The boards are following the design correctly. There are no discrepancies or faults in this regard. Ideas about what you may like to do differently are not accountable as fixing errors in the boards. This is a well seasoned and tried out project with tons of ''all well'' feedback. If you don't like it, post your own, make a thread. Enough is enough.
Any modification to the boards of any system that is referred as ''DCB1'', ''Mezmerize'', ''Hypnotize'', carries the name ''Salas'', or makes use of shunt regulators same as those incorporated to the above listed, is unofficial, not endorsed, not recommended, and not allowed to use those titles and PSUs. Any new idea, modification, spin off, or PCB resembling those, should be presented and discussed in another thread and be an entirely different project not carrying any reference to my name.
If you had the opportunity to use a volume control source with steady output impedance in the recommended 10-20kOhm range, the bandwidth would be steady too. That is due to keeping a steady relation with the Jfet input capacitance. If that could be a subjective improvement I am not in a position to tell since I haven't used anything like that.
Start relay delay... or lack of.
Hi guys,
When I switch on my DCB1 the relay clicks within .5 sec of when I plug it in which is a lot shorter than the 3-7 seconds it's supposed to take.
I'm a newbie so I don't know what do I need to look for. Does anybody have any ideas?
Thanks so much,
Peter
Hi guys,
When I switch on my DCB1 the relay clicks within .5 sec of when I plug it in which is a lot shorter than the 3-7 seconds it's supposed to take.
I'm a newbie so I don't know what do I need to look for. Does anybody have any ideas?
Thanks so much,
Peter
I'm not familiar with the circuit, but looked at the schematic in the first post, and I would say things to look at would be, the 47K resistor and the 47uF cap, if either of those is the wrong (too small) a value then the cap could be charging too fast and the relay switching on earlier than expected.
edit: but as andrew says, if you aren't getting any nasty noises on startup it shouldn't matter.
Tony.
edit: but as andrew says, if you aren't getting any nasty noises on startup it shouldn't matter.
Tony.
No it does not matter, as long as you get no pops from the speakers, its OK and no reason then to wait longer, so don't fix it if it ain't broken. You could use a larger resistor, but naah. All the relays clicked here till now, so no worries.
It Runs!
Hi all
I am happy to have just completed my Hypnotize preamp with LDR attenuator.
The buffer shows a clean audio output on my scope, however my dc offsets are +18mV and +20mV!!
I did take a couple of liberties with the design, one of which was using LSK117 FETs on the DCB1 (including buffer section) which maybe was not such a good idea. Could the offset be due to the different devices? or maybe not close enough pair matching?
My supply rails are almost identical at +9.65V and -9.64V.
Your thoughts or comments would be great.
Jeremy
Hi all
I am happy to have just completed my Hypnotize preamp with LDR attenuator.
The buffer shows a clean audio output on my scope, however my dc offsets are +18mV and +20mV!!
I did take a couple of liberties with the design, one of which was using LSK117 FETs on the DCB1 (including buffer section) which maybe was not such a good idea. Could the offset be due to the different devices? or maybe not close enough pair matching?
My supply rails are almost identical at +9.65V and -9.64V.
Your thoughts or comments would be great.
Jeremy
You need to measure the Idss of the two pairs in the "amplifier" section.
Your measuring technique must try to minimise the variations you will see in your measured results.
A 9V battery and a 1r0 1% resistor and a multimeter set to read 199.9mVdc is your test equipment.
Mount the G+S legs in an insulated crocodile clip. Connect this wire to battery -ve.
Attach an insulated croc clip to the Drain leg. Take this wire to the 1r0 resistor and then connect the other end of the resistor to the +ve battery terminal. No wait. Don't make that last connection. This becomes your "switch".
Clip your meter leads across the 1r0 resistor. Turn on the DMM.
Now close your switch to read the mV on the meter. That is approximately your Idss. Watch the value change. Clamp the jFET between your fingers. Watch the value change even more. This test is very much influenced by Tj. Everything around that jFET will do it's best to keep changing your readings.
You have to find a method that, for you, works by giving consistent readings for your approximate Idss value.
Then adopt that method precisely to measure your stock of jFETs.
select a pair that have the same Idss.
The 1r0 and the 199.9mVdc scale set the resolution of your measurements. You cannot get better then +-0.1mA.
If you feel that your final procedure deserves a finer resolution, then swap the 1r0 to a 10r0 1% to allow results to come out to +-0.01mA
If you do get a good repeatable measuring method and can find a pair of devices that have the same Idss +-0.1mV then you will find that your output offset <=+-0.2mV.
If you get +0.1mV or +0.2mV then swap the two jFETs around. You want -ve output offset or zero output offset, not +ve.
Your measuring technique must try to minimise the variations you will see in your measured results.
A 9V battery and a 1r0 1% resistor and a multimeter set to read 199.9mVdc is your test equipment.
Mount the G+S legs in an insulated crocodile clip. Connect this wire to battery -ve.
Attach an insulated croc clip to the Drain leg. Take this wire to the 1r0 resistor and then connect the other end of the resistor to the +ve battery terminal. No wait. Don't make that last connection. This becomes your "switch".
Clip your meter leads across the 1r0 resistor. Turn on the DMM.
Now close your switch to read the mV on the meter. That is approximately your Idss. Watch the value change. Clamp the jFET between your fingers. Watch the value change even more. This test is very much influenced by Tj. Everything around that jFET will do it's best to keep changing your readings.
You have to find a method that, for you, works by giving consistent readings for your approximate Idss value.
Then adopt that method precisely to measure your stock of jFETs.
select a pair that have the same Idss.
The 1r0 and the 199.9mVdc scale set the resolution of your measurements. You cannot get better then +-0.1mA.
If you feel that your final procedure deserves a finer resolution, then swap the 1r0 to a 10r0 1% to allow results to come out to +-0.01mA
If you do get a good repeatable measuring method and can find a pair of devices that have the same Idss +-0.1mV then you will find that your output offset <=+-0.2mV.
If you get +0.1mV or +0.2mV then swap the two jFETs around. You want -ve output offset or zero output offset, not +ve.
Last edited:
BOM confusion
I'm just ordering the components that I dont have for my DCB1 trial.
I'm confused with the BOM.
On the schematic there are 4 x 47R resistors fitted between VCC+, VCC- and the Sources of the IRFP240 and IRFP9240.
They do not seem to appear on the BOM.
I can guess that they should be 1W each but then they would be too big to fit the board.
The BOM does show 4 x 470R 0.5W Carbon types. The only 470R resistors on the scematic are Gate drivers which surel;y don't need to be 0.5W.
I'm just ordering the components that I dont have for my DCB1 trial.
I'm confused with the BOM.
On the schematic there are 4 x 47R resistors fitted between VCC+, VCC- and the Sources of the IRFP240 and IRFP9240.
They do not seem to appear on the BOM.
I can guess that they should be 1W each but then they would be too big to fit the board.
The BOM does show 4 x 470R 0.5W Carbon types. The only 470R resistors on the scematic are Gate drivers which surel;y don't need to be 0.5W.