High pinched whistling

[VDS]

Got the Jensen PI-2xx installed.  The annoying higher pitched sound went away! 
But I have a hiss that remains. I feel like the hiss was there before, but somewhat hidden by the high pitched tone. So it’s definitely an improvement, but I’m not there yet.

Hiss is audible from 15’ away.

I’m using Wireworld 3 conductor rca to xlr, 1.5’ cables from Jensen to Pass amp, super cheap amazon xlr to xlr from Xilica to Jensen.  
Anybody experience reduction in background hiss by using better cables?

@mikebse2a3, you obviously have lots of experience with Jensen isolators, per you setup, do the little slide switches on the bottom offer any possibilities?

[VDS]

On 7/12/2021 at 4:24 AM, Newfangled said:

Yup, I experienced the same exact thing when I tried using a First Watt SIT-3 amplifier.

 

I ran XLR from Xilica XP4080 to RCA on the First Watt.

Monoprice 104784 3' Premier Series XLR Female to RCA Male 16AWG Cable

https://www.monoprice.com/product?p_id=4785

I confirmed that this is a 3 conductor cable. Signal + goes to center pin on the RCA and the - and shield are soldered together on the RCA outer conductor.

I experimented desoldering the shield and leaving it floating on the RCA end and it didn't make a difference. Whine was still present.

 

I only heard the whine from the Jubilee HF stock compression driver left and right. Not noticeable form the LF cabinets.

I disconnected everything in my setup and traced the noise to the Xilica.

 

Unplugged everything.

I didn't plug in any inputs into the Xilica.

I plugged in the First Watt SIT3 and connected the left speaker cable. Turned amp on. Silent.

I plugged in the Xilica and connected the Monoprice XLR to RCA cable. Silent

Turned on the Xilica and when the internal relay turns on after a few seconds I hear the high pitched whine.

 

Is it possible that this is an issue with the Xilica? Should I contact them? The date code on my Xilica is from December 2020. Curious if the original poster and I have issues with our units. Or is this just an inherent issue with using XLR to RCA with high sensitivity drivers?

 

I didn't hear the noise when I previously used the Crown D75a or a pair of Amp Camp monoblocks which both had balanced inputs. I'm Debating now if I want to  experiment with the Jensen transformers or sell this amp and look into other amps that offer balanced inputs. Also considering other amps with balanced inputs; Cyrus Stereo 200, First Watt J2, Benchmark AHB2.

 

 

Exact same situation, Jensen helped a lot, no high pinched sound, but still a hiss.

[Edgar]

52 minutes ago, VDS said:

Exact same situation, Jensen helped a lot, no high pinched sound, but still a hiss.

 

Short the amp inputs to ground. If the hiss remains, then it's the amp.

[mikebse2a3]

On 7/14/2021 at 1:51 PM, mikebse2a3 said:

I personally use the PI-XX, PI-2XX and PC-2XR (Uses a 4:1 transformer to match Pro Reference Level to Consumer Reference Level which is about a -12db gain reduction).

I use the PI-XX (single channel unit) and PI-2XX (dual channel unit) with my McIntosh amplifiers and my First Watt F3 amplifiers (F3 benefits from the higher drive level) and the Schiit Vidar sub amplifier.

The PC-2XR has advantages in systems where the gain structure is such that the Pre-Amplifier Volume Control can’t be adjusted beyond about 10:00 o’clock or 11:00 o’clock without it becoming to loud and often you will have audible noise/hiss at the listening position from the HF Compression Driver/HORN even at idle with no music playing. In these situations the Isolation plus (-12db gain reduction) gives the best performance.

 

 

 

 

@VDS  This is from the ISO-MAX manual…. “SEE SECOND PARAGRAPH”..

If this is how you would describe the Hiss Noise you have gain issues most likely and most likely the DIP switch options most likely want help but it want hurt to try them if you would like other than some positions could lead to some HUM and BUZZ again.

 

HERE IS THE MANUAL for information and switch option descriptions.

 

PI-2XX_manual.pdf

 

 

 

 

System Gain Structure Issues are separate and unrelated to Ground Loop Hum and Buzz Issues.

 

I suggest you troubleshoot for the gain issue.causing Hiss which the PC-2XR might have been a solution for both the HUM/BUZZ and HISS although you could possibly use attenuators on the amplifiers input as another option.

 

First I suggest you make sure you don’t have channel output gain levels turned up above “0db” on the XILICA and also Note does the HISS change with channel output level changes.? If it does make adjustments to the channel output levels to minimize the HISS. Maintain INTER-CHANNEL  BALANCES by lowering all the same amount.

 

With no music playing and system just at idle note the HISS Level.

If the Hiss changes with Volume Control Changes then the issue is Pre-Amp or Source associated.

 

If HISS stays the same Disconnect the INPUT CABLES to the XILICA:

(If HISS stops check Pre-Amp, Pre-Amp to Xilica interconnects.)

If HISS stays the same Disconnect the OUTPUT CABLES at the XILICA:

(If HISS stops you most likely have a gain issue due to Pro-to-Consumer conversion and/or if Amplifier has a high sensitivity input design.)

(If the HISS stays the same remove Interconnect at Amplifier Input and if HISS is the same it is amplifier related or if HISS goes away check Interconnects but most likely again indicates an issue due to Pro-to-Consumer levels and possibly in combination with an Amplifier having a high sensitivity input design.

 

If its determined to be a gain issue between the Xilica/Amplifier then the ISO-MAX PC-2XR offers -12db of attenuation or possibly an Input Attenuator on the Amplifier as another option.

 

 

Note: all this disconnecting would best be performed with dummy plugs for best signal to noise but will probably be OK doing as described above.

 

miketn

 

 

[babadono]

dumb question....did you get dummy plugs also?

[PrestonTom]

First, take Edgar's advice. It is quick and simple and can help pinpoint the problem

Although, didn't "we" already eliminate this problem a few days ago?

 

BTW, has the sloppy grounding on the "Rawson" Amplifier been cleaned up yet?

 

[Edgar]

2 minutes ago, PrestonTom said:

Although, didn't "we" already eliminate this problem a few days ago?

 

I've lost track of what has been tried, and what hasn't.

[VDS]

Update, I forgot to order another pair of cables for Xilica to Jensen, ordered Monoprice, hopefully here tomorrow. I stole the cables from Xilica to bass amp to test the Jensen on the high frequency drivers. Like I said much improved, hiss still there. Reinstalled F3 to listen to music and let go of some frustration.

i need to reread some of the more technical suggestions tonight, get Pass fully installed with Jensen as soon as cables arrive.  
I thing I never thought of, now that I’m dealing with only hiss, is gain. Some of you have mentioned this. My preamp has adjustable gain up to 30db, which is where I always set it. The Pass has 20 dB gain, so I was running it with 50db gain.  Maybe too much?  I will try to turn down gain to 10 or 20, to get total gain of 30 or 40db instead of 50. 

Like I said I’m rereading everyone’s suggestions more throughly tonight. 

[babadono]

15 minutes ago, Edgar said:

 

I've lost track of what has been tried, and what hasn't.

I think that is Rule #1 in the IsoMax troublshooting guide: Write everything down! It is very easy to get confused/distracted and go completely off track down a path that leads nowhere. Often times as I think @PrestonTom posted a problem likes this gets fixed and you don't know WTF fixed it.

[VDS]

17 minutes ago, Edgar said:

I've lost track of what has been tried, and what hasn't.

Me too! Going to regroup know that problem has changed somewhat to hiss only, high pitch whine is gone with Jensen.

 

22 minutes ago, PrestonTom said:

 

BTW, has the sloppy grounding on the "Rawson" Amplifier been cleaned up yet?

No, but trying to focus on getting Pass to work quietly. Rawson has to be sent out to get refurbished and straightened out. Going to be weeks.  

[VDS]

@PrestonTom, Do you have a Benchmark ahb2? Or am I thinking of someone else?

if I can’t get this cleared up, and now that I’m using active XO, I’m entertaining the thought of this amp, super low distortion from a company that doesn’t seem to care about anything but engineering. And true, balanced inputs.  Just a possibility.

 

[PrestonTom]

1 minute ago, VDS said:

@PrestonTom, Do you have a Benchmark ahb2? Or am I thinking of someone else?

if I can’t get this cleared up, and now that I’m using active XO, I’m entertaining the thought of this amp, super low distortion from a company that doesn’t seem to care about anything but engineering. And true, balanced inputs.  Just a possibility.

 

You are thinking of someone else. I tend to be old school when it comes to electronics

[babadono]

so @VDS did you get the dummy plugs?

[VDS]

12 hours ago, Edgar said:

 

Short the amp inputs to ground. If the hiss remains, then it's the amp.

How exactly do I do this?

[VDS]

6 hours ago, babadono said:

so @VDS did you get the dummy plugs?

Emailed Jensen yesterday, told them I wanted a pair.

[Edgar]

1 hour ago, VDS said:

How exactly do I do this?

 

Disconnect the amp from all sources, but leave it connected to the speakers.

 

If the amp uses balanced XLR connections, then connect all three pins together at the amp input. (Both + and - connected to ground.)

 

If the amp uses unbalanced RCA connections, then connect the center to the shield at the amp input. (Short the input to ground.)

 

Whatever hiss you hear in this configuration is the noise floor of the amp.

 

 

[VDS]

4 minutes ago, Edgar said:

 

Disconnect the amp from all sources, but leave it connected to the speakers.

 

If the amp uses balanced XLR connections, then connect all three pins together at the amp input. (Both + and - connected to ground.)

 

If the amp uses unbalanced RCA connections, then connect the center to the shield at the amp input. (Short the input to ground.)

 

Whatever hiss you hear in this configuration is the noise floor of the amp.

 

 

I get I, with rca the center is signal the outer ring is ground.  Any noise coming through speakers is the amp itself and I will never get below that noise level, only add to it? I’ll try it later today. Thanks

[mikebse2a3]

18 minutes ago, Edgar said:

If the amp uses unbalanced RCA connections, then connect the center to the shield at the amp input. (Short the input to ground.)

 

Whatever hiss you hear in this configuration is the noise floor of the amp.

 

 

11 minutes ago, VDS said:

I get I, with rca the center is signal the outer ring is ground.  Any noise coming through speakers is the amp itself and I will never get below that noise level, only add to it? I’ll try it later today. Thanks

Just make sure you short the input with amplifier power off and then afterwards you can turn the power amp on to test for noise..  

 

Caution: Shorting input with amp power on could send a signal spike into the loudspeaker. 

 

Note: If you have a cheap RCA interconnect you can cut the wires and twist or solder them together to create a shorting plug.

 

miketn

[VDS]

1 minute ago, mikebse2a3 said:

 

Caution: Shorting input with amp power on could send a signal spike into the loudspeaker. 

 

Note: If you have a cheap RCA interconnect you can cut the wires and twist or solder them together to create a shorting plug.

Glad to hear this caution, I will use an old rca cable! Turn power on after cable is connected. Thanks

[Edgar]

21 minutes ago, VDS said:

Turn power on after cable is connected. Thanks

 

That is good advice under all circumstances.