Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 8, 2011 16:08:02 GMT
In this thread I will discus the amp I am working on. suggestions and questions/remarks are welcome. The LM4562 amp (plastic DIP versions) in it's experimental stage. It uses an LM4562 'half' for amplification, one 'half' for DC servo . 4 opamps per channel are used as 'ideal power output' stages. It has selectable output resistances (4, 43 and 100 Ohm) AND the output power is not affected by this output resistance. It will deliver 100mW to 200mW depending on used HP impedance and can drive all 'normal' type headphones. One can select a bandwidth of 18 kHz, 25 kHz, 60 kHz or 750kHz (all - 3dB) and select a highpass filter (30Hz) or DC coupled (0.2Hz by DC servo). The gain can be set between 6, 13, 20 or 28x It also features a DC protection, slow on fast off output relay and RCA out. The power supply is anything but a standard regulator and has extremely low noise and a very low resistance over a large bandwidth (at least upto 100kHz). Power consumption is rather high so even when idle temperatures of the opamps soar to 45 to 50oC with the top lid closed. This will be better in the final design. Final schematics (differs from the amp pitured above): www.mediafire.com/?x072544y4n4xobfAll info on the final design of this amplifier (21 pages) is in this pdf (almost 5 MB): www.mediafire.com/?ix63elqpci2hn9eI tried to measure distortion and noise but it is lower then the test equipment treshold I have at my disposal can show so below 80dB in any case as I do not have Rightmark Audio analyzer yet
|
|
|
Post by PinkFloyd on Apr 8, 2011 21:52:23 GMT
Frans, That looks fantastic...... why oh why don't you "advertise" your headphone amps on here? Feel free to make yourself a sub section (or I can do it for you)..... You are part of this joint mate and, as such, free to do what you like (within reason! as long as you keep your clothes on etc.)...... Do you have any review samples? I would LOVE to hear one of your amps. Mike. The LM4562 amp (plastic DIP versions) is finished in it's experimental stage. I MIGHT make a PCB for it .. It uses an LM4562 'half' for amplification, one 'half' for DC servo . 4 opamps per channel are used as 'ideal power output' stages. It has selectable output resistances (4, 43 and 100 Ohm) AND the output power is not affected by this output resistance. It will deliver 100mW to 200mW depending on used HP impedance and can drive all 'normal' type headphones. One can select a bandwidth of 18 kHz, 25 kHz, 60 kHz or 750kHz (all - 3dB) and select a highpass filter (30Hz) or DC coupled (0.2Hz by DC servo). The gain can be set between 6, 13, 20 or 28x It also features a DC protection, slow on fast off output relay and RCA out. The power supply is anything but a standard regulator and has extremely low noise and a very low resistance over a large bandwidth (at least upto 100kHz). Power consumption is rather high so even when idle temperatures of the opamps soar to 45 to 50oC with the top lid closed. for those who like to view the (prelimenary) schematics: www.mediafire.com/?t3mibdb373waczeI tried to measure distortion and noise but it is lower then the test equipment treshold I have at my disposal can show so below 80dB in any case.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 8, 2011 23:28:40 GMT
Hi Frans I would suggest that the presets be changed to give lower gain values. Ian and others prefer amps like the Neco to have as low as 3 x gain. Some people prefer the original 2x gain of the Jaycar HA for example. Others are even happy using unity gain buffers with higher level sources.I would suggest that 20 x gain is more than enough for most normal applications. Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 9, 2011 6:06:34 GMT
It's a matter of changing resistor values. to get the 'selectable gain' range one wants. Also this is just a first attempt to suit my personal needs and do some testing on. at the highest gain I get a faint hum... When the right transformer (a single or 2 separate ones) are mounted it will be O.K. again. When it is exactly the way I want it I could send it out for review.
Should I ever decide to make a PCP it won't have the (too small) transformers on it.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 9, 2011 6:32:08 GMT
That looks fantastic...... +1!!!! Frans, do you have graphs or numbers (FR, THD, IM, etc.) even if at its initial stage?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 9, 2011 7:40:55 GMT
FR can be selected to be: 0.2Hz to 18 kHz (- 3dB) 30Hz to 18 kHz (- 3dB) (very 'tuby' sounding without the tube distortion I am afraid so not really fully comparable) 0.2Hz to 25 kHz (- 3dB) (a bit like the standard G2 but again without the tube distortion ) 30Hz to 25 kHz (- 3dB) 0.2Hz to 60 kHz (- 3dB) 0.5Hz to 25kHz (-0.5dB) with some phase shift in the upper audible band. 30Hz to 60 kHz (- 3dB) 70Hz to 25kHz (-0.5dB) with phase shift in the audible band. 0.2Hz to 750 kHz (- 3dB) 0.5Hz to 200kHz (-0.5dB) with no phase shift at all in the audible band. 30Hz to 750 kHz (- 3dB) 70Hz to 200kHz (-0.5dB) with phase shift in the lower audible band. THD and IM I cannot measure, they are below the capabilities of the test equipment available to me at this moment. So well below 0.001% They will probably somewhat less then the specs of the LM4562 (distortion/noise wise) due to layout not being optimal. Since the Opamps datasheet talks about -120 dB and my cans cannot even reach 120dB SPL with 200mW (my ears won't like it either) any added noise or distortion should always remain below the hearing treshold so in wide bandwidth mode close to a wire with gain. HP drivers themselves already distort at 0.1% if you have some pretty good cans and the 95% of all recordings also show rather high amounts of distortion.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 26, 2011 17:22:41 GMT
update -
schematics have changed a bit and a PCB is designed. It will be going in (limited) production and a finished/finalised PCB will probably be available around the start of June Only 7 PCB's available... Once it is available and a manual is constructed I will start a thread for it. I expect this around the end of June 2011. It doesn't use DIP switches anymore but jumpers.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 26, 2011 19:05:38 GMT
Frans, are you designing the PCB with a commercialy available case in mind?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 26, 2011 21:02:28 GMT
NO .. no commercial case in mind. the PCB will be 100 x 116 mm so should fit some commercial available housings. One board with everything on it... only needs 2 transformers (dual mono design), in and output sockets, power switch and a volpot. amps, power supply (rectifiers, superregs) and protection (DC, slow on, fast off) are on the board. More to come when the amp is built/tested/optimised and ready for 'copying' in its own thread instead of this thread by that time. If I had ordered just 2 PCB's (this amp needs a real PCB to really get the quality of the opamps out) the boards would be E 75 a piece. Price dropped till E 25.- with 10 boards so I figured at least a few RG members would like to give it a try too perhaps. I do not make money of of it, just trying to keep the hobby affordable to myself and others and offer something other manufacturers don't have (easy configurable) or at least not for huge amounts of money. Also not doing this for fame .... just for the fun. Not going to offer them ready built or in kit form but will offer support. Now only 4 boards left
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 29, 2011 9:31:26 GMT
here is a sneak preview of the PCB: www.mediafire.com/?4czbr7hmcp8hqn2There is no silkscreen on this preview nor will it be printed on the PCB (it will be provided with the build manual though) as it would be impossible to have a silkscreen (the white text stating the parts) as the board population is too dense. It shows top and in darker the ground layer and bottom and in darker the power layer. It will actually look like this. When it is built and configured correctly I will start a thread on it.
|
|
XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on Apr 29, 2011 9:46:24 GMT
here is a sneak preview of the PCB: www.mediafire.com/?4czbr7hmcp8hqn2There is no silkscreen on this preview nor will it be printed on the PCB (it will be provided with the build manual though) as it would be impossible to have a silkscreen (the white text stating the parts) as the board population is too dense. It shows top and in darker the ground layer and bottom and in darker the power layer. It will actually look like this. When it is built and configured correctly I will start a thread on it. Hi Frans, I didn't know you already have your HA designed as it's in a LM4562 thread. What is it based on? Fully discrete or op amp based? If op amp based through out I will pass unless I'm going portable as well which I don't see myself doing so even later. Thanks.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 29, 2011 11:11:39 GMT
Fortunately for me ... you will have to pass this one ;D 100% opamp based The supply voltage (48V) and power consumption (a few Watt) are too high for portable use plus the PCB is way too big to fit in portable gear.
|
|
|
Post by bjarne on Apr 30, 2011 20:10:30 GMT
Haven't found this thread until now - so Kudos to you Frans! Your PCB and measurements looks great! Can't wait to get my solder iron on it!
|
|
XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on May 3, 2011 2:32:46 GMT
Fortunately for me ... you will have to pass this one ;D 100% opamp based The supply voltage (48V) and power consumption (a few Watt) are too high for portable use plus the PCB is way too big to fit in portable gear. Thanks Frans. Great! Ha, ha, I love it as that will give me more time for music instead of more projects. Alright, guys, enjoy Frans' full op amp based HA as I'm very sure that will measure very well technically. Hopefully, there will be a Frans' discrete HA which I'm also sure a well established design engineer of his calibre is very capable of coming up with as well .......... Frans, I'm the first one in the que for your discrete HA, ok?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 3, 2011 2:58:21 GMT
I hope you feel confident using Surface Mount devices like the present design ? ;D
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 3, 2011 5:56:20 GMT
It's just a few resistors in surface mount. And they are the BIGGEST standard surface mount resistors (1206), those are real easy to place and solder. It's a crammed board but has to be too... so not for the novice probably. Given the fact so many peeps like C'moys and other amps containing their favorite opamps. Also you can configure it to your needs without the need to resolder parts... Ah ... Chong ... you will be missing out on something. After all any reasonably built discrete amp usually is a higher power and simplified copy of the early opamps. Now only 4 boards available left It is unlikely I will have more boards produced in the future.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 19, 2011 20:53:40 GMT
The PCB's came in this morning. I populated one board and it's running O.K. directly from the start. Good news is the little hum I had on the highest gain setting with the breadboard version is completely gone (which I had expected) When I am done experimenting with some values and parts I will create a thread with info.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 20, 2011 7:13:42 GMT
Great news Frans, can you please post some pics?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 20, 2011 17:27:35 GMT
Here is a pic of the assembled board. Don't mind the 2 zeners 'on a stick' experimenting with those. It's still under development but the final product is going to look like this (without the elevated zeners ) I used sockets fro the audio IC's to conduct some experiments. In the final version for myself there will be no sockets.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 20, 2011 21:09:19 GMT
Looks great but I see there are some tiny SMD resistors, that is going to be a real challenge for noobs like me.
I see the 4562s and the 634s but, what's the 5534's task?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 20, 2011 21:27:58 GMT
5534 and BUF634 are a superregulator (low noise wide bandwith voltage regulator) I already thought of seling boards with and without SMD mounted. This has to be done 'custom' if someone wants different gain settings/steps. SMD is not hard to solder b.t.w. it only looks that way. Soldering SMD IC's is another story, SMD resistors is quite easy.
The audio IC's may still change, the 5534 and BUF634 are there to stay, they only need to provide a steady DC with low noise and low internal resistance and that's what they do. You can opt to NOT install the superregs and connect the amp part to other PS.
|
|
joethearachnid
Been here a while!
Old head on young shoulders.
Posts: 380
|
Post by joethearachnid on May 21, 2011 9:24:15 GMT
Gosh, really don't know how I missed this thread! That looks fantastic. What was the overall cost inc. PCB and all parts?
And are there any boards left?
-JoetheArachnid
|
|
|
Post by PinkFloyd on May 21, 2011 10:12:21 GMT
I'll have a board Frans.... OR, you can sell me a fully populated animal.... either / or.
Mike.
|
|
|
Post by dicky on May 21, 2011 11:11:28 GMT
Hi Frans I just stumbled across this thread. If you have any boards without a home I'd like to take one off your hands.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on May 21, 2011 11:22:57 GMT
Congratulations Frans. It looks like an amp to suit so many tastes. The gain adjustment and the FR adjustment are a brilliant idea. While I tend to use lower gains on amps, I have found the AKG's need a lot put into them to drive properly. (K601 as well!!) So having an option with a huge amount of gain with adjustable output impedance would put paid to that problem!! Even a proper K1000 driver. Loads of flavours all in one box. It really looks like a serious piece of gear. You really should be looking for fame and fortune!!! (Well, fortune at least!!) Ian
|
|