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A guitar amp build

Discussion in 'General Electronics Discussion' started by 19Sambo52, Jan 1, 2013.

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  1. 19Sambo52


    Apr 16, 2012
    :):) I built a 9 tube stereo amplifier in high school in 1968. Well its been sitting around for the past 40 years doing nothing. It uses 4 6BQ5 output tubes, a 5U4 rectifier, 2 12AX7s and 2 12AT7s. It sounded pretty good. I used to use it when my EICO 3070 was on the fritz, which was often, I used to blow the 1 amp B+ fuses alot and when they ran out I'd use a very thin wire. Well you know what happened next, the guys in the local electronics store knew me on s first name basis. The EICO works like a champ now and has been for over 40 years. I want to roll up a small tube guitar amp and thought of the old high school electronics project, went up and found it in the attic. I know you can't connect the outputs together on a solid state amp, except for some car amps. But everyone I asked about connecting the outputs from a tube amp together are sitting on the fence. Some say yes, some say no, some say maybe or I don't know. I did it with an old Harmon Karden Citition II amp to power a sub woofer years ago and it didn't seem to hurt it. It did sound good, if I rented an apartment it would have gottn me evicted for sure, This little amp is about 20 watts on a good day and it needs some work and TLC before I apply the AC, I hate having to setting off a fire extinguisher in my garage. I have read many of the blogs on this forum and you guys seem to know what your doing, I'd like to know what you've forgotten. If I was using 2 speakers in the amp I could just connect each channel to a speaker, but I'm using 1 12" Jensen. What do you think, Think it would work or smoke with a mini light show in the outputs? Thank You and Happy New Year
  2. duke37


    Jan 9, 2011
    I think you should be OK to connect the two outputs in parallel as long as there is no feedback. The output impedance of a valve amplifier is high and the current supplied by one will not affect the other.

    If there is feedback, the output impedance will drop, the amplifier will want to set a certain voltage and, if the two amplifiers do not match exactly, they will fight each other.

    Make sure that the outputs are connected the same way round.
  3. Rusty


    Nov 30, 2012
    Im not 100% sure of this,but I certainly would be careful with connecting two tube amps together. Or output stages in general.. I dont see the point. Where do you want to get with this?

    You'll have to make sure that the impedance is matched with the speaker, otherwise you'll blow the output transformer. New transformers cost lots of money compared to other parts.
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