Microtube 200 Procured -- Getting Some Feedback

[uraniumwilly]

I recently bought an MT200 and, generally speaking, all is well.

I do have a personal problem though, I like to crank things. When I liberally turn up the volume on the unit I often get feedback.

It's being fed by an MP-1 into the mono-bridged config into a GCS-3 cab sim pedal with the input pad on. I suspect I'm pushing it a bit.

Just curious if the feedback thing is normal. The rig always behaves when I don't push the MT200 vol.

BTW, it's all been a pleasant surprise. This tube-on-tube tone, that is. Good stuff.

[rnolan]

Hey uraniumeilly, Just to confirm, MP-1 > MT200 (bridged mode) > GCS-3 > ? (headphones?, DAW input?, ??? ).
First thing to note from the manual (Please note that the GCS-3 is NOT A LOAD BOX, and the power amplifier must remain connected to the speakers or have a proper impedance load connected to it in place of the speakers.) So the Thru output needs to be plugged into a cab or a load box (that provides the same load the cab would (minimum 8 ohms for MT200 in bridged mode)) or you risk damage to the output stage of your MT200.  If you just used one of the MT200 speaker outs (in stereo mode), you need to have either a load box or a speaker cab connected to the GCS-3 Thru out (so the amp "sees" a load).  The amp needs a speaker load (cab or load box) or the output stage will blow up.
The GCS-3 lets you "peel off" a cab emulated signal to feed line level things (e.g. mixer input, DAW input, full range powered speaker etc).  So I'm guessing you want the amp sound as well as the preamp sound in your cab emulated signal.  This is fine but you must have a load on the amp.  For on stage the GCS-3 is designed to go between either the preamp out and your amp (and feed the cab emulated signal to the PA or full range monitor) or between you amp output and a cab to "peel off" that signal for the PA or full range monitor but still feed the cab.  Some feedback is normal at high volumes just like when you crank up a guitar amp, and they emphasize that in the manual.  I suspect that this is because some cab emulators  don't have any/much feedback like you normally get on stage when it's cranked.

[uraniumwilly]

Hey thanks a million for the response and looking that up in the manual.

I bought the GCS-3 unit off craigslist, sans manual, and am generally clueless about amp load management. I should have been more suspicious since load units are expensive.

The 200 popped into standby yesterday. It wasn't powered up for very long. It seems to be OK, but I've learned my lesson!

I ordered a high end reactive load unit that is not supposed to ship until the 3rd week of November. Until then I'll let the 200 rest.

It sure sounded good through the GCS-3 -- while it lasted. I'm real happy with the sound.

Thanks again. You probably just saved my 200 from some serious, stupid abuse.

[rnolan]

No worries, as luck would have it, the MT200 has a protection circuit which saved it for now  .  I just looked through the MT200 manual (attached) and the mono bridged out is a single 1/4" jack (so this advice (prev post) was incorrect: Alternately, you could put a load box on one of the MT200 speaker outs and use the other to feed the GCS-3 (with -30 pad "in") but only in bridged mode. ).  So to connect the load (min 8 ohms) plug the MT200 mono/bridged out > GCS-3 in (-30db pad) and the GCS-3 Pass Thru output into the load unit.  The GCS-3 In and Pass Thru are directly connected so this way the amp will "see" the load  .  I've also attached the GCS-3 manual for you, though you can also download it from the A/DA site (https://www.adaamps.com/gcs-3)

[uraniumwilly]

Hey, you are one very thorough gentleman. And you're so kind to read these manuals and post them. I am much informed!

Enormously helpful stuff. I'll have a look at the attachments.

Thanks so much.

[rnolan]

We like to help  :wave:

[MarshallJMP]

Rnolan is the manual specialist over here  ;D

[uraniumwilly]

Well, hats off to you guys.

Very cool.