followed exactly from dcb1 schematic taken from post 4
http://www.diyaudio.com/forums/anal...as-hotrodded-blue-dcb1-build.html#post2269468
relay is turning a led on as a test circuit.
tapping 12V from LDR volume control
http://www.diyaudio.com/forums/anal...as-hotrodded-blue-dcb1-build.html#post2269468
relay is turning a led on as a test circuit.
tapping 12V from LDR volume control
That gives an RC time constant of 4.7s.
The capacitor will charge to ~62% of final voltage in ~4.7s if there is no other current draw on the 47k.
But the DCB1 does not work like that.
The cap does not get a chance to charge to 62% of final voltage. It's a screwed up delay circuit, that relies on the reverse breakdown of a bjt to mimic a Zener. Stoopid.
I changed mine by adding an extra bjt + cap and throwing away the unnecessary 517.
It works properly.
I think I must step in to moderate this posting. I am really sorry if I am causing uneccessary remarks by members. Nonetheless, I am merely seeking advise on my circuit connection since it is not working properly. not to have silly remarks about the design. I am sure the delay has proven itself well.
So to sum thing up, I am using a regulated 12V supply. I tried with multiple 12V supplies I have on hand and outcome is the same: no delay in relay. The relay energizes when I feed 12V to it so there is no problem on the relay side. I am not using a resistor to lower the V to 5V. I am using 18V transfo into rectifier feeding an lm7812.
I am about to build a dcb1 and I have a standard B1 needing a delay relay so I decided to use the dcb1 delay relay circuit. The circuit has its own 12V supply so I am not tapping from existing supplies for B1 nor LDR volume control. The delay does not seem to work. As I said earlier, the 550 center pin is getting supply from the 100uF cap and I see it increase to about 4V, no more, no less. I'll try to post pics later.
thanks and kind regards.
So to sum thing up, I am using a regulated 12V supply. I tried with multiple 12V supplies I have on hand and outcome is the same: no delay in relay. The relay energizes when I feed 12V to it so there is no problem on the relay side. I am not using a resistor to lower the V to 5V. I am using 18V transfo into rectifier feeding an lm7812.
I am about to build a dcb1 and I have a standard B1 needing a delay relay so I decided to use the dcb1 delay relay circuit. The circuit has its own 12V supply so I am not tapping from existing supplies for B1 nor LDR volume control. The delay does not seem to work. As I said earlier, the 550 center pin is getting supply from the 100uF cap and I see it increase to about 4V, no more, no less. I'll try to post pics later.
thanks and kind regards.
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Don't be sorry.
You have a problem.
You are asking for help.
You are one of a long list of Members who found that this delay circuit is not 100% reliable. Many for quite different reasons.
Your problem sounds a bit different from the usual, since the more common failure is to not pull in.
Can you post a detailed pic of your plugboard and maybe someone can see the error.
In the attached schematic, it show's 3 pin input and output connectors. If those connectors are XLR connectors then they are mis-wired. The XLR connector pin #1 is only connected to the chassis, it is not part of the audio circuit and should not be connected to audio ground or circuit ground.
Do a search on the "pin 1 problem".
Thank you. Voltages across the resisitors are 1.57 v. and 1.81v.. DC at the outputs is -1 mvdc and 6mvdc, totally acceptable, IMO. I have it hooked to my F5 and signal coming fom a DVD player (don't have a signal generator) and the sound is very good. It makes my old Infinity shop speakers really sing. I just had a "goose bump" moment on the last track
.It is still a surprise to see the Fairchild MOSFET's running at such a low temp, just inches away are another two pairs of Fairchilds on the F5, they are a bit warmer.
6mV is not the norm, usually the builders report less. It shows your other channel with -1mV has even more successful audio jfet pair matching. See how much of a DC offset is created at F5's output eventually and if it is still low enough. As for running current, since you got a sturdy construction with big trafo and copper bars under the Mosfets and is so cool, its easy you parallel another 6.8R on the 1.57V side 10R and a 8.2R on the 1.81V side 10R so you go circa 400mA each side. That will give it a ''bigger'' sound. The Fairchild Mosfets are still IRFP9240/240 types?
Kevin, thank you for looking over my proposed diagram.
I am no expert but as I understand it Rane note’s are correct if you're dealing with equipment with fully differential (non-ground referenced) topology. However the DCBI are ground-referenced modules, so therefore would need to be connected to XLR pin 1, and since that signal is the shield, then it needs to be connected to the chassis as well.
I may have to use a ground loop breaker though, since this will be a single chassis build.
Do you agree?
I am no expert but as I understand it Rane note’s are correct if you're dealing with equipment with fully differential (non-ground referenced) topology. However the DCBI are ground-referenced modules, so therefore would need to be connected to XLR pin 1, and since that signal is the shield, then it needs to be connected to the chassis as well.
I may have to use a ground loop breaker though, since this will be a single chassis build.
Do you agree?
The Ground Reference is actually the Signal Return in an unbalanced DCB1.
The Signal Return is common to the two channels of the unbalanced DCB1.
If you connect a +IN signal to one channel and a -IN signal to the other channel then the DCB1 behaves as a balanced buffer. It reads the difference at the two INs and it's output is directly related to the two INs. The commoned Signal Return does not need to be connected to the PIN 1 of the XLR. But this is an electronically balanced circuit. The INs are not "floating" as in a real balanced impedance receiver and so at some point the commoned Signal Return must be referenced to an Audio Ground reference point. Rane and Jensen and Self and Jung all show ways to do this without the PIN1 problem.
BTW,
your volume adjustment pots ruin the whole reason for adopting balanced topology. The pots guarantee that the receive impedances will not match and now balanced DCB1s offer no advantage over unbalanced DCB1 in noise/interference rejection.
The Signal Return is common to the two channels of the unbalanced DCB1.
If you connect a +IN signal to one channel and a -IN signal to the other channel then the DCB1 behaves as a balanced buffer. It reads the difference at the two INs and it's output is directly related to the two INs. The commoned Signal Return does not need to be connected to the PIN 1 of the XLR. But this is an electronically balanced circuit. The INs are not "floating" as in a real balanced impedance receiver and so at some point the commoned Signal Return must be referenced to an Audio Ground reference point. Rane and Jensen and Self and Jung all show ways to do this without the PIN1 problem.
BTW,
your volume adjustment pots ruin the whole reason for adopting balanced topology. The pots guarantee that the receive impedances will not match and now balanced DCB1s offer no advantage over unbalanced DCB1 in noise/interference rejection.
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Thanks Kevin and Andrew,
I shall connect pin 1 only to the chassis, I will also connect the signal return to audio ground via a Rane and Jensen and Self and Jung approved method.
Andrew,
In regards to the volume adjustment pots, you’ve stated in the Mesmerize build thread that if the sum of components in the two balance halves were 0.1% or better matched this could be done.
Other than this time consuming solution is there a better alternative for a balanced DCB1 build? I don’t really know if this is achievable without running into these inherent problems, I keep hitting a brick wall...
I shall connect pin 1 only to the chassis, I will also connect the signal return to audio ground via a Rane and Jensen and Self and Jung approved method.
Andrew,
In regards to the volume adjustment pots, you’ve stated in the Mesmerize build thread that if the sum of components in the two balance halves were 0.1% or better matched this could be done.
Other than this time consuming solution is there a better alternative for a balanced DCB1 build? I don’t really know if this is achievable without running into these inherent problems, I keep hitting a brick wall...
Thanks, Salas. I did see a rise through the miscreant channel at the F5 outputs, perhaps to 12mvdc ( I need to record these numbers, d^%%mit). I will pass along your advice about the resistors to the owner. Yes, the copper heat spreaders and the mass of the case keep everything very cool, I was seeing interior case temps of 84 f. and case temps on the IRFP 9240/240 pairs in the neighborhood of 91-94 f..
wipers on tracks can never give the matching required for balanced impedance connection.
Switched settings could be used to achieve much better matching, but that would take a lot of accurate trimming to achieve the matching at every step of the volume control.
How well will the switched pot retain that <0.1% matching during the life of the switch?
Switched settings could be used to achieve much better matching, but that would take a lot of accurate trimming to achieve the matching at every step of the volume control.
How well will the switched pot retain that <0.1% matching during the life of the switch?