I wasn't sure which forum to put this in but here I am anyway.
I built my son a sub a little while back (see photo's) which has been working great, but as soon as I gave it to him I realised I should have designed in an easy way to boost the sub volume if required. Prior to the Sub I built him an amp/crossover that combines a Icepower ASX125 amp and MiniDSP setup and made sure I had a Sub Out in it as I knew I would need it eventually. The MiniDSP splits the signals to the main speakers & to the sub but there is no way of upping the sub volume without connecting the computer to the MiniDSP to change the settings which is obviously a pain to do.
The sub is powered by a bridged Icepower ASX125 amp. What I am thinking is maybe I could use a buffer/headphone amp/preamp or similar to boost the signal. So the sub would just have a volume knob that boosts the incoming signal.
My knowledge is limited so I'm not really sure if this is a good idea or not, and have no idea what to use to do it if it is a good idea. Oh yer it would have to be SMALL 🙂
Any and all suggestions will be gratefully received.
I built my son a sub a little while back (see photo's) which has been working great, but as soon as I gave it to him I realised I should have designed in an easy way to boost the sub volume if required. Prior to the Sub I built him an amp/crossover that combines a Icepower ASX125 amp and MiniDSP setup and made sure I had a Sub Out in it as I knew I would need it eventually. The MiniDSP splits the signals to the main speakers & to the sub but there is no way of upping the sub volume without connecting the computer to the MiniDSP to change the settings which is obviously a pain to do.
The sub is powered by a bridged Icepower ASX125 amp. What I am thinking is maybe I could use a buffer/headphone amp/preamp or similar to boost the signal. So the sub would just have a volume knob that boosts the incoming signal.
My knowledge is limited so I'm not really sure if this is a good idea or not, and have no idea what to use to do it if it is a good idea. Oh yer it would have to be SMALL 🙂
Any and all suggestions will be gratefully received.
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Hi, it looks like there is a Volume pot on the opposite side of the box to the Ins/Outs ? Is this already @ Max ?
You would need something similar to a Buffer, but with gain. Not difficult to do, but first,
What are the + - Voltages to the Amp/s ?
You would need something similar to a Buffer, but with gain. Not difficult to do, but first,
What are the + - Voltages to the Amp/s ?
Hi
The Subs Icepower amp input rating is Max Input + - 3.3Vp
The MiniDSP sending the signal to the Sub says it's output is Max 2Vrms
I hope that helps.
The volume control is a global volume so it equally effects the main speakers & the sub at the same time.
The Subs Icepower amp input rating is Max Input + - 3.3Vp
The MiniDSP sending the signal to the Sub says it's output is Max 2Vrms
I hope that helps.
The volume control is a global volume so it equally effects the main speakers & the sub at the same time.
I meant, what is the + - DC Power Supply Voltage to the Amps 😉 Once i know that i can design a simple circuit for you !
The Icepower amps (D Class) have a + - 24v unregulated auxiliary supply available that's good for -250mA +250mA max. I dont think you would be able to draw power from anywhere else on this amp.
Thanks for the help I wasn't expecting someone to design a circuit for me, but wouldn't say no 🙂
I do have a couple of unused buffer boards designed by Nisbett as input buffers for the Icepower amps, I was wondering if they could be modified and with the right choice of OPA might do the trick. I wouldn't know what the right choose of OPA would be or what mods the board might need.
The details on the Buffer are at Project files: Opamp buffer for ICEpower ASX-modules | theslowdiyer
Ahh, now we can do business. This should do what you want. I've shown a NE5534 OpAmp, but you can use any you choose. The diodes are 1W Zener types which will regulate the DC supply to the OpAmps. You might be able to use the Nisbett PCB's to constuct it.
I'm not clear if the ASX125 has an internal bridge circuit/switch, or requires one input to be inverted externally ? My circuit should be fine if it has the internal, if not let me know & i'll add an inverter !
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🙂 Thank you very much.
I'm not sure exactly what you are referring to re the "internal bridge switch" I have clipped out sections of the Icepower amp manual re the Aux power supply and attached them that may be a help.
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Pleasure 🙂
Actually rethinking things, you would be fine with 400mW Zeners & 250mW Resistors. Higher ratings won't hurt anything, just might cost a bit more.
Well usually Amps that are sold as Bridgeable, have a switch so you can just feed a signal into one input & an internal on board inverter then feeds the other input out of phase. You need to find out from somewhere whether this is how it is. If there is one you should see the switch & it would be labeled as Invert for eg. If not you need the extra OpAmp inverter i referred to earlier. Let me know either way.
OK if that's an Inverter I didn't install one 😀 I't not in the amp
My understanding is the MiniDSP combines the R&L channels and that's what I'm sending to the amp.
Whats the inverter do?
Please don't tell me a mashed signal at the amp output.
I didn't think it was in the Amp, so how is the Amp getting an Inverted signal to the other input from your main signal input ?
OK, so it's a mono signal which is fine & exactly what you need. But is that just going to one input on the Amp ? What's connected to the other input ?
Inverts the signal output from the PreAmp/MiniDSP etc, to feed the other half of the Amp. So the Amp gets one input in phase & the other out of phase. That's how bridging works ! 1 stereo Amp connected as 2 mono Amps @ the output, with the speaker connected between the speaker positive terminals. There should be NO connection to the negative terminals !
Maybe ! it depends on your answers.
X 6.1 = 15.75dB Which is most likely more than you need, but that's what the 10k Pot is for, to set the level you require ! You could reduce the 5k1 resistor to 1k which would give you x 2 = 6db, or any other suitable value between 1k & 5k1. Try 5k1 first & see what it's like.
Let's get the Inverter details sorted first !
The mono signal from the MiniDSP is feed to both inputs of the amp.
Excellent thanks
I had a look at the OPA chooses at Mouser and there are only!!!1377 to choose from in the single channel range 😕
I tried comparing the parameters with the one in your drawing but have no idea whats what really. All I can say is I'm happy to pay more for the OPA if you think it will make any difference to the sound quality and you can recommend one or tell me what parameters I need to focus on.
I tried comparing the parameters with the one in your drawing but have no idea whats what really. All I can say is I'm happy to pay more for the OPA if you think it will make any difference to the sound quality and you can recommend one or tell me what parameters I need to focus on.
Well as you said that you havn't put in an inverter, as expected the Amp must already have one, & possibly be configured for Bridging/BTL? BTL = bridged tied load.
Did you buy it pre configured ?
Is the speaker + & - connected across BOTH the +'s of the Amp ? If so then it must have been pre configured by "someone" ! If not, it's not in BTL, but will still work as a single Amp.
If it is already in BTL then you don't need to configure it. As i mentioned before, it must have a switch, or jumper etc, on board to turn it into BTL by using an onboard inverter.
In the icepower PDF i don't see any mention of how to configure the Amp for BTL ? Wierd !
Anyway, you won't need the extra inverter, so my circuit will achieve what you want.
Re OPA's
As it's only for bass, quite honestly almost any would be fine. The one i showed for eg.
Let me know how it goes.
My understanding is that with the 50ASX there are 2 completely separate modules one for SE & one for BTL but with the 125ASX, 250ASX etc the one module will do both, having read the user manual & the Designers manual I assumed all I had to do was wire it as per the attachment although as mentioned I didn't install an inverter as I had no idea what the symbol was. In the attachment it says "When using the BTL module" which makes you think there is a separate BTL module, but in lots and lots of places in the documents it refers to "BTL mode" just like the example below.
BTL Sync pin
"The BTL synchronization pin is used when the amplifier is
operated in BTL mode. When the amplifier is used in BTL
mode, the BTL sync pin must be pulled low (0V). By setting
the BTL sync pin low it is ensured that the switching frequencies
of the two separate amplifier channels are tied
closely together for optimized THD performance."
I fairly confident that as long as you wire it as per the attached diagram, including the BTL sync pin it should be operating in BTL mode. But I not so confident about the inversion of the one of the channels. I'll do a bit more looking to see if I can find any reference to it anywhere on the Web.
Thanks again
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Yes their "manual" is not very clear at all !
The inverter IS shown as external to the Amp ! However, i "think" they are "attempting" to explain/show that, CH1 is inverted internally when the BTL sync pin is tied to ground.
Keep me posted,
Regards
The inverter IS shown as external to the Amp ! However, i "think" they are "attempting" to explain/show that, CH1 is inverted internally when the BTL sync pin is tied to ground.
Keep me posted,
Regards
Lt Spice Schematic
How's this look?
I'm thinking I will rebuild the sons amp and include this Bass boost in the amp as I also want to add in a power sequencing circuit (to stop the bad noises from the MiniDSP) that I have a design for, and maybe an signal sensing on/off circuit that I have PCB for.
This thread leads me to believe I do need to invert the signal but I'm not getting any response.
http://www.diyaudio.com/forums/clas...design-ideas-icepower-125asx2-btl-mode-3.html
How's this look?
I'm thinking I will rebuild the sons amp and include this Bass boost in the amp as I also want to add in a power sequencing circuit (to stop the bad noises from the MiniDSP) that I have a design for, and maybe an signal sensing on/off circuit that I have PCB for.
This thread leads me to believe I do need to invert the signal but I'm not getting any response.
http://www.diyaudio.com/forums/clas...design-ideas-icepower-125asx2-btl-mode-3.html
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