I know johnwmclean and I are both planning on building balanced DCB1's (hot-rod). I've got my two boards mostly built, and I'm waiting on some SumR transformers to arrive before I trying powering them up.
I look forward to hearing your thoughts on how it turns out. Right now I am building a simple borberly design. Taking baby steps into this crazy diy world. Then again, simple is not aways bad!
My v+ is 9.90, the v- is -9.66. Is that close enough? I wonder if I toasted one of the LEDs when I put it in backwards. DC offset is .1 on the left and .5 on the right. Which resistor do I need to measure for the CCS?
Yes still going for balanced (of course), but have have switched back to the new Hyno boards from the recent GB, saw you’re down for 5?? My builds going something like this sumR transformers, Nichicon KZ for the 4700uF, Silmic II for the 100uf, 0.22uf auricap (thanks qusp) for the ref bypass, Takman Carbon for the 470R, Mills 10R 5W for current, PRP for the rest, I’m aiming for hotrodding up to 300mA.
buzzforb the only balanced info I can dig up, which you’ve probably seen is this:
An externally hosted image should be here but it was not working when we last tested it.
I’m going to draw it up again with inputs, outputs, attenuator with left and right channels and re-post it up here for scrutiny. I plan to have it up this weekend.
Yup, mV. I'll give it a listen to make sure everything's 100% before I attempt hotrodding.
I did put myself down for (5) blue hypno's. I've already got the blue mez's populated, so I'm committed to finish that one. I figured I might want to try an all out balanced hypno (super hot-rod style) in the future with a lightspeed attenuator. Bought a few extra boards for shunt power supply purposes.
I just plugged the DCB1 into my F5, it's making beautiful music as I type. The passive pre I was using before never sounded quite right with the F5, probably because it used a 100k stepped attenuator, but the DCB1 is just as clear and more tonally "correct" to my ears. Seems to have more kick to it, too.
Next up is a Pearl 2 phono. Firstwatt is rapidly taking over my whole audio chain!
Next up is a Pearl 2 phono. Firstwatt is rapidly taking over my whole audio chain!
Balanced DCB1 Diagram
Here’s a wiring diagram for a balanced DCB1 I’m planning, I would appreciate any feedback as whether this would work or not. I’m not sure whether a zobel is necessary or not.
Beyond the default and hotrod configurations are there any board changes or parts that need to be addressed for this to work?
Cheers
John
Here’s a wiring diagram for a balanced DCB1 I’m planning, I would appreciate any feedback as whether this would work or not. I’m not sure whether a zobel is necessary or not.
An externally hosted image should be here but it was not working when we last tested it.
Beyond the default and hotrod configurations are there any board changes or parts that need to be addressed for this to work?
Cheers
John
Hi john,
your use of adjustable attenuators at the front end of the balanced receiver completely wipe out any hope of maintaining a balanced connection.
All the input impedances must be matched very accurately. This includes the capacitors, not just the resistors. Similarly all the output impedances must be matched very accurately.
your use of adjustable attenuators at the front end of the balanced receiver completely wipe out any hope of maintaining a balanced connection.
All the input impedances must be matched very accurately. This includes the capacitors, not just the resistors. Similarly all the output impedances must be matched very accurately.
Hi Andrew,
Although the diagram shows separate attenuators for input and grounds, it will actually be one conventional 4 channel volume pot.
Balanced impedance, I have a feeling that’s a big spanner coming my way, I can probably match the resistances for better than 0.1%, and may have some success with balanced voltage but exact impedance matching, my eyes are glazing over. I don’t have the know how (yet) or equipment needed (I’m guessing), silly question here goes - is this a very complex undertaking?
Although the diagram shows separate attenuators for input and grounds, it will actually be one conventional 4 channel volume pot.
Balanced impedance, I have a feeling that’s a big spanner coming my way, I can probably match the resistances for better than 0.1%, and may have some success with balanced voltage but exact impedance matching, my eyes are glazing over. I don’t have the know how (yet) or equipment needed (I’m guessing), silly question here goes - is this a very complex undertaking?
Hi,
a pair or a quad of potentiometers cannot be made such that Rupper and Rlower are always exactly matching at all positions of the potentiometer. The total of Rupper + Rlower can easily be selected to match to sufficient accuracy, but that is totally irrelevant as soon as the balanced attenuator is moved away from infinite attenuation.
A switched attenuator could be made to sufficient matching accuracy, but it will cost a fortune, i.e. even more than the $50 to $200 seen as asking prices for a normal stereo switched attenuator.
a pair or a quad of potentiometers cannot be made such that Rupper and Rlower are always exactly matching at all positions of the potentiometer. The total of Rupper + Rlower can easily be selected to match to sufficient accuracy, but that is totally irrelevant as soon as the balanced attenuator is moved away from infinite attenuation.
A switched attenuator could be made to sufficient matching accuracy, but it will cost a fortune, i.e. even more than the $50 to $200 seen as asking prices for a normal stereo switched attenuator.
What about something like the balanced shunt attenuator the guys over at K and K Audio use for their balanced linestage? It's stated, "no change in common mode rejection as different volume settings are used..." I realize that stepped control is expensive, but is this a reasonable and "correct" way to handle balanced attenuation?
K & K Audio - Lundahl Transformers, audio DIY kits and more
K & K Audio - Lundahl Transformers, audio DIY kits and more
Attachments
So would something more like TPA's Joshua Tree attenuator be a better solution if you were to closely match all the resistors between the (4) boards?