Thanks Salas,
Well I want to use your dcb1 with the optivol (dvb-projekt, btw think I got one of the last ones
) which will be seperately powered with a salas shunt regulator +5V (also dvb-projekt). So that's the reason I was thinking of a star grounding configuration, with or without cl60.
Kind regards,
Joffrey
Well I want to use your dcb1 with the optivol (dvb-projekt, btw think I got one of the last ones
) which will be seperately powered with a salas shunt regulator +5V (also dvb-projekt). So that's the reason I was thinking of a star grounding configuration, with or without cl60.Kind regards,
Joffrey
Greetings,
I have completed my first DCB1 in standard stage (68R resisters) and seems to work well.
Startup shows 0mV output. After 14 minute warmup, I get about 4mV output and I beleive this is acceptable.
also, the IRF mosfets closer to the power caps get warmer than the others. Is this an indication of badly matched mosfets? I read that it was not necessary to match the irf's but I may be wrong. I did not match mine.
Now, I would like to move on to hotrodding to the first stage (10R power resistors) but before going on, I need to know if it is better to match the IRF's and if so, how?
regards.
I have completed my first DCB1 in standard stage (68R resisters) and seems to work well.
Startup shows 0mV output. After 14 minute warmup, I get about 4mV output and I beleive this is acceptable.
also, the IRF mosfets closer to the power caps get warmer than the others. Is this an indication of badly matched mosfets? I read that it was not necessary to match the irf's but I may be wrong. I did not match mine.
Now, I would like to move on to hotrodding to the first stage (10R power resistors) but before going on, I need to know if it is better to match the IRF's and if so, how?
regards.
Its normal those closer to the caps get warmer, easy to feel different in lower CCS currents especially. The reason is they run all the current times (Vin-Vo) when the output ones share some to the load. What DCin you got (see on main filter capacitors)? Matching the IRFPs Vgs could only ensure same current setting per rail, something easily fixed by offsetting the CCS setting resistors OTOH. What voltage drop you got on 2X68 per side as for now?
The CCS draws constant current.
The DC input levels do not change with or without an output load.
12+12Vac runs a 9 to 10Vdc DCB1 at lowish voltage drop across the CCS.
15+15Vac will run a 9 to 10Vdc DCB1 at adequate voltage drop across the CCS for all normal variations of mains supply voltage.
18+18Vac driving a 9 to 10Vdc DCB1 will make the CCS FETs run hot.
Have you fitted adequate heatsinks before you hotrod?
Do you have sufficient space to add even bigger heatsinks after you have hotrodded?
The DC input levels do not change with or without an output load.
12+12Vac runs a 9 to 10Vdc DCB1 at lowish voltage drop across the CCS.
15+15Vac will run a 9 to 10Vdc DCB1 at adequate voltage drop across the CCS for all normal variations of mains supply voltage.
18+18Vac driving a 9 to 10Vdc DCB1 will make the CCS FETs run hot.
Have you fitted adequate heatsinks before you hotrod?
Do you have sufficient space to add even bigger heatsinks after you have hotrodded?
The currents are balanced enough in yours, its the high input voltage that accentuates the heating differences further as Andrew said. Otherwise your DCB1 shows predictable functioning. Having the proper sinking will be the only requirement.
thanks,
nice to know my first build is acceptable. I'll keep this one for testing.
Note that my dc offsets now are close to 0 since I feed from the plitron. My initial measurements were from an el-cheapo 18-18V tfo. Is it possible that a tfo quality has impact on DC offset?
Since I have more boards, I'll be hotrodding a new board and I have acceptable sinks that I salvaged from a denon car amp I found lying around. The amp was not working as I think it bathed in water for a while so I recuped the sinks from it. I'm going to stage 1 10R so those sinks should be adequate.
thanks again
nice to know my first build is acceptable. I'll keep this one for testing.
Note that my dc offsets now are close to 0 since I feed from the plitron. My initial measurements were from an el-cheapo 18-18V tfo. Is it possible that a tfo quality has impact on DC offset?
Since I have more boards, I'll be hotrodding a new board and I have acceptable sinks that I salvaged from a denon car amp I found lying around. The amp was not working as I think it bathed in water for a while so I recuped the sinks from it. I'm going to stage 1 10R so those sinks should be adequate.
thanks again
Just finished my dcb1. I get (using an antek 12v 50va transformer):
output -9.57V and 9.4V
1.6V and 1.54V across 5Rs
All the leds came up. Hooked it up and played my backup turntable with a $20 Grado cartridge. How does it sound? The three records I played sounded better than my flacs/dac through my old preamp (a vintage PS Audio 4.5 in passive mode). It has much better detail, dynamics, bottom end and imaging. Best of all, dead silent, both no-hum-wise and background distortion/noise floor for the music. I don't know why I waited so long to try to build one of these...
So even if there's something wrong with it and I have to troubleshoot it (I think the numbers above are ok?), it already sounds way better than my old setup.
Again, thanks to every one for all their help so far (specially Teabag, for parts and heatsinking tutorial!).
output -9.57V and 9.4V
1.6V and 1.54V across 5Rs
All the leds came up. Hooked it up and played my backup turntable with a $20 Grado cartridge. How does it sound? The three records I played sounded better than my flacs/dac through my old preamp (a vintage PS Audio 4.5 in passive mode). It has much better detail, dynamics, bottom end and imaging. Best of all, dead silent, both no-hum-wise and background distortion/noise floor for the music. I don't know why I waited so long to try to build one of these...
So even if there's something wrong with it and I have to troubleshoot it (I think the numbers above are ok?), it already sounds way better than my old setup.
Again, thanks to every one for all their help so far (specially Teabag, for parts and heatsinking tutorial!).
An externally hosted image should be here but it was not working when we last tested it.
palmito congrats mate, that’s sure a hotty with 5R’s in there, looks great!
I’m planning on going all out with 3R3’s, I’ll be sinking the mosfets and diodes via a 10mm thick aluminum plate (111 x 222) which is also bolted to a 3mm aluminum base (435 x 350).
Is a hefy heat sink for 7812 necessary for running higher currents, or can I leave it as the BOM?
I’m planning on going all out with 3R3’s, I’ll be sinking the mosfets and diodes via a 10mm thick aluminum plate (111 x 222) which is also bolted to a 3mm aluminum base (435 x 350).
Is a hefy heat sink for 7812 necessary for running higher currents, or can I leave it as the BOM?
The 7812 is only supplying current to pull in the relay and activate the trigger circuit.
A 12V relay draws ~11mA. If the voltage input to the regulator is 22V (from a 15Vac transformer) then the 7812 dissipates ~140mW when the relay is pulled in.
You can add an indicator LED to show when the DCB1 is passing signal. That will increase the dissipation very slightly.
Hotrodding does not affect this part of the circuit.
I have added a current reducing resistor to the relay to minimise dissipation in the relay coil. This also reduces dissipation in the 7815 that I have used.
The resistor fits on the standard PCB where allowance for a dropping resistor is provided for a 5V relay.
The 1040r coil has a 1k8 resistor in the 14.8V supply. It triggers using a cap charged to 14.8Vdc and runs at ~ 5.5Vdc (~5mA)
A 12V relay draws ~11mA. If the voltage input to the regulator is 22V (from a 15Vac transformer) then the 7812 dissipates ~140mW when the relay is pulled in.
You can add an indicator LED to show when the DCB1 is passing signal. That will increase the dissipation very slightly.
Hotrodding does not affect this part of the circuit.
I have added a current reducing resistor to the relay to minimise dissipation in the relay coil. This also reduces dissipation in the 7815 that I have used.
The resistor fits on the standard PCB where allowance for a dropping resistor is provided for a 5V relay.
The 1040r coil has a 1k8 resistor in the 14.8V supply. It triggers using a cap charged to 14.8Vdc and runs at ~ 5.5Vdc (~5mA)
Last edited:
See about the DC offset on audio outputs its small too. Nice, enjoy. Will do even better when solder wired to the pot properly.
Thanks johnwmclean, good luck on yours, you will like it!
Thanks Salas (and thanks for the support and work on the dcb1). I forgot to post it, the output offset is 4mv. I'm looking for a case to put it in, I'll solder everything when it goes in the case. I'm considering a lightspeed attenuator too but the photocopy machine broke and I have not been able to print more money...
Does getting a Plitron or SumR transformer make an audible improvement in sound? The Anteks seem to be very good value for the $.
Thanks Salas (and thanks for the support and work on the dcb1). I forgot to post it, the output offset is 4mv. I'm looking for a case to put it in, I'll solder everything when it goes in the case. I'm considering a lightspeed attenuator too but the photocopy machine broke and I have not been able to print more money...
Does getting a Plitron or SumR transformer make an audible improvement in sound? The Anteks seem to be very good value for the $.
Last edited:
Advice, please
I have 4 MUR840G rectifier diodes at hand. Given my CSS currents, should I try Hot Rodding it even more with some resistors in place of 10R? What values could I safely try?
My heatsinks for TO-247 are standard ones from the BOM.
I have 4 MUR840G rectifier diodes at hand. Given my CSS currents, should I try Hot Rodding it even more with some resistors in place of 10R? What values could I safely try?
My heatsinks for TO-247 are standard ones from the BOM.
I have had my DCB1 running for a few days now. Sound is very clear and quick. I am only running about 80mA through the current sources, I will try doubling this to see if it gives the sound a bit more body.
I built mine back-to-front...
1st I SOTed two pairs of matched JFETS - IDSS within 20uA @ 10V.
Then is experimented with what voltage rails gave the lowest offset, using a bench PSU. For some reason the + supply needs to be about 10% higher than the - supply to get no measureable dc offset.
I then (tried to) SOT the LEDs to give the 10% difference. In fact the LEDs were very closely matched and I ended up with only about 0.4V (~4%) difference. This resulted in dc offset of 0.4mV and 1.4mV. To aim for perfection I could have added a 1N4148 in the + Vref chain, but <2mV is good enough.
Anyway, I'm very pleased with the DCB1. Thanks Teabag for providing the pcbs!
Question:
How much more to come by changing from Alps blue and a 50VA toroid?
I built mine back-to-front...
1st I SOTed two pairs of matched JFETS - IDSS within 20uA @ 10V.
Then is experimented with what voltage rails gave the lowest offset, using a bench PSU. For some reason the + supply needs to be about 10% higher than the - supply to get no measureable dc offset.
I then (tried to) SOT the LEDs to give the 10% difference. In fact the LEDs were very closely matched and I ended up with only about 0.4V (~4%) difference. This resulted in dc offset of 0.4mV and 1.4mV. To aim for perfection I could have added a 1N4148 in the + Vref chain, but <2mV is good enough.
Anyway, I'm very pleased with the DCB1. Thanks Teabag for providing the pcbs!
Question:
How much more to come by changing from Alps blue and a 50VA toroid?
Last edited: