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PostPosted: Wed Nov 08, 2017 9:55 pm 
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Curious how many watts I’m pushing with a pair of Nikko Alpha 220 bridged through a Nikko BTL-I.
The 220’s are rated at 120 watts into 8 ohms. Can anyone help me with the math?


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PostPosted: Thu Nov 09, 2017 4:51 am 
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From what I've read online its somewhere between 300-500 watts.

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PostPosted: Thu Nov 09, 2017 4:54 am 
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Bridging an amplifier effectively doubles the output voltage, which in term means four times the power under ideal circumstances.
So in theory, your amps would deliver four times 120 watts, or 480 watts in bridged.

However, rarely will an amp have sufficient power supply or a strong enough output stage to actually achieve this x4 power level. I don't know enough about your Nikko's build to say with any certainty, but you're probably in the 300-350 range...


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PostPosted: Thu Nov 09, 2017 6:07 am 
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According to the service manual, the Nikko Alpha 220 is rated at 130 wpc into 4 ohms @ .02% THD, so that would give you 260 watts into 8 ohms bridged, per amp. Probably a little more at clipping.

Nice looking rack set-up 8)


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PostPosted: Thu Nov 09, 2017 6:29 am 
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3x the 8 Ohm rating would be considered good - as other posts indicate, there are p s limits - when the amp is bridged.
Likely less than 360 watts p/c, imho.


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PostPosted: Thu Nov 09, 2017 6:32 am 
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Its going back awhile :? but with the proprietary adaptor and you have it............ I believe it doubles the power
There was a Nikko 450 amp in that era that did 220 watts a side and with adaptor and 2 450's connected you did over 400 watts a side


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PostPosted: Thu Nov 09, 2017 7:03 am 
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Alpha 220's and 230's have fairly fine wiring on their mains transformers. One of them, the 220 or the 230, can't remember which..has 22g wiring on it's output, the other has 20g. These are barely sufficient to work, at all. 20g is the more acceptable, obviously. The 22g wiring is, to me, unacceptable. This is a recommended line level gauge of wiring, not mains transformer output wiring.

It is a fairly robust design, but almost purposely kneecapped by 'current control' via small gauge mains transformer wiring. the thinner wiring tends to blunt transients under loading. so the amp might sound a bit light, uneven and slight bumpy/uneven/blurry in it's bass delivery. Now think of what people say when they use these amps. Their listening impressions have a source point.

When you go to the high voltage balanced configuration, you'll be trying to get twice the current from each channel. This is not possible with this amp. but with lets say a belles 450, not as much of a problem, with it's 1500va rated transformer, and approx 50A 'potential' in current swing per channel (8x 7A Hitachi mosfets per channel, 4 per rail). bigger capacitors and it might be possible with the belles 450. It has the grunt to back things up.

The alpha 230-220 series should not be bridged. Not going to work very well, unless one has 10-12 ohm speakers, minimum. The 230-220 series does not have the current swing to back things up.

To do this best, or ..functionally, ie less chance of amplifier failure, one generally needs an amplifier that can do maybe a 3-2.5 ohm load, per channel, all day long, at high power.

Eg the belles 450, when I tested one, did about 525 watts continuous, clean undistorted sine wave, at 2.7 ohms. (per channel) This is with a 1500va transformer, that has dual output windings, and is connected in parallel, to cut transformer output impedance in half. (a pair of big gauge wired 750va rated windings, run in parallel)

It's coming back to me..the 220 transformer has the 20g wiring. The 230 is thoroughly kneecapped with the 22g wiring on the output of the mains transformer.

Considering the build of these amplifiers, bridging them is likely stressing them to the max. Also, nikko's primary design or common design among most of the amps in this series, is prone to failure at turn on when aged. replace all the small capacitors on the main amplifier board, if it has not been done. Otherwise nikkos will do what nikkos do, and go 'poof!' one day, when you turn it on. Almost every single alpha 220 and 230 that has died, has died this way. 450-440's all go the same way.

There will be zero hints that something may be wrong or is nearing. It will just..one day.. go bang -at turn on. Untouched older nikko amps are a hard core Russian roulette game, when you hit the power switch. Original output transistors and the small fet pack are pretty well extinct and tend to have to be pulled from other dead nikkos or amps from the same time period that were using them. So save some coin, big time,and re-cap all nikko amp main boards, if one owns a nikko amp. Always. yesterday.

That's more information than people wanted, but I'm chock full of a pot of coffee right now.. so..

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PostPosted: Thu Nov 09, 2017 12:01 pm 
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Thanks for all the great information guys! Both of these amps have been re-capped and wiring has been upgraded.
It’s curious that the Nikko Bridging Network owners manual shows the 220 in the connection diagram.


Last edited by Scoup on Thu Nov 09, 2017 5:11 pm, edited 1 time in total.

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PostPosted: Thu Nov 09, 2017 1:15 pm 
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Scoup wrote:
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Thanks for all the great information guy! Both of these amps have been re-capped and wiring has been upgraded.
It’s curious that the Nikko Bridging Network owners manual shows the 220 in the connection diagram.

They may use 220 in Japan.

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PostPosted: Fri Jan 19, 2018 8:13 am 
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Hi Scoup,
This is an old thread, but I thought I would leave a post.

Don't bridge the Nikko power amplifiers. They are fine for normal stereo use and the design was never intended to be used as you are. I did warranty service on those models and have a few 220's and 230's myself.

The comments about wiring being insufficient are true when you consider using them in bridged mode. The actual power out will be on the order of 2 ~ 3 times the stereo power. This is for other brands of amplifier, your output power will be lower than this with the Nikko amplifiers.

Bridging amplifiers will cut the damping factor in half right off the bat. In addition, you need to provide far more cooling than you have in your rack. Your rack placement isn't recommended for even one Alpha 220/230 amplifier. So you're probably causing heat damage that occurs slowly but will bite you in the end. Sometimes overheated amplifiers can't be repaired reliably ever again.

Want to make a killer system? Go active crossover and drive each speaker directly (bypassing the internal crossover). You need the help of a technician to set this up, but you will have more power, and much cleaner sound than what you are doing now.

-Chris


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PostPosted: Fri Jan 19, 2018 8:50 pm 
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anatech wrote:
Hi Scoup,
This is an old thread, but I thought I would leave a post.

Don't bridge the Nikko power amplifiers. They are fine for normal stereo use and the design was never intended to be used as you are. I did warranty service on those models and have a few 220's and 230's myself.

The comments about wiring being insufficient are true when you consider using them in bridged mode. The actual power out will be on the order of 2 ~ 3 times the stereo power. This is for other brands of amplifier, your output power will be lower than this with the Nikko amplifiers.

Bridging amplifiers will cut the damping factor in half right off the bat. In addition, you need to provide far more cooling than you have in your rack. Your rack placement isn't recommended for even one Alpha 220/230 amplifier. So you're probably causing heat damage that occurs slowly but will bite you in the end. Sometimes overheated amplifiers can't be repaired reliably ever again.

Want to make a killer system? Go active crossover and drive each speaker directly (bypassing the internal crossover). You need the help of a technician to set this up, but you will have more power, and much cleaner sound than what you are doing now.

-Chris


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PostPosted: Sat Jan 20, 2018 4:32 am 
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dcrooks wrote:
Bridging an amplifier effectively doubles the output voltage, which in term means four times the power under ideal circumstances.
So in theory, your amps would deliver four times 120 watts, or 480 watts in bridged.

However, rarely will an amp have sufficient power supply or a strong enough output stage to actually achieve this x4 power level. I don't know enough about your Nikko's build to say with any certainty, but you're probably in the 300-350 range...

wrong, not all amp double up . nikko amp in particular are far from doubleing up.all amp will push the sum of both channel driven at half the impedance, so bridge at 8 ohm will be the same as the sum of both channel at 4 ohm.
so if pushing 200 watt /channel at 4 ohm , bridge at 8 ohm will be 400 watt
when bridging the amp see a 4 ohm/channel load,when the load is 8 ohm .
so if amp cannot go lower then 4 ohm stereo. she cannot be bridge lower then 8 ohm.


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PostPosted: Sat Jan 20, 2018 10:29 am 
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Hi zon001,
You're right in the case of Nikko amplifiers not delivering the power one might guess they would.

As far as using the 4 ohm load figures for bridging, it's true that the amplifier will "see" a 4 ohm load from an 8 ohm load, but that is taken into account when the normal way of calculating bridged output power, ie 2X the voltage and 2X the current.

Nikko amplifiers will go into current limit quite early compared to something like a BGW or amplifier that is designed for this use. In the rack system pictured, you would want open sides and a pair of BGW 750C or something similar. These products suck air from the rear and exhaust it from the sides. Heat travels out and not up. Other amplifiers may exhaust through the front (or suck air), but these will have a lot more fan noise. Not something tolerable in a home system.

I feel it is but a matter of time before the amplifiers in the system pictured fail. Overheating doesn't normally kill an amplifier right away (unless you are being really silly). Unfortunately, the amplifiers, or any equipment, will just sit there and cook until they fail. Then the damage is greater and the product may have greatly reduced reliability with repeated failures for different things. That's because for every 10 °C rise in temperature, the failure rate doubles. This means you are rapidly aging the amplifier in this case.

It's really too bad that ads for sound equipment often portray the system in a closely packed rack. If you read the owners manual, they all clearly state that clearance is required at the top and the air underneath should be cool, room temperature air. That rules out the pictured system installations. But, the equipment will normally last the warranty period and fail sometime later. Then its a customer pay situation and not warranty. But hey!, it looked good, didn't it?

I'm just trying to keep people out of repair shops. There is enough work out there, we don't need to create more. Take my word for it, I'm a service technician specializing in audio service.

-Chris


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PostPosted: Wed Jan 24, 2018 10:36 pm 
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Thanks for all the great advice! I carefully tested it and while it seemed to work, it did not like my 5 ohm KOSS CM-1030’s which are fairly efficient compared to my AR9LSI’s. I ended up scrapping the idea. Went with a Carver TFM-45 for the AR’s and everything is handled nicely through either the Alpha 220 or my Alpha II.


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PostPosted: Thu Jan 25, 2018 5:07 am 
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Hi Scoup,
Good to hear. I'm sure it all sounds great!

The TFM-45 has some maintenance issues due to it's age. If it starts to thump or make loud sounds in your speakers without any music playing (or with), get it into service right away. There are some procedures that will fix that problem for all time. It could probably do for service now, but no one ever brings equipment in until they can't play it anymore.

-Chris


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