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Post by Deleted on May 21, 2011 11:47:46 GMT
I only made 10 boards, the costs of the boards are the highest, then the BUF634 and the used opamps for audio. The rest are cheap parts... Further costs will be the 2 trafo's (dual mono design), the housing, volume control and in/output connectors.
I have noted Joe, Mike and Dicky down for a board too so now only 1 board left it seems !
Should there be more then 10 more people looking for a board I can order a new batch. It has to be tat least 10 to keep the costs down. As it is now a board will be around 30 Euros incl. shipping and SMD resistors soldered in place.
It is quite universal amp that can be 'tuned' to suit your needs. a disadvantage... to change specs you will need to take the cover off and swap tightly spaced together jumpers. Also since the audio circuit consists of well decoupled dual opamps a plethora of dual opams can be used. conditions: they must be unity gain stable and be able to operate on +/- 18V or more and have DIP8 package or SMD with an adapter.
gain steps can be made to 'custom specs'. My range is big so I can attach CD players (higher output voltage) and portable MP3 gear (very low output voltage) to the same amp.
It cannot drive: K340, K1000, eletrostatics and some very inefficient cans. Some 600 Ohm cans can't play at maximum volume.
it will deliver about 200mW in all types of headphones between 8 and 300 Ohm and can't blow low Ohmic headphones when used in 0 Ohm output configuration, also it has DC protection (because the amp can be DC coupled as well as AC coupled) 0 Ohm, 33 Ohm and 100 Ohm can be selected the difference between 100 and 120 Ohm will be hardly noticeable. 200 mW is about the maximum rating for a lot of headphones. Only some headphones can handle upto several watts ( mostly orthos)
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joethearachnid
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Post by joethearachnid on May 21, 2011 15:00:58 GMT
Hmm, looking into it it seems that the price of the ICs alone comes to nearly £60, plus the PCB, casing and toroids... not to mention the fact that I don't even have a decent DAC yet. Whilst I would love to build one of these I'm not sure that I have the funds, time or technical skill (or family inclination ) to bring something like this to fruition. I could probably still buy a PCB and build one when I've got a bit more disposable income and fewer exams, but I wouldn't want to feel like I was depriving anyone else of the opportunity. I might still buy one, but I wouldn't mind giving up my board to a more worthy candidate. -JoetheArachnid
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Post by Deleted on May 21, 2011 15:16:57 GMT
Don't worry... nobody is obligated to buy one and I will contact those who asked first. First I am going to play with it and experiment with opamps and other parts. After that I am going to make it ready for sale (parts list etc.) so this will take a few weeks too. One IC will probably remain an LM4562 the power output devices (4 ports in parallel) may become other opamps. I have a few opamps in mind.
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joethearachnid
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Post by joethearachnid on May 21, 2011 15:28:35 GMT
No chance of replacing those BUF634s with something a little cheaper? A couple of questions, just out of interest: How do you limit the power to headphones to 200mW at the varying impedances (am I reading that right)? Why did you decide not to mount the trafos on the board? Why did you decide to use jumpers instead of dip switches? How do you spend all your time thinking about these circuits but still manage to come up with an awesome name for the amp? Thanks in advance, -JoetheArachnid
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Post by Deleted on May 21, 2011 15:50:07 GMT
Alas ... the BUF634 needs to deliver the current. There are other options but not as suited and have other footprints. You could opt to leave the supeerregs out and feed the board with another regulated power supply. The superreg on this board is specifically designed to do an optimal job on this specific board/amp and tuned for the power needed. it does get hot though, tinkering with that.
The current is limited because there is always a 100 Ohm output resistance. By varying the point of feedback this resistance gets smaller but remains in place. Trafo's on aboard makes the board bigger and limits the type of trafo's that can be used. The DIP switches made some important traces too long for my taste, jumpers can be positioned more strategically. I design a lot of products for my job and have fun playing with letters and abreviations to come up with 'fun' or catchy names.
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joethearachnid
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Post by joethearachnid on May 21, 2011 22:10:50 GMT
I guess I'll wait until you're done with a full BoM before counting up the pennies and seeing if I think it's worth it for me. It certainly seems smarter than the average amp. How big is the PCB? I have an ammunition box (exactly like this one upload.wikimedia.org/wikipedia/commons/a/ab/Ammunition_box.jpg) that I keep thinking would make a pretty avant-garde amp enclosure if I could find some way of mounting a PCB inside it. In fact most casework would be next to impossible, but it'd look very cool and have a built-in carrying handle... -JoetheArachnid
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jonclancy
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Post by jonclancy on May 21, 2011 22:15:03 GMT
Nice work, Frans. Could this be used with similarly specced high end op amps like the LME4990?
I'm intrigued enough to request a board if you have one left, please. I think I will have quite a few parts in stock...
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Post by Deleted on May 22, 2011 6:39:07 GMT
The LME49990 is unity gain stable and can handle +/- 18V so can be applied. You will need a DIP adapter of coarse and the decoupling caps might have to become a different value. This would have to be tested to know for sure. Farnell only has US stock which will make them very expensive for me to try. It is slightly better then LM4562, both have noise and distortion values far below the hearing treshold, even when used with sensitive cans. the board dimensions: 100 x 116 mm You can't slide the 100mm in rails as 2 caps are located almost on the sides of the board All boards are now 'spoken for' unless someone decides not to buy it.
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jonclancy
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Post by jonclancy on May 22, 2011 9:43:25 GMT
Thanks for the info, Frans. The LME has astonishing specs and I was looking into this op amp earlier in the year. The US stock thing with Farnell is a pain, but I am sure we could ask one of our US resident members if they could help. I have no real beef with getting a job lot sent to the UK, but that charge is a pain. Another option might be samples leading to a firm bulk order. Anyway, that's a long way downstream from here.
Could this be used as a preamplifier as well???
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Post by Deleted on May 22, 2011 10:54:17 GMT
Samples or asking US citizens to order and forward might be an idea.
Noise (and thus also distortion in this case) is about 3 times lower (9dB) then the LM4562 which already is below human hearing capabilities in case of headphone usage. as a pre it might be a different story.
pricewise they cost about the same (not counting the adapter)
Using the amps as a pre is a bit 'overkill' and the variable output resistance does nothing for preamps. Of coarse the PS could be much simpler in that case (as it will be running in class-A in this case) and a lot of parts wouldn't have to be fitted if it is only to serve as a preamp (the PCB itself I mean)
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Post by Deleted on May 22, 2011 11:43:44 GMT
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Post by Deleted on May 22, 2011 12:12:45 GMT
hmmmm didn't notice it right away. It's a single opamp... it needs to be dual opamp... sorry
LME49722 is a dual version, spec'd between the 2 opamps
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XTRProf
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Post by XTRProf on May 24, 2011 4:16:16 GMT
Ah, Frans, great to see that your HA is coming along well. I will be an observer from the side line for sure. Excellent!
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jonclancy
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Post by jonclancy on May 24, 2011 10:29:44 GMT
hmmmm didn't notice it right away. It's a single opamp... it needs to be dual opamp... sorry LME49722 is a dual version, spec'd between the 2 opamps I would just use one of my Brown Dog single to dual SOIC converters. A bit fiddly to solder, but I have had excellent results from these in the past. I could even offer this as a service...
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Post by Deleted on May 24, 2011 11:26:18 GMT
There is very little room surrounding the IC footprint but perhaps it is possible. You could decide to use it only in the voltage gain/DC servo and use other opamps to drive the HP's. The LME49990 opamps aren't designed to drive low Ohmic outputs but since 4 are used in parallel they just can. There are other opamps more suited for the driving task like the LM6172 I am currently using. They are faster then the input stage and have higher drive capabilities. Pretty much done with the tinkering now. In my design I am gonna use LM6172 as the output power parts and the LM4562 for amplification. The LM6172 can also be used in this position and will give a slightly better 300kHz squarewave response compared to LM4562 but the bandwidth I measured (-3 dB) is virtually the same. I tried some NE5532 and OPA's in that position but they simply perform less at 100kHz squarewaves. Upto 50kHz sinewaves appear to be the same bandwidth is dependent of the used opamp. using faster opamps is pointless as the FR is limited by other factors at 350kHz (-3dB) in wide bandwidth setting. The LM4562 will give about 10dB lower noise floor and distortion compared to the LM6172 in the amplification stage. In the output stage noise level is not important so the ultrafast and current capable LM6172 is used for that. Will do more measurements in the coming days when I have time. MAX. output powers (regardless of used output resistance) in headphones: 8 Ohm = 60 mW 16 Ohm = 100 mW 32 Ohm = 150 mW 64 Ohm = 200 mW 120 Ohm = 200 mW 300 Ohm = 160 mW 600 Ohm = 80 mW As most headphones are specified for about 200mW (some much higher) it can drive most headphones to the maximum allowable level without a chance of blowing them up due to overvoltage. The 'heat' problem has been solved and everything runs cool or marginally warm to the touch. No more 50oC inside the cabinet after 1 hour or so. Oh ... sounds good too
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joethearachnid
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Post by joethearachnid on May 25, 2011 16:40:59 GMT
<technical talk>snip</technical talk> Oh ... sounds good too I think this is what we refer to as a 'Fransian response'. -JoetheArachnid
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Post by Deleted on May 25, 2011 16:55:20 GMT
;D I am satisfied with the results. This is the build as is.. only the 230V needs to be done correctly (a fuse aded and wires done correctly) Now comes the painstaking task of measuring all the specs in various settings. creating the parts list and assembly instructions, operation manual e.t.c. When all is done the people who have 'reserved' boards will be contacted. Will take up 1 or 2 weeks probably ... for easy assembly all electros and diodes face one direction so less mistakes can be made and on the PCB pin number 1, polarity of polarised parts, transistor/FET abreviations and other remarks have been incorporated in the top copper layer.
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jonclancy
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Post by jonclancy on May 25, 2011 20:18:15 GMT
Nice job there, Frans!!
The adapters I have used are where one SOIC device in on the underside of the adapter, and the other on top. The single to dual DIP adapters have the devices side by side, so you need more room. I have some 4562 in stock anyway, so will start off with those initially.
Cheers
Jon
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Post by Deleted on May 26, 2011 5:14:45 GMT
There is more then one way to skin a cat.. Perhaps it is possible to use a turned DIP socket (like in this amp) and mount 2 of those single SMD opamps vertically in the open slot with thin wires and then pore some glue in to make it more solid... Seems do-able....
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Post by Deleted on May 26, 2011 18:43:50 GMT
Final schematics of the amplifier: www.mediafire.com/?x072544y4n4xobfPCB: www.mediafire.com/?4czbr7hmcp8hqn2a pdf with more info will follow at a later date. Did some quick 'standard' measurements (output voltage 7.7V rms no load attached): Frequency range regardless of gain and output resistance and LM4562 in pos 1/8: DC coupled: < 0.5Hz (below that DC protection kicks in) to 400 kHz - 0.5dB DC coupled: < 0.5Hz to 600 kHz - 3dB (slew rate limited) AC coupled: 80Hz - 400kHz (-0.5 dB) = 30Hz to 600kHz - 3dB with LM6172 in pos 1 and 8 : DC coupled: < 0.5Hz (below that DC protection kicks in) to 400 kHz - 0.5dB DC coupled: < 0.5Hz (below that DC protection kicks in) to 4 MHz - 3dB AC coupled: 80Hz - 400kHz (-0.5 dB) = 30Hz to 4 MHz - 3dB With LT1361 in pos 1 and 8 : DC coupled: < 0.5Hz (below that DC protection kicks in) to 1 MHz - 0.5dB DC coupled: < 0.5Hz (below that DC protection kicks in) to 5 MHz - 3dB AC coupled: 80Hz - 400kHz (-0.5 dB) = 30Hz to 5 MHz - 3dB With TL072 in pos 1 and 8 : DC coupled: < 0.5Hz (below that DC protection kicks in) to 250 kHz - 0.5dB DC coupled: < 0.5Hz (below that DC protection kicks in) to 500 kHz - 3dB AC coupled: 80Hz - 400kHz (-0.5 dB) = 30Hz to 500 kHz - 3dB With NE5532 in pos 1 and 8 : DC coupled: < 0.5Hz (below that DC protection kicks in) to 200 kHz - 0.5dB DC coupled: < 0.5Hz (below that DC protection kicks in) to 250 kHz - 3dB AC coupled: 80Hz - 400kHz (-0.5 dB) = 30Hz to 500 kHz - 3dB The frequency response does not change with higher gains (ranging from 5x to 23x) (With LT1361, LM6172 or LM4562) bandwidth setting (DC coupled) BW limit # 1: <0.5 Hz to 80kHz (- 3 dB) BW limit # 2: <0.5 Hz to 30kHz (- 3 dB) BW limit # 2: <0.5 Hz to 22kHz (- 3 dB) Output resistances selectable: 0.5 Ohm 33 Ohm 100 Ohm
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Post by Deleted on May 26, 2011 19:51:10 GMT
Frans, where are the LM6172s in the pic? according to the schematics there are4 per channel but if they are DIP8 ICs I can't see them on any of the pics you have posted, only the LM4562s.
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Post by Deleted on May 26, 2011 20:13:46 GMT
Just on the left on the middle of the PCB (picture post #41) you see 4 opamps separated by 6 transistors and 4 small electros as it were. Those are the LM6172 (each LM6172 has 2 amps in it) the 2 on the far left are LM4562 (above and below the output relay).
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Post by Deleted on Jun 2, 2011 7:38:20 GMT
The instruction manual/ build manual is finally ready. www.mediafire.com/?ix63elqpci2hn9eThanks also to Alex for checking the prelimenary pdf and commenting on it for improvements. schematic in pdf (is also included in the manual) www.mediafire.com/?x072544y4n4xobfFor those that 'pre-ordered' a board now is the time to read the pdf (almost 5MB) and decide if you want to take the boards of my hands judging from what has been written about it. board price (bare board) E 29.30 board with SMD resistors already mounted E 31.80 shipping costs: around 2 to 3 Euros.
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Post by Deleted on Jun 2, 2011 8:00:26 GMT
Frans has outdone himself with this manual. It would have to be about the most comprehensive manual that I have seen. It also includes some very thorough graphs detailing tests of various I.C.s that Frans carried out. That section alone, is worthy of a separate thread of it's own, and perhaps saved as a reference.I would be surprised if it doesn't attract the attention of members from several much larger forums. Even if you don't intend building this HA, there is a wealth of technical information, and explanations included. Alex
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jonclancy
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Post by jonclancy on Jun 2, 2011 18:21:35 GMT
Downloading as we speak!!!!
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