I just finished my Buffer and I love it. As next step I would like to build up a lightspeed attentuator to replace my Alps Pot. I'm just not fully sure how to connect the Buffer to the Lightspeed Attentuator board. Anyone who has done it before and can give me some advice? Sorry I'm quite a noob regarding these things...
Thanks
Carsten
Thanks
Carsten
@Marra I'm going to use a sepeate power supply for the lightspeed.
@dimkasta Okay, but what to do with the third contact? Lightspeed has ground and signal, but how to deal with the third one on a normal potentiometer (2x connectors to resitance material 1x wiper connector). Not sure how to handle that part on the Buffer Board.
@dimkasta Okay, but what to do with the third contact? Lightspeed has ground and signal, but how to deal with the third one on a normal potentiometer (2x connectors to resitance material 1x wiper connector). Not sure how to handle that part on the Buffer Board.
Which lightspeed do you use? Uriah's?
Imagine the two LDRs on lightspeed as the two parts of the pot
"Signal in" is the front of the Series LDR. "Signal out" is its back.
"Signal out" is also the front of the shunt LDR, so imagine it as the wiper of a pot. And the back of the shunt LDR goes to ground or RCA return/shield.
Imagine the two LDRs on lightspeed as the two parts of the pot
"Signal in" is the front of the Series LDR. "Signal out" is its back.
"Signal out" is also the front of the shunt LDR, so imagine it as the wiper of a pot. And the back of the shunt LDR goes to ground or RCA return/shield.
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Hi Gents, happy New Year,- hope i am in the right place???- I have a word…HELP!!
I have built my first project a Memorize (if you can read a London Underground map you can read a circuit diagram right?)—it lights up (hooray!)- But it’s not well!!
Having populated the board (Except for the BC 517—can’t get one in this town!) checked all transistors and cap orientations and all links are in (or bridged with 2 x 300 ohm resistors for the 5 v relays I have in.)
I have matched the LEDS up quite closely and I have tried to match up the four 2SK470BL using a battery as gleaned from the forum. (The information not the battery!)
I have wired it up and turned it on to find I have a all LEDs lit (Hooray!)- But the two IFRP240 gets quite hot,
On The other side the two IFRP9240 get a little warm but nothing like the two IFRP 240 (I can touch them for around 20 seconds, so it’s less that 50 degrees?)
Also I have used 5 volt relays (only ones I could get) and used 2 x 300 ohm resistors across the link
But still get 11. 9 volts at the switch (between the switch earth and selected relay pole on the switch) the 300 ohm resistors don’t seem to do much (should it be a 600 ohm pair here?)
The salient points are : Transformer is 50 V/A 2 x 12 volts with the “0v” wires tied together for a “faux” centre tap unloaded the AC voltage is 14.3v and 14.53v (AC) but I thank that’s fine?
II get: across the two 68 ohm resistors I get 1.80V on the IFRP9240 side-
and get 1.6 v on the IFRP240 side
On the “3 pads/test points” with 0v in the center I have +10.75 and -10.12 respectively (not to bad?)
But I think I am sinking more current on the IFRP240 side despite sticking to the design?
(The only difference I have is the BC 550 was replaced by a BC546C (but according to the data sheet for that device they are similar enough?)
I can’t yet check the DC offset till I get a BC 517—or is there a work around for this?
To be honest I am not sure where to go from here or where to measure, any ideas boys?—sorry for the long post.
Regards
Johnny
I have built my first project a Memorize (if you can read a London Underground map you can read a circuit diagram right?)—it lights up (hooray!)- But it’s not well!!
Having populated the board (Except for the BC 517—can’t get one in this town!) checked all transistors and cap orientations and all links are in (or bridged with 2 x 300 ohm resistors for the 5 v relays I have in.)
I have matched the LEDS up quite closely and I have tried to match up the four 2SK470BL using a battery as gleaned from the forum. (The information not the battery!)
I have wired it up and turned it on to find I have a all LEDs lit (Hooray!)- But the two IFRP240 gets quite hot,
On The other side the two IFRP9240 get a little warm but nothing like the two IFRP 240 (I can touch them for around 20 seconds, so it’s less that 50 degrees?)
Also I have used 5 volt relays (only ones I could get) and used 2 x 300 ohm resistors across the link
But still get 11. 9 volts at the switch (between the switch earth and selected relay pole on the switch) the 300 ohm resistors don’t seem to do much (should it be a 600 ohm pair here?)
The salient points are : Transformer is 50 V/A 2 x 12 volts with the “0v” wires tied together for a “faux” centre tap unloaded the AC voltage is 14.3v and 14.53v (AC) but I thank that’s fine?
II get: across the two 68 ohm resistors I get 1.80V on the IFRP9240 side-
and get 1.6 v on the IFRP240 side
On the “3 pads/test points” with 0v in the center I have +10.75 and -10.12 respectively (not to bad?)
But I think I am sinking more current on the IFRP240 side despite sticking to the design?
(The only difference I have is the BC 550 was replaced by a BC546C (but according to the data sheet for that device they are similar enough?)
I can’t yet check the DC offset till I get a BC 517—or is there a work around for this?
To be honest I am not sure where to go from here or where to measure, any ideas boys?—sorry for the long post.
Regards
Johnny
Your PSU voltages read good. About the voltage drop on the CCS resistors there is not much difference when divided by their value between sides. I hope you got no oscillation on the negative side, which is not too easy to get on a given proven layout. Are there any sinks? Use another 550 or 546 to populate the 517 place. BUT solder a 100nF capacitor between its collector and base pins underneath the board. It should work activating the output relay without mechanical chatter. Then you will be able to have output and see about DC offset. Happy new year!
Hi Salas,
the trick with the BC 556 and cap worked very nicely, about 5 seconds and a nice "click" ta! for that.
With regards to the DC offset, its in the mili volt range but is jumping around (or so my volt meter tells me) when measured with 0v at the common earth and pos probe on the left/right channel output pins (i have installed a "molex" type socket)
but is very quite (no noise in fact) when applied directly to my Fostex 206E speakers, one channel is OK gives the same out volume as in so it unity gain?- sounds nice to!!
The other channel is very weak, can hardley hear it (i have acrapply 50 K ohm alps pot on just now for testing, will change when funds allow)
I dont know if the way to go is to buy some matched transistors (the IFRP 240/IFRP9240 and 4 x matched smaller ones from a very nice gent on this forum) , but i guess if the "normal sounding " side is Ok i could make A/B comparison checks and do it that way? (that sounds logical to me!) - also must adress the 12 v on my 5 v relays-- 2 x 600 ohm resistors required??
Cheers johnny
the trick with the BC 556 and cap worked very nicely, about 5 seconds and a nice "click" ta! for that.
With regards to the DC offset, its in the mili volt range but is jumping around (or so my volt meter tells me) when measured with 0v at the common earth and pos probe on the left/right channel output pins (i have installed a "molex" type socket)
but is very quite (no noise in fact) when applied directly to my Fostex 206E speakers, one channel is OK gives the same out volume as in so it unity gain?- sounds nice to!!
The other channel is very weak, can hardley hear it (i have acrapply 50 K ohm alps pot on just now for testing, will change when funds allow)
I dont know if the way to go is to buy some matched transistors (the IFRP 240/IFRP9240 and 4 x matched smaller ones from a very nice gent on this forum) , but i guess if the "normal sounding " side is Ok i could make A/B comparison checks and do it that way? (that sounds logical to me!) - also must adress the 12 v on my 5 v relays-- 2 x 600 ohm resistors required??
Cheers johnny
Having one channel OK and its offset in the mV, your PSUs should be OK too by simple reasoning, because they are common to both channels. Address the proper relay voltage issue first. Start with 2x270 Ohm relay voltage drop resistors, then measure across the diode next to one of them activated relays for a voltage between 3.75V-5V. If not in there, trim the resistors values. Maybe the other channel weakness is a struggling relay contacts issue, I hope you are lucky enough for no 5V relay to have got it bad at 12V. After the above is done, let us know where it stands.
Hi Salas,
Well i changed the battery on my multimeter and so did my voltages on my Mez!!
I now have : 4.46 volts at the switch/relay coil (nice!)
0.28v/0.19v DC offset at the output (OK?)
+ 10.63/- 10.09 on the board (acceptable?)
Apart from changing my multimeter battery i did nothing different from my last reading (apart from turn it on!! i will check all joints on the PCB again.
The IFRP240 side gets quite hot, but i have heatsinked it for now, but compared to the other side (which is quite cool) it seems to be working hard but volume at output is the same for each side.
I don’t know why this is?
Apart from that i don’t know if supplying it with a hexfred rectifier or (more realistically) getting two mundorf M lytics on the inputs would help as well as getting a light speed attenuator when funds allow, for now i will put two 50k series resistor across the 50k Alps pot to keep things in order.
By the way did i say it sounds great!- thanks Mr Salas.
Well i changed the battery on my multimeter and so did my voltages on my Mez!!
I now have : 4.46 volts at the switch/relay coil (nice!)
0.28v/0.19v DC offset at the output (OK?)
+ 10.63/- 10.09 on the board (acceptable?)
Apart from changing my multimeter battery i did nothing different from my last reading (apart from turn it on!! i will check all joints on the PCB again.
The IFRP240 side gets quite hot, but i have heatsinked it for now, but compared to the other side (which is quite cool) it seems to be working hard but volume at output is the same for each side.
I don’t know why this is?
Apart from that i don’t know if supplying it with a hexfred rectifier or (more realistically) getting two mundorf M lytics on the inputs would help as well as getting a light speed attenuator when funds allow, for now i will put two 50k series resistor across the 50k Alps pot to keep things in order.
By the way did i say it sounds great!- thanks Mr Salas.
H I Salas,
My Multimeter is an old Fluke, buts it seem OK.
My offset voltages were incorrect they are actully: 0.028v and 0.018v respectively,
(bit high---still not in the 5 Milivolt ballpark)
The voltages across the r1/r2 set are 1.50v (IFRP240 side) / 1.8v (IFRP 9240 side)
The gate source voltage is 2.65v and 6.28v (IFRP240) the Gate /Drain is 3.60v and 4.02v on this side.
The gate source voltage is 2.36v and 7.20v (IFRP9240) the Gate Drain is 2.36v and 7.20v on this side.
I got the LED sides as symmetrical as possible and attempted to get the gain of the 2 pairs of input transistors as similar as possible, is the bad offset due to a mismatch in the Buffer input pairs of the 2SK740BL? Or is there something more fundamentally wrong on the bias side? (or both?)
Any ideas gratefully received (it still sounded good during initial testing though!)
Cheers all
Johnny
My Multimeter is an old Fluke, buts it seem OK.
My offset voltages were incorrect they are actully: 0.028v and 0.018v respectively,
(bit high---still not in the 5 Milivolt ballpark)
The voltages across the r1/r2 set are 1.50v (IFRP240 side) / 1.8v (IFRP 9240 side)
The gate source voltage is 2.65v and 6.28v (IFRP240) the Gate /Drain is 3.60v and 4.02v on this side.
The gate source voltage is 2.36v and 7.20v (IFRP9240) the Gate Drain is 2.36v and 7.20v on this side.
I got the LED sides as symmetrical as possible and attempted to get the gain of the 2 pairs of input transistors as similar as possible, is the bad offset due to a mismatch in the Buffer input pairs of the 2SK740BL? Or is there something more fundamentally wrong on the bias side? (or both?)
Any ideas gratefully received (it still sounded good during initial testing though!)
Cheers all
Johnny
2SK740BL? What is that part? The right JFETs are 2SK170BL. If the DMM is still OK (old Flukes are usually reliable for decades) then the offset is still high also.
Are the PSU voltages on regulated side about +/- 10VDC? Can you check that also? If its really a matter of matching, yes it will solve when all other things are OK. But your data is not very cohesive yet so to tell for sure. Flukes are good and old ones usually stay good as I have mentioned. Try a borrowed meter just to cross check results before doing anything else though. If you need a second cheap DMM to own, I would recommend UNI-T UT61E around $60.
It s not a matter of quality, rather an issue of "by design" expected deviation/error.
It usually is in the range of 1-2% or one digit, whichever is bigger, which makes it more critical for measuring near the bottom end of the scale.
Hi GUYS,
Swapped multimeters for another one from work-- on my Mez PCB my voltages on the 3 copper pads are + 10.61/- 10.07 on the board - not really any diffrent from my origional multimeter readings-, so i think my problems in offset are down to matching the four 2SK170BL? (as far as i can tell!)
I will purchase a matched set and let you know what occures.(offset wise)
Thanks as ever
johnny
Swapped multimeters for another one from work-- on my Mez PCB my voltages on the 3 copper pads are + 10.61/- 10.07 on the board - not really any diffrent from my origional multimeter readings-, so i think my problems in offset are down to matching the four 2SK170BL? (as far as i can tell!)
I will purchase a matched set and let you know what occures.(offset wise)
Thanks as ever
johnny