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What is your favorite vintage ADA cabinet simulator?

MicroCAB I
- 0 (0%)
MicroCAB II
- 3 (37.5%)
Ampulator
- 3 (37.5%)
MP2
- 2 (25%)

Total Members Voted: 8


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Author Topic: Favorite vintage ADA cabinet simulator  (Read 16283 times)

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GuitarBuilder

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Tell us why!
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rnolan

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Re: Favorite vintage ADA cabinet simulator
« Reply #1 on: Time Format »

The only ones I've used are the MP2 cab sims, always been very happy with them, even used them for MP1 by running the MP1 outs into the MP2 loop returns, also sounded good.  More recently MikeB put a GCS-3 in his MP1 loop, that also sounds great through my studio monitors.
Mmm why? For the MP2 cab sims (which I've use allot for recording and rehearsing at home), they just sound like playing through the cabs but heaps more convenient and I don't upset the neighbors LOL. So in a way I find them transparent (if that makes sense).
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MarshallJMP

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Re: Favorite vintage ADA cabinet simulator
« Reply #2 on: Time Format »

The ampulator,why,well because it's special,you have alot of tonal options.
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RobbHell

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Re: Favorite vintage ADA cabinet simulator
« Reply #3 on: Time Format »

The Ampulator is a Gem.
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MarshallJMP

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Re: Favorite vintage ADA cabinet simulator
« Reply #4 on: Time Format »

A Gem?
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Casey_Butt

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Re: Favorite vintage ADA cabinet simulator
« Reply #5 on: Time Format »

I don't know how old this thread is because the board is not showing me the date, so forgive me if this is severely necro...

I like the MicroCabs because they can be modded to be more cab-like.  On their own, none of the ADA cab emulators that I know of (I don't know about the new GCS's) are really that accurate to any actual cab responses I've seen.  You could make the argument that the Ampulator has the closest and most sophisticated response (though it's very similar to the MicroCabs), but its notch filters are still a bit too extreme (as are the MicroCabs).

In practice, it doesn't matter too much though... because all of them still sound good and your ears really aren't that sensitive to the areas where they're 'weak' anyway.

But some simple mods can make the MicroCabs more cab-like.  Another simple low-pass filter on the output increases its high-end rolloff to much more like an actual cab.  And a simple resistor in series with the wire that goes to the cab selection buttons (one resistor for each channel) can adjust the frequency notches to more like a real cab.

There are lots more other things you can do to make the MicroCabs almost identical to a real cab frequency response (at least close enough that your ears couldn't detect the difference) but some of them get more involved and provide additional control 'options' rather than improve the ones that are already there.  Just the simple additions mentioned above put the MicroCab responses closer than practically any of the analog cab sims available.

Here's a modded MicroCab with a slew of 'additions'...



That one has a switch for guitar or open-back (or bass) cab, a knob to adjust the cab resonance point from 125Hz to 240Hz (like a 4x12 to open 2x12), switches to tweak the mic types (bright, flat, mild to mimic the presence boosts some mics have), a mid-shift button to mimic Marshall style vs. American or German cabs, depth knobs that mimic the distance the mic is from the cab or the effect of multiple mics, and speaker baffle switches to mimic the effect of floating vs fixed baffles.
« Last Edit: Time Format by Casey_Butt »
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El Chiguete

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Re: Favorite vintage ADA cabinet simulator
« Reply #6 on: Time Format »

Rob get working on this!!!
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MarshallJMP

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Re: Favorite vintage ADA cabinet simulator
« Reply #7 on: Time Format »

That sounds interesting.Can you give some more details?
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Casey_Butt

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Re: Favorite vintage ADA cabinet simulator
« Reply #8 on: Time Format »

Sure.  I took the frequency responses of the MicroCabs and compared them to dozens of actual cab frequency responses that I either took myself or collected from a host of sources (other people's cabs, the FFTs of cab impulses, Axe FX models, etc).  Then I went about mimicking the responses of the cabs I wanted to emulate by tweaking the filters in the MicroCab and also adjusting some of its behaviours to be more accurate to the real things.  The "extra" features, like the resonance adjust, baffle type, depth, etc, were put in to mimic cabs that the existing circuit couldn't do without affecting some of it's other cab settings... so adjustment ranges were needed and pots and switches added for that.

I also added another circuit board in the MicroCab that adds more frequency notches to the existing response.  In stock form, the MicroCab has four major notches in the 4x12 settings.  A real cab has many notches - four major notches are sufficient, but there are also other, smaller, notches that characterise the response.  So I added 3 extra notch filters on an extra circuit board to match the cabs I was emulating.

But, the first thing that jumps out about the MicroCab is that its frequency notches (at points determined by the circuit) are too extreme.  The Ampulator is the same; the MP-2 cab emulation is different.  In practice, that doesn't matter a huge amount because the notches are very narrow at their peaks and only affect a narrow range of frequencies.  But it's an easy "fix" (add a resistor), so why not do it?  The next thing is that the MicroCab only has a 2nd order low-pass filter on the high-end roll-off.  Cabs roll-off more aggressively than that.  Some emulators have 5th order roll-offs but, from the real cab responses I have, that's too aggressive.  Most cabs roll-off more like a 3rd or 4th-order LPF, and that's easy to achieve in the MicroCab by simply adding one cap in the right place (and forming a 1st-order LPF in series with the existing filter = 3rd-order).

I wanted to better emulate open-backed cabs (or large and ported cabs) so I could use it with bass and get a more authentic Fender response.  So I added the cab type switch, which lets more bass through and attenuates the big resonance point that closed 4x12's have.  2x12's also resonate at higher frequencies than 4x12's (or, more accurately, they don't have a strong resonance point below ~240Hz), so I put in the pot to dial the resonance from 125 Hz (like a Marshall 1960B or big slant cab) to 240 Hz (like a typical 2x12).

The Mic switches are to account for the presence peak that some mics have (like the Shure SM-57), but others don't (like many condensers), and some are in the middle (like the original Sennheiser MD421).

Most closed-back cabs will have a major frequency notch at 500-625 Hz.  The mid-shift button accounts for that by shifting the major notch in that region around by ~125 Hz.  For instance, some Engl and Peavey cabs seem to notch lower, but Marshall and Mesa cabs usually mid-notch in the 600-620Hz range.

A single mic, up close to a 4x12 cab, will produce many deep frequency notches as the proximity of the speakers to the mic cause phase cancellations.  But as the mic is moved away from the cab the response will smooth out.  The summed response of multiple mics will also smooth out the response.  So the "Depth" controls dial the depth of the frequency notches up and down to mimic mic distance and/or multiple mics.

Floating baffle cabs don't have a pronounced notch in the mid-frequency range.  This is a large part of the reason why vintage cabs tend to be middier and honkier than modern cabs.  Plywood baffle boards don't have as strong a notch there as MDF boards, either.  So the "SPKR BAFFLE" switches control the depth of that notch to either be characteristic of a modern 4x12, a vintage style floating baffle board, or a plywood board 2x12/4x10.

I know that might all sound vague and arbitrary when laid out like that, so I'll try to post some example frequency responses.
« Last Edit: Time Format by Casey_Butt »
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Casey_Butt

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Re: Favorite vintage ADA cabinet simulator
« Reply #9 on: Time Format »

This is the response of a Peavey JSX 4x12 cab with four UK Celestion G12M-25 Greenbacks with an SM57 on-axis in the centre of the cap...



This is the response of a stock MicroCab...



This is the response of a modded MicroCab with the extra board added to produce the "mini notches".  (All the "extra features" controls are set to neutral so they aren't affecting the response)...


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Systematic Chaos

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Re: Favorite vintage ADA cabinet simulator
« Reply #10 on: Time Format »

...some totally awesome stuff...

WOW, that´s an interesting read and def something worth following! Could all that be integrated in one of MJMPs Monstercabs as well??
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rnolan

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Re: Favorite vintage ADA cabinet simulator
« Reply #11 on: Time Format »

Hey Casey, great read  :thumb-up: There's a temp fix for the time of post time/date issue (link in the news feed which cycles on top of home page), you need to set a time zone/display preference in your profile, I put some instructions in a post which the news thingy has a link to (hey Dante, we need to fix this LOL).
@SC, I daresay MJMP could indeed incorporate/integrate into his Monstercabs (seems very plausible (do I here some PMs going on LOL)).
So with the SM57 proximity, do you add some bass for the close mic proximity effect ?
Another mic worth emulating is a Bayer M88 (in my day often used for kick drum as is designed as a male vocal mic with 80hz enhancement).
From memory, Seni 421's were reasonably flat, also a popular tom mic, but hi SPL capable so good cab mic
57/58 obviously 5khz boost (presence/cut)
EV RE20 flattest of them all
It's great your doing it for real in analogue not using DSP.
And thanks for sharing  :wave:
Cheers R
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Casey_Butt

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Re: Favorite vintage ADA cabinet simulator
« Reply #12 on: Time Format »

WOW, that´s an interesting read and def something worth following! Could all that be integrated in one of MJMPs Monstercabs as well??

I think you'd have trouble fitting the additional board to make the mini-notches because it sits in the spot where the load resistors would be placed.  But if you could find the room to squeeze it all in there, there's no reason it wouldn't work.

Here's a gut shot of the modded MicroCab as I was doing the mods.  You can see the extra board on the right (it isn't mounted as of that photo, just laid there as I tested it)...



I didn't want to put in load resistors because I modded a Marshall Power Brake to more accurately mimic an actual speaker load.  So I didn't need the MicroCab to act as a load box.  I took frequency traces of some amps' outputs at their transformers and compared that to their behaviour when connected to various loads (actual speaker cabinet and a few load boxes and attenuators).  Then I tweaked the Power Brake to get the amps' signal at the amp's output transformer reacting the same.  Speakers don't provide a flat impedance, their impedance changes with frequency and that varying impedance is reflected back to the power amp and effects how amp reacts and distorts.  Some people actually prefer a flat resistive load rather than a real speaker (as evidenced by all the Palmer and 'big resistor' users like Satriani and Eddie Van Halen ;)), but I was going for maximum speaker load 'authenticity'.

Here's what a typical guitar speaker impedance curve actually looks like...



Here's the output of my Marshall JVM (at the transformer) through a 4x12 cab (two Celestion G12T-75s and two G12-65s in the cabinet)...



Here's the output of my Marshall JVM (at the transformer) through a resistive attenuator...



As you can see, the amp is reacting very differently through a resistive load... though, like I said, some people prefer that.  (And there are reasons for that, like no resonance at ~130 Hz and the high frequencies tend to sound 'smoother'.)

And here is the output of my Marshall JVM (at the transformer) through a Power Brake modded to mimic the load of my cabinet...



As you can see, that's just about dead-on.

So with the SM57 proximity, do you add some bass for the close mic proximity effect ?

The stock MicroCab already does that as much as you'd ever need it to with the "Thump" control. :)  I didn't need to touch that.

Quote
Another mic worth emulating is a Bayer M88 (in my day often used for kick drum as is designed as a male vocal mic with 80hz enhancement).
From memory, Seni 421's were reasonably flat, also a popular tom mic, but hi SPL capable so good cab mic
57/58 obviously 5khz boost (presence/cut)
EV RE20 flattest of them all
It's great your doing it for real in analogue not using DSP.

As someone with an engineering background, and having done my share of DSP courses, I understand that I shouldn't feel this way... but I don't feel entirely 'comfortable' with the idea of using DSP on guitar.  I have some very nice DSP-based effects (like reverbs, delays, modulation effects, and even overdrives/distortions) but given the choice, I still 'like' the idea of analogue more... except for maybe reverb, delay and chorus.  I think the less DSP you can use before the signal hits the board, the better.

I realize the SM57 is pretty much the industry standard for miking electric guitar cabs, but I wanted to give the uCab the option of mimicking different mics purely for the convenience of it.  Of course, you could accomplish the same thing with an EQ, but there was still a little space on the front so I thought, "Why not build it in?"  I just looked at the frequency responses of some popular guitar mics and tweaked the high-end to match.

I should also mention that I voiced the two channels of the uCab differently.  One is based around a particular set of cabs (a Marshall 4x12 with G12M Greenbacks on the Vintage 4x12 setting) and the other mimics different cabs (a Marshall 4x12 with G12-65s on the Vintage 4x12 setting).  Because there are enough settings to cover lots of bases there's also a Mesa-Boogie 4x12 with V30s in there, some Fenders, some bass cabs, etc.  I used probably 50 real cab responses to match them up as best I could.  Even the settings that had to be partially compromised for the sake of other settings with a few dB here and there on an EQ and you can nail them.
« Last Edit: Time Format by Casey_Butt »
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Casey_Butt

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Re: Favorite vintage ADA cabinet simulator
« Reply #13 on: Time Format »

I promised to post some samples in another thread, so here they are.

The first one is the raw signal through the uCab bypassed...
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Casey_Butt

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Re: Favorite vintage ADA cabinet simulator
« Reply #14 on: Time Format »

This is through the modded uCap, but before the extra board to produce the mini-notches was added.  The reverb is from a Lexicon MX300 set for a mild 'room' reverb.

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