Dinasetta : a boomb...
 

Dinasetta : a boombox in reflection - Advice required !  

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Schmurtz
(@schmurtz)
New Member Registered
Joined: 2 months ago
Posts: 1
21/06/2019 5:46 am  
Hi,
 
I've got this idea to make a kind of boombox based on a mix of isetta (from Paul Carmody), Dinas (from 123Toids) and voxel.
I would like something that is not portable but impressive on power and clarity.
 
This is a description of the project that I've got in mind :
 
Design :
A design similar to isetta with a centered TB W5. 
Sub part :
I read that port tubes of the voxel can make anoying noise (chuffing) so may be I will try to make a slot port instead the tube. So something similar to a horizontally lying Dinas but if the port could be at the bottom it will be more aesthetic.
Full range part :
I remove the 2 Fountek FE85 of the isetta to replace it with two Dayton Audio rs100-4 with an enclosure pretty similar to the Dinas.
amp :
For the amp I would like to avoid TPA3118 which are really great but with some distortions. 
So I will choose 2 mono LM1875 (25w) for the Dayton Audio rs100-4 and one mono TDA7293 for the TB W5. (I choose these one because JohnAudioTech test it and they have very low noise and very low distorsion).
pre-amp & filter
To create a 2.1 amplification from a 2.0 source may be I could use a NE5531 but I don't have many informations on the quality of this thing (still a little test on parts-express forum ). May be that this 2.1 coupled with full range rs100-4 will allow to not add filters ...?
If I were very courageous I will make active filter with a DSP to replace this NE5531 but it's a more complex way...
Audio source :
As audio source I don't use a bluetooth module but an old iphone (or ipod touch) because this is cheap and the quality of the output is exemplary .... and it's a good way to have spotify connect.
May be I could add a bluetooth module anyway but in this case I would have to see how to implement 2 different sources properly.
 
 
Please I I would like to have your opinion and advice on this idea !  What do you think about each point ?
I will be very happy to have advice of this community, I read a lot these last days but I still not an expert on boombox :p
And I also have got also many question 😄
 
Thank you.

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Douglas Blake
(@douglas-blake)
Estimable Member Registered
Joined: 2 months ago
Posts: 102
21/06/2019 9:04 am  

For your amplifier and filter, a few thoughts....

The LM1875 is a 20 watt class AB chip that, while offering apparent simplicity in design also brings complications about heat dissipation and power supply into the game. So it's no advantage over the class D equivalents which deliver more output from simpler power supplies.

The current favoured chipset for general stereo use is the TPA3116d2 amplifier with NE5532 pre-amplifier. I've worked and lived with this combination for a couple of years now and I have no grumbles about them. Here are links to the data sheets...

http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf

http://www.ti.com/lit/ds/symlink/ne5532a.pdf

The TPA3116 will give you 35 watts into 8 ohms with a 24 volt supply at less than .1% distortion (usually much less). The NE5532 chip is perfectly happy at 24volts and will deliver almost immeasurably low distortion in audio applications.  Most people use laptop style SMPS  "bricks" with this setup, which has the added advantage of putting the audio power output on a regulated voltage.

I would suggest you look for a ready to mount board that does your job, unless you want some rather extensive design work along with the other parts of your project.  If you are planning a 2.1 system there are quite a few perfectly good boards available... do some searches on Amazon and Parts Express, there are lots to choose from.

 


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123Toid
(@123toid)
Estimable Member Admin
Joined: 2 years ago
Posts: 172
22/06/2019 12:50 am  
Posted by: Schmurtz
Hi,
 
I've got this idea to make a kind of boombox based on a mix of isetta (from Paul Carmody), Dinas (from 123Toids) and voxel.
I would like something that is not portable but impressive on power and clarity.
 
This is a description of the project that I've got in mind :
 
Design :
A design similar to isetta with a centered TB W5. 
Sub part :
I read that port tubes of the voxel can make anoying noise (chuffing) so may be I will try to make a slot port instead the tube. So something similar to a horizontally lying Dinas but if the port could be at the bottom it will be more aesthetic.
Full range part :
I remove the 2 Fountek FE85 of the isetta to replace it with two Dayton Audio rs100-4 with an enclosure pretty similar to the Dinas.
amp :
For the amp I would like to avoid TPA3118 which are really great but with some distortions. 
So I will choose 2 mono LM1875 (25w) for the Dayton Audio rs100-4 and one mono TDA7293 for the TB W5. (I choose these one because JohnAudioTech test it and they have very low noise and very low distorsion).
pre-amp & filter
To create a 2.1 amplification from a 2.0 source may be I could use a NE5531 but I don't have many informations on the quality of this thing (still a little test on parts-express forum ). May be that this 2.1 coupled with full range rs100-4 will allow to not add filters ...?
If I were very courageous I will make active filter with a DSP to replace this NE5531 but it's a more complex way...
Audio source :
As audio source I don't use a bluetooth module but an old iphone (or ipod touch) because this is cheap and the quality of the output is exemplary .... and it's a good way to have spotify connect.
May be I could add a bluetooth module anyway but in this case I would have to see how to implement 2 different sources properly.
 
 
Please I I would like to have your opinion and advice on this idea !  What do you think about each point ?
I will be very happy to have advice of this community, I read a lot these last days but I still not an expert on boombox :p
And I also have got also many question 😄
 
Thank you.

First of all I love the build.  I am in the process of designing something very similar.  SO I will be excited to see how yours comes out.  I personally would stick with a class D amplifier.  They use very little amperage, typically.  Which is really what you want for a portable build.  I would also mention that I didn't see anything about battery power.  Most class D amplifiers are high voltage low amperage devices.  So it would help to run something like 24 volts to it to get the best output.  At least that is my 2 cents.


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