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  • Speaker out jack...

    I have a few questions concerning the speaker out jack on a tube amp (8 ohm speaker), 22 W amp.

    I've read many threads on this, but none have nailed it.

    1. What is the jack's main purpose?

    2. When you plug in an external speaker into the jack, does it disable the internal speaker?

    3. Can you unplug the internal speaker and then plug in an external speaker to the speaker out jack?

    4. If plugging in an external speaker disables the internal speaker, what's the point of having an external
    speaker jack? Why not just unplug the internal speaker and plug the ext. speaker into the internal
    speaker jack?

    5. Finally, what is the modification to the external speaker jack that allows line-in recording?

    TIA!


  • #2
    1: to allow a second cabinet
    2: On some amps yes...on others, no. It comes down to impedance balancing. If you check the manual on your amp it will tell you if the external speaker has to be a certain impedance.
    3: yes, just match the impedance and the power handling capability of the external speaker
    4: seems dumb, doesn't it, but if your amp came with an 8ohm 6" speaker, a 12" is gonna sound better..
    Some amps are not designed with a 'capable' output transformer...
    5: That is a whole different issue, speaker out is not line out...you don't sound like you are going to want to try to mod an amp for line out...trust me, just buy an amp with a line out if that is what you want.
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    • #3
      Originally posted by daddymack View Post
      1: to allow a second cabinet
      2: On some amps yes...on others, no. It comes down to impedance balancing. If you check the manual on your amp it will tell you if the external speaker has to be a certain impedance.
      3: yes, just match the impedance and the power handling capability of the external speaker
      4: seems dumb, doesn't it, but if your amp came with an 8ohm 6" speaker, a 12" is gonna sound better..
      Some amps are not designed with a 'capable' output transformer...
      5: That is a whole different issue, speaker out is not line out...you don't sound like you are going to want to try to mod an amp for line out...trust me, just buy an amp with a line out if that is what you want.
      Thanks for helping daadym.

      1. If the intent is to allow a second cabinet, does this mean, add the second and have two speakers playing at the same time?
      Or add a second and by doing so, disable the internal speaker?
      2. Yes the second speaker must also be 8 ohms.
      3. So unplugging the internal speaker and just plugging in a cab to the external jack won't harm the amp? (8 ohm).
      4. I am not talking about going from 6" to 12" 8 ohm. There is a 12" 8 ohm internal and the external speaker is also 12" 8 ohm.
      So the output transformer is dealing with the same load.
      5. I know there is a big diff between, speaker out, line/recording out.
      I was told that modding the speaker out to recording out is not difficult.
      If I am not going to be able to use two speakers at the same time (which I thought I would be able to), then
      I would like to have a line out instead of speaker out.

      Comment


      • #4
        1. Typically it's both at once.
        2. The speakers will be in parallel, which means the amp will see 4 Ohms and you'll need to set it accordingly.
        3. Not as long as the impedance is the same.
        4. See #2.
        5. You can do it but the mod makes the level of the ''Line out'' dependent on the setting of the gain/volume controls and it won't be EQed to emulate a speaker. Do a Web search for ''Add line out to amp'' and you'll find instructions for various simple projects. I mentioned wanting to do it to a little Vox SS combo a while back and was roundly Pooh Poohed even though it's a common mod.
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        • #5
          Originally posted by DeepEnd View Post
          1. Typically it's both at once.
          2. The speakers will be in parallel, which means the amp will see 4 Ohms and you'll need to set it accordingly.

          Thanks very much Deep!
          So basically with the external plugged in (and assuming the internal does not cut out) I would have the ability
          to place two speakers to target the audience better, but each speaker would be 'half as loud' as one would be
          at the same Vol setting?

          Comment


          • #6
            everything would be much easier, if you would tell about which amp we are talking about?

            cause most of the answers are "depends on the amp" answers, some amps disable the internal speaker if ext. cab is connected, some can run both, but each at lower power, some can run both in parallel and both get about the same power.

            on a tube amp this all depends on the output transformer and its capallities and how it is wired.

            unplugging the internal speaker at a tube amp without knowing what you exactly doing could damage the amp depending what model it is. so it is not a good idea without knowledge

            Comment


            • #7
              Originally posted by Jazzer2020 View Post
              Thanks very much Deep!
              So basically with the external plugged in (and assuming the internal does not cut out) I would have the ability
              to place two speakers to target the audience better, but each speaker would be 'half as loud' as one would be
              at the same Vol setting?
              Not quite. If each speaker sees half the power its output will be reduced by 3dB but ''half as loud'' means 1/10 the power.
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              • #8
                Originally posted by Jazzer2020 View Post

                Thanks for helping daadym.

                1. If the intent is to allow a second cabinet, does this mean, add the second and have two speakers playing at the same time?
                Or add a second and by doing so, disable the internal speaker?
                2. Yes the second speaker must also be 8 ohms.
                3. So unplugging the internal speaker and just plugging in a cab to the external jack won't harm the amp? (8 ohm).
                4. I am not talking about going from 6" to 12" 8 ohm. There is a 12" 8 ohm internal and the external speaker is also 12" 8 ohm.
                So the output transformer is dealing with the same load.
                5. I know there is a big diff between, speaker out, line/recording out.
                I was told that modding the speaker out to recording out is not difficult.
                If I am not going to be able to use two speakers at the same time (which I thought I would be able to), then
                I would like to have a line out instead of speaker out.
                You're making a bunch of generalizations there. Some may be right and some totally wrong depending on the type of amp you own.

                The thing that's important here is to know what YOUR amps capabilities are. They may of may not match another amps capabilities.

                It would be nice to know what amp we're talking about here because I could give you a definitive answer involving yes and no answers for your specific amp model.

                First - ALWAYS read your amp manual and memorize the part on connecting speakers. It should give you specific instructions and tolerances for your amp.

                For example - If this was a tube amp that had an 8 ohm speaker and a head that had a variable impedance. It MAY allow you to plug in as second 8 ohm speaker and run the amp at 4 ohms. Another amp may require you to flip a switch to switch the head transformer over to 4 ohms. Another amp may have separate jacks for connecting 8 and 16 ohm speakers and still others cant be run at 4 ohms and disconnect the internal speaker and allow you to connect an 8 ohm cab only.

                Doesn't matter how many speakers are in that extension cab has so long as the total impedance matches what the manufacturer recommends and a minimum or maximum load.

                That impedance may be fixed or variable. It all depends on the particular amp you're using so NEVER assume its OK to do this or that simply because you did it before and got away with it. That's merely a testament to how well the amp was over designed to handle abuse. Unfortunately your luck ran out and now you have to pay the price with a fat repair bill for blowing out the power amp.

                You cant believe how many times I heard the excuse when doing repairs. The owner say Well I do this all the time and never had a problem My response would be you did it before and were simply lucky you didn't burn it up sooner. (What I'd like to say is it that's a long time to be so ignorant on a product you've owned that long. My repair bill will educate you quick enough when you see how much that abuse costs you)

                I've even had people who had the repairs, and detailed instruction on how it should be run. They promise you they wouldn't abuse it like that again, then take it home again and turn right around and did the same thing again. They'd bring it back for a second repair, usually with even more damage then the first time. They don't realize components can be weakened and still function. A second failure can be twice as bed because the components are fatigued.



                If its a SS amp and the manuals says it will run 4, 8, 16 ohms or no load at all, then you don't want to try running it at 2 ohms. If it says 4 or 8 only, you better be dam sure your impedances total that much or you'll risk smoking the amp and taking it to the hospital because you were too lazy to read the manual.

                Tube amps in general can take lower impedances safely. If the amp is 8 ohms its likely to be able to run 4 ohms safely. Its not usually wise to run a tube amp with high impedances. a 4 ohm head may be OK for 8 ohms but running it at 16 will quickly fatigue your tubes because the voltages aren't being consumed properly and it winds up cooking the tubes.

                On transistors its just the opposite. you can usually run those higher but running a lower impedance (like plugging in an extension speaker in parallel) will put a greater load on the output transistors, overheat them and fry them.

                Again, because there are so many different designs and hybrids of all kinds, these rules are only general guidelines and should never be taken at gospel. Read your manual and follow it.

                Comment


                • #9
                  The speaker is a HUGE part of the sound of the amp, so (even if you overcome the loading issues as above) a direct out never sounds good unless a simulated "Impulse Response" of a speaker is added somewhere downstream (eg: software plugin).

                  Way better to just use a microphone in front of the amp or get a Kemper or Fractal if you need silent recording.

                  Comment


                  • #10
                    This is a custom built boutique amp, modeled after the Fender Princeton.
                    There is no variable impedance and no owner's manual.

                    Comment


                    • #11
                      In that case it's likely designed for an 8 Ohm load. The '65 Reissue had a 10" 8 Ohm Jensen C10R. You can safely connect an 8 Ohm extension cab but I wouldn't run it in addition to the internal speaker. I'd think of it as an either/or proposition.
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                      • #12
                        Originally posted by Jazzer2020 View Post
                        This is a custom built boutique amp, modeled after the Fender Princeton.
                        There is no variable impedance and no owner's manual.
                        See if you can get the number and/or manufacturer name off the transformer. If it's a kit build or custom made it may have a transformer with different impedance taps. This one for example is a replacement/upgrade to smaller Princeton builds and has 4/8/16 ohm taps. https://s3.amazonaws.com/tubedepot-c...pdf?1487779490 You'd need to add a switch for the different impedances when using the extension cab but a simple rotary switch could handle that. You could also use switched plugs which provide an 8 ohms transformer tap with a single speaker and 4 ohms with two jacks plugged in.

                        Not knowing what kind of transformer is in there is the tough part. As I said earlier, its usually OK to run a tube amp with a lower impedance but this is a smaller amp and the transformer type in unknown. On an actual Fender amp you take a hit on both tone and headroom running 4 ohms on an 8 ohm transformer.

                        My advice would be, If I were going to be running two speakers all the time, buy two 16 ohms speakers and you'd have the recommended 8 ohms.

                        If you are wanting to add the second speaker as needed, then you have to use a multi tapped transformer. They aren't that expensive nor are they too hard to wire up. Mercury Magnets makes some excellent OT's which are excellent for that amp. If the amp has a stock Fender type transformer its may even be a big improvement for tone and headroom.

                        The other option is to simply buy a speaker with a higher SPL efficiency (louder speaker) so the additional cab is unnecessary.

                        Comment


                        • #13
                          Originally posted by DeepEnd View Post
                          In that case it's likely designed for an 8 Ohm load. The '65 Reissue had a 10" 8 Ohm Jensen C10R. You can safely connect an 8 Ohm extension cab but I wouldn't run it in addition to the internal speaker. I'd think of it as an either/or proposition.
                          Well yes, as I said in my original post it's designed as an 8 ohm load amp.
                          This is a more powerful amp than the original though, with a 12" speaker. 6L6 power tubes.
                          Last edited by Jazzer2020; 10-11-2017, 10:23 PM.

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                          • #14
                            Originally posted by WRGKMC View Post

                            See if you can get the number and/or manufacturer name off the transformer...

                            My advice would be, If I were going to be running two speakers all the time, buy two 16 ohms speakers and you'd have the recommended 8 ohms.

                            If you are wanting to add the second speaker as needed, then you have to use a multi tapped transformer. They aren't that expensive nor are they too hard to wire up. Mercury Magnets makes some excellent OT's which are excellent for that amp. If the amp has a stock Fender type transformer its may even be a big improvement for tone and headroom.

                            The other option is to simply buy a speaker with a higher SPL efficiency (louder speaker) so the additional cab is unnecessary.
                            Thanks WRG.I'll see if I can track down the transformer specs.

                            I don't think I'll be running two speakers all the time. It would be second speaker as needed.

                            I just plugged in a second 8 ohm speaker now for the first time and wow! What a great sound!
                            True full stereo sound.
                            I didn't hear any hit on the sound quality nor on the volume. Sounds better than with just one speaker.

                            I'm going to have to contact the builder and get more specs and what are do's and don'ts.
                            I'm glad I went with the a speaker out now instead of line/recording out.

                            Comment


                            • #15
                              Originally posted by Jazzer2020 View Post

                              Thanks WRG.I'll see if I can track down the transformer specs.

                              I don't think I'll be running two speakers all the time. It would be second speaker as needed.

                              I just plugged in a second 8 ohm speaker now for the first time and wow! What a great sound!
                              True full stereo sound.
                              I didn't hear any hit on the sound quality nor on the volume. Sounds better than with just one speaker.

                              I'm going to have to contact the builder and get more specs and what are do's and don'ts.
                              I'm glad I went with the a speaker out now instead of line/recording out.
                              Stereo? Two speakers yes, stereo no. You need two amps and a stereophonic source for stereo.
                              A guitar only puts out a mono signal. You need split or Hexaphonic pickups with strings panned left and right for true stereo or at least some pedals which create some pseudo stereo effects like stereo chorus or auto panning between two amps.

                              Like I said, you may get away with running two speakers on an 8 ohm transformer so long as the transformer is beefy enough, But I wouldn't push the amp up into saturation levels like you can with a single speaker. There's a balance between the primary and secondary of a transformer in how much current is being used.

                              The tubes produce a high voltage low current in the primary and the transformer inverts the two so you have higher current and lower voltage in the secondary and its the current that does the work moving the electromagnetic voice coil.

                              When you double the load the secondary is starved for enough current to do the job so it tries to draw more form the transformers primary and the tubes that drive the primary. You may not hear a difference right away but it can cause accelerated fatigue on power tubes and components that comprise the power amp.

                              Transformers themselves have maximum current ratings and the extra heat caused by the additional load can reduce the lifespan of any or all components. These components usually have fairly high tolerances but its the long term results that are important. That's where I mentioned owners saying things like Well I do this all the time and never had a problem. It starts like you have connecting extra speakers and risking the amps components. Then you think its fine because you don't hear a difference, then you push it hard at a couple of gigs and then the fun begins.

                              I had to learn that lesson the hard way first hand. Back in the late 60's when I bought my first Fender Bassman head, I didn't know $h!p from shinola when it came to matching impedances. The head was designed for 4 ohms and the cab has two 16 ohm Altecs, which was apparently OK for that head only being off by 4 ohms. Later I added two more 4 ohm speakers and ran it up to 10 ohms and that's when the fun began. The tubes started loosing their sound quality within a few weeks. Then the elements began to glow cherry red and then the smoke would start pouring out of it.

                              I was blowing screen resistors and tubes out over and over and I didn't have a clue. It sounds fine with new tubes.
                              I eventually figured it out it had to be the impedance. I wasn't sure exactly why the fix worked, I simply followed the label on the amp and ran it at the right impedance and my issues disappeared.

                              I eventually got a formal education in electronics and then it all made sense. I was simply lucky I did that with an old Fender amp that had extremely durable transformers.

                              Once I took a job doing guitar amp repairs full time I saw the results of running amps with the wrong impedance every day. The Fender I owned was point to point so damage was isolated to a few components.

                              Some of the amps I repaired which used PCB boards instead of point to point. The same failure caused so much heat on the PCB board it converted the fiber glass board to solid carbon which is an electrical conductor and arced out the High voltage totaling the amp. It blew the power transformer, tubes, components and the boards themselves needed to be replaced, and since the manufacturer didn't sell spare boards I had to etch new ones.

                              I wouldn't have even done the work if it hadn't been a warrantee repair. He brought it in the first time and he got away with just changing the screen resistors and new tubes. The board had only browned a bit from the heat. I didn't get to warn him about overloading the impedance. He brought it back within 30 days and the board had shorted and turned to charcoal taking out nearly everything.

                              Ever since then I warn people right up front, you may get away with it or you may not. Just remember you're rolling the dice and when you smell the aroma of cooked components you only have yourself to blame for taking that gamble.

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