Audible Illusions Modulus

[olds1959special]

I don't know what the result will be. It does sound like your pre might have some issues. Suppose the tech fixes the PSU or other issues and you get it back. Now quiet, functioning properly etc what if it has no identifiable sound quality? I think SIY's point that it probably doesn't have a sound if functioning properly is not so extreme.

Here are measurements done by Stereophile for a Modulus 3A.

Audible Illusions Modulus 3A preamplifier Measurements

Sidebar 3: Measurements Line-level measurements of the Audible Illusions were taken from the CD inputs to the main outputs; the phono measurements were taken at the tape outputs. The Modulus 3's output impedance at its line output measured 1775 ohms (L) and 1802 ohms (R) with the level controls...

www.stereophile.com

There not a lot there to make you think it has much of a sound. They do note moderate levels of DC output and that they fluctuate considerably. Maybe why you have gotten the pops on your amps at times when turning them off. They also show a rather high output impedance which might dull the sound a bit with some cables.

Tubes, Tubes, TUBES! They have great musical sound.......or so goes the myth. Just put tubes in the signal path and you might like it. You probably will like it better. I used tubes for years, and years. Tube power amps have a sound. Tube pre amps, not so much. SS pre amps not so much. So many want that tube sound and think a tube preamp gets that without the hassle of a tube power amp. Sorry, it very rarely is so.

Now if you just like the idea nothing wrong with that. But you seem to be suffering lots of trouble to gain something that is based upon a myth. SIY is actually trying to help you out.

someone else said the pop could have been from an arcing power switch from relay contacts sticking closed, and that dc offset from the preamp wouldn’t cause this if I turn the amp off first.

 

[Sylvanus]

If the coupling capacitors are not leaky, you shouldn't have any significant DC offset on the outputs as long as your power amp remains connected and the interconnects are fine.
Power amplifiers should always be turned on last and turned off first. This is a preferred standard practice for all audio equipment setups. And it's normally a good idea to wait for a few seconds after power amp turn off to let the internal capacitors bleed off.

If your technician is worth his salt, he should be able to identify any issues with your preamp.

The guys here are just not interested in subjective evaluations of audio equipment without some sort of explanation of how it was done.

 

[SIY]

If the coupling capacitors are not leaky, you shouldn't have any significant DC offset on the outputs as long as your power amp remains connected and the interconnects are fine.

Depends. I've seen some designs where the feedback is taken from the output end of the coupling cap, which can cause some unpredictable offsets.

The guys here are just not interested in subjective evaluations of audio equipment without some sort of explanation of how it was done.

Subjective evaluations are great as long as they're ears-only. The questions go to how that was achieved. And if controls aren't there, the "subjective" evaluation usually has little to do with actual sound. That's a tough pill for many to swallow.

 

[Sylvanus]

Assuming the schematic I posted above is correct, that's not the case here.
But, it's been a long time since I looked under the hood of an AI preamp so I'm not 100% sure.

I don't see the need to get indignant with people about their own listening evaluations of their own equipment. (Whether the evaluation had proper controls or not.)
Subjective evaluation is incontrovertible regardless of the form it takes.

 

[SIY]

Subjective evaluation is incontrovertible regardless of the form it takes.

It is absolutely controvertible. If unlikely sonic claims are made without evidence, you'll be called on it; it's no different than being on a gym site and claiming you can deadlift 1200 pounds and do 5 reps.

 

[Blumlein 88]

Assuming the schematic I posted above is correct, that's not the case here.
But, it's been a long time since I looked under the hood of an AI preamp so I'm not 100% sure.

I don't see the need to get indignant with people about their own listening evaluations of their own equipment. (Whether the evaluation had proper controls or not.)
Subjective evaluation is incontrovertible regardless of the form it takes.

Not just controvertible, but maybe the most easily controvertible. If you mean when a subjective evaluation is done, the one doing it won't let anything controvert it, then maybe you are right. But that is not the same as it being incontrovertible.

 

[Sylvanus]

Not just controvertible, but maybe the most easily controvertible. If you mean when a subjective evaluation is done, the one doing it won't let anything controvert it, then maybe you are right. But that is not the same as it being incontrovertible.

You're creating an argument out of nothing. It's obvious what I meant. Get a life.

 

[olds1959special]

I heard back from the tech. He said the circuit board is corroding, causing hum. Also the NOS tubes I just bought were bad, and he replaced them with gain matched tubes of different brands. (Does that matter?) Also the volume knobs were crackly. He said it’s fixable and will call me tomorrow. In the mean time I’m asking the seller for a partial refund to cover the costs of repairs. Unfortunately, communication with the seller has been poor.

 

[Sylvanus]

Your unit is at least 30 years old and the boards in those were not conformal coated.
Depending upon what sort of environment it was in, some scratchy carbon potentiometers and pc board deterioration would not be unexpected.

 

[olds1959special]

Your unit is at least 30 years old and the boards in those were not conformal coated.
Depending upon what sort of environment it was in, some scratchy carbon potentiometers and pc board deterioration would not be unexpected.

Now I’m confused. So I get the amp back. Here’s what he did. Resoldered circuit board completely - cold joints. Repaired volume control. Replaced noisy tubes. Bench tested for 8 hours. I plug it in and I’m getting crackling white noise on the left side. It plays sound, and then I noticed it is microphonic, amplifying the sound of the mute switch when I push it. I’m going to call them tomorrow but it’s disappointing.

 

[olds1959special]

My tech got it working! After agonizing for days, it's finally back, and it works. No hum or buzz. Right now I have the volume controls set to 9 o clock, and DAC set to 50 on the volume, and the sound is smooth and wonderful.

The tech replaced another tube and a capacitor.

 

[olds1959special]

On the Modulus 2C, is the tape input the same as aux input (and tuner input?) Are the two sets of pre outs the same? Is there a change in impedance when both sets are connected at the same time?

 

[Blumlein 88]

My tech got it working! After agonizing for days, it's finally back, and it works. No hum or buzz. Right now I have the volume controls set to 9 o clock, and DAC set to 50 on the volume, and the sound is smooth and wonderful.

The tech replaced another tube and a capacitor.
View attachment 396667

Are those Vandersteen speakers?

 

[olds1959special]

Are those Vandersteen speakers?

Yes, 2Ce Sig II's. I'm running four amps to power them, utilizing the four pre-outs of the Modulus. I'm trying to figure out if I'm okay impedance-matching wise. I believe the four pre-outs on the Modulus 2 are the same (unlike the Modulus 3).

 

[olds1959special]

Reviving this thread. I'm still using this pre-amp, but in a different system on my desk (SMSL DL200 - Audible Illusions 2C - Kenwood L-05M's - Elac Debut 2.0 B6.2, SUB1010). The two sets of outputs allow me to directly connect my subwoofer. I'm also using shorter (3 ft) interconnects from pre-amp to amp/subwoofer. I like listening to music with this system, but I sit close to the speakers, so I hear the hum and hiss, which is a little worse in the left side (not tube related, switching the L/R tubes does nothing. It sounds like a 60hz hum so probably capacitor related but it's not bad enough to bother trying to have it fixed.) The tubes in the line stage are labeled RCA Made in Germany which the tech said were Telefunken. I put one of the tubes from the phono stage into the line stage and it hissed like crazy, making me wonder if this thing eats tubes in the phono section. I have this set up on my desk next to my computer, and had to disable the wifi to stop interference which sounded like popping sounds. I also learned the tape out can be used for a headphone amp or something with a volume control and works quite nicely. It seems a bit mid-bass centric and probably sounds better with intimate vocals more than complex music.

 

[SIY]

It sounds like a 60hz hum so probably capacitor related

If it's 60Hz, there's almost zero chance that it's related to capacitors. It's a grounding or radiation issue. Depending on the heater circuit used (AC or DC), it could be originating there as well.

 

[KenFen]

The tubes in the line stage are labeled RCA Made in Germany which the tech said were Telefunken. I put one of the tubes from the phono stage into the line stage and it hissed like crazy, making me wonder if this thing eats tubes in the phono section. I have this set up on my desk next to my computer, and had to disable the wifi to stop interference which sounded like popping sounds. I also learned the tape out can be used for a headphone amp or something with a volume control and works quite nicely. It seems a bit mid-bass centric and probably sounds better with intimate vocals more than complex music.

Look for the service bulletin Art put on tubes. I have owned a 3A and now and now a 3B and there is only one tube you can use. NOS Vostok Rockets (tube designation is a 6H23NEB). When I say nothing else will work and hiold up.. I mean nothing. These are the only tubes AI recommends. Good things were said about the new EH version. I had them in three months before they went microphonic. These rockets I have had in for three years amd they are quiet. Also.. the phono section is not in the audible circuit unless you are using a TT. However, never run the preamp without all four tubes in. Note 2:. The Auxillary input is the one you should he using. The CD one has a resistor inline that causes wickded rolloff and frequency anomaly.

 

[SIY]

Look for the service bulletin Art put on tubes. I have owned a 3A and now and now a 3B and there is only one tube you can use. NOS Vostok Rockets (tube designation is a 6H23NEB). When I say nothing else will work and hiold up.. I mean nothing. These are the only tubes AI recommends. Good things were said about the new EH version. I had them in three months before they went microphonic. These rockets I have had in for three years amd they are quiet. Also.. the phono section is not in the audible circuit unless you are using a TT. However, never run the preamp without all four tubes in. Note 2:. The Auxillary input is the one you should he using. The CD one has a resistor inline that causes wickded rolloff and frequency anomaly.

All of this points to incompetent design.