[mgbills]

Good Morning,

I was reworking some minutiae on my rack yesterday. I have it in my head, that in a prior configuation I had a little less noise. It actually has very little compared to my other amps, but thought I'd test some small moves. I moved the SMS farther away from the Mc250 for starters. Thought perhaps the tubes would pick up interference from the transformers. I also had some suspicians about the first channel on the GCX.

Then I realized...I have Speaker cable going from the SMS to the Mc. I just went back to the SMS manual and it says "guitar-type", which I would assume is be best served with a high quality (Mogami or Canare) cable. I guess what had me confused is the "Hot" signal statements.

I'd love to hear the detail on this. What are others doing?

Mr. Sarno?
Peace
M

[TRG]

Hey there - I just have Mogami guitar cable (with 1/4 y-split going into the MC250) and don't have any issues with noise at all.

[Quarterpounder]

A speaker cable is only used between the speaker and the final power amp in the chain. If you work or think of it backwards, the only speaker cable ever in the chain is speaker to the power amp. All others in the chain are guitar type cable. A speaker cable has equal size wire on both negative and positive(like a lamp cord). With a guitar cable, the middle wire(postive) carries the signal with the outer wrap(negative) dumping the garbage(interference) to the ground(literally). Hope this helps.

[mgbills]

Thanks. I do understand the difference, but am a little confused when it comes to "Line Level." I know the pickup signal is of very low voltage, and understand what shielding that signal (hopefully) accomplishes. I twisted it up in my brain. I started thinking about the 2 gain stages in the SMS pre. Also, I didn't know whether the pot on the back was set up as strickly an attenuator, or if it had gain attached. I'm a bit fuzzy on the voltages between preamp & power stage on a standard combo-type chassis.

That's where I confused myself. Shouldn've just re-read the manual.

Thanks to all.

[SarnoMusicSolutions]

Definitely use shielded guitar-type or audio signal cable from the preamp to the Mac. It's hot line-level, but guitar cord is exactly the type of cable you want in an unbalanced, line-level situation like that.

The rear knob on the SMS Classic is a passive attenuator. Fully cranked, the preamp is just like a real Twin preamp. But since that signal is inherently SO super hot, I added a pot there so people could tame it down to match with some amplifiers. The McIntosh amps have a pot at their input so they can handle anything. With a Mac, you'd want to crank the rear SMS knob and use the Mac's input knobs to dial in a "master" level.


Brad

[mgbills]

Thanks Brad! I knew there was a design plan. I used a cheap cable for tonight. Out of quality cable ends. It already eased the minimal noise problem.

Much appreciated.
Marty

[SarnoMusicSolutions]

Shielding is the main issue here. Any shielded audio cable is gonna be fine there, but sure something decent, Belden, Canare, Mogami, is a nice way to go.

B

[tcsned]

I've been using a relatively cheap 1/4" to RCA cable to go from the SMS to the Mac and I've not noticed any noise issues. I got it from Radio Shack. I've got a little nicer one, heavier cable, gold connectors and sounds the same (I don't use it because it is a stereo cable and I'm only using half of the MC2100 right now). It's short though, only 3' so it'd probably make more of a difference if it was longer.

The one thing I have noticed was that originally I had the SMS at about 3/4 cranked, at my last gig I noticed that it wasn't up all the way so I turned it all the way up and it seemed to make a big difference in the tone. Man, I've used a lot of really nice amps and I've never been so blown away by my guitar tone as I have with this one.

[mgbills]

Gotta say...I love this stuff. The whole rack thing is a much bigger deal than an assembly of parts, as I'm sure any of you seasoned players would surely attest. I had my SMS choked. Before I changed that 1 (not so silly) cable, I'd bring the trim-pot up only until the noise was apparent. Then I'd throttle up the Mc. As I originally stated, it was never really noisy...I'm just fussy.

After these last posts...I can't wait to crank that sukka! A while ago I was playing regularly with a LOUD drummer. I would have my 250 cranked, and it was just enough. Last night I had the trim-pot to 1:00 (as I believe it says in the manual), and whoa....there's my volume. No noise. Tons of headroom.

Details. Details. Details.

Thank you all....Sincerely. I really dig this journey.
M

[TRG]

I have the rear trim pot maxed, the gain about 10:30 and the mac (both sides in stereo) set to about 10:00 and I can get plenty of volume...with much much more available!

Absolutely love the sound I get out of the SMS/MAC combo!

[mgbills]

Max the POT! Max the POT!
(Maybe I should make a crytic t-shirt!)

Made a short Mogami/Amphernol cable last night.

Now un-strangled Mc250 is on about 8:00 for garage volume. Love the tone. There is still very minor noise at idle. I'm still wondering about the #1 loop on my GCX. I have way more Uuuumph/noise unit now. Very low. Maybe I need to make a tin-foil hat for the fluorescents in my man-shed.

Thanks Everybody. Help appreciated.
Peace
M

[NSP]

Max the POT! Max the POT!
(Maybe I should make a crytic t-shirt!)

Made a short Mogami/Amphernol cable last night.

Now un-strangled Mc250 is on about 8:00 for garage volume. Love the tone. There is still very minor noise at idle. I'm still wondering about the #1 loop on my GCX. I have way more Uuuumph/noise unit now. Very low. Maybe I need to make a tin-foil hat for the fluorescents in my man-shed.

Thanks Everybody. Help appreciated.
Peace
M

I have an SMS > MC250 combo as well and have been experimenting with the settings. Initially I didn't have the rear attenuator cranked on the pre but did so after reading this thread. Sounds awesome and increases the headroom substantially on the Mac...but, it seems to be messing with the Qtron. It seems the signal is too hot and the Qtron distorts. Has anyone else noticed this with their EF, or is my Qtron flaking out on me?

[tcsned]

I have an SMS > MC250 combo as well and have been experimenting with the settings. Initially I didn't have the rear attenuator cranked on the pre but did so after reading this thread. Sounds awesome and increases the headroom substantially on the Mac...but, it seems to be messing with the Qtron. It seems the signal is too hot and the Qtron distorts. Has anyone else noticed this with their EF, or is my Qtron flaking out on me?

Are you using a unity gain buffer and an OBEL? That combo seems to tame the wild envelope filter.

[NSP]

I have an SMS > MC250 combo as well and have been experimenting with the settings. Initially I didn't have the rear attenuator cranked on the pre but did so after reading this thread. Sounds awesome and increases the headroom substantially on the Mac...but, it seems to be messing with the Qtron. It seems the signal is too hot and the Qtron distorts. Has anyone else noticed this with their EF, or is my Qtron flaking out on me?

Are you using a unity gain buffer and an OBEL? That combo seems to tame the wild envelope filter.

Yeah, should have mentioned....I do have Waldo's buffer and OBEL on my PRS with DAllen VooDoo pups.

-Tim

[NSP]

I have an SMS > MC250 combo as well and have been experimenting with the settings. Initially I didn't have the rear attenuator cranked on the pre but did so after reading this thread. Sounds awesome and increases the headroom substantially on the Mac...but, it seems to be messing with the Qtron. It seems the signal is too hot and the Qtron distorts. Has anyone else noticed this with their EF, or is my Qtron flaking out on me?

Are you using a unity gain buffer and an OBEL? That combo seems to tame the wild envelope filter.

Yeah, should have mentioned....I do have Waldo's buffer and OBEL on my PRS with DAllen VooDoo pups.

-Tim

Oh, also same results with 2x12 with K120's and 1x12 with E120.