Hello All,
My vintage Tobshiba SC-M15 power amps have a built-in BTL mode to run them bridged/mono.
Unfortunately, having lost my original owner's manual, and an lengthy on-line search for a replacement, I have not been able to find information on how to connect the speaker leads when running it in this fashion.
I was able to find a manual with schematics and such, but nothing with specific instructions on how to connect the X/- leads.
I seem to recall that both the "+" leads were used without a connection to either "-" lead, is that correct? Is this type of connection pretty standard when a mono set up is used?
I'd hate to blow something up. I now have 3 of the amps, and am curious to see how 2 of them can push my Epicure 400's in which I replaced all 8 woofers with Huw Powell's (Human Speakers) gear.
Many thanks
Onward and upward,
Puff
image of the amp:
toshiba sc 15 - Bing Images
First a word of caution.
You must make sure the speakers are rated at 8 ohms or more in the power range to bridge that amp or you will blow it up.
Now I know your speakers claim to be 8 ohm.
This is the very nasty crossover for serial numbers after 2200.
As you can see those woofers are all in parallel. Now those speakers will be no more than 16 ohms, so the impedance has to be 4 ohms or less. If you bridge that amp into those speakers you will blow it.
Now if you have serial number below 2200, then you have this nasty crossover.
As you can see, this is a series/parallel arrangement which could conceivable give you 8 ohm impedance.
In both situations the woofers are not crossed over and operate full range. Since they will be operating way out of usable pass band you can expect a complex load. So be cautious even if you have the lower serial number.
The parallel arrangement has a resistor in series with the woofers, presumable to slightly lessen the risk of blowing amps. However a resistor in series with woofers is something you should never do.
Now bridging will double the power, which is only a 3db increase in sound pressure level. So you need to decide if 3db is worth the risk.
So this is how you do it. Select A or B speakers, not both. Switch the front panel switch to bridged mode.
You now connect the speaker between the left and right positive terminals. Connect nothing to the negative terminals or the amp will blow instantly.
I'm astounded on browsing the Net how often you see advocates of a very nasty crudely designed speaker like that, and claim they have audio nirvana. I have designed speakers for over 60 years and I know you can only get highly colored and inaccurate sound from a crude contraption like that.
