Anybody know the specs of the Sega Naomi audio amp?

F

FusionITR

Krauser's Shoe Shiner
Joined
Aug 18, 2005
Posts
243
andy251203 said:
Go here: http://www.sega-naomi.com/forum/viewtopic.php?t=1265

Typically these amps come with a 12 VAC transformer. I wouldn't buy one if it didn't come with the transformer.
Click to expand...

Exactly what I needed. Thanks.

Question about the transformer, I am very unlikely to find one FS on ebay so I will have to buy a regular one. Any info on the 4 pins that use the transformer? Usually transformers come with 2 power leads and a center tap, but in this case there are 4 leads. Are there just two center tap leads?
 
Hewitson

Hewitson

Metal Slug Mechanic
Joined
Mar 6, 2008
Posts
2,198
FusionITR said:
Usually transformers come with 2 power leads and a center tap, but in this case there are 4 leads. Are there just two center tap leads?
Click to expand...
Eh? Having a centre-tap hasn't been the norm since rectification diodes were expensive (decades ago).

The centre-tap used to be mainly used for cutting production costs. Only 2 diodes are required for full wave rectification as opposed to four. These days they're mainly used in audio equipment.

You've got two inputs and two outputs. (0 and 12V).

Either way, why did these morons make it require an AC power supply, when its going to be sitting next to an existing DC supply in the cab?? :S
 
Last edited:
MKL

MKL

Basara's Blade Keeper
20 Year Member
Joined
Mar 8, 2002
Posts
3,686
The official transformer is 17VAC. The secondary winding is double (2x17VAC, hence the four wires) and wired in series so the actual output is 34VAC. The amp ICs (LM3875) need at least 20VDC so a single 17VAC winding wouldn't be enough.
For a replacement you can get a 2x18VAC toroidal transformer and if you can find the appropriate connector (a JST VH) you're set.
 
Hewitson

Hewitson

Metal Slug Mechanic
Joined
Mar 6, 2008
Posts
2,198
Terrible design. 12v is more than enough for a power amplifier, and it could have been run off the existing power supply to boot.

I suggest you design your own. That sega one is a POS that has obviously been designed by an idiot.
 
MKL

MKL

Basara's Blade Keeper
20 Year Member
Joined
Mar 8, 2002
Posts
3,686
:oh_no:

You get less noise in the audio signals with a toroidal transformer (or an R-Core like the kitamura kiden one officially used by Sega). In fact they are the standard for hi-end audio amplifiers and all good arcade amps use them too.
 
S

SSS

neo retired
Joined
Sep 27, 2002
Posts
10,771
I have a tendency to keep shit I gut from arcade cabs. It was working when I removed it, but I have no way to test it now so it would be sold as is. All molex connectors for volume in and out look like they are attached to that coin box bracket with the 2 volume pots on it. Make me an offer if you're interested:

2010-04-02_090451.jpg
 
Last edited:
F

FusionITR

Krauser's Shoe Shiner
Joined
Aug 18, 2005
Posts
243
Ok so basically two ~17VAC, got it.

SamuraiShodownSensei, PM sent.
 
Hewitson

Hewitson

Metal Slug Mechanic
Joined
Mar 6, 2008
Posts
2,198
MKL said:
:oh_no:

You get less noise in the audio signals with a toroidal transformer (or an R-Core like the kitamura kiden one officially used by Sega). In fact they are the standard for hi-end audio amplifiers and all good arcade amps use them too.
Click to expand...
That may be true, but there is absolutely nothing wrong with a standard onboard arcade amp. We aren't talking about audiophile quality sound here.

Personally I'd build my own 12v unit for simplicity's sake.

Thanks for the tip on toroidal transformers though, I'm planning on building a power amplifier in the near future. What exactly is an R-core?

Cheers
 
E

EtotheNGSPD

Mr. Big's Thug
Joined
Jan 27, 2009
Posts
199
I got one of those naomi amp, but i dont know how to make it work. i tried a few times with no luck. so, if anyone knows how to do it, please drop me a PM.

P1010058.jpg


P1010093.jpg


P1010100.jpg
 
F

FusionITR

Krauser's Shoe Shiner
Joined
Aug 18, 2005
Posts
243
Can someone post the current spec of the stock transformer? Finding a suitible replacement is harder than I thought.
 
F

FusionITR

Krauser's Shoe Shiner
Joined
Aug 18, 2005
Posts
243
Also, anybody know what type of connector is used for the volume pot socket?
 
You must log in or register to reply here.
Top