Thanks Andrew.
I was ready to write it off as a voltage issue, but your reply made me go and have another look at my board.
Just noticed I have Q1 backwards.....
Not sure how I managed it considering how clearly marked the board is, but I was doing it at about 2:30am. Is that any sort of excuse? 😱
I'll repair it tonight and test it when I get to work.....
So, aside from this issue do you think 40v rails is a concern? The lowest impedance dip these amps will see is 7 ohms. They will be crossed actively above 600hz.
I was ready to write it off as a voltage issue, but your reply made me go and have another look at my board.
Just noticed I have Q1 backwards.....
Not sure how I managed it considering how clearly marked the board is, but I was doing it at about 2:30am. Is that any sort of excuse? 😱
I'll repair it tonight and test it when I get to work.....
So, aside from this issue do you think 40v rails is a concern? The lowest impedance dip these amps will see is 7 ohms. They will be crossed actively above 600hz.
Thanks Andrew.
I was ready to write it off as a voltage issue, but your reply made me go and have another look at my board.
Just noticed I have Q1 backwards.....
Not sure how I managed it considering how clearly marked the board is, but I was doing it at about 2:30am. Is that any sort of excuse? 😱
I'll repair it tonight and test it when I get to work.....
So, aside from this issue do you think 40v rails is a concern? The lowest impedance dip these amps will see is 7 ohms. They will be crossed actively above 600hz.
I was ready to write it off as a voltage issue, but your reply made me go and have another look at my board.
Just noticed I have Q1 backwards.....
Not sure how I managed it considering how clearly marked the board is, but I was doing it at about 2:30am. Is that any sort of excuse? 😱
I'll repair it tonight and test it when I get to work.....
So, aside from this issue do you think 40v rails is a concern? The lowest impedance dip these amps will see is 7 ohms. They will be crossed actively above 600hz.
The rail voltages are way too high - the LM3886 is rated only for +/- 42V absolute max. The safety margin of 2V is wafer thin. Try to swap with a 22-0-22 or 24-0-24 Trafo.
It's possible that the protection relay will not pull in when the supply to the protection circuitry crosses a certain threshold. However, I haven't actually run a MyRef at 29 VAC, so this is uncharted territory.
Check the values, polarity and orientation of every component in the protection circuit - it's easy to mix transistors or connect them in the reverse orientation. Then measure the voltages in the protection circuitry - the supply for the protection circuitry should be no higher than ~24 VDC, to ensure longevity of the relay.
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OK, I put Q1 in the right way and the amp now works fine 
Is it worth trying my luck with the 40v rails?
Is it just an issue of the spike protection cutting in, or are there other downsides?
I'm no expert, but from looking at specs of different amps, it seems that raising rail voltage always reduces distortion for any given output power.
Is it worth trying my luck with the 40v rails?
Is it just an issue of the spike protection cutting in, or are there other downsides?
I'm no expert, but from looking at specs of different amps, it seems that raising rail voltage always reduces distortion for any given output power.
Can you measure the current mains voltage and compare to the highest voltage available from the your Aus 240Vac system?
Expect up to 254Vac as worst case "normal operation". Can you get confirmation of the range of voltage that you can be supplied with?
Anything above this is not "normal" and if your equipment suffers damage as a result of excessive (>254Vac) then I think you can trying claiming damages from the supply company. But let's stay clear of that can of worms.
What would be the DC voltage on the supply rails if the mains does rise to 254Vac? Is that worst case maximum "normal" still within the specified limits of the chipamp? If not then you must reduce the voltage. Come back once you know those answers. There are solutions, but let's see the extent of the problem before we give out those suggestions.
Expect up to 254Vac as worst case "normal operation". Can you get confirmation of the range of voltage that you can be supplied with?
Anything above this is not "normal" and if your equipment suffers damage as a result of excessive (>254Vac) then I think you can trying claiming damages from the supply company. But let's stay clear of that can of worms.
What would be the DC voltage on the supply rails if the mains does rise to 254Vac? Is that worst case maximum "normal" still within the specified limits of the chipamp? If not then you must reduce the voltage. Come back once you know those answers. There are solutions, but let's see the extent of the problem before we give out those suggestions.
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When I tested my amp initially, mains voltage was 245V, and I was getting 40V at the rails.
At 254V, I guess I'd be at ~41.5V. That's pretty darn close to 42V isn't it.... 😱
I was using amp #1 at moderate volume for about 3 hours today, powering a CSS FR125 which is ~7ohms. No problem so far.....
At 254V, I guess I'd be at ~41.5V. That's pretty darn close to 42V isn't it.... 😱
I was using amp #1 at moderate volume for about 3 hours today, powering a CSS FR125 which is ~7ohms. No problem so far.....
Actually, Uriah did start a new thread back then but there hasn't been much activity there.
MyREFC untouched - Source's Experimented With
I'm one of those who encouraged that effort but have been so busy with some other projects I too have not gotten back to input choices. Maybe the two threads can be combined.
MyREFC untouched - Source's Experimented With
I'm one of those who encouraged that effort but have been so busy with some other projects I too have not gotten back to input choices. Maybe the two threads can be combined.
bcmbob
Well, I can't see why it wouldn't be. The amp spans the world and electrical mains are varied in quality so I'm sure there's lot to discuss in optimizing the attenuator. There is also the impedence matching issues for those using different line stages. Well, there are plenty of readers here so if we just encourage them to post all attenuation issues there it should take off and be a good resource..
Well, I can't see why it wouldn't be. The amp spans the world and electrical mains are varied in quality so I'm sure there's lot to discuss in optimizing the attenuator. There is also the impedence matching issues for those using different line stages. Well, there are plenty of readers here so if we just encourage them to post all attenuation issues there it should take off and be a good resource..
The "sonic hologram" idea is really quite bright IMHO.
Remember the Polk SDA "stereo dimensional array" speakers which had:
- additional drivers on the left side, running some of the right-channel material out-of-phase
- additional drivers on the right side, running some of the left-channel material out-of-phase
They also broadened the soundstage similarly. In a fundamental way, the "sonic hologram" generator does nearly the same thing very well in the electronics instead of with additional power amp watts and speakers. I don't personally like the effect, and I find essentially the same irritating thing on many TVs now labelled "stereo wide" since the patents expired.
Carver's autocorrelator from back then is still interesting for phono users who don't have any competing analog, digital, or hybrid noise reduction.
Always entertaining and making you think, love him or hate him. I wish he'd embrace DIY and show up at Burning Amp, but I don't know the gentleman personally, nor wheher he's patient and generous or an egomaniac. But it would be interesting. He's indisuptable creative, and there's definitely potential for some interesting conversation. Every interview triggers discussion or often controversy. I'd prefer my friends not be boring.
Hey folks,
Can anyone tell me if I am asking for trouble with this configuration? These are .25" spacers. Will this cause any field, flux, induction or other problems?
Thanks.
Can anyone tell me if I am asking for trouble with this configuration? These are .25" spacers. Will this cause any field, flux, induction or other problems?
Thanks.
I would bet it won't. Air dielectric is high enough for avoid arcing, and I cannot see anything bad or "too" close. Have you tried it, does it make any funny thing?
I have done that with half inch spacers several times with good results. With that said, being that close I would still put a blank board (a thin piece of 1/8th inch plexiglass) between them or something for PHYSICAL issues such as dropping the amp accidentally.
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troystg
When stuff is that close you never know what might bend or bounce into contact. The other obvious thing is to bend the pins down as close to the board as you can without breaking them, time and heat may warp the boards toward each other so I'm with troystg on being better safe than sorry. I'm going to try and influence the discussion on the control thread by kicking off the conversation there. What are the audio consequences of using a higher resistance attenuator instead of the 10K one recommended by Mauro? Please post your answer in this thread. That should get the ball rolling over there.
When stuff is that close you never know what might bend or bounce into contact. The other obvious thing is to bend the pins down as close to the board as you can without breaking them, time and heat may warp the boards toward each other so I'm with troystg on being better safe than sorry. I'm going to try and influence the discussion on the control thread by kicking off the conversation there. What are the audio consequences of using a higher resistance attenuator instead of the 10K one recommended by Mauro? Please post your answer in this thread. That should get the ball rolling over there.
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Bob, I've used the same configuration with longer plastic spacers (~0.5") without any problems. There is a possibility of crosstalk/interference in the small-signal section, if the boards are too close. A sheet of aluminium foil sandwiched between two antistatic foam sheets between the boards may be of some help.
I notice that you've upgraded R1/R4 to Kiwame/Koa Speer CFR - is there a perceptible improvement in sonics?
In a back-to-back arrangement such as that, how do you support the pair of boards inside the enclosure? And those power supply caps are a pretty heavy load on the board itself. I don't think PCB's are designed for that.
I would feel a lot safer with 1/2" spacers, not from a direct short, but from any possible intereference between the two circuits.
Peace,
Tom E
I would feel a lot safer with 1/2" spacers, not from a direct short, but from any possible intereference between the two circuits.
Peace,
Tom E
Thanks All,
I tried to digest everyone’s ideas and decided it was time to get out the Plexiglas, Superglue and band saw to solve the issue
These supports provide a full .75" separation of the boards.
Plexiglas is a static electricity collector so I'm hoping the anchor bolt will dissipate any build up.
From an earlier discussion, I cut in some relief grooves to eliminate contact between the edge of the PCB and the metal plate.
As this is a bi-amp project, combining two MyRefs and two BPA150s, I went with a modular design. This plate is .25 x 3" aluminum with posts that don't protrude through the plate. (Ground of enough of the end of a tap to get started and ground off a second to create a bottom tap.)
BPA-150 Pair
Attached to plate ala Shine7.com.
Heat sinks were salvaged from some Intel Xeon coolers that were left over from a liquid cooling motherboard project.
So the big three are almost done. All the mating surfaces will be smoothed with a surface grinder (or maybe by hand).
Honestly, I haven't a clue about the final build/appearance of this project other than my desire to do a vertical/tower arrangement just for the sake of doing something different and unique. Any and all suggestions welcomed.
It's been a busy and fun weekend.
Again, Thanks All.
I tried to digest everyone’s ideas and decided it was time to get out the Plexiglas, Superglue and band saw to solve the issue
These supports provide a full .75" separation of the boards.
Plexiglas is a static electricity collector so I'm hoping the anchor bolt will dissipate any build up.
From an earlier discussion, I cut in some relief grooves to eliminate contact between the edge of the PCB and the metal plate.
As this is a bi-amp project, combining two MyRefs and two BPA150s, I went with a modular design. This plate is .25 x 3" aluminum with posts that don't protrude through the plate. (Ground of enough of the end of a tap to get started and ground off a second to create a bottom tap.)
BPA-150 Pair
Attached to plate ala Shine7.com.
Heat sinks were salvaged from some Intel Xeon coolers that were left over from a liquid cooling motherboard project.
So the big three are almost done. All the mating surfaces will be smoothed with a surface grinder (or maybe by hand).
Honestly, I haven't a clue about the final build/appearance of this project other than my desire to do a vertical/tower arrangement just for the sake of doing something different and unique. Any and all suggestions welcomed.
It's been a busy and fun weekend.
Again, Thanks All.
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