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Thread: Crate V5 "MODS" will commence!

  1. #20
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    Just a thought on that active tone control circuit. You are changing the phase of the input signal by quite a bit. Any tone control circuit that is for the most part made up of resistors and capacitors will change the phase of the signal passing through it but within approx 90 degrees. With the active tone control shown the mid range frequencies at the output of IC2C will be 180 degrees out of phase from the treble from IC2B and the bass from IC2D. So quite a bit of phase change from the original signal. It could be interesting to invert the signal from IC2C with a unity gain inverting stage before connecting it to the summing junction of IC1B to see how that affects the tone.

  2. #21
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    Ooooo.... Nice thought! I do believe that is the point of the original circuit. Any thoughts on how to put that into a switched application. Okay never mind.. I was over complicating the circuit. I could do that. I have thought about your ideas on this circuit... so I'm going to make sure this a plugin circuit and can be removed easily. I'm ordering another board and building a new circuit that I can spend some time modding. Thanks Jim!

  3. #22
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    jim p, Just a thought..... It is because of the phase change of the mid range that it cannot overdrive the input of the tubes......Therefore will adding the unity gain inverter put the midrange back closer in phase with the bass and treble thus increasing total output gain and overdriving the input tube? Turning it basically into an overdrive circuit. Please say yes.... or is it not that simple?

  4. #23
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    The mid frequencies being out of phase from the high and low frequencies would have no real effect on your ability to overdrive the input tube stage of the amp, you need more gain and headroom for that. If you want to use the PCB for overdrive also the best thing to do would be to mod it to run off the +/- approx 16 volt supplies in the V5 for the stock op amp circuit or a 32 volt supply. Then you could take a gain of up to approx 10 at the summing amp IC1B without any op amp stage clipping. To me it looks like IC2A is not really necessary to the operation of the PCB you could just connect from IC1A to R7 and free up IC2A to use as a unity gain inverter for the mid frequencies or use it for a variable gain stage of 1-5. Also if you mod the board for plus and minus supplies then IC3 could be used for an inverting stage.

  5. #24
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    I had already talked to the author of the circuit about running it off the Crates 12.9 supply and all of the caps I've been using are rated at 25V. The TL072 are rated at a supply voltage of plus or minus 18V so running them off of the 16.5V supply shouldn't be any problem. The mods to the board are getting beyond my level but I'm studying the circuit and the specs and am slowly getting back up to par. May at this time just think about putting in a boost stage... Got to get off the paper and into the circuit. I'm no good at computer simulations... I have to be hands on. But man you have got my creative juices flowing.... There is an easter egg in the bloviator circuit I am missing... Just something I remember from a circuit I worked on years ago. Gonna dig out some of the old books and see if I can find it.

  6. #25
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    I preformed the bypassing the op mod from jim p just would like to let you know that thanks to your mind and my hands I have a wonderful little amp. I upgraded the speaker with an Electro- Harmonix put there brand of tubes in I don't know if it was needed but i drilled a couple of holes in the back to help cool the insides. It was a pretty easy mod and I had no trouble doing it. I play a lot of jazz and blues so I like clean sounding amps. I own 3 amps and made my own abc block so I can turn them all on if I wish my Vox AC30 T/B was my main amp then my Hughes @ Kettner switch blade was next then the V5. I now use the V5 almost all of the time it just sounds incredible and the response from picking dynamics makes it a joy to play and it now has the power to run with the other two. The best part is if I want to play out anywhere I don't have to lug around a heavy amp just grab the V5 and my Zoom G2 and out I go. I might even try the reverb tank in the future, thanks for your time and hello to the Fretnet gang

    Glen

  7. #26
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    Welcome to The Fret, Glen! Introduce yourself over at the players section so everyone else can say a nice hello. Again, welcome aboard.

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