I wanted to double-check the required ohms settings when using a PS2A in the switched loop of the ZMACS. I read the manual, but I’m still a big confused with when to use the BYPASS OVERRIDE MODE on the ZMACS.
I have a 16ohm head and 16 ohm cab. The ZMACS is set to 16 for the amp and 16 for the cab.
Do I need to turn on BYPASS OVERRIDE MODE (engaging the matching transformer)? What happens if I don’t?
The manual says to set the amp and cab ohms settings on the PS2A to 8 ohms. Is that correct, even with everything else being 16ohms?
What happens when I run 4, 8 and 16 ohm amps and cabs? Which Bypass mode do I use? Does the PS2A still stay at 8ohms no matter what?
Thanks!
I am assuming because the matching transformer is engaged, keeping the PS2A at 8ohms for amp and cab is ok?
When the ZMACS AMP and CAB impedance buttons are set the same, meaning, 4/4, 8/8 and 16/16, the internal matching transformer is bypassed AUTOMATICALLY. This is DEFAULT Impedance bypass override mode.
So what is BYPASS OVERRIDE MODE?
You can use this mode when you have an attenuator in the loop. I believe the manual is intentionally vague on what is going on because it is related to the design of the ZMACS transformer. But the advice is clear and only do this if you amp and cabs have the same impedance 4/4, 8/8, 16/16
Set Power Station to 8 ohms on both AMP IN and SPKR OUT
Set the AMP and CAB impedance on ZMACS to match the selected amps and cabs (16 and 16 in your case)
Thanks for the reply and answers. I think I am still curious about a few things…
When running a 16ohm head and cab, the instructions say to use BYPASS OVERRIDE MODE (engaging the matching transformer), but “only do this if you amp and cabs have the same impedance 4/4, 8/8, 16/16”. I don’t really get the point of that because when using DEFAULT MODE where the transformer is out of the circuit, they are matched anyways. Is BYPASS OVERRIDE MODE only needed when using the Power Station (set to 8ohms) in the attenuator loop? Why not then just set the power station to 16 ohms to match the head and cab?
I know you are looking into this - but curious how I will run the zmacs and powerstation when mix and matching heads and cabs of different ohms. Do I use BYPASS OVERRIDE MODE and leave the Power Station on 8ohms even when the amp and cab ohms will change?
For an example: say I have a 16ohm head, 8ohm head, and 4ohm head and a 16ohm and 8 ohm cab and mix and match them all. Do I use DEFAULT or BYPASS OVERRIDE MODES? What do I set the Power station to? What if I only use the powerstation with one or two of the amps and not all of them?
Thanks for the help! Loving these products and the options they open up.
These are real-life rig questions, and after reading the manual and your initial answers, there are lots of grey areas or a lack of clarity with certain rig possibilities that I laid out. I own lots of high end vintage amps that I plan on using with this stuff life and in the studio, so that is why I am looking for clarity and not going to leave the safety of my amps to statements like “If you are not surprised by what you hear, well, sometimes it’s OK to not be a total gear nerd”. They may be redundant questions as I still need clarity or certainty even, but it’s only because I don’t want to have to make the YouTube video “Fryette gear blew up my '66 JTM45”.
This is still a critical question I need clarity on. I know you said you were going to look into this. My current understanding is:
If I have a 16ohm head and 16ohm cab, I should turn BYPASS OVERRIDE MODE on (engaging the matching transformer) and keep the power station amp/cab on 8ohms. Is this correct?
If so, I am guessing that is because the engaging transformer will take care of the impedance mismatch between the 16-ohm amp/cab and the 8-ohm power station?
If I have a 4ohm head (62 Blonde Bassman lets say) into a 16ohm cab, I keep the bypass in its DEFAULT MODE (not bypass override mode), which also engages the matching transformer to match 4ohm head to 16ohm cab - do I still keep the power station amp/cab settings at 8ohms?
My current understanding is to ALWAYS run the power station amp and cab settings at 8ohms, regardless of whatever the amp and cabs are. Is this correct?
Again, sorry if these feel like redundant questions, but the manual and rig diagrams (which don’t have hypothetical ohms of the heads and cabs) don’t give me enough clarity or confidence on these questions.
Here is what you should do in the case of using an attenuator and having different impedance amps and cabs. For example, 4 Ohm head and a 16 Ohm cab:
Select amp impedance on ZMAC to match the amp
Select speaker impedance on ZMACS to match the speaker
Select Power Station input impedance to be 8 Ohms (AMP IN)
Select Power Station ouput impedance to be 8 Ohms (SPKR OUT)
The manual is pretty clear on this (after reading it again).
… the proprietary design of the ZMACS transformer helps mitigate the effect of an attenuator induced impedance mismatch. To take advantage of this feature, first set the AMP and CAB impedance to match the selected amps and cabs… If using a Power Station PSA-1, PS-2, PS-2A or PS-100, set both the AMP IN and SPEAKER OUT impedance switches to 8 OHMS.
ZMACS knows what is connected to it and it can match both the amp and speaker independently.
So in summary to your questions:
Yes.
Yes. don’t do anything special; this will be handled automatically.
Yes, this is what the ZMACS expects so that it can do its matching magic.