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SVT clone power supply high B+

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  • #31
    Originally posted by PauloP View Post
    Good morning forist friends, I'm new to this forum and I'm starting to plan the mound of an SVT.
    I wonder if friends have this or another svt layout drawn not handwritten? I am having some difficulties with this layout.I also ask about the specifications of the transformers because I live far away and I will have to order the manufacture of the transformers.
    Thanks in advance.
    PauloP - we may by comparing a lot of pictures and notes!

    I, too, am about to embark on the journey of building an SVT for a friend. He has been asking me since our college days over 20 years ago to build him a bass amp. Back then I built a tube hi-fi preamp and a couple 300B single ended tube power amps. Preamp was point to point, 300B was point to point with turrets. Since he saw me do that, he has been asking to build his dream amp. Then I put down the soldering iron for years (career, kids, 2 cross country moves, etc.) This year I have built and upgraded 9 First Watt / Pass Labs solid state hi-fi amps. Now I'm getting ready for his build.

    Discovering this thread is inspirational! The wiring is phenomenal, and the layout drawings are very nice. It makes a very intimidating project a little more approachable. Fantastic work!

    My buddy's dream bass amp:

    He runs his bass into Carvin X100B guitar amp using the Lead channel for processing (Gain, EQ, Distortion), out the effects loop, and into a 1970's black line SVT. I have his spare Carvin and his SVT to reference in my basement. He us using a 300W Sunn amp while the SVT is at my place.

    I ordered some cables to do some testing, and some dummy load resistors. I'm going to his band practice this week to get a better idea of how he's using the Carvin - exact settings, etc. I will mimic the settings on the spare Carvin, then run it through my oscilloscope to look at gain / eq and graph that.

    I also want to understand how he's using the SVT. It appears he's using channel 1 only. He has little paint dots on his default settings.

    Based on this, I want to make a sketch of the gain / processing stages to design his amp.

    Example:

    Carvin
    12AX7 input (? dB Gain)
    5 - band EQ: 75, 150, 500, 1500, 3000Hz (get the settings)
    12AX7 (20 dB Gain) - turned to "2" on the knob, very loud. 2.5 is deafening. Can this pot be changed to give better range?
    Out the effects loop send jack to the SVT

    SVT Channel 1 - Pre
    Input - Bright or Normal?
    V1 - 12DW7 Input
    Ultra Low switch set to +
    Bass knob set to about 4 o'clock
    Ultra-Hi switch set to off/zero
    Treble knob set to 0
    V3 - 12DW7
    Mid switch set at 220 hZ (left)
    Mid set at about 1:30 o'clock
    V4 - 12DW7
    V5 - 6C4

    SVT power amp section
    V1 - 12DW7
    V2 - 12BH7
    V3 - 12BH7
    V4-9: 6550 Power Tubes

    Ideally I'm not redesigning much.

    Things I'm thinking about at this early stage:

    Can I take SVT-CL design (one channel) and put a 5 band TH Custom EQ into the chain between input jack and first tube. Maybe jack, EQ, switch for normal/bright, and then to SVT-CL circuit? This will be simpler than the 2 channel design and use more modern tubes. Will it get the distortion the Carvin/SVT combo gets? Could adding one more gain stage do it?

    To test this theory I'm thinking of going with my buddy to a guitar store with a SVT-CL and use an EQ pedal (Behringer 5 band, MXR, or other) and see if he can get the sound he wants. If not, EQ pedal into a distortion or gain pedal...

    Turret boards vs. fabricating / buying PCBs. Does anyone make SVT PCBs? Does anyone have drawings / gerber files? I have had PCBs fabbed before using existing gerbers, but I have know knowledge or skills for the design/drawings.

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    • #32
      Nice work.
      Here's an other fool that has made an SVT clone. I built it some 16 years ago. I also built the 8x10" cab. Has worked without any troubles, Has still the first sextett of EH 6550s.
      SVT is great amp and cab.

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