Blog Forums DIY Amplifiers and Electronics Can you help me with an amplifier problem?

last updated by dameo182 3 months ago
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8 replies
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    • #25919
      dameo182
      Participant

      Tv manufacturers have this annoying habit of only adding an optical out on the back of their products now, which makes it very hard for me to connect my speakers to it. I have a pair of small two way speakers that I made at the base of my bed and a small 2×50 watt bluetooth amplifier at the side of my bed to power them. The issue I’m having is that I can connect the audio to my speakers with bluetooth and it sounds really good, no noticeable lagg, but it keeps stuttering for a second every two minutes or so, interrupted connection I assume.  It’s very annoying. My old tv had an aux out which worked perfectly, so I tried using an optical to aux converter which also worked, but then I have no volume control at all. So I’m now back to using bluetooth.

      I really hope one of you guys can direct me to a cheap amp board (I plan to build a little bed side lamp/docking station that also controls the tv audio and radio etc with the amp built in) that will work with this stupid tv and also allow a wired connection and volume control, does such an amp exist?

       

    • #25920
      cornut
      Participant

      I don’t know for sure if this would work/give you a variable audio signal, but maybe something like this would work?

       

       

      I didn’t shop around to see if there’s less expensive options, I’m wondering if you can’t use the HDMI/ARC port to make it work? Somebody may very well come behind me and say it won’t. If something like that would work, it might take care of the no variable audio control part.

    • #25923
      dameo182
      Participant

      Sorry but I can’t see the link you added, maybe because I’m in the uk?

    • #25924
      cornut
      Participant

      do a search for an HDMI to HDMI + audio adapter. Find one that has aux out. I’m not saying it’ll work, I’ve never used one, but it’s possible?

    • #25926
      dameo182
      Participant

      @Cornut that may work yeah thank you, seems like a lot of extra stuff just to run audio to a set of speakers though 😃 why they can’t just use a simple cable I dont know 🤷

      Do you have any idea what they use inside of the cheap soundbars? My brother used to have one where the optical cable just plugged into the back, it then worked just like the aux cable used to work for me before, they allow you to use the normal remote for volume too. Id love to know what amp unit they use to do that

    • #25936
      AJC
      Participant

      @Dameo – so the splitter does NOT solve your volume problem, it will just split the audio from the HDMI source and leave you with the same problem. What you want to seek out is a volume controller, preferably an analog volume controller.

      What TVs and computers often do are to send a full signal out of the device. What that means is it is super loud. And as you figured out, the volume control does not change the signal.

      Instead of getting the TOSLINK to Aux, I would have recommended getting a decent quality Digital to Analog Converter that has TOSLINK and Coax inputs. If you buy a good one, like some of the Topping, they come with a remote and the ability to change the volume. That would solve your issue instantly.

      Basically, similar to car audio, you want the signal turned as high as possible without clipping. You then have one unit, the head unit, control the volume. In home audio, they expect you to go from your devices, like a TV, to a receiver or pre-amplifier, which then either gets processed there or volume control applied, then sent to the internal amp for a receiver or to the external amplifier, then onto the speakers.

      What normally happens is you have the digital signal go through the digital to analog converter, giving an analog audio signal that is usable. From here, usually you send it to a pre-amplifier. This allows the signal to be controlled, meaning volume alteration. From there, it is fed to the amplifier.

      In many receivers, they also have HDMI decoders and act as HDMI switches, that way everything plugs into them and you use them to select the input source. The audio is decoded, then sent to the speakers (either through pass through out if available on the receiver or the receiver acts as the pre-amp and volume control, then sends it to the internal amplifiers, then out to the speakers).

      So, you have choices. You can either buy a pre-amp or you can buy a volume controller.

      Here are some examples of volume controllers:

      Now, to make it more complicated, you should look for a volume controller that is analog. Why? Because of Signal to Noise Ratio (SNR). I’ll be writing an article on this soon. Basically, digital processing of volume, if at 16-bit, will greatly reduce the SNR, meaning that it can effect the quality of the sound at low volumes. This depends on the device used, etc. If it has 32-bit processing and it has direct access to the audio path, then the 32-bit would be fine with very low reduction in SNR (still researching this and implementations into DACs). But, analog volume controls will keep the SNR practically intact. That makes it the best option. However, you then are limited to the SNR of the analog volume controller (or the lowest SNR in the chain, often is the amp, but it can be elsewhere). You just need to make sure that the SNR of the other devices are higher than the amplifier to give very clear production. Otherwise, the noise floor would be that of the processors in the chain.

      I know, complicated. But I hope this helps.

      If instead of buying something like those you decide for a DAC, just pay attention to if it has single ended or balanced outputs and what the input to your amplifier unit is. If it is simple L+ and ground, that is single ended. If you have L+ gnd L-, you are looking at a balanced input for the amplifier and I would recommend finding a DAC with balanced out.

      If you have any more questions, feel free to ask.

    • #25938
      tvor-ceasar
      Moderator

      Or…

      You could always splice a pair of switched jacks into your TV’s speaker leads, sending the signal out to your amp, through attenuation if necessary. Could solve a whole host of problems at a lower cost.


    • #26041
      dameo182
      Participant

      Sorry guys, had some stressful family news earlier this week that took up most if my time, but I’ve got some time to look into this tonight now,


      @Tvor-Ceasar
      it sounds like a good idea, only I’m no where near qualified enough to make it happen, I’d end up breaking my tv or something 😂 but thank you for your input

      @AJC I appreciate the work you put into that post to help me with this, after reading the options you gave I think I’ll go down the DAC route, I was hoping that a single wire would suffice as I hate to have multiple boxes doing what a simple aux leads used to do. But given that I don’t have enough credits with the mrs to be allowed to buy a DAC of substantial cost I’m gonna be stuck with a cheap one. After I have a quick google search I’ll post a link to the product for your opinion if you don’t mind taking a look?

       

    • #26042
      dameo182
      Participant

      Had a quick search and found this,

      Not sure if it’s a balanced output though, the amp I’m using is just a cheap little bluetooth amp board with an aux in port which I intend to put inside the bedside organiser, it has good sound but as it’s just to watch tv in the bedroom its works well apart from the bluetooth breakup. It does have L/R+ and L/R- connections too. Would this DAC be sufficient?

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