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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Vox AC10C1 Owners Club

Discussion in 'Amp Owners Clubs' started by StormJH1, Sep 28, 2015.

  1. Staggerlee666

    Staggerlee666 Tele-Meister

    130
    Jul 24, 2014
    MPLS
    Question regarding the cut control. I read that there is a set value resistor on the earlier 15 customs that had no cut controls and that by changing that reaistor value you could approximate the cut pot being at 12 for example if you wanted to shave off some treble. Are you able to identify that resistor on the AC10 schematic?
     

  2. Staggerlee666

    Staggerlee666 Tele-Meister

    130
    Jul 24, 2014
    MPLS
    I guess I meant one of the earlier versions of the Chinese 15's that has only a TB channel and no cut control. Forget the exact model number.
     

  3. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    The AC10C1 diagram doesn't indicate a fixed cut control like you have described. There is a 47pF cap (C37) across the PI outputs, but it doesn't also have the series resistor for you to tweak. I believe the AC15C1 has both the fixed cap and the cut control, so this cap isn't really the equivalent anyway.
     

  4. Tubeboy

    Tubeboy TDPRI Member

    99
    May 20, 2017
    Saratoga Springs NY
    It must be noted that Vox clean is not really clean like a Fender.
     

  5. Staggerlee666

    Staggerlee666 Tele-Meister

    130
    Jul 24, 2014
    MPLS
    Thanks for the clarification!
     

  6. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    WAIT - I goofed. I was thinking of the AC15C1. The AC15CC is in fact a single-channel amp, with Top Boost channel only. So it does appear that for the most part, the AC10C1 is a 10W version of that amp, except that the 10 has digital reverb and no tremolo. I don't know if the Top Boost circuit is exactly the same on both amps, however.
     

  7. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    The schematic I have for the AC15CC is hand drawn, and so who knows if it is correct. But taking it on faith, the preamp / power amp are an all tube circuit. The AC10C1 schematic shows that it contains some transistors in key places. In fact, the very first stage of the preamp is a transistor, as is the last stage just before the phase inverter. The AC15CC doesn't appear to have this topology at all. It seems to be all tube from input to speaker (not counting the effects). The tone stacks use different value caps too (.1uF vs. .022uF). There are some other differences as well. But having said all of that, there are a lot of similarities too.
     

  8. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    That's interesting (I have an AC10C1). Do the transistors in this circuit provide the preamp overdrive?
     

  9. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    The first stage is a transistor. There is a gain control after the transistor, and then the signal moves on to the first tube stage. So, I think, if I am interpreting the circuit correctly, the gain pot controls how much signal hits that first tube stage. If you crank the gain, you are driving the tube harder, and causing the tube to overdrive. Turn the gain control down, and the tube sees less signal, and so it remains cleaner. So I think the transistor is running clean. And it is the first tube stage that overdrives.
     

  10. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    Okay, thanks. I was wondering because I had a JCM900 back in the 90's, and when I opened it up, I saw the full load of tubes. But I also saw a row of red LEDs that illuminated when I struck a chord....
     

  11. Big tuna

    Big tuna Tele-Holic

    578
    Oct 28, 2012
    east side
    I love mine i wish an alnico speaker would fit though.
     

  12. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    if you look at the schematic in the area of that first transistor stage, you will see some diodes. LEDs are just another form of diode, so it is certainly possible that some of the grit comes from that first transistor and the diodes connected. Afterall, a Vox is never totally clean sounding. But the gain pot is not interacting with that part of the circuit. It is allowing more or less signal headed to the first tube stage, which then distorts more or less as a result.

    Its hard for me to fully understand a schematic and the implications of any given part of the circuit without experimenting, which I don't plan on doing (I hate working on PCBs - the traces lift so easily). But its nice to know that we finally have the schem in case anyone ever has to repair something, or feels so inclined as to design a mod.
     
    3-Chord-Genius likes this.

  13. mysteriousfish

    mysteriousfish TDPRI Member

    17
    Jul 7, 2014
    Ontario
    After a long run with the greenback I've joined the club of people who have switched back to the VX10 and so far have enjoyed the difference even with the speaker not fully broken in (if that matters). Less lows, more clarity, but the greenback overdrive sound is missed. I'm interested in a G10N-40.
     
    Big tuna likes this.

  14. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    A more knowledgeable friend from another forum has informed me that those diodes are not for any sort of clipping - they are Zeners, and are probably there to protect the MOSFET. So, it seems that the clipping is either occurring in the MOSFET itself, or in the first tube stage (oddly named V2). Still awaiting more opinions from that forum on why the amp breaks up so early.

    Maybe the MOSFET is driving V2 really hard????
     
    3-Chord-Genius likes this.

  15. SOYRAFA

    SOYRAFA TDPRI Member

    40
    Feb 22, 2010
    Spain
    Solid state in preamp?

    I feel ripped off by vox
     
    Big tuna likes this.

  16. tom310

    tom310 Tele-Meister

    196
    Jul 30, 2008
    Kansas
    It's fairly common practice. I believe the Tweaker 15 also has a transistor as the first gain stage.
     

  17. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    It really doesn't matter as long as it sounds good. Some of the JCM800 amps had clipping diodes in the preamp, and those amps sound great and are highly sought-after. Some JCM900s had them also. It matters even less if you're running solid state stomp boxes into the front end anyway. It's still a tube amp.
     
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  18. SOYRAFA

    SOYRAFA TDPRI Member

    40
    Feb 22, 2010
    Spain
    Holy ****.

    Not for me!!!!

    I really feel cheated !!!!!

    When buying a valve amplifier should be at least in preamp and power amp, (rectifier is something else).

    But an amplifier with transistors in the preamp is a hybrid !!!.

    A technician explains to me, seeing the scheme that the diodes are for the first stage preamp !!! and the return of the reverb, while the 2 tubes are for gain and phase inverter !!!

    The diode preamp should have been replaced by 12xa7 to be valvular.

    According to him is a hybrid amplifier in all rule.
    Intolerable, I want my money back already.

    And this must be denounced x deception. I'm very annoying, it's a rip-off !!!
     

  19. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    Is that what you meant to say, or annoyed? :)
     
    Big tuna and 3-Chord-Genius like this.

  20. sliberty

    sliberty Tele-Holic

    805
    Mar 19, 2007
    East Brunswick, NJ
    So the second MOSFET does come after the reverb, but it is not really a reverb return / gain makeup stage. That would be U1B (NJM2115). The MOSFET is really just there to drive the PI harder, and perhaps (not sure) match the impedance.

    Ignoring the reverb circuit, it is certainly a hybrid, there is no denying that. And MOSFETs cost less than tube sockets, let alone tunes, so I can see why they would want to do this. Vox wasn't transparent about that fact at all, though. But damn, this is a good sounding amp. So, its hard to be too upset about it.
     
    3-Chord-Genius likes this.

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