1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Ampeg Portaflex 350 head - Static and Hiss?

Discussion in 'Amps and Cabs [BG]' started by Skygoneblue, Mar 25, 2013.


  1. Skygoneblue

    Skygoneblue

    Nov 13, 2007
    Orlando, FL
    I recently got a Portaflex head, and it came standard with the typical Ampeg high frequency hiss when I run it through the 2x10 Portaflex cab. I turned the tweeter off, so it's not that big of a deal.

    What bothers me though (and that I'm not sure is normal) is that when I plug my headphones into the head, I get the same LOUD staticky hissing sound when I'm not playing. It sounds like I have my ear pressed up against the tweeter with the gain on 10.

    Is this normal? I've never had an amp with a headphone jack before, and I was expecting it to be rather quiet considering it's a signal right from the bass.
     
  2. MBauer

    MBauer

    Jan 13, 2016
    Did you ever get a response to this? I picked one of these up today and I am noticing the same thing with the headphones (I am waiting on my cab to show up, but wanted to try the amp)

    michael
     
  3. megafiddle

    megafiddle

    May 25, 2011
    Headphones, like a tweeter, can easily reproduce the high frequencies present in the hiss produced by the first preamp stage.

    If the hiss stops (or is greatly reduced) when the instument cable is unplugged from the amp, then it is most certainly input noise in the first stage.

    If this is the case, the only way to reduce it is to reduce the impedance at the input. For a passive bass, keep the bass volume at 10. An active bass, or a pedal with a low impedance output will also help.

    -
     
    Last edited: Jan 13, 2016
    MBauer likes this.
  4. MBauer

    MBauer

    Jan 13, 2016
    Thanks - interestingly, the noise does not seem to change whether my bass is plugged in or not. It also doesn't seem to matter what the volume and tone on the bass are set to, which is why I was wondering if perhaps it's being caused from the fan. My super cheap Acoustic 15w practice amp is completely silent (but it also has no fan)

    Michael
     
  5. Highly doubt the fan is the cause. The "problem" is in a gain circuit. Have you contacted Ampeg/LOUD Tech customer service?
     
    MBauer likes this.
  6. MBauer

    MBauer

    Jan 13, 2016
    No - not yet - I literally just got it this afternoon, tried it, googled around a little bit to see if anyone else was having the issue, the posted here - I will contact them next.
     
    B-string likes this.
  7. I quiet "hiss" maybe acceptable but I am talking very soft and you have the right to a quiet amp. Most amps are rated for -90db of noise at rated power which would be barely detectable with phones. So long as there is gain there will always be some noise in the circuits.
     
    MBauer likes this.
  8. MBauer

    MBauer

    Jan 13, 2016
    It's definitely more than just barely detectable - and I found it interesting that it didn't matter if the gain was up or down, or if the bass was plugged in. The only thing that affected it at all was cranking the volume knob up all the way.

    I sent a note to Ampeg - I guess I'd be curious if anyone else on here (I've seen one other) has this happen with theirs.

    Next time I'm at GC, I'll plug my phones in. I'll also be curious if it will be heard through the cab, or if it's limited to the headphone out

    Michael
     
  9. If you play through a cab with no tweeter horn and poor high frequency response you won't hear it until you plug in your headphones. It is not your headphones fault, just so you don't get confused. If the Volume (master) affects how loud it is the noise is in the preamp of your unit.
     
    MBauer likes this.
  10. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Try connecting a device to the amp's audio in via a stereo ⅛" plug and see if this affects the noise level with the headphones connected.

    The signal being sent to the headphone is a mix of the instrument and audio in. If noise is getting in at the audio in, connecting something to this input might eliminate it.
     
    Last edited: Jan 13, 2016
    MBauer likes this.
  11. MBauer

    MBauer

    Jan 13, 2016
    Thanks all - I stand corrected a bit - tried a different set of phones...it appears cranking the gain and the treble both increase it somewhat - same with the master. (I also noticed the gain pot was a little scratchy towards the top, but not a big deal)

    I"ll see what happens with the audio in. I'll also see what happens with the cab - it's just the straight 15 - no tweeter/horn

    update: tried connecting audio to the audio in - no change. It would seem this is par for the course, but I would be curious to know if anyone else has seen/heard this that has a pf head
     
    Last edited: Jan 13, 2016
    beans-on-toast and B-string like this.
  12. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I don't use tweeters, but I used to have a couple cabs with tweeters and I never had this problem with my PF350 powering them, nor do I have it when I plug it in direct. You are either juicing the treble or you've got a problematic head. Increasing treble also increases the noise floor of the treble.
     
    MBauer likes this.
  13. MBauer

    MBauer

    Jan 13, 2016
    My cab hasn't arrived yet, so this has all been through the headphone out. I tried it with the treble set at 0, and at 12 o'clock. Same result. I am really curious to try it with the pf-115LF cab, but it's still a couple days out
     
  14. MBauer

    MBauer

    Jan 13, 2016
    From Ampeg Support:

    "
    Hi Michael,

    This is normal operation for this amps in this series. The more you crank it up, the louder it gets, and the more you can actually hear the fan. Nearly all audio gear has some amount of audible hiss, that’s just the nature of the beast!

    All the best,"
     
  15. Well, THAT sucks. I just looked at the manual: S/N 75db, not as quiet as I would expect.
     
    MBauer likes this.
  16. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Pfft! Back in the day we'd have killed for 75db SN ratio!
     
    MBauer likes this.
  17. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    On the positive side, the speaker cab will reduce the noise that you are hearing.
     
    MBauer likes this.
  18. Back in the day you could fit an 810 in your trunk, but the car drank gas like a wino and would kill insects with it's exhaust at the same time too.
    You also couldn't get a 350 watt amp that weighed less than 90 lbs.
    What's Back in the day have to do with it?
     
    MBauer likes this.
  19. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Well the PF350 seems pretty quiet to me, that's what it has to do with it. Would I use it as a studio reference amp? No. But I'm also not paying less than $300 new for a reference amp, either. A little perspective is required on that front, IMHO.
     
    MBauer likes this.
  20. MBauer

    MBauer

    Jan 13, 2016
    Thanks all - I'm sure that once I plug the cab in, it will be much less noticeable. I was just honestly surprised to hear it through the phones... my $100 practice amp is almost whisper quiet, but it also doesn't have a fan.

    JimmyM - do you still have a 350? What do you hear if you plug a set of headphones in to it?

    ~m
     

Share This Page