Rabbit
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Post by Rabbit on Feb 26, 2014 18:26:19 GMT
If I'm going to the trouble of taking an amp anywhere, I use a shoulderbag, so once it gets to a certain size, it wouldn't matter too much if it were even a bit bigger in order to accommodate the electronics and an even bigger battery imo. I don't use the O2 walking around, but might carry it, plugged in to the DAP with a short patch 'through' the bag which means the size isn't too important. Especially as this one will drive bigger headphones like the T40/50. No one would walk around mobile with that on their head surely? It's a case of semi portable .... so battery life might be quite important in that case. I wonder how long it would be before the 8 hours drop to 6 after charges? O2 battery life 'seems' quite short when you consider that one album is often over 1 hour. So 8 albums before running out of steam which will more likely be 7 once it's been charged over a period. I know - a car battery?
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solderdude
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Post by solderdude on Mar 26, 2014 7:09:10 GMT
Question....
If you could choose between a lever toggle switch that is operated up/down or left/right what would be most convenient on a 'portable' amp ?
Starting to work on the PCB and like some input.
'charging LED' on the front or rear next to the charge connector ?
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Post by deireleire on Mar 26, 2014 7:42:55 GMT
LED close to charge connector and L/R for the toggle switch.
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solderdude
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Post by solderdude on Mar 26, 2014 17:46:30 GMT
On the switch.
I planned to use one mounted on the PCB (like garage1217 amp switches) but this limited the amount of switches that can be used. Also the switch and output socket (as well as input socket) won't be inline.
So what I plan to make now is only the output connector is mounted on the board (same one as Garage 1217 amps) which fastens the board to the front channel. The 3.5mm input socket is going to be front panel mounted and connected via wires. Now different types of sockets can be used and there is a certain freedom of placement. Likewise for the power switch. Now one can choose up/down or L/R and choose the type of switch (push button/toggle for instance) and has freedom of placement.
Only contemplating the power LED(s). I can put them in a specific spot so they can be bent through the front panel or connected with wires and create freedom of front panel layout.
This makes it a bit more complex to build (using pieces of wire) but simplifies front panel machinery IMO.
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solderdude
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Post by solderdude on Mar 26, 2014 19:53:18 GMT
Working on the PCB ... finally...
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solderdude
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Post by solderdude on Mar 28, 2014 11:04:21 GMT
PCB finished... going to check the PCB's this weekend.
When I think they are O.K. I will order a few PCB's and hope it works well after assembly. Hope to have finished the complete proto amp + a few filter PCB's by end of April.
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solderdude
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Post by solderdude on Mar 28, 2014 19:53:26 GMT
Here is a quick mock-up with the PCB and batteries in it. 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.
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Rabbit
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Post by Rabbit on Mar 28, 2014 20:43:17 GMT
How will the batteries be held in place Frans?
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Javier
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Post by Javier on Mar 28, 2014 20:46:19 GMT
How will the batteries be held in place Frans? Blu-Tack?
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Rabbit
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Post by Rabbit on Mar 28, 2014 20:49:26 GMT
Nothing a nail can't fix. I did that to kill a lithium ion battery for one of my helis. It blew up.
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solderdude
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Post by solderdude on Mar 28, 2014 21:28:38 GMT
double sided sticky tape. They are rechargeable NiMH so don't need to be replaced that often anyway, about once every few years or so. If someone wants to use alkalines probably make a 'bed' for them with rubber.
There is a jumper so it can be used with alkaline or rechargeable NiMH. Other rechargeable batteries cannot be used (Lithium or NiCd).
There is also a jumper that switches the amp off as soon as the charger is connected (well when it is powered up). For those that want to keep listening while the amp is connected to the charger (it won't charge much in that case though) the jumper needs to be removed. There is also a thermal protection for the output devices present.
It switches off automatically when the rechargeable batteries need to be recharged. It will still draw some current though so must be shut off with the power switch.
There is a charging LED that will light up when charging and slowly goes off when the battery is almost full. You can't 'overcharge' the batteries though so charging is very slow (overnight ?).
When 4 screws in the back are removed the top panel slides off and the gain/filter module can be replaced (fixed with 2 bolts) for another one.
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Dave
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Post by Dave on Mar 29, 2014 8:58:34 GMT
Hi Frans, Can I register my interest in obtaining one of theses portable amps when they become available please? ATM I use a portable C-Moy which I like but it was bought a few years ago when I knew even less about audio than I know now, i.e. nowt! . This sounds (sorry, pun not intended) as though it might be an improvement on my C-Moy. Subject to total cost it would be nice if it became available by mid June when we scoot off to Crete for a week. TIA, Dave.
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solderdude
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Post by solderdude on Mar 30, 2014 8:35:37 GMT
I plan on ordering 20 boards (+70 filter boards). For a 'set' of 1 board + 3 filter boards the PCB price alone = € 17.- Enclosure around € 20.- 2 Rechargeable batteries = € 20.- The rest of the parts will determine the DIY price of an amp. I figure at least that of the O2 (around € 100 or perhaps above it) A fully built version will depend on many factors. That may be between € 150 and € 200 ? It will be MUCH more powerful than a C'Moy though, around the same power as O2 for higher impedance headphones and a bit more powerful in low impedance headphones. Filter modules can always be bought separately and won't be expensive. You can also alter or populate filter boards yourself or make a 'flat' or 'bass boosted' power amp that can be connected to all headphones. The added value of this design is: - Portable working on rechargeable batteries.
- Can be charged (>8 hours !) from 5V adapter (and also USB with the correct wiring).
- Filter plug in module equalizes a LOT of headphones (most of the ones listed in filter board).
- Can be used as a 'normal' or slightly tonal balanced headphone amplifier.
- Can drive 'hard to drive' low impedance headphones.
- Can drive high impedance headphones to at least above decent levels.
- well publicly documented design
- design not compromised by financial decisions (profit margin)
- custom design possible
- continuous support for headphones to be corrected and technical problems
- Intended to help out a forum member (not me)
The ABSENCE of a volume control dictates it can ONLY be connected to the headphone output of a portable player/Phone/laptop/PC/tablet/mediaplayer. This amp therefore can NOT be used from line-outs UNLESS the source has a volume control and a 'low' output resistance (< 100 Ohm which even most line-outs are) So in that aspect it differs / is limited compared to most other portable amps that have their own volume control. The reason I designed it is because: I wanted to have something like this myself and on a nice PCB instead of experimental board. Like to design stuff like this (stuff that isn't on the market). Want to help fellow forum members out (one in particular). The design is 'thrown over the fence' (a bit like NwAvGuy did but not under conditions) and won't be making ANY money of it as I WON'T be selling them myself. I really don't mind putting in the hundreds of hours and some € to realise this amp because I think of designing it as a hobby rather than launching something too soon and with components that are a compromise based on maximizing financial gain.
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Rabbit
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Post by Rabbit on Mar 30, 2014 9:35:40 GMT
The reason I designed it is because: a) I wanted to have something like this myself and on a nice PCB instead of experimental board. b) Like to design stuff like this (stuff that isn't on the market). c) Want to help fellow forum members out (one in particular). d) The design is 'thrown over the fence' (a bit like NwAvGuy did but not under conditions) and won't be making ANY money of it as I WON'T be selling them myself.a) It's briliant when you are able to customise your own listening. I lost my nerve years ago!! b) That's exactly why it's so good. If you want an O2, it's already there and doesn't need to be reinvented. c) That's what many don't appreciate. Who's the 'one' though? Sounds like the Matrix .... Neo? d) I think you should be, Frans. It's only right. You are one of the very few people who makes this stuff without profiteering. Others do it in a disguised way while others are blatant. Those people don't believe that you don't make from it as well which is quite funny!!! Thing is Frans, you are a gold mine of information in the real world of making stuff that actually does the job well. Those 3 amps are quite amazing value; even going via a retail outlet with a level of support that is totally unrivalled on an original product. Also, you are not always quite the objectivist that you are 'accused' of being!! I know that you use your ears in a very sensitive way along with all that detailed measuring stuff that you do. I've been having a good experiment with measurements this morning, which has been a real eye opener for me actually. I'll post in another place. It's mainly due to you that I have become 'cooler' towards my approach to headphone sound as I get older and try to kind of distance myself from my 'gut' feelings and then once I've done that, my gut feelings become tempered!! You get a more realistic view of the headphone then!!! (However, it's really not black and white, which I guess is the magic of hi fi)
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solderdude
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Post by solderdude on Mar 30, 2014 10:07:31 GMT
c) Who's the 'one' though?
Someone that likes to play around with Blu-Tack
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