I think I'm going to call my DCB1 finished. I took care of my heat issue with more substantial "wings" on the fets. No pics, but easy enough to explain. Same length as Hypnotize, 2.75" tall (full span from bottom to top, and supports the top mesh), and .188" thick. Drilled new mounting holes for the right side buffer to move it further away from the left, and a row of holes between the two buffers in the bottom panel to allow some convection. The whole thing looks mean, and can easily run 24/7 without issue. I'm still very happy with this preamp and want it to last a long time.
Did not attempt to change the R1's again to try and balance the currents as I mentioned before. I've changed these R1's three times already, no lifted pad issues but don't want to push my luck so it will stay as is (10.4 ohms).
I think I prefer the Takman carbon films over the PRP's on the amp feeding my satellite speakers, but I'd have a hard time explaining why. Maybe just a bit more forgiving but still detailed. But close really. Anxious to get started on some other projects, maybe that Toshiba'ed F5 as I have many of the parts already.
Did not attempt to change the R1's again to try and balance the currents as I mentioned before. I've changed these R1's three times already, no lifted pad issues but don't want to push my luck so it will stay as is (10.4 ohms).
I think I prefer the Takman carbon films over the PRP's on the amp feeding my satellite speakers, but I'd have a hard time explaining why. Maybe just a bit more forgiving but still detailed. But close really. Anxious to get started on some other projects, maybe that Toshiba'ed F5 as I have many of the parts already.
My Dcb1 with Optical volume control
My build is almost coming to an end, just waiting on a few more parts to arrive to finish off...so i thought id take down some measurements.
Negative Rail -10.32v
Voltage across 68r/68r 2.04v
Positive Rail +10.19v
Voltage across 68r/68r 1.73v
Do these voltages seem ok?
Some pics...taken with my phone...so not very good quality, sorry.
My build is almost coming to an end, just waiting on a few more parts to arrive to finish off...so i thought id take down some measurements.
Negative Rail -10.32v
Voltage across 68r/68r 2.04v
Positive Rail +10.19v
Voltage across 68r/68r 1.73v
Do these voltages seem ok?
Some pics...taken with my phone...so not very good quality, sorry.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Thanks Salas, I hav'nt measured the dc offsets yet...will get to that soon and report here...Also i will probably not balance the currents yet...as i have a feeling i will be hotrodding and adding some propper heat sinks...but just want to get it up and running, get it burned in, so that i can assess the difference when hotrodded, later. I have done the cap mod, from the start and used 0.22uf Ansar supersounds for this. I have also used Charcroft nude z-foils for input/output resistors
Will keep you all updated.
Alon
Will keep you all updated.
Alon
don't remove the 68//68r.
Add an extra parallel resistor to listen to the effect if any.
you have 2.04/34 = 0.06A in the higher voltage polarity.
You have 1.73/34 = 0.0509A in the lower voltage polarity.
Try adding 1.73V / {0.6-0.509} = 190r.
Use 180r or 200r or 220r. Just tack it on the back of the PCB to hear if it has an effect.
Add an extra parallel resistor to listen to the effect if any.
you have 2.04/34 = 0.06A in the higher voltage polarity.
You have 1.73/34 = 0.0509A in the lower voltage polarity.
Try adding 1.73V / {0.6-0.509} = 190r.
Use 180r or 200r or 220r. Just tack it on the back of the PCB to hear if it has an effect.
Do that just if you want to balance currents on both rails. If you want to hottrod it, you will need to change the resistors for higher wattage ones.
Thank Andrew and regiregi22,
When my Ldr's arrive, i will finish up, and then listen to it as is. Let it burn in, and then i will add a 200ohm resistor that i have in my spares to balance the currents and listen for a change...i will then hotrod it and listen again for a change in sound.
When i hotrod, which resistor wattage will i need to use? i currently have 2, 1 watt 68r resistors, would it be ok for example to use???
68r(1 watt)//68r(1 watt)//15r(5 watt) = 10.408
on the 2.04v side...2.04/10.408 = 0.196ma
68r(1 watt)//68r(1 watt)//12r(5 watt) = 8.8696
on the 1.73v side...1.73/8.8696 = 0.195ma
Thanks for your help.
Alon
When my Ldr's arrive, i will finish up, and then listen to it as is. Let it burn in, and then i will add a 200ohm resistor that i have in my spares to balance the currents and listen for a change...i will then hotrod it and listen again for a change in sound.
When i hotrod, which resistor wattage will i need to use? i currently have 2, 1 watt 68r resistors, would it be ok for example to use???
68r(1 watt)//68r(1 watt)//15r(5 watt) = 10.408
on the 2.04v side...2.04/10.408 = 0.196ma
68r(1 watt)//68r(1 watt)//12r(5 watt) = 8.8696
on the 1.73v side...1.73/8.8696 = 0.195ma
Thanks for your help.
Alon
No problem Allan
At the moment i've been using a p2p b1 buffer with Alps blue in shunt mod with tx2575 nude resistors in series(Shunt Pot Volume Control - World-Designs-Forum). Sounds very transparent to me, so this is what i will be comparing the Ldr volume control with dcb1 to. Cant Wait.
Power (P) = Voltage (V) squared, divided by Resistance (R).
You have 1.73V and 2.04V available to drive the CCS resistors.
The existing 68r dissipate ~ 2.04^2/68 = 61mW. ~10% of maximum power rating of a 600mW resistor.
Add an extra 200r (on the 1.73V side), it will dissipate 15mW, ~3% of maximum rating.
Replace all the 68r and the 200r with a single 20r resistor. Dissipation is now 208mW ~35% of maximum rating. It's going to be warm but reliable.
Try 10r, 416mW ~70% of maximum rating. It's going to run hot, it's value at elevated temperature will be significantly different from it's cold temperature and it may become unreliable.
I prefer to never run any resistor at >50% of maximum rating and in some parts of the circuit <<10% of maximum rating.
You have 1.73V and 2.04V available to drive the CCS resistors.
The existing 68r dissipate ~ 2.04^2/68 = 61mW. ~10% of maximum power rating of a 600mW resistor.
Add an extra 200r (on the 1.73V side), it will dissipate 15mW, ~3% of maximum rating.
Replace all the 68r and the 200r with a single 20r resistor. Dissipation is now 208mW ~35% of maximum rating. It's going to be warm but reliable.
Try 10r, 416mW ~70% of maximum rating. It's going to run hot, it's value at elevated temperature will be significantly different from it's cold temperature and it may become unreliable.
I prefer to never run any resistor at >50% of maximum rating and in some parts of the circuit <<10% of maximum rating.
As a general thumb rule for this project, I recommend a 10ohm resistor per side and 5W rated. That is what I have. They get barely warm, just a bit hot. You could do with 4W resistors, but I wouldn't go lower.
To my inexperienced eye, that BF862 looks like an absolute gem!
SMT on that scale should be no problem. Are there any other drawbacks or sonic inferiority compared to 2SK170?
Thanks Again Andrew and Regiregi22,
Correct me if im wrong, but my understanding is that when resistors are used in parralel, there wattage is added on, so for example a 68r(1 watt)//68r(1 watt)//15r(5 watt) would be equivalent to a 10r(7 watt) resistor???
However im not sure if i correct in this understanding
Alon
Correct me if im wrong, but my understanding is that when resistors are used in parralel, there wattage is added on, so for example a 68r(1 watt)//68r(1 watt)//15r(5 watt) would be equivalent to a 10r(7 watt) resistor???
However im not sure if i correct in this understanding
Alon