Yes, stepped attenuators like the Goldpoint. There are also some coming out of Asia and Australia at good prices.
But you still have the problem of overall volume vs the gain of each section. The multi-gang attenuators will give you overall volume control of all 6 sections, but you still need to adjust the amps. Some fine tuning can be done in the DCX, but the gross adjustment to gain should be done at the amp. If your amp has a volume control, then you're good to go. Same list applies for the pot in the amp as for the multi-gang volume control.
If that does not make sense, please ask for further details.
But you still have the problem of overall volume vs the gain of each section. The multi-gang attenuators will give you overall volume control of all 6 sections, but you still need to adjust the amps. Some fine tuning can be done in the DCX, but the gross adjustment to gain should be done at the amp. If your amp has a volume control, then you're good to go. Same list applies for the pot in the amp as for the multi-gang volume control.
If that does not make sense, please ask for further details.
I will be using the DCX and amps for subs only, 2 channels for mid-bass (which will probably end up having similar levels) and either one or two for LF (depending on whether I decide to use a single driver sub with bridged output from one of the amp modules or two infinite baffle manifolds). The amps have 4 channels, but are pretty basic... no volume control. I was originally thinking of just using the DCX to control the levels, but now understand that it would be better to keep the levels fairly high on the DCX channels and use attenuators on the amp inputs for the main level control. I think I could probably get away with two 2-gang attenuators, one for each amp module. Once I get the levels (and filters) right between the DCX and amps for each of the subs, I shouldn't have to change anything there. Here is a picture of the amp - there is some extra space between the PS and transformer that I could use to mount the attenuators on the front panel. Does this sound reasonable?
-Doug
An externally hosted image should be here but it was not working when we last tested it.
Hey Doug, nice looking build on that amp! Neat work.
Sorry, I'm not getting your system and signal flow. Your 1st sentence above has me confused. Maybe it's just me....
Anyhoot, can you give us a better idea of the systems parts and signal flow? That should make it easier to help you. Just a quick and dirty flow chart would be nice, or a fuller description.
Sorry, I'm not getting your system and signal flow. Your 1st sentence above has me confused. Maybe it's just me....
Anyhoot, can you give us a better idea of the systems parts and signal flow? That should make it easier to help you. Just a quick and dirty flow chart would be nice, or a fuller description.
Here is a bit of extra info if it helps... The subwoofer level on my receiver can be set as high as +10db. I have read elsewhere that it is good to have the input signal to the DCX set as high as possible, correct?. I could opt to use the 3 front channel pre-outs to feed the DCX if I wanted to (LFE can be assigned to those if I want), but I would not be able to set the levels that high. Also, if it was not obvious, the subs are/will be DIY units without their own amps.
The DCX was sitting on my front doorstep when I got home, so I guess I can't justify procrastinating any more on the cables. Do folks think that the wiring method that I asked about on the last page is OK?
Thanks for the compliment on my amp build, Pano.
-Doug
The DCX was sitting on my front doorstep when I got home, so I guess I can't justify procrastinating any more on the cables. Do folks think that the wiring method that I asked about on the last page is OK?
Thanks for the compliment on my amp build, Pano.
-Doug
OK Doug, let me see if I get this right.
The DCX is driving ONLY the bass channels? The mains are coming from the Yammie.
You say 3-4 channels from the DCX. Do you mean channels 3&4 or "3, maybe 4 channels driving bass"? I assume the second.
So is the preamp out of the RX-Z7 volume controlled (variable)? Some preamp outputs are, many are not. If it is not, how do you plan to get the subs to follow the volume of the mains? If it is variable, that's good news. And this assumes that you are going into the DCX via the analog inputs, right?
You will need some sort of level control to set the relative levels of your sub amps. You can think of these as "trimmers." As you mention, once it is set, you won't need to change it. If you are just driving LF stuff, then a good pot will be just fine for these trimmers. I don't think you need to go to the expensive of stepped attenuators.
Did I get it right?
EDIT: Yes those cables will work. There might be better ways for the output, but those will certainly work.
The DCX is driving ONLY the bass channels? The mains are coming from the Yammie.
You say 3-4 channels from the DCX. Do you mean channels 3&4 or "3, maybe 4 channels driving bass"? I assume the second.
So is the preamp out of the RX-Z7 volume controlled (variable)? Some preamp outputs are, many are not. If it is not, how do you plan to get the subs to follow the volume of the mains? If it is variable, that's good news. And this assumes that you are going into the DCX via the analog inputs, right?
You will need some sort of level control to set the relative levels of your sub amps. You can think of these as "trimmers." As you mention, once it is set, you won't need to change it. If you are just driving LF stuff, then a good pot will be just fine for these trimmers. I don't think you need to go to the expensive of stepped attenuators.
Did I get it right?
EDIT: Yes those cables will work. There might be better ways for the output, but those will certainly work.
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That's the reason I developed my level control for the DCX2496. I do the level control entirely in the analog domain, between DCX and power amps, for max dynamic range. It has level control (and balance control) for all 6 channels but can also (pre)set the levels of the different channels to compensate for different amp and speaker sensitivities in each channel. All via a remote of course. Details on my website.
jd
staying with the power amp and speaker as our example.
The amplifier sees the speaker as Rload = 8ohms//cable capacitance+cable resistance
The amplifier has an output impedance Rout and this is usually ~0.1ohms
The speaker sees the source impedance Rs and this equals the output impedance of the amplifier + the cable resistance //cable capacitance.
The speaker also mimics Rin as far as the amplifier is concerned, i.e. the amplifier sees Rin = speaker impedance//cable capacitance+cable resistance
Rsource is what the receiver sees looking back to the source.
Rload is what the transmitter sees looking forward to the receiving cables.
Rin is what the transmitting cable sees looking forward to the receiver.
Rout is what the receiving cable sees looking back to the transmitter.
N.B.
if we ignore the capacitance and resistance of the interconnects, then Rin = Rload and Rout = Rsource.
BTW,
an amplifier specified as recommended minimum speaker impedance of 40hms is saying Rload>=4ohm. I would generally read this to mean the amplifier will not blow up driving 4ohms speakers at domestic listening levels, not partying.
I also believe that few amplifiers work well at this minimum recommended reliability determined Rload. I reckon that an 8ohm amplifier should be reliable driving a 4r0 load and a 4ohm amplifier should be reliable driving a 2r0 load and the output into both these resistor loads should not drop below -0.8dBV from the next higher resistor loading.
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if the receiver sets the volume at the speakers and it also sets the volume going into the DCX. This is bad.
If the receiver sets the volume going to the speakers but sends an unattenuated signal to the DCX then you are still in trouble. There is no way to gang the DCX output with the receivers volume control.
All channels need to be ganged attenuated before the speaker amplifiers. Using a receiver to drive the mids and/or trebles defeats this necessary option.
If the receiver sets the volume going to the speakers but sends an unattenuated signal to the DCX then you are still in trouble. There is no way to gang the DCX output with the receivers volume control.
All channels need to be ganged attenuated before the speaker amplifiers. Using a receiver to drive the mids and/or trebles defeats this necessary option.
Well, I will be using the receiver to control the overall volume, and I don't plan to run everything through the DCX (the amps on the Z7 are quite good and there is no direct amp-in option). I guess I will just have to live with less dynamic range and a higher noise floor on the subs when operating at lower volumes, then. Ideally, I would like to just like to leave the amps wide open, do the level balancing between individual subs and also for the subs relative to the mains with the DCX, and control the overall volume with the receiver. I know there are a lot of people who use a DCX to control subs this way, but they don't seem to be chiming in here.
Your volume control mod sounds like it would enable me to do what I want, but now I am wondering whether I'd just be better off using something with a better analog section to begin with like a dbx driverack 260, perhaps (the price difference is around the same as modding the DCX).
-Doug
My advice: Try the DCX as is with your receiver as the preamp to control the volume. I don't think you will be finding a dynamic range/noise floor problem, especially since this is for a sub only.
Yes, -10 to +10 db on the sub output. So, I could set that relatively high and then set the DCX levels relatively low to compensate. When I get everything ready I'll give that a try (the subs are still not fully assembled). It would be easy enough to add some pots as trimmers for the inputs. What defines good vs bad ones for this application?
- Doug
- Doug
best solution
Hi all!
Ok, I have tried to read all the message, but the thread keeps growing as I read it
I have learnt a lot, but I need an advise from you experts.
The first lesson is: try to keep the input level as high as possible (whithin clippin threshold of course). That's "easy" if you use the digital input, but also using the analog one, I have a preamp with enough gain.
Second lesson: keep the gain in the dcx around 0dB, if possible: I will.
Third lesson: volume regulation should be done between the DCX and the amps. Ok, I have planned to put a six channel ALPS after the DCX, followed by a tube buffer stage.
Fourth lesson: the DAC AKM4393 is not bad at all.
Fifth lesson: the analog output of the DCX is nothing to write home about. The two last lessons are asking for a better output stage. Say tranformers?
Ok, so far so good. I have then
DCX-trafos-potentiometers-buffers-amps
Seems ok, what do you think? But....
would it be possible to reduce the number of stages? I mean, can I avoid trafos connecting the potentiometer right after the DAC? Or, but I don't like it very much, putting the tube stage right after the DAC and after that the potentiometer? Other options?
Thanks for your help!
Ciao
Paolo
Hi all!
Ok, I have tried to read all the message, but the thread keeps growing as I read it
I have learnt a lot, but I need an advise from you experts.
The first lesson is: try to keep the input level as high as possible (whithin clippin threshold of course). That's "easy" if you use the digital input, but also using the analog one, I have a preamp with enough gain.
Second lesson: keep the gain in the dcx around 0dB, if possible: I will.
Third lesson: volume regulation should be done between the DCX and the amps. Ok, I have planned to put a six channel ALPS after the DCX, followed by a tube buffer stage.
Fourth lesson: the DAC AKM4393 is not bad at all.
Fifth lesson: the analog output of the DCX is nothing to write home about. The two last lessons are asking for a better output stage. Say tranformers?
Ok, so far so good. I have then
DCX-trafos-potentiometers-buffers-amps
Seems ok, what do you think? But....
would it be possible to reduce the number of stages? I mean, can I avoid trafos connecting the potentiometer right after the DAC? Or, but I don't like it very much, putting the tube stage right after the DAC and after that the potentiometer? Other options?
Thanks for your help!
Ciao
Paolo
Ciao Paolo,
You seem to have a pretty good idea of what is needed. You should not have much trouble.
One thing that is important to know: There is 2.5 volts on the output pins of the DAC chip. That is 2.5V on both positive and negative. So somehow you have to block the DC before going to your volume control amps, etc. This can be done with a cap on each leg, or a transformer. Or some active circuit like the opamps in the DCX. But you can't leave out this part.
I don't think you will need the tube buffer stage, but it sure won't hurt to try. What you want is a buffer that delivers more current to drive the amplifier input stages. I doubt you will need more voltage.
You seem to have a pretty good idea of what is needed. You should not have much trouble.
One thing that is important to know: There is 2.5 volts on the output pins of the DAC chip. That is 2.5V on both positive and negative. So somehow you have to block the DC before going to your volume control amps, etc. This can be done with a cap on each leg, or a transformer. Or some active circuit like the opamps in the DCX. But you can't leave out this part.
I don't think you will need the tube buffer stage, but it sure won't hurt to try. What you want is a buffer that delivers more current to drive the amplifier input stages. I doubt you will need more voltage.
One other thought.
I might be possible to put a dual triode right after the DAC. Each grid driven by one of the DAC outputs (+/-). That would give you a push-pull with the dual triode. Might be able to go to the pot after that.
But I'm not "tubey" enough to know how to work out the details. I'm sure someone here is.
I might be possible to put a dual triode right after the DAC. Each grid driven by one of the DAC outputs (+/-). That would give you a push-pull with the dual triode. Might be able to go to the pot after that.
But I'm not "tubey" enough to know how to work out the details. I'm sure someone here is.