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  • Power amp question

    Can a power amp be damaged in such a way that it will still produce output, but all of that output will be clipping/square waves, thus damaging every speaker it touches, so to speak?

    I ask because I want to make sure I can blame my ****************ty old speakers instead of the amp, before I hook new, better speakers up to it.

    (long story short, see http://acapella.harmony-central.com/forums/showthread.php?s=&threadid=968558&highlight=MOSFET +2000M ) There was a much longer thread about that amp (The general idea I got, I think, was that it was a decent amp, if a bit old and outdated), but the recent post-count killing purge seems to have wiped it out.
    <div class="signaturecontainer">Member of the HCBF P-bass Club<br />
    Member of the HCBF Tube Amp Club<br />
    <br />
    <font size="1">[on curly patch cords] They would look cool if you were playing a telephone. - Joey Joe Joe<br />
    that and i play with more treble than jesus - Zeromus-X<br />
    if I had to think like Madonna or choose a frontal lobotomy, I'd go with the choice that woul leave me with the highest IQ. &quot;Oh surgeon.......&quot; - lug <br />
    i know that &quot;vintage&quot; is supposed to translate into better tone, but i guess i dont have expensive enough ears - 77mustangman <br />
    i broke a string once, back in '68 - jpt<br />
    Sometimes during one of our longer jams, I will build an effigy of Little Debbie out of sugar cubes and then simulate a sex act with it. Brings the house down every time. - catphish<br />
    it took about 4 seconds of playing and I just wanted to lie down on it and gyrate slowly but they said I had to buy it first. - Duggimon <br />
    I like to just go in, plug into the biggest amp I can find, dime the volume, and just drop the bass on the floor. - TwYzTyR<br />
    </font><br />
    <a href="http://www.myspace.com/tomcatcombat" target="_blank">Tomcat Combat</a><br />
    </div>

  • #2
    If it goes DC,I believe it will kill anything connected to it.
    <div class="signaturecontainer"><a href="mailto:tlbonehead@yahoo.com">tlbonehead@yaho o.com</a><br />
    <a href="http://www.myspace.com/tbone_tommy" target="_blank">www.myspace.com/tbone_tommy</a><br />
    -For Sale: <br />
    -set of GFS Dream 90s- gold and black pearl- $40 shipped in the cont. US<br />
    -(2) Celestion G12M-70 16 ohm guitar speakers in good condition $40 ea. + shipping.<br />
    - Vox VT15 Valvetronix very clean - $85 + shipping<br />
    - Hughes Kettner Edition Tube 20 (the early Voxy sounding one) Sounds &amp; looks good. $250 + shipping. <b>SOLD</b><br />
    - Crate Palomino V8 - 10&quot; Celestion - Very clean - on Ebay (sold)</div>

    Comment


    • #3
      An unfortunate possibility with any amp, but seemingly more common with MOS-FET technology amp is the occurance of oscillation, an unwanted high frequency signal that can destroy both speakers and power amps in a hurry.

      Have a qualified amp tech evaluate your problem to eliminate this possibility.

      Comment


      • #4
        Will (in either case) the amp do this when it's not recieving an input signal? ie, if I just plug it in to to the speakers and turn it on, will it damage the speakers? I don't mind wrecking the old ones...
        Also, would a limiter/compressor do any good? or is is a frequency thing and not an amplitude thing (in the case of oscillation)
        <div class="signaturecontainer">Member of the HCBF P-bass Club<br />
        Member of the HCBF Tube Amp Club<br />
        <br />
        <font size="1">[on curly patch cords] They would look cool if you were playing a telephone. - Joey Joe Joe<br />
        that and i play with more treble than jesus - Zeromus-X<br />
        if I had to think like Madonna or choose a frontal lobotomy, I'd go with the choice that woul leave me with the highest IQ. &quot;Oh surgeon.......&quot; - lug <br />
        i know that &quot;vintage&quot; is supposed to translate into better tone, but i guess i dont have expensive enough ears - 77mustangman <br />
        i broke a string once, back in '68 - jpt<br />
        Sometimes during one of our longer jams, I will build an effigy of Little Debbie out of sugar cubes and then simulate a sex act with it. Brings the house down every time. - catphish<br />
        it took about 4 seconds of playing and I just wanted to lie down on it and gyrate slowly but they said I had to buy it first. - Duggimon <br />
        I like to just go in, plug into the biggest amp I can find, dime the volume, and just drop the bass on the floor. - TwYzTyR<br />
        </font><br />
        <a href="http://www.myspace.com/tomcatcombat" target="_blank">Tomcat Combat</a><br />
        </div>

        Comment


        • #5
          Originally posted by megadan
          Will (in either case) the amp do this when it's not recieving an input signal? ie, if I just plug it in to to the speakers and turn it on, will it damage the speakers? I don't mind wrecking the old ones...
          Also, would a limiter/compressor do any good? or is is a frequency thing and not an amplitude thing (in the case of oscillation)
          Don't take my word as absolute truth but common sense would tell me that it wouldn't matter if anything was plugged into the inputs on the amp and therefore it wouldn't matter if there was a comp/limiter in front of the amp. The problem seems to be inside the amp,therefore,beyond the amp's inputs. But I don't really have any knowledge,that's just what my common sense tells me. but take the words of the knowledgeable ones here over mine on this.
          <div class="signaturecontainer"><a href="mailto:tlbonehead@yahoo.com">tlbonehead@yaho o.com</a><br />
          <a href="http://www.myspace.com/tbone_tommy" target="_blank">www.myspace.com/tbone_tommy</a><br />
          -For Sale: <br />
          -set of GFS Dream 90s- gold and black pearl- $40 shipped in the cont. US<br />
          -(2) Celestion G12M-70 16 ohm guitar speakers in good condition $40 ea. + shipping.<br />
          - Vox VT15 Valvetronix very clean - $85 + shipping<br />
          - Hughes Kettner Edition Tube 20 (the early Voxy sounding one) Sounds &amp; looks good. $250 + shipping. <b>SOLD</b><br />
          - Crate Palomino V8 - 10&quot; Celestion - Very clean - on Ebay (sold)</div>

          Comment


          • #6
            Amplifier oscillation problems are a fault (either design or component) within the inside of the amplifier. Nothing can help this as it's an equipment fault (if that is what's truely happening).

            Comment


            • #7
              Another question, hopefully not to derail this thread too much-But, if I have a clipped signal several units before the power amp, does it still have the ability to fry a speaker? In other words, if I clip the signal at the board, but the EQ and Comp (or anything else) is at unity gain, will it still fry the speaker?

              My guess is that it still will since the square wave is still hitting the amp regardless of input gain???

              Thanks for your patience!!!

              Johnny

              Comment


              • #8
                Originally posted by JohnnyGraphic
                Another question, hopefully not to derail this thread too much-But, if I have a clipped signal several units before the power amp, does it still have the ability to fry a speaker? In other words, if I clip the signal at the board, but the EQ and Comp (or anything else) is at unity gain, will it still fry the speaker?

                My guess is that it still will since the square wave is still hitting the amp regardless of input gain???

                Thanks for your patience!!!

                Johnny
                I think you have been fed somewhat of an old wive's tale.
                <div class="signaturecontainer"><a href="mailto:tlbonehead@yahoo.com">tlbonehead@yaho o.com</a><br />
                <a href="http://www.myspace.com/tbone_tommy" target="_blank">www.myspace.com/tbone_tommy</a><br />
                -For Sale: <br />
                -set of GFS Dream 90s- gold and black pearl- $40 shipped in the cont. US<br />
                -(2) Celestion G12M-70 16 ohm guitar speakers in good condition $40 ea. + shipping.<br />
                - Vox VT15 Valvetronix very clean - $85 + shipping<br />
                - Hughes Kettner Edition Tube 20 (the early Voxy sounding one) Sounds &amp; looks good. $250 + shipping. <b>SOLD</b><br />
                - Crate Palomino V8 - 10&quot; Celestion - Very clean - on Ebay (sold)</div>

                Comment


                • #9
                  Originally posted by tlbonehead
                  I think you been fed somewhat of an old wive's tail.


                  Not quite.

                  A cliped signal is a clipped signal, reguardless of where in the signal path it is created. An amplifier reproduces what you feed it, only at a higher level. If you feed it a clipped signal, it'll output a clipped signal.

                  Comment


                  • #10
                    One of my first bad experiences in that respect was an amp going dc while practicing. I instantly plugged into another speaker to see if the amp was still working and lost that as well. You plug in the speaker and it sounds like a bit of a hum / buzz backgroundy noise.... that's your voice coil frying!

                    Comment


                    • #11
                      Originally posted by bigmike216


                      Not quite.

                      A cliped signal is a clipped signal, reguardless of where in the signal path it is created. An amplifier reproduces what you feed it, only at a higher level. If you feed it a clipped signal, it'll output a clipped signal.
                      Yes,obviously. However,speakers can usually handle a clipped signal if it isn't above their capability. It has been perpetuated that a clipped signal is a guaranty that you are going to fry VC's.
                      <div class="signaturecontainer"><a href="mailto:tlbonehead@yahoo.com">tlbonehead@yaho o.com</a><br />
                      <a href="http://www.myspace.com/tbone_tommy" target="_blank">www.myspace.com/tbone_tommy</a><br />
                      -For Sale: <br />
                      -set of GFS Dream 90s- gold and black pearl- $40 shipped in the cont. US<br />
                      -(2) Celestion G12M-70 16 ohm guitar speakers in good condition $40 ea. + shipping.<br />
                      - Vox VT15 Valvetronix very clean - $85 + shipping<br />
                      - Hughes Kettner Edition Tube 20 (the early Voxy sounding one) Sounds &amp; looks good. $250 + shipping. <b>SOLD</b><br />
                      - Crate Palomino V8 - 10&quot; Celestion - Very clean - on Ebay (sold)</div>

                      Comment


                      • #12
                        Originally posted by tlbonehead
                        I think you been fed somewhat of an old wive's tail.


                        You meant TALE, did'nt ya? I'd hate to be force fed grandma's ass

                        V.

                        Comment


                        • #13
                          Originally posted by gruvjack


                          You meant TALE, did'nt ya? I'd hate to be force fed grandma's ass

                          V.
                          Oops! No,there was no MILF pun intended there.
                          <div class="signaturecontainer"><a href="mailto:tlbonehead@yahoo.com">tlbonehead@yaho o.com</a><br />
                          <a href="http://www.myspace.com/tbone_tommy" target="_blank">www.myspace.com/tbone_tommy</a><br />
                          -For Sale: <br />
                          -set of GFS Dream 90s- gold and black pearl- $40 shipped in the cont. US<br />
                          -(2) Celestion G12M-70 16 ohm guitar speakers in good condition $40 ea. + shipping.<br />
                          - Vox VT15 Valvetronix very clean - $85 + shipping<br />
                          - Hughes Kettner Edition Tube 20 (the early Voxy sounding one) Sounds &amp; looks good. $250 + shipping. <b>SOLD</b><br />
                          - Crate Palomino V8 - 10&quot; Celestion - Very clean - on Ebay (sold)</div>

                          Comment


                          • #14
                            Originally posted by JohnnyGraphic
                            Another question, hopefully not to derail this thread too much-But, if I have a clipped signal several units before the power amp, does it still have the ability to fry a speaker? In other words, if I clip the signal at the board, but the EQ and Comp (or anything else) is at unity gain, will it still fry the speaker?

                            My guess is that it still will since the square wave is still hitting the amp regardless of input gain???

                            Thanks for your patience!!!

                            Johnny


                            Absolutely correct... except as it's been pointed out, total power level of the pre-clipped signal does matter.

                            The speaker's thermal rating must be "de-rated" appropriately in order to account for the additional heat in the squared off signal. On many drive units, mechanical issues may also come into play.

                            With a conservatively (or accurately) rated driver, a 50% derating is customary. This IS in fact considered when calculating power ratings of electric guitar speakers that are used with distorted signals.

                            For high frequency driversm another phenomona comes into play, the clipped signal contains a higher % of HF information due to harmonics. Additional derating is necessary... say ANOTHER 50% or so.

                            Comment


                            • #15
                              semi-related to this supposed wives tale is my pondering of, 'why don't all good PA's use all tube power amps?' - if indeed clipping causes speaker destruction, and since tube cliping doesn't seem to kill speakers, then it seems like a logical idea.

                              The answer to my own question, is, of course, the massive size, weight, heat, cost, and reliability of all tube power amps (24, 36 6L6's! )



                              I will however attempt to sacrific one speaker and listen for the VC's frying
                              <div class="signaturecontainer">Member of the HCBF P-bass Club<br />
                              Member of the HCBF Tube Amp Club<br />
                              <br />
                              <font size="1">[on curly patch cords] They would look cool if you were playing a telephone. - Joey Joe Joe<br />
                              that and i play with more treble than jesus - Zeromus-X<br />
                              if I had to think like Madonna or choose a frontal lobotomy, I'd go with the choice that woul leave me with the highest IQ. &quot;Oh surgeon.......&quot; - lug <br />
                              i know that &quot;vintage&quot; is supposed to translate into better tone, but i guess i dont have expensive enough ears - 77mustangman <br />
                              i broke a string once, back in '68 - jpt<br />
                              Sometimes during one of our longer jams, I will build an effigy of Little Debbie out of sugar cubes and then simulate a sex act with it. Brings the house down every time. - catphish<br />
                              it took about 4 seconds of playing and I just wanted to lie down on it and gyrate slowly but they said I had to buy it first. - Duggimon <br />
                              I like to just go in, plug into the biggest amp I can find, dime the volume, and just drop the bass on the floor. - TwYzTyR<br />
                              </font><br />
                              <a href="http://www.myspace.com/tomcatcombat" target="_blank">Tomcat Combat</a><br />
                              </div>

                              Comment

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