DSL Deep Switch and General Hum/Buzz

Discussion in 'Marshall Amps' started by GetTheFunkOut, Apr 28, 2013.

  1. BenH

    BenH New Member

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    Hi, thanks for the reply.

    When I spoke to Marshall they weren't interested in dealing directly with me and said to send it back to the dealer and let them sort it. Which is fine, except that guitarguitar think it's normal. This is what they say: "Like i say when you engage a button like the deep button it will always add more noise as you are literally boosting that part of the signal. There is buzzing there but this is an electrical item with a speaker in it. 99% of amps have some level of buzz or hum to them."

    What gets me is that the buzzing appears even when there isn't a guitar plugged into the amp, i.e. there is no input signal!
     
  2. ricksteruk

    ricksteruk Well-Known Member

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    All amps will make a small amount of noise, both hum and hiss.

    And when you increase gain, by turning up the gain knobs, master volumes, activating boosts and so on the noise will increase. I'm sure you know this anyway! Was this hum happening with all the volumes on full?

    So the question is - Do you think the hum you have with nothing plugged in is unacceptable?

    If yes, then just try to get a refund. Will they do that?
     
  3. BenH

    BenH New Member

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    Simple answer, no, I don't think the hum/buzz is acceptable. And no, they won't acknowledge there is a problem and want me to pay for them to send it to Marshall!

    If it wasn't for the fact that we have a toddler in the house I'd just play my Silver Jubilee combo in the evenings and not need to worry about a 1W amp to avoid waking him up!!
     
  4. Wylde Chylde

    Wylde Chylde Active Member

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    I have the same issue with my DSL1C. Even without anything plugged in, it hums. Push in the deep switch, it hums louder. Also, when pushing in the deep switch and or shutting the amp down there is a distinct 'pop' sound. I dropped mine off at the tech about a week ago. He said he wouldn't be able to get around to it for 3-4 weeks. I'll let you know what he says when I hear something.
     
  5. BenH

    BenH New Member

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    I'll be interested to hear what he says. Cheers.
     
  6. ShawnMH

    ShawnMH New Member

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    My DSL1C 50th Anniversary does the same thing, and always has. There is a slight bit of hum present that I consider normal for a Marshall, yes. Engage the deep switch, and it is almost triple the hum.

    I have a full size Laney VC50 that you have to literally touch you ear to - to hear the normal hum.

    I do not like it, but it sounds and plays great in all other aspects, I don't really "need" the deep switch, but it would have been nice to use it without additional noise.

    All of the noise was heard without any volume or guitar/anything plugged into it.
     
  7. NSV-Andy

    NSV-Andy New Member Silver Supporting Member

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    I am a little late to this party, but have just repaired one of these with this symptom, and will share what I found. Perhaps someone will find this through a search engine and benefit from it.

    In addition to the heater, bias and high voltage supplies in this amp, there are 3 additional voltages, +24 Volts, +15 Volts and -15 Volts. In my case, I found that the -15 Volts supply was being loaded down. This causes an imbalance in the amplification chain, particularly in IC2b on the front panel PCB. This is responsible for the "Deep" tone function.

    In the case of the particular amplifier I've been working on, this excessive load on the -15 Volts supply was caused by a faulty IC2 on the rear panel PCB. This is responsible for the effects loop amplification.

    The problem of an excessively-loaded +/- 15 Volts power supply can be caused by any of the Integrated Circuits in the amplifier. I would caution anyone trying to troubleshoot such a problem that the chassis ground connection for these supplies is made through connections on the front panel PC Board. If the tech tries to troubleshoot where the excessive load is coming from and unplugs Con3 (on the rear panel PC Board) or Con10 (on the front panel board), it will complicate the process of tracing the load down because the chassis ground connection has been lifted.
     
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  8. Vesperado

    Vesperado Active Member

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    Hmm...my CLEAN Deep just crapped on me last night, wondering if its the IC? I did socket and replace the REAR PCB FX Loop IC, and removed the ground hum by linking the caps to make the IC lifted. I was planning on socketing the Deep IC's, but the VPR is now doing some funny start-up hash so I think I will socket everything under the hood now. Thanks for the heads up!
     
    Last edited: Mar 14, 2021
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  9. Vesperado

    Vesperado Active Member

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    So yes, the stock Deep IC (4558P) is noisy. I replaced this with a OPA2134, so much better now :)
     
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