Very cool coffee can. So much better than a $30 project box from an electronics store.
I'm getting a little crazy, I'm afraid. I'm considering buying some 12 gauge magnet wire.
Bigger is better!
-dr_vega
Today I purchased the amp board on ebay. I also have sourced a cheaper SMPS, seems identical to the meanwell but it is 20 usd cheaper.:24V DC 14.6A 350W Regulated Switching Power Supply New - eBay (item 160377276159 end time Dec-10-09 18:53:02 PST). 40 usd is not bad for a 350 watt smps I guess.
I'm planning to use the dac from DDAC.de. My only question is how do I control the volume with this amp. (I'm quite a noob). Are there any suggustions for volume control?
I'm planning to use the dac from DDAC.de. My only question is how do I control the volume with this amp. (I'm quite a noob). Are there any suggustions for volume control?
I would like to use an Alps "Blue velvet" 50k log pot. Is this a good choice, and are there any problems I might run into when using this impedance value?
While mounting tank caps on the back of the amp board, I noticed that all the negative return current goes through a small trace "neck" on the board near the negative connector.
I was going to add some jumpers to give a bigger, more direct path for the return current, but the Tripath docs say there should only be one return path. So I scrapped off the paint on the neck and added a bead of solder, like Sure did on the supply lines. That should help the current capacity of the return. After all, the current flow is the same everywhere in the circuit. The return carries as much current as the supply.
Since my DCX2496 is dedicated to this installation, I removed its output caps. Now there is nothing but wire between the output pins of the DAC chip and the input caps of the Sure amps. Another veil lifted.
Of course I labeled the DCX as not having output caps so in the future I don't accidentally use it somewhere else.
As my system improves, my ears get used to the new level of sound quality and it doesn't seem so remarkable anymore. But I visited a friend who has a superb tube amp that cost thousands. I have long aspired to the kind of sound quality he has.
Well this time, after living with the Sure air-core coils at home for a week, his magnificent tube amp sounded congested and slightly blurred to me. No question my modded Sure amp is much better than his high end tube gear!
I'm beginning to realize that what I thought was great detail and micro-detail was really high order distortion products, giving the impression of a fast and crisp presentation. And what I thought was warmth and body was really low order distortion products fattening up the sound.
With the air-core Sure, questions of detail and warmth don't even enter into the discussion. It just has a tremendous feeling of clarity. Beyond that, it's just the music.
-dr_vega
I was going to add some jumpers to give a bigger, more direct path for the return current, but the Tripath docs say there should only be one return path. So I scrapped off the paint on the neck and added a bead of solder, like Sure did on the supply lines. That should help the current capacity of the return. After all, the current flow is the same everywhere in the circuit. The return carries as much current as the supply.
Since my DCX2496 is dedicated to this installation, I removed its output caps. Now there is nothing but wire between the output pins of the DAC chip and the input caps of the Sure amps. Another veil lifted.
Of course I labeled the DCX as not having output caps so in the future I don't accidentally use it somewhere else.
As my system improves, my ears get used to the new level of sound quality and it doesn't seem so remarkable anymore. But I visited a friend who has a superb tube amp that cost thousands. I have long aspired to the kind of sound quality he has.
Well this time, after living with the Sure air-core coils at home for a week, his magnificent tube amp sounded congested and slightly blurred to me. No question my modded Sure amp is much better than his high end tube gear!
I'm beginning to realize that what I thought was great detail and micro-detail was really high order distortion products, giving the impression of a fast and crisp presentation. And what I thought was warmth and body was really low order distortion products fattening up the sound.
With the air-core Sure, questions of detail and warmth don't even enter into the discussion. It just has a tremendous feeling of clarity. Beyond that, it's just the music.
-dr_vega
It really depends on the output impedance of your source. But, generally speaking, for any commercial source (i.e., CD player, preamp, DAC, etc.) anywhere from 10k to 100K will work fine.
-dr_vega
I'm thinking the Meanwell 36V 9.7 amp power supply is a real good match for the Sure 2*100 amp.
36V DC 9.7A 350W Regulated Switching Power Supply New - eBay (item 160380145916 end time Dec-20-09 22:06:52 PST)
I'm running all three of my amps on 36V 3 amp unregulated supplies that can hit 37.8V. Lots of power, great sound, no problems (needs a fan on the heat sink).
-dr_vega
Indeed, I was looking at the current rating for 18AWG wire and the current rating was 2A, so I'm agreement that bigger is better!
The coffee can works a treat, I've been using the amp a lot more now. 😎
So you can go straight from the DCX's DAC's output pins to the inputs of the sure with no components between?
I've was thinking about using line level trafo's in my DCX, but if I can get away with not using these then it will be one less thing in the chain. Are there any downsides with going for this route, as I also have a dedicated DCX for my setup. 🙂
Do you have any sort of volume control?
I ended up going for the 27V version of this SMPS:
27V DC 13A 350W Regulated Switching Power Supply New - eBay (item 160377277178 end time Dec-10-09 18:58:17 PST)
I remember after reading thru this thread that some components on the sure board were set for an input voltage of 30v... Are there any other benefits in going for a higher input voltage apart from extra output power?
The AWG current ratings are based on voltage drop, not heating, so we're talking about performance, not safety, which gives us some leeway. I doubt if I ever actually push 2 amps (70 watts at 36v) through the coil, but, no doubt, bigger is better.
The basic passive out mod for the DCX2496 includes an RC filter to block high frequency noise. I never installed that filter, so, yes, my DCX ribbon cable is soldered directly to the XLR plugs.
For volume control, I use a hybrid tube pre-amp before the DCX. I know it isn't the preferred way, but it works for me.
Exellent choice, since it can be adjusted up to 32v, which I believe is the sweet spot for the Sure amp (see post #483). Since I'm an old hot rodder, I have to run it at 36v, just because I can.
For those who are still looking for a power supply: the drawings in the Sure manual show the tank caps to be 35v. However the text specifies 50v and the installed caps are 50v. The specs for both the Tripath chips and the voltage regulator identify 36v as the max operating limit and 40v as the absolute limit.
So you can use anything up to 36v without worry. Sure has optimized the feedback resistors for 32v, so I think that is the sweet spot for this amp.
Both the Meanwell 27v and 36v power supplies can be adjusted to 32v. The 27v gives you more amperage (both have plenty, but more is good). The 36v gives you the opportunity to try some higher voltages (up to 40v, if you dare - where did that smoke come from?).
-dr_vega
I would like to use this amplifier to bi-amp my speakers. Is it possible to connect two amplifiers to the same source (DAC). I guessing that two times the load on the singal doesn't do it any good.
I'm interested in the answer to this one as well. If we need a buffer what would be a good choice. Are there any good ones on Ebay.
Terry
Coil Dispenser
So I had an idea of a way to hear the sound of every value air core coil from 10.5uH down. Start at the top and listen to the changes while unwinding a turn each time. Now I know that I want to concentrate on the values around 7.5uH which together with the .47uf and .22uf caps I am using, give just enough ultrasonic peaking to get out of the way of cymbals without throwing away too much suppression of the 650kHz emissions. Surprisingly, the 10.5uH air core cylinders were very quiet in the AM radio. No louder than any of the other cored torroids that I have tried. It must have been the ultra low 4uH value of my first cylinders that made them blast out the EMI so much more. 7.5uH is a bit louder than 10 but they are still acceptably quite even without a case. Should sound better and emit even less when I trim the loose ends. Add a dash of zobel and I may finally feel my filter is finalized. The values anyway. I still need to try to find a cheaper source for the Belden and also wind up some 12ga. 1/2 inch wide foil under teflon coils.
So I had an idea of a way to hear the sound of every value air core coil from 10.5uH down. Start at the top and listen to the changes while unwinding a turn each time. Now I know that I want to concentrate on the values around 7.5uH which together with the .47uf and .22uf caps I am using, give just enough ultrasonic peaking to get out of the way of cymbals without throwing away too much suppression of the 650kHz emissions. Surprisingly, the 10.5uH air core cylinders were very quiet in the AM radio. No louder than any of the other cored torroids that I have tried. It must have been the ultra low 4uH value of my first cylinders that made them blast out the EMI so much more. 7.5uH is a bit louder than 10 but they are still acceptably quite even without a case. Should sound better and emit even less when I trim the loose ends. Add a dash of zobel and I may finally feel my filter is finalized. The values anyway. I still need to try to find a cheaper source for the Belden and also wind up some 12ga. 1/2 inch wide foil under teflon coils.
Attachments
This depends on the output inpedance of your DAC. The Sure amp has an input impedance of about 10k ohms. Two of them in parallel have an iinput impedance of about 5k ohms.
As long as the total input impedance of the load (the Sure amps) is greater than the output impedance of your DAC, everything is fine.
Most commercial gear, like DACs and preamps, have an output impedance of about 600 ohms, so the average DAC should drive two Sure amps with no problem.
Technically speaking, sending the same signal to two amps and hooking the amps to the bi-wire terminals of a speaker system with a passive crossover is not really bi-amping. It's sort of bi-wiring with two amps.
Bi-amping requires the crossover to be before the amps so one amp receives only the highs and the other only the lows and the amps drive the speakers directly, without going through a crossover.
You get a sound improvement with bi-wiring and, I imagine, a further improvement with bi-amping with separate amps, so I think it is worth doing. But true bi-amping, where the amps can tightly control the speaker drivers is another level of improvement.
-dr_vega
Sendler, we really appreciate the real-world testing you are doing and passing along to us. I'm glad you also observed minimal EMI/RFI with the 10uH coils, as I did. I thought I was doing something wrong in my testing.
Knowing that the EMI/RFI problems are negligible with 10 uH air coils makes them a no-brainer to me. They are cheaper than anything you can buy, take less than an hour and no particular skill to make (you have to be able to count to 22), and sound just amazing - even with cheap 18 AWG magnet wire.
I bought 100 ft of 18 AWG magnet wire on ebay for less than $10. It was enough to make 12 coils for my three amps with plenty left over. 12 AWG is about $30 and I'm thinking about it.
Can you describe what you have in mind with "12ga. 1/2 inch wide foil under teflon"? Is this copper foil separated by teflon film?
-dr_vega
foil
The raw copper foil is .5 X .010 inches. Available from McMaster- Carr. They also sell the .75 inch wide Teflon tape. I have been using the foil as speaker wires jacketed only by Tekflex. These are the best speaker cables I've heard so the foil should make a nice sounding coil.
This strikes me as a brilliant idea, Scott. I'm impressed. I can't wait to hear your impression of the results.
-dr_vega
Can you measure the impedance of the DAC the same way as a speaker/resistor? I'm still waiting on the arrival of the DAC, I cannot find any related information on the web.
I'm guessing this means the removal of the build-in crossovers in the speakers. I'm not so keen on that. 🙂
First I'll try the bi-wiring.
I'm wondering if a 50k Pot can be used as a volume control, when using two amplifiers.
Thanks
Bi-amping
.
Bi-amping can be done with many passive cross speakers either of two ways which carry the vernacular of horizontal vs. vertical bi-amping but I am not sure if anyone agrees on which term is which. Most people that bi-amp use one superior sounding stereo amp for the left and right tweeter and one powerful amp for left and right woofer. I tend to use great sounding amps such as the Sure 2X100 all around and have one chassis and power supply (or two mono amps) for left and one chassis for the right to get the best stereo separation and avoid level matching issues that come with using different styles of amps.
.
My direct out modified Behringers have great sound into my 4k attenuators and it has been my experience that the vast majority of modern sources sound really excellent into the tougher than usual 4k load so parelleling the inputs of a 2X100 for a vertical? bi-amp configuration should be no problem unless you use a tube preamp which often don't really like working into tougher loads than 100k.
.
There is an extra 22k shunt resistor terminating the input of the Sure amps that isn't specified in the Tripath schematic and may not be necessary but I have been too chicken to try removing it until I get to a point where I am not doing comparisons between all three of my amps. Removing this resistor would increase the input back up to 22k and make the amps 6db? louder/ more sensitive.
We usually call this active crossover.
.
Bi-amping can be done with many passive cross speakers either of two ways which carry the vernacular of horizontal vs. vertical bi-amping but I am not sure if anyone agrees on which term is which. Most people that bi-amp use one superior sounding stereo amp for the left and right tweeter and one powerful amp for left and right woofer. I tend to use great sounding amps such as the Sure 2X100 all around and have one chassis and power supply (or two mono amps) for left and one chassis for the right to get the best stereo separation and avoid level matching issues that come with using different styles of amps.
.
My direct out modified Behringers have great sound into my 4k attenuators and it has been my experience that the vast majority of modern sources sound really excellent into the tougher than usual 4k load so parelleling the inputs of a 2X100 for a vertical? bi-amp configuration should be no problem unless you use a tube preamp which often don't really like working into tougher loads than 100k.
.
There is an extra 22k shunt resistor terminating the input of the Sure amps that isn't specified in the Tripath schematic and may not be necessary but I have been too chicken to try removing it until I get to a point where I am not doing comparisons between all three of my amps. Removing this resistor would increase the input back up to 22k and make the amps 6db? louder/ more sensitive.
Residual
The residual 650kHz is normal and shows the limitations of the two element passive filter in suppressing the switching wave. Don't know about the random spike but it is probably normal as well. It could actually be a slight glitch in either the driver chip or power chip. I don't know if I would necessarily blame the power supply for that.
It usually is an active crossover, i.e., one with active amplification elements like tubes, transistors, or opamps. Certainly all the commercial ones that I know of are. This makes it easy to adjust the crossover frequencies and volumes, and (sometimes) slopes.
However, if you know what crossover frequencies you want and what the impedance of your amps are, you can build passive crossovers for the amps and gain some sound quality benefits. I have done this in the past, back in the dark ages before digital crossovers, which give you astounding flexibility with no sound quality loss at all.
This is what we did back in my sound reinforcement days: Big BGW amps for the bass bins and lovely delicate Yamahas for the tweeter horns.
Now that we have amps that are good at everything, vertical bi-amping has become more popular. The presumed benefit to vertical bi-amping is that, since the tweeter generally uses less power than the woofer, the power supply can feed more current to the woofer amp. This keeps the power supply happier than if it has to feed two woofer channels pumping out the beat in unison.
-dr_vega
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