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 #128913  by Pete B.
 Fri Jun 07, 2013 11:04 am
One other observation about the Mc's.
The two JBL-E120's I have happen to be 4-ohm, so if I run them in paralell, the Mc actually supports a 2-ohm load when bridged to Mono.
Nice!
Also, I have noticed that, in many cases (Ebay/Craigslist/Vintage-shops) vintage/original 16-ohm JBL''s are very inexpensive compared to 8-ohm models, and the Mc has a 16-Ohm tap right on the front. Nice!
 #129549  by JustinJohn
 Thu Jun 27, 2013 2:32 am
I've been reading some conflicting info regarding a "warmup" period required by McIntosh amps, specifically the MC250. Being solid state amps, I was under the impression these amps didnt require warming up... Can someone clarify this?

Thanks in advance!!

=)
 #129564  by NSP
 Thu Jun 27, 2013 6:28 am
JustinJohn wrote:I've been reading some conflicting info regarding a "warmup" period required by McIntosh amps, specifically the MC250. Being solid state amps, I was under the impression these amps didnt require warming up... Can someone clarify this?

Thanks in advance!!

=)
Yeah, there was a recent thread stating a theory that the larger caps require a long period of time (24hrs?) to fully charge and thus provide optimal tone. So, should one just leave it powered up all the time if used regularly? That seems plausible, but leaving my Mc250 powered up like that concerned me a bit.

So, I contacted Terry DeWick this morning. He recently worked his magic on my amp and I figured he would be able to shed some light on the subject. He was quick to reply and this is what he had to say:

"My philosophy is if not in the room it is OFF, I don’t like to leave valuable equipment unattended and adding to my electric bill and heat load. Once a month usage (minimum) is more important to long life and better sound than continuous on."

I guess that backed up what I was feeling, so mine will be off when not in use.

Peace
 #129570  by TI4-1009
 Thu Jun 27, 2013 7:18 am
NSP wrote:Yeah, there was a recent thread stating a theory that the larger caps require a long period of time (24hrs?) to fully charge and thus provide optimal tone. So, should one just leave it powered up all the time if used regularly? That seems plausible, but leaving my Mc250 powered up like that concerned me a bit.
Knowing very little about the subject he began talking anyway.... :-)

Do the caps in a solid state amp not hold their charge like they would in a tube amp? I know in many tube amps you have to drain the filter caps before working on the amp because they can hold their charge for a long time (unless they have that draining resistor).
 #129577  by schmidtz
 Thu Jun 27, 2013 8:26 am
The only thing that will affect a cap's dissipation is schematic specific. In theory, if a cap is charged and is not part of a closed circuit, it will hold its charge forever. In practice, all caps will slowly lose their charge. Like you said earlier, some are hooked up to a resistor which completes the circuit, and thereby drains the cap over time.

If all of this seems interesting, I would suggest taking a Electricity & Magnetism course (typically Physics 2) over at your local college! Essentially, the circuit we are discussing (NOT the full McIntosh circuit) is an RC (resistor-capacitor) circuit, and each one has a specific time that functions as the exponential charge decay value, denoted by the Greek letter "tau".
 #129578  by mgbills
 Thu Jun 27, 2013 8:41 am
To clarify the "Leaving it on" post...

That was my post. I think the SS Mc's do sound marginally better when left on. But amongst the 2 audiophile repair guys I contacted, I recieived 2 diffent answers. 1) Leave it on. 2) Leave it off when not in in use. Run it at least once a year so you don't ruin the caps.

I posted it to see if someone with fancier ears than mine could do a study. I left mine on for a week...and then the treehugger in me couldn't bare it. (...or bear it??).

Regard or disregard as your personal preference dictates. At this point science (and Pat Hickman) appear to be in the "Turn it off" camp.

Sorry for any confusion.
M
 #129585  by TI4-1009
 Thu Jun 27, 2013 9:47 am
Tip from Lovelight:

"AND LEAVE IT ON!"

(and it's bear- bare it around here and you could get arrested...)
 #129594  by JustinJohn
 Thu Jun 27, 2013 12:09 pm
thanks for the replies guys! Currently I've had mine on for about 3 days - I play a show this Saturday (big show on a big stage in Portland with our friends Shafty - local Phish tribute act - https://www.facebook.com/events/331236537004499/) - So I wanted to make sure the MC is ready to go for that gig.

I'm not honestly sure that I can tell the difference when the MC is "warmed up" (after being on for a few hours), but I think it sounds more seasoned after this time.... or maybe my ear adjusts... I'm not sure.
 #129602  by TI4-1009
 Thu Jun 27, 2013 1:41 pm
Some have the same opinion about tube amps- that they sound better after being on for a few hours. My old ears sure can't hear it.
 #154587  by kurt eye
 Sun Nov 20, 2016 6:32 am
mijknahs wrote:It looks like that has to be wired in parallel. So if you are using only one channel separately (switch on "stereo") you would use the 4 ohm tap and the appropriate input. As Pete B. does, you could also run each speaker from separate channels (8 ohm tap - still on "stereo" setting) but you would need to run a signal into both inputs (split your single preamp signal into two cables).

If you bridge the channels, you would bridge the 8 ohm taps together (and com taps together) and flip the switch to "mono". Then the 8 ohm taps would "become" a 4 ohm tap. You could hook up to either side since they are bridged. I think its the right channel input and gain knob that would contol it.
I'll be receiving my first McIntosh MC 250 in a couple of days and have a couple of questions:

1. Besides independent volume control, when using 2 speakers is there any advantage/disadvantage to using a split preamp signal and running a speaker off of each channel in stereo mode vs bridging and running speakers in parallel?

2. Would anyone mind posting a pic or two of their 1/4 jack input and output mods?

Thanks
 #154603  by Searing75
 Sun Nov 20, 2016 5:59 pm
It's a two channel amp. No need to bridge. Just run one speaker on each side. Stereo. Independent volume controls.
 #154604  by waldo041
 Sun Nov 20, 2016 6:27 pm
Just guessin', but wouldn't the input volume controls be in parallel thus halving their resistance? If so, wouldn't this change the knee of the high pass filter that is created with the preamps output capacitor and that resistance? probably not that much of a difference with the fenders stock .1uf output capacitor, but when that cap is lowered i believe their could be an audible difference.




~waldo
 #154610  by Searing75
 Mon Nov 21, 2016 4:59 am
The inputs are isolated from one another? Right? Perhaps not? I have only ever worked on a mono MC50. I'm just assuming here.
 #154623  by Searing75
 Tue Nov 22, 2016 4:58 am
Yeah. Set it to stereo, and you have two independent Amps.

I wouldn't split your pre amp signal though. Just run it mono in, and send that signal to both amp channels feeding separate speakers. One input. Amp set to mono mode. Each speaker will see one half of The amp. 50watts. Probably a bit more actually.
Last edited by Searing75 on Tue Nov 22, 2016 10:50 am, edited 1 time in total.