Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Mar 30, 2014 10:14:26 GMT
What .... Javier? I always thought of him as perverted!!
|
|
Javier
Administrator
Digital bytes
Posts: 987
|
Post by Javier on Mar 30, 2014 10:50:20 GMT
What .... Javier? I always thought of him as perverted!! who says I'm not?
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Mar 30, 2014 10:59:31 GMT
|
|
juke
very active
Posts: 396
|
Post by juke on Mar 30, 2014 11:20:30 GMT
Put me down for one please Frans. Pref ready built.
Could it power the HE6? (I'll want one either way)
Thanks
Syd
|
|
solderdude
Administrator
measureutternutter
Posts: 4,882
|
Post by solderdude on Mar 30, 2014 11:38:04 GMT
Could it power the HE6? (I'll want one either way) I figure you will be one of the first few that can tell if it does or not. At least as loud as the O2 can drive it and seen some reports that the O2 can drive the HE-6.
|
|
solderdude
Administrator
measureutternutter
Posts: 4,882
|
Post by solderdude on Mar 31, 2014 8:13:24 GMT
PCB's are ordered. They should have arrived around half April. By the end of April the first proto will be operational, tested and tweaked if all goes well. Should have written the documentation as well.
As gain and filter options are individual things all filter components will be calculted on request or when ordering filter PCB's. Filter PCB's (plug in modules) will be available separately. There will also be 'standard' modules with different amount of gain and or 'bass boost' in degree. No potmeters so adjustments have to be made by changing component values or by jumpers (in case of gain modules only)
|
|
juke
very active
Posts: 396
|
Post by juke on Mar 31, 2014 9:07:42 GMT
The whole project sounds great Frans, nice bonus if the HE-6 works out OK. A nice DACT preamp in matching case?
Syd
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Mar 31, 2014 16:26:42 GMT
As gain and filter options are individual things all filter components will be calculted on request or when ordering filter PCB's. Filter PCB's (plug in modules) will be available separately. There will also be 'standard' modules with different amount of gain and or 'bass boost' in degree. No potmeters so adjustments have to be made by changing component values or by jumpers (in case of gain modules only)Wow, this will involve quite a lot of decisions!! Frans, will the filter pcb have to be removed in order to have a 'straight' amp? I'm guessing that a 'straight amp' pcb has to replace the filter for it to be a more normal type of amp? Not switchable between filtered and standard amp? With choice of bass amounts and power, this is going to be one heck of an amp as it is without the filters. I'd have to decide which headphone to use .... DT770, HD650, T40 ...... this is going to be difficult!!!! I think I need 5 of them. ...... or more?
|
|
solderdude
Administrator
measureutternutter
Posts: 4,882
|
Post by solderdude on Mar 31, 2014 16:53:24 GMT
There is one big PCB (the one in the picture) that will remain in its place. Between the 2 opamps you can see another 'opamp socket'. This is where the filter PCB will be inserted. mounted above the components of the fixed bottom PCB. The module can be fixed with 2 screws or 2 bolts (will have to look for the easiest way), have a few ideas to try. The filter 'module' will have to be replaced by another 'module' that has the function you want it to do (flat low gain, flat high gain, bass boost etc.) Without a module there will be no sound at all. A switch was not feasible without running into several other problems. Depending on how the top cover is mounted the filter PCB will be easy to replace. Will be thinking of an easy method. The filter PCB's won't be expensive as they only have a few passive components on them. I plan to make a filter for my favourite headphones. T50RP, DT1350, HD650 for instance as these all improve greatly with some EQ. Also I will make a gain module with a jumper on it so I can select high gain (for high impedance headphones or when I need more juice) and low gain (for low impedance headphones) just in case I ever need a 'flat' or 'slight bass boost' amp. Most people have only few headphones so if one can change the modules fairly quickly it won't be a problem. Since this amplifier is intended for portable usage (batteries) it will in practice always be connected to something like a DAP (as in my case) or a phone, tablet or laptop... something transportable. Those devices all have a volume control and HP out. Most people are afraid the HP out is of bad quality in general but as the output circuit is not loaded with a headphone but with a relatively high load resistance these output stages are not loaded and work very well as a 'buffer'. Not having a lot of options by using potmeters or switches may seem limiting but in practice one plugs in a headphone and a cable to the player and simply operates the player. Of course one could always give Javier something to do and order 1 or more amps as well. One for each occasion...
|
|
dicky
quite active
Posts: 230
|
Post by dicky on Mar 31, 2014 18:11:54 GMT
Hi Frans, I suppose you'd better put me down for one too. D'oh! Dicky
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Mar 31, 2014 19:02:31 GMT
Since you mentioned the amp had no vol control Frans, I have tried it from various devices and tbh, there is no problem at all. In fact, I now wonder why they haven't been built this way before for portables.
It's no big deal.
This means that the amp will be working at whatever gain you choose and the output varies with the input, so what is the s/n ratio like if you play at lower volumes? I guess, it might be better to switch it to low gain in order to improve the s/n ratio?
It could be issues like this that could influence what gain you'd need in order to get minimal noise.
|
|
solderdude
Administrator
measureutternutter
Posts: 4,882
|
Post by solderdude on Mar 31, 2014 19:27:39 GMT
Gain is a funny thing.
For IEM's you need around 0.5x gain for very sensitive portable HP's 1x to 2x Less sensitive ones 3x to 4x high impedance headphones 3 to 5x the likes of HE-6 maybe even more.
It also depends on what you connect to it. Usually the output voltage of small DAP's (say i-devices and Sansa thingies) is much lower than line level. Often around 1V fully maxed out.
The amp can deliver about 5.6V max. To reach that the gain must be at least 6x, maybe even more as you want it to play a bit louder on some passages.
So gain depends on if you want to reach the maximum headroom/output voltage, efficiency of the headphone and output voltage of the DAP.
Most DAP's/phones etc will be able to deliver 1V so the gain will most likely be set acc to the efficiency/impedance ratings of the headphone and is determined by the 'module'. Because the module is suited for only 1 headphone (but may work wonders on some others as well sometimes) it is easy to determine the gain.
As for a separate gain module (flat) it is possible to create 3 gain levels simply by setting jumpers on the 'module' so that is covered as well.
Needless to say we want to remain below noise levels of the DAP/Phone/source. If that happens to be a crappy or noisy one than that device is better not used or the gain is lowered (by calculation of other resistor values)
|
|
|
Post by deireleire on Apr 1, 2014 20:05:42 GMT
Is javier taking care of the pre-builts? I wanna order a kameleon with a fostex t50rp module Frans you pwn!
|
|
solderdude
Administrator
measureutternutter
Posts: 4,882
|
Post by solderdude on Apr 2, 2014 5:08:17 GMT
Is javier taking care of the pre-builts? That is the plan. By the end of the month the proto will probably be ready. There will still be a lot of mechanical things to figure out once the PCB's are in an functional. Working on the documentation in the meantime. Will have to make different filters for stock and modified T50RP's as they are not the same. Then comes the task of whipping up filters for various 'popular' headphones as they components differ drastically from the filter PCB. The enclosure I picked is available in 3 colours, silver, black and blue. There are also various colour front panels available. Initially I thought of making it 'O2 style' meaning all components are on the board and one only needs to slide it in an enclosure. That (IMO) severely limits the choice of components and layout of the amp. As is currently the case for the O2 it seems the power socket is no longer available and there are no alternatives. This problem I encountered myself with quite a few components over the years so made it the way it is. More mechanical work but also more customizable.
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Apr 2, 2014 8:17:22 GMT
What with choice of sound and colours, some will have severe difficulties making a choice!! Sounds absolutely brilliant.
Sent from my ZTE Blade V using proboards
|
|