Crispy
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Madrigal music is playing - Voices can faintly be heard, "Please leave this patient undisturbed."
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Post by Crispy on Apr 4, 2014 20:00:58 GMT
Also thought of a name for it. Kameleon which is Dutch for... Chameleon. And that describes what the amp does. It can change its tonal 'colour' depending on the module you insert. The amp makes headphones audibly transparent as it were. I was a bit bored Frans so I decided to do you a logo for your new portable amp. It was only a quick doodle nothing too serious but if you like it you can certainly use it. Chris
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solderdude
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Post by solderdude on Apr 10, 2014 18:07:06 GMT
PCB's are in ! Now to assemble the proto. Stiil waiting for a few parts to arrive.
Nice stylistic drawing Chris. Don't know if Javier is going to use decals though.
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Javier
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Post by Javier on Apr 11, 2014 4:20:38 GMT
I'm not sure decals would go along with a portable, unless one is very, very careful they wouldn't last that long, would they?
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Rabbit
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Post by Rabbit on Apr 11, 2014 9:52:30 GMT
Portables need to be slightly ugly perhaps and slightly cumbersome in some situations so they don't get pinched!!! (However, the draw of a pretty amp is just too tempting)
I have suffered this quite a few times. Put an amp down for a few seconds and it's gone. The O2 wins out in this respect since it's not particularly nice to look at.
Just some last minute observations regarding O2 in case it can be avoided on the Chameleon.....
The on/off switch is nice and easy and it's a simple push button. Problem is that it switches itself on too easily in a bag and you open it to find it flat too easily. A charging led would have been nice since I'm never really sure it's charging or even when it's fully charged. I don't like that. Don't cheap out on cheap sockets .... I'll say no more about those nasty sockets on my version. Black looks sexy, but it scratches in a mobile situation. I'd rather have a heavy battery with longer life than so short - you kind of feel that you need to charge all of the time because the O2 is going to run out of steam quickly, so I end up taking a spare amp which kind of defeats the object!! It would help if the sockets are plain to see for headphone/line in. So easy to plug in the wrong way round.
The sound of the O2 is fine, but there are some (let's say) subtleties like that which would make it a better amp in real life. (Especially socket quality which is the part of the amp that will wear out first given the amount of insertions it will need to take)
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solderdude
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Post by solderdude on Apr 11, 2014 11:44:34 GMT
The on/off switch is nice and easy and it's a simple push button. Problem is that it switches itself on too easily in a bag and you open it to find it flat too easily. A charging led would have been nice since I'm never really sure it's charging or even when it's fully charged. I don't like that. Don't cheap out on cheap sockets .... I'll say no more about those nasty sockets on my version. Black looks sexy, but it scratches in a mobile situation. I'd rather have a heavy battery with longer life than so short - you kind of feel that you need to charge all of the time because the O2 is going to run out of steam quickly, so I end up taking a spare amp which kind of defeats the object!! It would help if the sockets are plain to see for headphone/line in. So easy to plug in the wrong way round. The sound of the O2 is fine, but there are some (let's say) subtleties like that which would make it a better amp in real life. (Especially socket quality which is the part of the amp that will wear out first given the amount of insertions it will need to take) You can choose the type of on/off button because it is NOT integrated on the PCB. Also you have a choice of position (rear or front and the location on that panel, within limits) It can be a rocker, lever or pushbutton as long as it fits in the panel and isn't too big. The charging LED can be mounted in the front or rear and will be lit bright when charging an empty battery and go dimmer the higher the charge level is (function has yet to be figured out/ tweaked) The power LED and 'needs to be charged and turned off' LED can be either mounted on the PCB and poke through the front or mounted elsewhere using wires and hotmeld glue to fix it. Using nice panel mount LED's is also possible. There is only going to be 1 socket in it for the filter PCB, this one is NOT going to be turned pin because of the headers that need to make contact. The audio opamps will be soldered directly onto the PCB because the filter PCB is above the opamps. Only PP3 9V NiMH batteries can be used as the charging/discharging is wired for these. They will be LSD (low Self Discharge) types. Using larger ones would involve changing charging currents. Lithium batteries cannot be used as they require dedicated charging. The output socket = 6.35mm and is integrated on the board, it is used to keep the PCB in its place. The input socket is a 3.5mm (in my case) and NOT the PCB type so you can choose the quality and easily replace it should it ever be needed. It will depend on how much time it will take to produce these amps when demands differ for switch/LED/socket/connectors. In the O2 case all components are board mounted which is handy for production but limiting in choice. I would like people to have some choices and not be limited to specific connectors so I went for a more complex assembly (sorry Javier !)
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Rabbit
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Post by Rabbit on Apr 11, 2014 12:42:57 GMT
Sorted!!
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solderdude
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Post by solderdude on Apr 13, 2014 19:19:39 GMT
This is how the proto is coming along. Tinkering with the charging circuit and ordered some parts that I thought would just fit but didn't so mounted some other parts. Hope to get it working in the coming week.
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solderdude
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Post by solderdude on Apr 16, 2014 20:07:43 GMT
Have it up and running now. a few pictures of the prototype. frontview with top off: amp with accessories I made for it. Charger (5V adapter), USB charge cable so it can be charged from an USB port or USB adapter, a few filter PCB's for my favourite headphones. Inside without a filter board inserted. Inside with a filter board mounted (HD650) and 2 filter boards (Bass boost and DT1350) above it. The filters can be secured with 3 mm nuts and the 2 long bolts align the PCB so it fits in the socket. After changing the filters the top cover slides over it (left out for the pics as I am still refining the filters). The 4 power supply caps are not the ones that are meant to be in there but I ordered the wrong height so used much smaller 1000uF caps. It should be using 4x 2200uF caps. It runs on 2 LSD NiMH Vapextech 280mA/h 9V PP3 batteries that are taped in there using double sided sticky tape.
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Rabbit
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Post by Rabbit on Apr 16, 2014 20:32:07 GMT
The filter is a doddle to fit too Frans. Well done. Beautifully thought out.
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solderdude
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Post by solderdude on Apr 16, 2014 21:12:59 GMT
The filter board fits only when oriented correctly as the PCB is slightly asymmetric. When mounted the other way around it doesn't make contact. It has FRONT and REAR on it as well for proper orientation and is very easy to remove/place/replace. It is not intended to swap filters regular or on a daily basis.
The next question will probably be: when will there be a desktop amp using a similar setup. No plans yet....
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Post by deireleire on Apr 17, 2014 19:28:43 GMT
Cool, can't w8....
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solderdude
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Post by solderdude on Apr 17, 2014 19:55:34 GMT
When the Easter weekend is over I will try to finalise everything and will contact Javier to get his part going. From then on it will be Javiers 'baby' which I will support and calculate/configure the needed filters for future customers.
The filters are not as 'precise' as the filter PCB and not all headphones can be corrected completely but many it will be able to bring closer to a more 'ideal' situation.
The headphones I have here are pretty well 'compensated' though and much more listen-able. HD650 is less 'warmish' a bit more sparkly and does the subsonics much better yet the sonic qualities remain, it just sounds more 'real'. The DT1350 (with HD25 pads) also improves and the 'honky-ish' mids are removed. The Bass Boost is for the K551 which makes it fuller bodied yet accurate and full of pleasant detail. The 'body' that it misses in some music is added. The T50RP is well extended but never 'harsh' and I gave this amp slightly more bass than the filter to make it 'different' from the desktop amp.
I also have a 'flat' module (next to the bass boost) and it is possible to configure a single board with a jumper so you can set one board to 'bass boost' and flat with the aid of a jumper.
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Post by deireleire on Apr 17, 2014 20:05:47 GMT
Would the HD650 filter go better with opera/classical?
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Rabbit
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Post by Rabbit on Apr 17, 2014 20:53:29 GMT
Funny you mention that. I find string tone a bit lacking on the HD650, but the filter helps to add a little sparkle.
I tend to use something a bit more toppy for orchestral, like the AKG k601. If the top end is too much, then 702 pads get it so close to Senn sound with a tad more sparkle. The K601/612 takes some driving though.
Fran's filter really makes the HD650 more of a portable possibility though!!
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solderdude
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Post by solderdude on Apr 22, 2014 8:58:23 GMT
some measured specs when set to 'flat' and 7.68x (18dB) gain. Measured with both channels driven and loaded with 30 Ohm resistive load.
U out no load, full batt = 15Vpp = 5.3Vrms U out 2x 30 Ohm load, full batt = 13.6Vpp = 4.8Vrms
15 Ohm = 600mW 30 Ohm = 770mW 50 Ohm = 560mW 64 Ohm = 400mW 120 Ohm = 200mW 300 Ohm = 100mW 600 Ohm = 50mW
R out = 0.3 Ohm
Phase from 20Hz – 20khz = 179° to 183° (180 degrees -1/+3)
Freq range under 30 Ohm load: - 0.2dB = 2Hz to 120kHz -1dB = <1Hz to 230kHz -3dB = <1Hz to 420kHz
exemplary squarewave reproduction.
Will try to finish the documentation this week. The parts list is largely completed for the more difficult parts with Mouser, Farnell, RS-online and Conrad part numbers where possible.
The T50RP and DT1350 WITH HD25 pads and HD650 filter as well as bass boost for modified K550 are ready.
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