Well Meridian have had DSP controlled active speakers since the early 90s, but they have never sold well due to the audiophile curse (and I found the D600s horribly bright, but didn't have time to fiddle with the settings in the demo). Given the computer audio/home recording boom means that active speakers are more acceptable, maybe this is the right time to launch something that crosses between lifestyle (wife in kitchen can play music from phone) and serious attack on state of the art in performance. Five years ago I would have said no chance, but now it may just be the right time. Certainly Bruno is cleverer than wot I am, and I wish him luck but don't think he needs it!
I think you are right. Several things seem to converge, like the availability of dirt-cheap DSP capability, class D challenging state of the art reproduction and also being quite cheap, small, efficient etc. Joachim Gerhard did it with Malcolm Hawksford in the 90-ies as well, and I think Canton in Germany had a DSP active speaker then too.
These guys were marching ahead of the band - perhaps too far ahead at he time.
Jan
These guys were marching ahead of the band - perhaps too far ahead at he time.
Jan
No offense to Bruno, but his Volume Control is something that would never make in a commercial product, and if it did it would put you out of business very soon.
Infinte gain when turned fully up is quite bad, but actually not the worst problem. Wiper lift-off is, and your speakers will most certainly go up in smoke when this happens... and it will happen, sooner or later.
Perfect channel tracking is futile because you always need to adjust L/R center balance by +-1 dB or so, since there always are other gain differences elsewhere (starting in the recording and ending in your speaker sensitivities).
Infinte gain when turned fully up is quite bad, but actually not the worst problem. Wiper lift-off is, and your speakers will most certainly go up in smoke when this happens... and it will happen, sooner or later.
Perfect channel tracking is futile because you always need to adjust L/R center balance by +-1 dB or so, since there always are other gain differences elsewhere (starting in the recording and ending in your speaker sensitivities).
Boris, I'm sorry, this BoM is for the complete modules in the Group Buy I have suggested here: http://1drv.ms/1JPOfR6, to get agreed the parts we will use there. The parts will be procured by the manufacturing company, they will use them in the build and won't supply them externally.
However there's no real specialities in there, e.g. Mouser has all of them on stock.
BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control...
KSTR, your concerns are absolutely valid, and important to take into account. For this reason, Hans Polak has designed an alternative volume controller which overcomes this. Linear Audio have published it here: http://linearaudio.net/sites/linearaudio.net/files/hp bruno potmeter 3.pdf
KSTR, your concerns are absolutely valid, and important to take into account. For this reason, Hans Polak has designed an alternative volume controller which overcomes this. Linear Audio have published it here: http://linearaudio.net/sites/linearaudio.net/files/hp bruno potmeter 3.pdf
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I have the PCB from Linear Vol 5 for this project on my table for few weeks with a plan to build it. So happy to see this project has finally found traction from others too.
I copied the BOM I have prepared to the shared XLS file
It is based on BOM from Linearaudio.net web but modified a bit here and there to more exactly match the schematic.
As I've not ordered the parts / built the project yet I can only hope the BOM is correct. I welcome fully if anyone would have time to check it too.
Ergo
I copied the BOM I have prepared to the shared XLS file
It is based on BOM from Linearaudio.net web but modified a bit here and there to more exactly match the schematic.
As I've not ordered the parts / built the project yet I can only hope the BOM is correct. I welcome fully if anyone would have time to check it too.
Ergo
Of course it depends on pot quality and operational conditions. If you have a good industrial/military pot with 2 or 3 spring-loaded wiper contacts, hermetic sealing etc it everything will be fine for decades, but with budget pots with rather fragile open frame construction and only a single wiper contact it can happen quite easily. Ask any repair tech, crackling pots (which is one step below full lift-off) is very common with older equipment.
One input looses its biasing and the output voltage will run away to a supply rail, or even start to oscillate.
I think it is well known good practive to always include high resistance fallback resistors so that biasing is guaranteed at all times.
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crackling pots I have seen, but never lift off.
Will run away, or may run away? Not sure of the LM4562 internal construction. I agree that a high-Z for safety is good, but my power amps, like many are AC coupled so the pre-amp railing wont kill anything. And lets face it the average DIY'er upgrades every 12 months anyway
Like NP BP doesn't give away ALL his design secrets for free to us. I suspect his commerical designs are significantly enhanced in certain areas.
Will run away, or may run away? Not sure of the LM4562 internal construction. I agree that a high-Z for safety is good, but my power amps, like many are AC coupled so the pre-amp railing wont kill anything. And lets face it the average DIY'er upgrades every 12 months anyway
Like NP BP doesn't give away ALL his design secrets for free to us. I suspect his commerical designs are significantly enhanced in certain areas.
Wiper lift off? Just wire a resistor of 10x between GND and opamp input.
Works very well on stepper attenuators as well on high input bias opamps like the 5532/34, although you might get a bit of zipper noise.
LM4562 has very low input bias currents (10 nA typical) so you can DC couple without problems directly from your pot wiper - see my X-Altra Mini One for an example.
Works very well on stepper attenuators as well on high input bias opamps like the 5532/34, although you might get a bit of zipper noise.
LM4562 has very low input bias currents (10 nA typical) so you can DC couple without problems directly from your pot wiper - see my X-Altra Mini One for an example.
By the way, if you are looking for an alternative to BP's approach, one way of doing it is to use 2 PGA2320's in your pre - each half of the PGA in balanced mode. Works a treat.
http://hifisonix.com/ovation-sca-1/
http://hifisonix.com/ovation-sca-1/
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That would probably be my preferred solution too. But I expect the ucontroller shies lots of people away.
Hans Polak's solution is an excellent middle point.
Jan
PGA2320 does have some charm.
I'm doing something a little odd. In going active (slowly) I realised that the miniDSP 2x8 has balanced outputs and the poweramps I am building have balanced inputs. Now call me old fashioned but I'm not yet ready to pass all volume control duties to the digital domain. So I'm putting the level adjust and course level setting in an 8 channel pre-amp. Most of the time (wife around) I'll probably have 15-20dB attenuation in. When she's out I can crank it up.
Significant overkill and realistically not needed, but hey, cos I can
I'm doing something a little odd. In going active (slowly) I realised that the miniDSP 2x8 has balanced outputs and the poweramps I am building have balanced inputs. Now call me old fashioned but I'm not yet ready to pass all volume control duties to the digital domain. So I'm putting the level adjust and course level setting in an 8 channel pre-amp. Most of the time (wife around) I'll probably have 15-20dB attenuation in. When she's out I can crank it up.
Significant overkill and realistically not needed, but hey, cos I can
PGA2320 does have some charm.
I'm doing something a little odd. In going active (slowly) I realised that the miniDSP 2x8 has balanced outputs and the poweramps I am building have balanced inputs. Now call me old fashioned but I'm not yet ready to pass all volume control duties to the digital domain. So I'm putting the level adjust and course level setting in an 8 channel pre-amp. Most of the time (wife around) I'll probably have 15-20dB attenuation in. When she's out I can crank it up.
Significant overkill and realistically not needed, but hey, cos I can
Actually a pga2320 is not a digital attenuator - it's a rather traditional resistive ladder attenuator, but in a small package rather than a huge mechanical contraption
It is digitally controlled.
In my DCX2496 mod I used an 8-channel CS3318 (sort of premium PGA23xx) for a 6-channel level control at the xover output.
Works like a charm.
If you are willing to invest some time in the software, as I did, you can have remote level-balance control as well as settable level differences between low, mid high to cater for driver and amp sensitivity differences.
Jan
Ah, confusion. I should have clarified, I'm not ready to let the miniDSP handle all the volume control duties!
Your DCX solution was very nice and I looked at that, but realised that my round tuit supply was limited and I needed something that, whilst potentially suboptimal would work. Laying out my own boards is currently not an option. This way as and when I do upgrade I get all the stereo linestages I need
Only risk I am taking is that the miniDSP in balanced mode is 20dBu FS according to their spec, which is clipping on Bruno's board. I need to measure to see if that is correct and adjust accordingly. But hey, if you are going to run hot, you might as well go the whole way!
Your DCX solution was very nice and I looked at that, but realised that my round tuit supply was limited and I needed something that, whilst potentially suboptimal would work. Laying out my own boards is currently not an option. This way as and when I do upgrade I get all the stereo linestages I need
Only risk I am taking is that the miniDSP in balanced mode is 20dBu FS according to their spec, which is clipping on Bruno's board. I need to measure to see if that is correct and adjust accordingly. But hey, if you are going to run hot, you might as well go the whole way!
Coming back to the topic of this thread, the Bruno Putzeys Preamp:
I have set up a Group Buy for this, as announced. You'll find the respective thread here:
Bruno Putzeys Balanced Preamp - Group Buy
Thank you,
Robert
I have set up a Group Buy for this, as announced. You'll find the respective thread here:
Bruno Putzeys Balanced Preamp - Group Buy
Thank you,
Robert