SUNN SA-21

[u163367]

Hi all,

I bought an old SUNN SA-21 for about $50 recently. I needed a more powerful amplifier to run my keyboard through. I am currently using a PEavey 100 watt amp and it gets distorted when I turn up.

Anyway, this Sunn head is not putting out much volume at all and for a 600 watt hea it should be pumping some sound out. I am only running one channel at 200 watts into 4ohms, but it is not getting out the volume it should. Also, when I turn the volume all the way up it cuts out like there may be a short or something.
Is anyone familiar enough with these amps to know off hand what might be going on with it?

The guy who sold it to me said "300 rms STEREO - 600 rms MONO (the MONO switch in LOCKED - but can most likely be switched if you move the (internally) lock switch."

-Would this affect the sound since I am not running it at the full 600 watts? 

[u163367]

Another thing is, it starts clipping and the volume is not really that loud. Also, on the indicator the A channel indicator lights up, but the B channel only sometimes lights up. I plug into the A channel, I cut on the amp and both lights flash across, when I start to play sometimes both A and B channel lights will flash across at the same time, sometimes only the A will.

[u163367]

Well,

I took the amp into a guy to look at it today. He told me that it was putting out as much volume as it should. Seems weird to me since my 100 watt peavey gets way louder. I don't understand why. He said both channels work fine, so I guess it is just not a very loud amp. Maybe I should try to have someone else look at it?

Does anyone else know of something I could do to make the sound louder? Right now I am just plugging my keyboard dorectly intot he amp channel A. Could a mixing board or pre amp make increase the volume?

[cromag]

what kind of speakers are you trying to push with it?  maybe you mentioned and i missed it.   your speakers may not be efficient enough with that kind of power.   hence the clipping.  ??

[JoeArthur]

what kind of speakers are you trying to push with it?  maybe you mentioned and i missed it.   your speakers may not be efficient enough with that kind of power.   hence the clipping.  ??

Yeah, definitely - if you're not pushing the same speaker load, then no volume comparisons are valid.

If you're just thinking that 600 watts should sound six times louder than 100 watts... well, it don't work out that way even through the same set of speakers.

On the other hand, I've been finding out that Peavey does overbuild their power amps in terms of wattage. Their RMS wattage ratings are usually lower than what other manufacturers would state for the same amp.

[djc]

watts is something many guitarists do not understand.
common sense would state that 600 is 6 times louder than 100. 
SPL or volume is exponential.  so 500 watts is really only twice as loud as 15 watts.  roughly

every 3 dB raise in volume in effect doubles your percievable volume, so, going from 100dB (fairly loud) to 103dB (generally where most concerts are or slightly above ie 110) doubles your percievable volume.  but it also takes an incredible amount of power (watts) to get those 3dB at that level.  noise floor or ambient noise is generally around 50dB (ish).  not much power is required to double that volume to 53dB.

just a rabbit trail
happy hunting

[Isaac]

Sorry, djc, but you're confused.

A difference of 3dB is a doubling of power, but not a doubling of perceived volume. That takes 10dB, which takes ten times as much power. So 150 watts is twice as loud as 15 watts. 500 watts v 15 watts is 15dB, and will be noticeably more than twice as loud.

You're ruight that not many guitarists understand it. Not many other people do, either.

[u163367]

I'm playing through a huge Peavey 3020 HT that is 400 watts @ 4ohms (. I play through one channel so I am really only getting the 200 watts @ 4ohms out of the head. I was thinking of adding another cabinet, but I am also wondering how many watts and ohms it should be. If I am only playing through one cabinet do you think I am getting the full range of the music?

I also have just been plugging my keyboard straight into the A channel. I haven't tried running through a mixer yet which I was wondering maybe it would have more punch if I could adjust the mids and highs.

I love the sound I get out of the head, I am just drowned out by the rest of the band and I can't figure out why (I am new to playing 'plugged' but learning more everyday). Our band is LOUD. Thanks for the help!!


-Desiree

[Isaac]

You'll get the full range of the music if the cabinet you're playing through is a full range cabinet. As for being drowned out, I think you've answered that yourself: your band is LOUD! Another cabinet similar to what you're playing through now, powered by the other side of the amp, will make you significantly louder. That ought to be enough, I'd think.

[basiklybass]

Did I understand that yopu are plugging your keyboard directly into the Sunn SA-21?

Anyone know what the input of the SA-21 wants?

Unless I am mistaken, you need a preamp of some sort...a mixer or other such animal. It would make sense that if the amp is looking for an input voltage of say .7 volts...and your plugging directly in with a voltage of .1....or less...you will not get any sort of volume.

[djc]

Sorry, djc, but you're confused.

A difference of 3dB is a doubling of power, but not a doubling of perceived volume. That takes 10dB, which takes ten times as much power. So 150 watts is twice as loud as 15 watts. 500 watts v 15 watts is 15dB, and will be noticeably more than twice as loud.

You're ruight that not many guitarists understand it. Not many other people do, either.

yeah, I knew it was something like that. 
the point is that 600 watts is not 6 times louder that 100 watts, and a 15 watt guitar amp is plenty in a club.  60 watts is plenty for bass, however I prefer alot more for a bass rig.

[Isaac]

yeah, I knew it was something like that. 
the point is that 600 watts is not 6 times louder that 100 watts, and a 15 watt guitar amp is plenty in a club.  60 watts is plenty for bass, however I prefer alot more for a bass rig.

And in this you are quite correct.