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Mesa Subway Plus preamp

#302
Sub41 said:
I’ve never used the Alpha. There was one in the classifieds recently I hesitated over until it was gone. Does it offer any drive or compression in conjunction with the Subway+ that would negate the need for separate drive/compression pedals?
Click to expand...
It adds subtle tube compression as ND lots of warmth but I still use a boost for grit and a separate compressor for limiting and balancing my signal.
 
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#304
Just got a Subway Plus preamp yesterday at a shop.
It sounds fantastic, but couldn't help but notice when I plugged it into my interface, the meters were showing constant signal. I looked at it through a scope and it's putting out a steady sine wave tone at 19.3khz. It wasn't audible really since it's such a high frequency, but this seemed to happen even with the mute engaged. Anyone else notice this?
Here are some screenshots.
Screen Shot 2023-04-19 at 3.27.43 AM.png
Screen Shot 2023-04-19 at 3.27.29 AM.png
 
#305
Goodnight Cody said:
Just got a Subway Plus preamp yesterday at a shop.
It sounds fantastic, but couldn't help but notice when I plugged it into my interface, the meters were showing constant signal. I looked at it through a scope and it's putting out a steady sine wave tone at 19.3khz. It wasn't audible really since it's such a high frequency, but this seemed to happen even with the mute engaged. Anyone else notice this?
Here are some screenshots.
View attachment 5036508 View attachment 5036509
Click to expand...
Power supply? Does it do it when battery powered?
 
#307
Goodnight Cody said:
It happens just the same with battery or plugged into a power supply. It makes it impossible to tune using a tuner plugin since it just sees that frequency. Thankfully it's not audible. It's not something I notice when plugged into an amp. Just wondering if anyone else can see that when monitoring through a DAW.
Click to expand...
It's the switching residual from the switchmode power supply. The frequency should be about 22kHz, but with workstation processing it will often truncate it down because 22kHz is out of band, a rounding error of sorts.

The switching residual is about -55dB to -60dB down from the signal, if you turn the gains up high enough you will be able to see it on the extended range of the metering, but if you were to play a normal level signal through it, you would be about 30dB into clipping and therefore unusable. I believe this is what's happening given the level indication of the meters.

If you don't hear it, don't worry about it. There are thousands of these pre-DI's out there working tours and recording sessions without any real world problems. This comes up about once a year, the answer remains the same.
 
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#308
agedhorse said:
It's the switching residual from the switchmode power supply. The frequency should be about 22kHz, but with workstation processing it will often truncate it down because 22kHz is out of band, a rounding error of sorts.

The switching residual is about -55dB to -60dB down from the signal, if you turn the gains up high enough you will be able to see it on the extended range of the metering, but if you were to play a normal level signal through it, you would be about 30dB into clipping and therefore unusable. I believe this is what's happening given the level indication of the meters.

If you don't hear it, don't worry about it. There are thousands of these pre-DI's out there working tours and recording sessions without any real world problems. This comes up about once a year, the answer remains the same.
Click to expand...
Thanks for the response and insight. I definitely didn't have the gain that high when I took those screens. Far from clipping or in the red. That's why I thought it was odd my tuner was picking it up & making it so I couldn't tune through Ableton.
 
#309
Goodnight Cody said:
Thanks for the response and insight. I definitely didn't have the gain that high when I took those screens. Far from clipping or in the red. That's why I thought it was odd my tuner was picking it up & making it so I couldn't tune through Ableton.
Click to expand...
Your metering shows +6dBu at the residual frequency which would be completely unusable in practice as the preamp wouldn't work without massive distortion. There's something wrong with the metering, or there's a level switch error somewhere in the software, that value should be about -60dB to -65dB relative to maximum output level (which is about +10dBu).

Which tuner are you using? Some do not have HPF's or LPF's in their firmware and it's possible that the residual is interfering with the ADC in the tuner. On the premium tuners, the LPF is generally set a little higher than the fundamental of the highest note the tuner was designed to detect... and for this kind of reason. The cheap Chinese tuners generally don't have this feature and is why they don;t work as well as the better tuners.
 
#310
agedhorse said:
Your metering shows +6dBu at the residual frequency which would be completely unusable in practice as the preamp wouldn't work without massive distortion. There's something wrong with the metering, or there's a level switch error somewhere in the software, that value should be about -60dB to -65dB relative to maximum output level (which is about +10dBu).

Which tuner are you using? Some do not have HPF's or LPF's in their firmware and it's possible that the residual is interfering with the ADC in the tuner. On the premium tuners, the LPF is generally set a little higher than the fundamental of the highest note the tuner was designed to detect... and for this kind of reason. The cheap Chinese tuners generally don't have this feature and is why they don;t work as well as the better tuners.
Click to expand...
Hmm I don't think there's anything wrong with the EQ or with my Apollo. Never experienced anything like this with any other pedals or pre's going into Ableton. There was no distortion when playing at the level I had it set to when that screenshot was taken.
The tuner I use when going direct is the stock Ableton tuner.
I recorded a bit of the noise and if I slow it down an octave, it is a very audible sine wave. So I think the frequency is right on the EQ.
Again, appreciate the troubleshooting. I am curious if others behave this way going direct in.
 
#311
If you slow the sample down by 50%, the frequency should be around 11kHz which would of course be audible.

What doesn’t make sense is the switching residual reading +6dB, that’s an impossible number. The preamp wouldn’t work with that reading (therefore assume it’s incorrect).

Are you sure there’s no meter scaling going on (like a +60dB range shift)?

A -60dB switching residual is normal, representing about 1mW with a 100 watt amp. They all do this yet there are thousands in use without any real world issues. If it’s not an audible issue then it’s not a problem.
 
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#313
There may be meter auto-ranging going on in the analysis mode.

The standard VU meter only reads to -20dB, -60dB is 1/100th of that amount to put things in perspective.
 
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#314
I once used a tc1044 to double the available voltage on a homebrew active DI, it showed the same kind of peak but even lower in terms of frequency on Cubase. It´s definitely not in the hearing range (I used my kids who were 8 and 10 at the time to make sure...).
 
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#316
I recently started using a Darkglass B7K overdrive pedal with my American Standard Jazz bass. The output of the passive Jazz really didn’t push the B7K pedal very well. I tried throwing the pedal in the Subway DI Plus’s Fx loop. With this, I was able to crank up the input and tweak the EQ which in turn feeds the loop. And, my gosh, I started getting that ripping Darkglass overdrive. Just one more reason to love this amazing preamp pedal. Only downside is they’re so hard to find. I have 2 so far.


BTW there’s one on Reverb. Mesa Boogie Subway + DI-Preamp 2018 | Reverb
IMG_0444.jpeg
 
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