the cable to connect my cassette deck to two line-level inputs at the rear and there are music without noises.




I thought of buying the phono amp mentioned before if it could solve all the problems. But I really suspect if it will help and I also wanna know what went wrong. I am leaving for my vacation so returning the TT needs to be done quickly if it's flawed. Your help could be greatly appreciated ...

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Ok I tested these scenarios:


1. TT + Teac amp (through RCA-RCA cables, with ground cable connected to TEAC AMP, both in the same outlets) - no hum, works very great

2. TT + Teac amp (switched on, ground only) + Orpheus (RCA-TRS cables) + Parasound amp (direct from Orpheus) = hum exists, loudly ...


So the culprit is the custom-made wire???? oh no ...

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sorry for so many posts, I just discovered a wierd thing. I plugged in the TRS cables, WITHOUT attaching to anything (not even the TT). The NOISE is still there (perhaps even louder). The software controller indicates Orpheus is taking it as instrument.


Further note that if I turn down the gain to minimum (11db) for the input channels, apply max voltage output, then the sound is ok. But I have to turn up to max volume level, and at this point, the hum is still there, although much severe.


So does it bring back to the point instrument cable is too sensitive to noise, especially with my cartridge output level? Or if I have use the wrong cable? I have used this:


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It seems I have discovered something more fundamental ... I discovered the following:


1. I started with the RCA-TRS unplugged (so it changed back to MIC position), but with the RIAA fiter switched on for input 1 and 2.

2. I increased the gain from its lowest 11db to more, 20, 30, 40 and so on.

3. Both faders of input 1 and 2 start to have some signals going up and down irregularly (see the pictures)

4. I turned up the volume there is very noticeable unpleasant NOISES coming out from both channel.

5. I switched to the flat curve, the noise is lowered, but still noticeable.





It seems to me with 30db of gain, A1 and A2 is already very noisy without any cable plugged in.


Is it normal???????? I heard Orpheus have a GREAT phono amp. I can't comprehend what happened in my case.

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I'm sorry for not seeing your posts earlier.


I'm astonished that the cable lady did not veto the use of coaxial cable, you use symmetric cables for this type of connection. This is the one I currently use, Belden will have something similiar.


But even with the wrong kind of cable, you should get this connection to work somehow. The gain for the 5.5 mV input should be set to something around 40 dB.


I just listened to your sound sample (really good idea!), and the sound of the turntable is absolutely drowned in computer noise. This is not hum, but the sound of your audio PC working. Usually you get this in a similiar way to a ground loop, but I cannot explain how a completely open ended source like a turntable is affected by it.


My own turntable is also not as quiet as it used to be, especially after the introduction of power line ethernet. But I never heard this kind of noise unless using unshielded wire near a mainboard. On the other hand, your cable currently is unshielded ...


Let me think about this and also try to find out how the Pro-ject is wired internally. Something for you to do in the meantime is try different power outlets and tell me how your audio PC is supplied.

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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Sorry, something seems to have gone wrong with your attachments.


In microphone mode the input impedance is not high, that means even in open loop mode you should not get too much noise from the input. The RIAA filter will essentially boost lower frequencies and attenuate higher ones, so probably noise will be less obnoxious with the filter inserted.


Is the noise identical to the sound sample posted above?

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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Could you please also conduct this last experiment with a line input?


1. Nothing connected to line input,

2. Line input routed to output,

3. Slowly increase volume.


Ideally you should hear hiss at very low volume (probably needing ear to speaker), increasing with output level if it's really coming from the input (and not your amplifier), but nothing else.

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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iago thanks for your responses.


You're basically saying what happened is really strange since:


1. even co-axial won't create such noises

2. even ground-looping won't create such noises


Yes, the noises throghout all scenarios are very similar. Sometimes a very high pitched sound will pop up. I experienced very strange 'explosive' sound when I touched and moved the instrument cables already plugged in the front panel. That's a horrible sound.


My direct impression is the Orpheus seems to have its mic and instrument totally polluted and can't be touched with any gain at all.



You asked me to expriment this:

1. Nothing connected to line input,

2. Line input routed to output,

3. Slowly increase volume.


Sorry I can't understand no. 2 ...


Here're the photos reattached:


2 Noise Level instrument input 3.JPG


Since the line-level experiment with my cassette deck has no noises issue, and the culprit is not also not the TT (since connecting to Teac mini amp has no such noises), the problem must be the mic and inst ... if it's such a complex issue to solve is buying a phono amp will solve the problem? A phono amp will bring up 60db and serve as line level input, feeding my Orpheus with no problem? (I am solving this problem by not tackling it ... though if there's easy fix I'd like to try ... but my busy job doesn't allow me to spend a month on solving this ... oh i just want to play my vinyls! I hope you understand) ...

2 Noise Level instrument input  2.JPG

2 Noise Level instrument input 1.JPG

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Hi PCmusic,


With regard to the latest developments, I would put it like this:


(1) The strangest thing is that you already have noise on the unconnected input. I have never seen this.

(2) The type of noise is well known. I have had it myself often enough. It's similiar to a ground loop, but different in sonic behaviour. This is why I asked how you supply your music PC with power.

(3) My feeling is that the coaxial cable should work somehow, but if you have noise on this input even without a cable, the point is moot.


I suspect that some amount of noise is also present on the line level inputs, that is why I asked you to check. "Routing" essentially means to "connect the signal internally", which is what you do via the input selection tab in your Orpheus' software.


Yes, the phono-pre would immediately solve this problem. I understand that you value your time more than the additional cost, but an unsolved issue like this would make me itch considerably.


If there is a fix, it's probably related to grounding and power supplies.

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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Thanks for your patience.


1. I have dedicated power lines for my audio-video system. But to some extent ... I am not sure. I said this since the extra power box (B2) is also linked to the mains (B1). The electricity men and some of my audiophiles say it's enough.


2. So far i am playing ditigal playback, mostly through my computer connected to B1, but frequently a Bluray Disc Player and CDP. The PC is 4m away from my Orpheus.


3. On the B2 box side, I have installed six outlets. One set is for active use. The other set is idle, just a reserve if I need to change the entire gear set position.


a. For the actively used set, B1, it has THREE outlets. The power amp use one single outlet, with a separate line. The OTHER SET of two outlets seems to be linked (I forgot). One is plugged with Orpheus. Another deals with the rest of things with an extension socket - TT, TV smart box, BDP, CDP, HDMI switcher (My TV, TV smart box, Blu-ray disc player, all of which connected to this switcher to feed my Plasma TV), an audio source selector ( Blu-ray, TV box audio-out ). So five sets of digital gears all connected to the extension socket. The only analog here is the TT.


(this implies Orpheus is connected to a different outlet, which led me to think it create a ground loop; I tested this by plugging in Orpheus into the socket in the extension block and see no improvement)


b. The 5 digital components are connected to each other in ways I couldn't really remember which and how each one is connected to the others.


c. I used a very long TRS-XLR balanced cable (6M or more ) to connect my Orpheus to my poweramp. I planned to place the gears from away from my poweamp but ended up putting them in the same place. So I just 'loop' this pair of wires in ways similar to this:




This pair of wires are placed one shelf under my Orpheus. I talked about this since I have no idea if these long pair of wires 'looped' this way will create bad influences.


That's why I could describe through words. Attached is a picture of the system. Don't know if you could figure out anything from it though :)


photo 2.jpg

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DO you mean I use XLR or TRS output of Orpheus to connect them back to Orpheus any TRS line input (? Will it do any harm? But ... the thing is I don't have this kinds of cables ...


No, not like this. Just the same experiment you made with the instrument /microphone input. Leave the high level input open (unconnected), enable it and select it as input. Slowly turn up the volume and listen for noise.

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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That's why I could describe through words. Attached is a picture of the system. Don't know if you could figure out anything from it though :)


Hmm, I can recognize some cables, but the description was more helpful ;-)


Two things are still unclear. Every active component seems to be plugged into the same set of outlets, but what about the audio PC? It's 4m away, but plugged into the same B1 line eventually leading to your audio rack? Or some completely different outlet on a another circuit?


The PC uses an internal power supply with protective earth (three pronged plug)? Or something different?


The PC is connected to the Orpheus by USB?


What confuses me is that you have massive interference on the high sensitivity inputs, but obviously none on the high level ones. Something else you could try is to repeat the microphone input test, but with the USB cable unplugged from the Orpheus. I would expect the noise to go away in that configuration.


Sorry for causing you so much effort!

Primary ::= Nabla music server | Mutec MC-3+USB w/ Temex LPFRS-01 RB clock | WLM Gamma Reference DAC; Secondary ::= Nabla music server | WaveIO | PrismSound Lyra

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