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Author Topic: Concert Lead issue  (Read 362 times)

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Mmazurek

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Concert Lead issue
« on: October 19, 2018, 01:50:33 pm »

Hello everyone, first post.

I have a Red Knob Concert Lead that seems to work fine outside of two issues.

1- The Distortion knob turned up lowers the volume without adding any distortion
     (Distortion switch engaged)

2- The overall volume seems lower than most have suggested, even clean.
     (Can comfortably run the volume on 10 with and without boost engaged)
  It's loud, but not anything close to any of my other amps.

Everything else seems fine.


EdBass

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Re: Concert Lead issue
« Reply #1 on: October 20, 2018, 12:15:23 pm »

Not sure what the issue is with the distortion, sounds like it needs a qualified  tech to put it on a bench. As far as loud, what amps are you comparing it to?

Mmazurek

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Re: Concert Lead issue
« Reply #2 on: October 20, 2018, 04:27:39 pm »

I have at least a dozen other various amps around.  When anyone describes this amp, they always note the volume.  Wasn't my first impression.

I did check all the output transistors with a multimeter, and all seem OK.

Didn't see any obvious issues on the board (burn marks or broken solder joints, etc...).


I DID notice I can hit the input pretty hard with a pedal to get a bit more volume as well.  Just need to work out the distorion issue.

From everything I searched, I shouldn't need the pedal, but I may try grounding the distortion wire on the pedal switch to see if there's a difference.
I assumed the distortion switch is doin the same function, but maybe not.

EdBass

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Re: Concert Lead issue
« Reply #3 on: October 20, 2018, 09:30:52 pm »

The later Concert series should output  50-60 watts into an 8 ohm load, 100 watts into a 4 ohm load, and 200 watts into a 2 ohm load; although far wiser transistor minds than myself question the stability of those amps with a 2 ohm load.
A watt is a watt. Bench your amp and see if it's healthy.

I've only owned one transistor Sunn, so I can't speak for how "loud" they are, but the old tube amps definitely punch above their weight class. The reason the 60, 80, 120, or 150 watt Sunn tube amps got the reputation for being so loud for their rating is because they were rated very conservatively. Those ratings were the original hifi standard Dynaco ratings of minimum continuous between 20hz and 20,000hz, +/- 1 dB, at <.5% THD, uber clean, which is around "3" on an old Sunn tube amp's volume knob.

Crank one up into 5-10% distortion and they are actually putting out almost twice their rated power, and combined with the efficient AlNiCo JBL cabs (you couldn't buy an old Sunn tube amp without at least one of it's matched cabs) making for an extremely LOUD 60, 80, 120, or 150 watt amp - hence the well deserved reputation for Sunn amps being so freekin' loud.

Not sure if the Concerts are any louder than any other similarly rated transistor amp. As I said bench it; a watt is indeed a watt.
I think maybe the post Sundholm era Sunns, including the transistor Concert series, just kinda got grandfathered in under that "Sunn amps are LOUD" banner.

loudthud

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Re: Concert Lead issue
« Reply #4 on: October 20, 2018, 10:55:27 pm »

Try plugging that pedal into the power amp input on the back of the amp. If that won't go any louder, the problem is most likely in the power amp section. Is there DC on the output of the power amp? Do the speaker cones move in or out from their resting position when the amp is turned on or off?