As stated in the title, this is not an inverting Gainclone or a clone of the Gaincard amp circuit ( quite well known by now ) but a personal "cheap & chic" copy, not quite a clone, of its case.
The main element is a couple of tin candy cans like this:
and this is the final result:
Since I didn't put analog amplifiers inside, like LM3875 or LM3886, but 2 mono TPA3118D2 digital amp boards, someone might think this thread in the wrong Forum, but dealing with Gaincard cases ...
Anyway I'll put a post in the TPA3118 thread of the Digital Amp Forum too, so everything will be in its place.
More information in the next posts.
Ciao.
Luca
The main element is a couple of tin candy cans like this:
An externally hosted image should be here but it was not working when we last tested it.
and this is the final result:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Since I didn't put analog amplifiers inside, like LM3875 or LM3886, but 2 mono TPA3118D2 digital amp boards, someone might think this thread in the wrong Forum, but dealing with Gaincard cases ...
Anyway I'll put a post in the TPA3118 thread of the Digital Amp Forum too, so everything will be in its place.
More information in the next posts.
Ciao.
Luca
Hi Luca
You must have small hands to get those connectors in. Top marks for invention with the candy cans, I haven't seen that done before.
John
You must have small hands to get those connectors in. Top marks for invention with the candy cans, I haven't seen that done before.
John
Materials
Here is a picture of the needed materials.
Along the way I avoided the use of binding posts and power supply connectors: there was not enough space and the back of the case seemed quite bulky.
So my choice landed to directly connected power supply cables and screws as binding posts, just like Gaincard has.
The potentiometers are built using 12 steps single switches, make before break type, with 11 resistances soldered on ( more information later ).
The amps, as I said previously, are digital TPA3118D2 boards: I wanted to test them since I’ve an LM3875 Gainclone already ( http://www.diyaudio.com/forums/chip-amps/275869-ikea-gainclone.html ).
Here the boxes, the front wood plate and the bottom plexiglass board, after cutting, drilling and painting.
Next episode: amps and potentiometers
Ciao.
Luca
Here is a picture of the needed materials.
An externally hosted image should be here but it was not working when we last tested it.
Along the way I avoided the use of binding posts and power supply connectors: there was not enough space and the back of the case seemed quite bulky.
So my choice landed to directly connected power supply cables and screws as binding posts, just like Gaincard has.
The potentiometers are built using 12 steps single switches, make before break type, with 11 resistances soldered on ( more information later ).
The amps, as I said previously, are digital TPA3118D2 boards: I wanted to test them since I’ve an LM3875 Gainclone already ( http://www.diyaudio.com/forums/chip-amps/275869-ikea-gainclone.html ).
Here the boxes, the front wood plate and the bottom plexiglass board, after cutting, drilling and painting.
An externally hosted image should be here but it was not working when we last tested it.
Next episode: amps and potentiometers
Ciao.
Luca
It's a honour to me to receive top marks from You, John: Your site "Decibel Dungeon" was one of my favourites while building my Gainclone, and still is.
As for the connectors, honestly they are not so close: I'll put some more pictures to show.
Best regards
Luca
Hi Luca.
Decibel Dungeon is not my site, it belongs to NUUK on this forum. It was the site that first hooked me into diy audio too!
John
Decibel Dungeon is not my site, it belongs to NUUK on this forum. It was the site that first hooked me into diy audio too!
John
Amps and potentiometers
The TPA3118D2 mono digital amps in use:
Please note the bands on the cables: they act as “stoppers” and are necessary to avoid the cables to be torn off the board, specially the power supply cables, since there are no connectors in the middle.
Moreover, I put little heatsinks on the IC, just in case …
The potentiometers are 12 steps mono switches, make before break type, with 11 resistances, ½ w type ( ¼ W are good too ), soldered on.
In order to have 20 Kohm total input resistance, I used these values: 10 KΩ, 4.7 KΩ, 2.7 KΩ, 1.2 KΩ, 560 Ω, 330 Ω, 200 Ω, 100 Ω, 47 Ω, 18 Ω, 10 Ω. General rule: each R is half the previous one.
If the switch is in 1 position, the amp is mute: the input signal is shorted to ground.
Be careful: generally this input ground loop is not a problem if digital amps are used. With analog amps ( e.g. LM3875 or LM3886 ) this could generate huge hum at the output ( that’s why the original Gaincard has a switch for muting ).
You solve this problem by putting another 10 ohm R ( or 5, or 1: make your tests ) between input pin and ground. Side effect: no mute but low volume output also with switch on position 1.
Next episode: building tips
Ciao
Luca
The TPA3118D2 mono digital amps in use:
An externally hosted image should be here but it was not working when we last tested it.
Please note the bands on the cables: they act as “stoppers” and are necessary to avoid the cables to be torn off the board, specially the power supply cables, since there are no connectors in the middle.
Moreover, I put little heatsinks on the IC, just in case …
The potentiometers are 12 steps mono switches, make before break type, with 11 resistances, ½ w type ( ¼ W are good too ), soldered on.
In order to have 20 Kohm total input resistance, I used these values: 10 KΩ, 4.7 KΩ, 2.7 KΩ, 1.2 KΩ, 560 Ω, 330 Ω, 200 Ω, 100 Ω, 47 Ω, 18 Ω, 10 Ω. General rule: each R is half the previous one.
An externally hosted image should be here but it was not working when we last tested it.
If the switch is in 1 position, the amp is mute: the input signal is shorted to ground.
Be careful: generally this input ground loop is not a problem if digital amps are used. With analog amps ( e.g. LM3875 or LM3886 ) this could generate huge hum at the output ( that’s why the original Gaincard has a switch for muting ).
You solve this problem by putting another 10 ohm R ( or 5, or 1: make your tests ) between input pin and ground. Side effect: no mute but low volume output also with switch on position 1.
An externally hosted image should be here but it was not working when we last tested it.
Next episode: building tips
Ciao
Luca
Oops, you're right John, it was my mistake. So let's give Nuuk what is Nuuk's: great site.
Ciao.
Luca
Building tips
Amps: just remember to put the stops on the output cables before putting them inside the boxes.
With amps that need to use the tin boxes as heatsink, it will be necessary to sold them to the board in a lying position, if the box is not tall enough. Here is an example:
Painting of wood, plexiglass and boxes: 2 coats of primer paint first, then 2 coats of spray paint.
Switches: cover their R’s with some tape before putting them in, to be sure that there are no contacts with the metal box.
Output connectors: use a screwdriver to press the speaker cables between the washers.
Well, I think that’s all folks: thanks everybody for reading ( and appreciating, I hope ).
Ciao
Luca
Amps: just remember to put the stops on the output cables before putting them inside the boxes.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
With amps that need to use the tin boxes as heatsink, it will be necessary to sold them to the board in a lying position, if the box is not tall enough. Here is an example:
An externally hosted image should be here but it was not working when we last tested it.
Painting of wood, plexiglass and boxes: 2 coats of primer paint first, then 2 coats of spray paint.
An externally hosted image should be here but it was not working when we last tested it.
Switches: cover their R’s with some tape before putting them in, to be sure that there are no contacts with the metal box.
An externally hosted image should be here but it was not working when we last tested it.
Output connectors: use a screwdriver to press the speaker cables between the washers.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Well, I think that’s all folks: thanks everybody for reading ( and appreciating, I hope ).
Ciao
Luca
Looks nice Luca but have you considered the WAF of such multiple boxes and cables ?
Cheers,
Jacques
Cheers,
Jacques
Hi Jacques,
the overall dimensions are quite small, so the wife ( and daughters, and cats, ... ) doesn't complain: she is used to much worse ...
Then, after listening sessions, the speakers are in rest position in a corner of the room.
Ciao.
Luca
the overall dimensions are quite small, so the wife ( and daughters, and cats, ... ) doesn't complain: she is used to much worse ...
Then, after listening sessions, the speakers are in rest position in a corner of the room.
Ciao.
Luca
- Status
- Not open for further replies.