OK, the B1 passed the smoke test but when I plugged the ipod into it all I got was dramatically reduced gain and a lot of distortion in both channels.
Not sure where to start but a set of mis-valued resistors would seem to be the most probable.
I am also using a 100K alps pot...not sure if that would contribute or not.
It was almost like an amp starved of power but I jumpered off of my chip preamp PSU and got the same results.
It sounded so bad that all I can reason is that I screwed up with the resistors somewhere.
Not sure where to start but a set of mis-valued resistors would seem to be the most probable.
I am also using a 100K alps pot...not sure if that would contribute or not.
It was almost like an amp starved of power but I jumpered off of my chip preamp PSU and got the same results.
It sounded so bad that all I can reason is that I screwed up with the resistors somewhere.
Thanks Blues! I'm about to try this myself. But do you have a schematic in a format that's less... Microsoft owned? I'm not able to read Word documents.
-d
ipods generally require MORE gain than the average 2v source. The B1 may not be enough. Do you have another item to use as a reference? Old CD player or DVD player for example? Even the line level out of a TV.
I just finished my B1. V-caps are 12 uF and they are from another project. Resistors are Takman carbon film. I made a mistake and ordered 50V version of 15000uf Nichicon caps but I don't regret it.
It sounds better than the 10K pot for the most part - it beefed up the bottom end. I like it so far. I am waiting for the enclosure I bought from Hong Kong to arrive to put it in. I also want to implement a remote volume control.
It sounds better than the 10K pot for the most part - it beefed up the bottom end. I like it so far. I am waiting for the enclosure I bought from Hong Kong to arrive to put it in. I also want to implement a remote volume control.
An externally hosted image should be here but it was not working when we last tested it.
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I imagine that you let the caps charge by leaving the circuit on for awhile to see if the distortion cleared?
If there is any doubt about the PSU then measure DC and AC voltage at the positive terminal of C1. There should not be an AC reading.
Verify that the voltage at the junction of R2/3 is at near 1/2 the supply voltage. If not, check the polarity of D1. Check to verify that this voltage is applied to R103/203. A problem here could take the fets out of class a territory and cause distortion.
Verify the the voltages at the sources of Q100/200 (drains of Q101/201) are approximately 1/2 the supply voltage. If not, double check that the pin connections are in accord with the schematic.
If the above voltages are correct I would disconnect R102/202 from the wiper and slam a signal straight onto the disconnected end of R102/202. You might not want do this if your speakers are worth a fortune.
I do not like the 317 regulator sending noise back into the input of the FET buffer.
I think the 317 should take it's supply from the 18Vdc line.
The 317 also needs it's stability caps on the input and output.
The 317's performance improves significantly if a cap is added in parallel to VR1. Without these caps, it cannot match the performance of a 7805.
Thank you! I should be able to take some readings tonight. FYI...I am using a laptop psu rated at 19.5V and 4.2 amps so I am thinking this should be ample supply.
Well there's no stopping anyone to pull the tricks to quiet things down and audiophile embellish parts. This is just something to start with and try...btw I have a a 1uF across Vout of the 317 with a quiet and stable 9V batt on the Vin (stable until it drains that is...
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Hi, there is a group buy project on this website where you can buy PCB's for this DC coupled version including shunt power supplies. Please be well aware that, although it sounds better with no need for buying expensive caps, there are also drawbacks which are pointed out.
There also was a version with input relay switching, power supply and volume control all on one PCB. The simple version is called Hypnotize and the deluxe version was called Mezmerize. "Was" because it will not be manufactured anymore, the Hypnotize though will be manufactured again in an enhanced version with more modding potential.
You'll find all the info in these threads:
http://www.diyaudio.com/forums/group-buys/147075-gb-dc-coupled-b1-buffer-shunt-psus.html
http://www.diyaudio.com/forums/pass-labs/145201-building-symmetrical-psu-b1-buffer.html
Dont mind if I give myself a plug for a minute. I offer and have been offering matched LDRs for a few years now. Check my signature if you are interested. Also provide a small mounting board for mounting the LDRs. It includes a balance circuit and protection resistors to keep from burning the LDRs. You do have to provide your own 100k Dual log pot and a power supply. I dont provide an entire kit out of respect for Mr. GeorgeHiFi. Its pretty easy to tidy up a variable voltage source to a pot then send that to my board.
I am sure that if cviller were to add this to the store I would sell a lot more LDRs and while I would promote LDRs at every step of the way and will and do help anyone to get them to work I would wonder why one would want to add a variable LDR attenuator circuit to a buffer. If you can vary your impedance you no longer need a buffer...
Uriah
I do not understand this. A buffer isolates the variable impedance of LDR's, potentiometers etc. by means of a solid non variable low output impedance, right ? So independent of the volume setting. With high input impedance that does not load the source (for instance LDR's ) and the possibility for connecting long cabling because of the low output impedance. At least that is what I learnt in the years.
So using highish impedance attenuators directly with long cabling without buffering would mean that cabling will have more influence than it has with the buffer. Also the power amp will see a varying input impedance when a buffer/preamp is omitted.
In other words: some people do need buffering....
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IMO the most desirable is an attenuator ( a variable voltage source circuit ) with no varying impedance for the following power amp. I fail to see the point varying impedance "to taste" ?!
It could be my english that is inadequate to fully understand what you mean but personally I vary only volume "to taste" ! AFAIK the situation you point out is very static with no flexibility for other amps than the one you "matched". There is also the possibility that the set sounds different with various settings of volume level... Varying impedance combined with the input capacitance of the power amp can make a nice variable filter.
It could be my english that is inadequate to fully understand what you mean but personally I vary only volume "to taste" ! AFAIK the situation you point out is very static with no flexibility for other amps than the one you "matched". There is also the possibility that the set sounds different with various settings of volume level... Varying impedance combined with the input capacitance of the power amp can make a nice variable filter.
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Blues has a variable voltage source in his schematic. You can change the total resistance of the LDR attenuator to anything you want. If you want 10k then set it there, 100k go ahead do that to.. When you change the volume the pot has points A, W and B. A 10k pot has at low volume maybe 1k from A to W and 9k from W to B. These two added together equal 10k. The total resistance. The value of the pot. I should stop saying 'varying impedance' and say 'varying total resistance.' You can vary the total resistance by varying the voltage to the LDRs, but in a perfect world, when you turn the volume pot of the Lightspeed circuit, the total resistance should stay the same. You can adjust this total resistance to taste. 6k sounds a lot different than 25k. I prefer 6k in my system to any other total resistance. If I can select the total resistance that is giving me the best sound because its a great match between my source and amp then again I dont need the buffer. So, if you use a regular Lightspeed, a buffer might be a good thing to have and DEFINITELY is something to try in the spirit of DIY and learning but if you can vary the total resistance then a buffer will get in the way more than it helps. Thats how it sounds to my ears.
Uriah
Uriah
You are right about "varying resistance" being the correct term but I adapted for communication purposes.
Mmm, this is a less easy subject than I initially thought it was because I failed to see that the total resistance of a lightspeed can be varied. Never tried LDR's despite the very positive reactions I read. They are and will be semiconductor devices which are non-linear by design. Old fashioned as I am I'll stick to potentiometers for that reason. I tell this to show my inexperience with lightspeed/LDR circuits.
So an attenuator with LDR's can also vary total resistance like one would change a standard volume potentiometer with the same standard one of a different value. A situation that normally practically never happens in real life when normal potentiometers are used. In that case also the lowest values sound best but once chosen one tends to leave it that way (when sources permit a low value like 10 k is to be preferred ).
But back to the subject: also with adapted optimal chosen "impedance" a buffer would still be a wise choice to make the power amp and cabling to it less susceptible for exactly that varying impedance/resistance. Unless one wants a filter with variable slope to "tune" sound like one can do with tone control.
Mmm, this is a less easy subject than I initially thought it was because I failed to see that the total resistance of a lightspeed can be varied. Never tried LDR's despite the very positive reactions I read. They are and will be semiconductor devices which are non-linear by design. Old fashioned as I am I'll stick to potentiometers for that reason. I tell this to show my inexperience with lightspeed/LDR circuits.
So an attenuator with LDR's can also vary total resistance like one would change a standard volume potentiometer with the same standard one of a different value. A situation that normally practically never happens in real life when normal potentiometers are used. In that case also the lowest values sound best but once chosen one tends to leave it that way (when sources permit a low value like 10 k is to be preferred ).
But back to the subject: also with adapted optimal chosen "impedance" a buffer would still be a wise choice to make the power amp and cabling to it less susceptible for exactly that varying impedance/resistance. Unless one wants a filter with variable slope to "tune" sound like one can do with tone control
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Quick question: I have a working B1 that I built on a proto board. It sounds right but I just wanted run a couple of tests to make sure I have everything wired ok.
My question is what is the proper voltage I should measure across C1 and C2 when it is not hooked up (no source or output) but plugged in? I was guessing the voltage I measure across C2 should be about half of the voltage across C1 which would be close to the ~18V I start with. I guessed this because it looks like R2 and R3 divide the voltage before C2.
Instead I read that C2 is withing a volt of C1 which is just less then the starting voltage. Is this correct or do I need to recheck my wiring?
My question is what is the proper voltage I should measure across C1 and C2 when it is not hooked up (no source or output) but plugged in? I was guessing the voltage I measure across C2 should be about half of the voltage across C1 which would be close to the ~18V I start with. I guessed this because it looks like R2 and R3 divide the voltage before C2.
Instead I read that C2 is withing a volt of C1 which is just less then the starting voltage. Is this correct or do I need to recheck my wiring?