Preamp on mute, but I can still hear it

Discussion in 'Amps and Cabs [BG]' started by Transverz, May 25, 2005.

  1. Transverz

    Transverz believer of the Low End Theory

    May 3, 2004
    Los Angeles, CA
    Just got an Ampeg SVP-Pro and I'm noticing that when I put it on mute to tune, I can still barely hear myself through the cabinet. Its not too loud nor is it a major deal, but what gives? I thought mute, was mute? Or is it just my preamp? Is something horribly wrong?

    And its not too much of a problem in rehearsal, but what about at shows at extra loud volume? Or what about when I'm going through the DI? Are they gonna hear me tuning?

    I'm sure this might even be a frequently asked question. I just couldn't find any answers on it. I'd appreciate it! Thanks!

  2. The SVT3 + 8x10 i used at a studio did this...

    My Trace does this, cant remember if my mate's trace does too.

    My guess would be that the mute switch kicks in a dB attenuater? takes out 95% of the voltage gain, perhaps? :meh:
  3. bassman314

    bassman314 I seem to be a verb, an evolutionary process... Gold Supporting Member

    Mar 13, 2005
    Bay Area, CA
    My SVT3-Pro does this as well..

    From look at the schematic, it looks like the mute sends the signal going to the pre-amp section to ground. There's still a small amount of signal that reaches the speaker output via ground, I guess..

    If your DI is in the signal chain between the bass and the mute, it'll go to the PA. If the DI is in the signal chain after the mute, it shouldn't be a problem.

    and uhm.. so what if people hear you tune? Atleast you are tuning!! :D
  4. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I don't know what you are hearing. But it would not surprise me if it were still *possible* to hear the sound....

    I don't want to *just ignore the issue*, so can you compare the level you get to something common? A watch ticking? Dropping a pin on concrete? A 2 year old 150mm from your ear?

    95% gone would only be 26 dB down.....not much

    The mute is probably attenuating by between 60 and 80 dB.

    By way of comparison, you can hear a signal which is -85 dB from a reasonably loud PA, but it will be only a tiny barely audible sound. The hiss from a cassette player (remember those?) without Dolby etc was about -50 dB.

    The mute isn't necessarily there to kill the sound without trace. It is supposed to knock down the signal to negligible level to allow you to tune, leave the amp set up without feedback worries, change guitars without a "ka-whump", etc, etc.
  5. Transverz

    Transverz believer of the Low End Theory

    May 3, 2004
    Los Angeles, CA
    The sound is comparable to putting the volume really low. Sorry, it doesn't get anymore scientific than that. Nope, not like a pin drop. That we would not hear in practice over the usual hiss and hums of both the guitar halfstacks and our band blabbing away. More like, loud enough for me to notice. So I asked the question.

    I don't want to "diss" you either but I wasn't making this remark because I have the ears of Superman. Nor am I the most nit-picky person in the world. I don't have to press my ears up against the grill of my cab to hear this. So no, it's not like a watch ticking or whatever other ridiculous comparison you decided to make. Trust me... it was more than *possible*...It was audible. Even my band asked me about it.

    I'm not sure where along the lines you thought I was making some sort of flaming rant or slam, but I think it was fairly obvious I was just trying to address a *possible* problem I might be having with MY specific preamp. This has no bearing on any other piece of gear I have, regardless of maker. Both my former SVT-4Pro and my current M-2000 mutes it beyond me being able to hear it. So my electronically challenged self assumed that "mute" meant that signal was totally cut and re-routed to only the tuner out. My fault for making a layman's assumption.

    I appreciate the additional information towards the end of your post Mr. Tiers. You have always been totally helpful and straightforward. But unless I'm reading your post totally out of context, I found it going towards insulting. I was just being curious. Regardless, I love the preamp.


  6. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    No such intended. Sorry if you thought there was. I'll take responsibility for any misunderstanding.

    When someone asks about a noise, one where SOME noise would be expected, it is easy to say "well, that's pretty normal".

    I have done that, only to later find out that there was about 10 times more than should be expected.........

    So rather than toss off a "that's normal", I wanted to be sure we are not talking about way too much noise getting through.

    The mute uses a small Fet to short the grid of the input tube. The parts vary. Even a edge-of-tolerance part should give about 50 dB attenuation minimum, but it averages considerably more.

    We don't publish a spec for the mute, but if you aren't getting what you should, we'd like to make sure you do.

    At 50 dB attenuation, a signal is still going to be "audible", but it should be very significantly attenuated.
  7. bassman314

    bassman314 I seem to be a verb, an evolutionary process... Gold Supporting Member

    Mar 13, 2005
    Bay Area, CA
    Hey Jerrold,

    Thanks for the explanation! I was going by the block diagram in the manual, and it obviously doesn't show all of the features.. (being a block diagram..)
  8. Audere

    Audere Supporting Member Commercial User

    Apr 7, 2005
    South Beach, OR
    Owner: Audere Audio
    Ampeg is shorting the grid to the cathode or to ground?
    What is the normal bias voltage and is this generated by a cathode resistor?
  9. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    My Eden Navigator preamp mutes to 100%, no sound whatsoever. Same with my former GK head.

    I'd personally be a bit peeved if my mute didn't mute when onstage.
  10. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Grid is grounded as per normal cathode bias....and shorted to ground. I know where you are going, you are thinking of a bias shift causing a thump. Not unless the tube has a problem.

    There isn't any "100%", but there are varying dB of attenuation..........

    I might point out that it being on the first stage, if you hit it with a larger signal from an active bass, you get more signal through. That will obviously give a different result from a passive bass in terms of output when in mute.

    Bottom line is that it is intended to effectively mute the signal for tuning, between sets, swapping instruments, etc. It should do that, and if it doesn't, that's what a warranty is for.
  11. prockenklang


    May 22, 2003
    It seems to me that if you say it is a mute,it should be silent! Every Glockenklang amp I have ever owned were dead silent when muted,so is my EBS Microbass II.

  12. Transverz

    Transverz believer of the Low End Theory

    May 3, 2004
    Los Angeles, CA
    Jerrold: I will take 50.1% responsibility of the misunderstanding. You have always been helpful without any need to be and I appreciate it. The information you stated makes sense and explains my concern. I do also appreciate that Ampeg stands behind it's product and if there was a warranty concern, they would back me up on it. That is all I ask from a manufacturer.

    True, my EBMM Bongo gets even more bleed thorugh the mute than my Sterling, and I now understand why this is so. I will continue to monitor its "normal gain attenuation on mute" factor and if it gets out of hand, I will let you or Ampeg know directly. I still do again appreciate the willingness to make things right if anything should be wrong.

    The preamp rocks and I don't know why I waited so long to get one. Tons of sound options and variety. Makes me want to try out a CL or a BSP! :D