Bridging adcom 555

DON73

I have a 555ll that can be bridged with a switch on the back panel. Can the 555 be bridged and would it be a good match for the 555ll? I need/want more power for my B&W 801s and the 555s are frequently more available than the lls. As i understand the Adcoms have no speaker protection against DC current. Is this true and would an in line fuse be a good idea? I understand that the best protection is volume control but could something fail on the amps to cause a problem for the speakers. Thank you.

DON73

I'm encouraged..........27 people don't know what I don't know.

george daniel

All I can tell you is that when I bridged my 555's it was the nastiest sounding debacle that I have ever performed.I sincerely hope you have better results than I did. Good Luck.

dorokusai

No in-line protection is neccesary and Adcom isn't the only one without DC protection.

FTGV

The orignal 555 and the MKII differ substantially.The original Nelson Pass designed circuit was developed with the idea that keeping the gain path simple in the interest of improved sound quality.Therefore it has fewer gain stages than typical designs and eschewed the use of complex protection circuitry.
With the MKII version Adcom made a number of circuit changes that added to the complexity but may have impacted sound quality in a negative way.
As for bridging,ideally the amplifiers should be identical if one wishes both channels to have the same sonic character. Since the designs are somewhat different IMO makes them less then ideal candidates for use as a mixed pair in bridged mode.

kawizx9r

Instead of bridging each 555/II to a speaker, why not use both amps to bi-amp your speakers?

Not sure if they can be bi-amped, but if they can I'd suggest this route.

DON73

The 555ll can be bridged.....I know it's different from the 555. I was just curious if it could be done. I think bi amping will still give me 200 watts to the speakers and the B&W801s need an enormous amount of current when playing classical music. On some classical discs the difference between the softest passages and the loudest can be as much as 21db. When I first auditioned them they were connected to Mark Levinson amps and IIRC the amps put out 600watts. The bass slam was unbelievable.....almost scary. I'm ok with the 250 watts I have now but I'd like to hear them with more power.
According to the latest life expectancy I should live to age 78 and I'm just trying to squeeze as many experiences in those 5 years as I can.
I appreciate all your suggestions. I think I'll just look for another 555ll even though it's not as well thought of as the 555. Maybe I should just spring for a ML or one in the same category. Thanks guys.....you're always helpful.

newrival

I had the 555 originals and mono'ed them quite successfully. They are only to be used with spekers rated at 8ohms nominal or higher. People throw the them into mono and then to a 4ohm speaker and are shocked when it sounds terrible. The 555 is rated to 4ohm in stereo with it's voltage, when you switch to mono, wattage increases from 200 to 625 (@8ohms) but current stays the same. Now, imagine what kind of distortion that is going to cause.

This goes for both the 555 and the 555 mkII

newrival

I think you're right. Spring for the ML. Life is too short to be messing around when you know how to get the sound you fell in love with.

FTGV

newrival wrote: »

People throw the them into mono and then to a 4ohm speaker and are shocked when it sounds terrible. The 555 is rated to 4ohm in stereo with it's voltage, when you switch to mono, wattage increases from 200 to 625 (@8ohms) but current stays the same. Now, imagine what kind of distortion that is going to cause.

Good point ,in bridged mode the the actual load as seen by the amp is half the nominal impedance so an 8ohm load will appear to the bridged amp as 4 ohms.The real issue with this lower impedance is the amount of excess heat that will be generated in the amplifiers output stage because of the increased current demand.If the heatsinking is not sufficient to dissipate the extra heat,long term reliability could/will be compromised.

kawizx9r

So, no to bi-amping?

Don't know why you'd think that if you bi-amp your speakers that you'd only see 200 watts to each speaker pair.

Here's what it says about each 555 -200 watts per channel (8 ohms) or 325 watts (4 ohms).

You'll see that much power per set of binding posts on each speaker meaning - each tower's tweeter/midrange combo gets 200 and woofer gets 200 if it's at 8ohms. Even more at 4ohms, plus it'll be stable since they won't be bridged.

FTGV

kawizx9r wrote: »

So, no to bi-amping?

Depending on vintage his 801's may? pre date the biwiring craze thus only have a single set of posts.

kawizx9r

FTGV wrote: »

Depending on vintage his 801's may? pre date the biwiring craze thus only have a single set of posts.

Yeah I wasn't sure or not but the OP never made it clear. He just said that he'd only see 200 watts per even if he bi-amped........

DON73

kawizx9r wrote: »

Yeah I wasn't sure or not but the OP never made it clear. He just said that he'd only see 200 watts per even if he bi-amped........

My bad maybe on bi amping. Can a 200 watt per channel put out 400 watts in a bi amped system..same power as bridging? What load would the amps see in this system. I wouldn't even know how to hook up a bi amped system...My 801 Matrix are series 3Ns with the bi wiring capability and they drop to 3+ ohms at some frequencies. Thanks for your help......"I don't understand all I know about this love we call audio"

DON73

Googled Mark Levinson and got a link to Amazon with a listing for a book by Kim Catrall and Mark Levinson about the female ****.:eek:

heiney9

FTGV wrote: »

The orignal 555 and the MKII differ substantially.The original Nelson Pass designed circuit was developed with the idea that keeping the gain path simple in the interest of improved sound quality.Therefore it has fewer gain stages than typical designs and eschewed the use of complex protection circuitry.
With the MKII version Adcom made a number of circuit changes that added to the complexity but may have impacted sound quality in a negative way.
As for bridging,ideally the amplifiers should be identical if one wishes both channels to have the same sonic character. Since the designs are somewhat different IMO makes them less then ideal candidates for use as a mixed pair in bridged mode.

Well said, I agree 100%

H9

heiney9

DON73 wrote: »

The 555ll can be bridged.....I know it's different from the 555. I was just curious if it could be done. I think bi amping will still give me 200 watts to the speakers and the B&W801s need an enormous amount of current when playing classical music. On some classical discs the difference between the softest passages and the loudest can be as much as 21db. When I first auditioned them they were connected to Mark Levinson amps and IIRC the amps put out 600watts. The bass slam was unbelievable.....almost scary. I'm ok with the 250 watts I have now but I'd like to hear them with more power.
According to the latest life expectancy I should live to age 78 and I'm just trying to squeeze as many experiences in those 5 years as I can.
I appreciate all your suggestions. I think I'll just look for another 555ll even though it's not as well thought of as the 555. Maybe I should just spring for a ML or one in the same category. Thanks guys.....you're always helpful.

Well, Levinson and Adcom aren't even close to being in the same category so it's a moot point asking any questions about Adcom and wanting to replicate even a small percentage of what the ML brings to the table. Look at Pass Labs........it's in the same category as the ML.

It's like asking if you can put a turbo charger on Mistubishi Eclipse so it can compete with the attributes of a Porsche 911.

H9

FTGV

DON73 wrote: »

...My 801 Matrix are series 3Ns with the bi wiring capability and they drop to 3+ ohms at some frequencies.

That being the case then you could use the Adcom's in what is called passive bi amping.(assuming the two versions of the 555 have identical gains).The amp hooked to the woofer would only see it's load while the one connected to the mid/tweet will see their load.
Theoretically you will have double the power potential,but the spectral distribution of music is such that far more power will be required of the amp driving the low frequency driver.In comparison the amp driving the mid/tweet will have a relatively easy time of it.

To sum up if the speakers are particularily inefficient and present a difficult load(which your 801's appear to be) then the added power headroom afforded by bi amping may prove advantageous but I would not expect huge improvements.

FTGV

DON73 wrote: »

Googled Mark Levinson and got a link to Amazon with a listing for a book by Kim Catrall and Mark Levinson about the female ****.:eek:

Yeah but in the end she ended up ditching him.

DON73

FTGV wrote: »

Yeah but in the end she ended up ditching him.

Mark didn't read the book!

FTGV

DON73 wrote: »

Mark didn't read the book!

Or can't put into practice what he preaches.:biggrin:

DON73

heiney9 wrote: »

Well, Levinson and Adcom aren't even close to being in the same category so it's a moot point asking any questions about Adcom and wanting to replicate even a small percentage of what the ML brings to the table. Look at Pass Labs........it's in the same category as the ML.

It's like asking if you can put a turbo charger on Mistubishi Eclipse so it can compete with the attributes of a Porsche 911.

H9

Thanks H9. Always helpful with sound advice I'm not trying to compare Adcom and ML. I said I first heard the 801s with MLs and said I would like to hear the 801s with more power. I didn't mean to imply that more Adcom power would in any way equal ML. I can easily buy MLs of 600 watts but I (and my grandkids) don't want to spend thousands if I can't hear the difference. It's been 14yrs since I bought the 801s and my hearing is probably not as good now. If I could listen to MLs in my home and be impressed to the point that I had to have them they would probably stay.
In the meantime spending 3-4 hundred $$ on another Adcom might just do the job.
I do appreciate all comments and suggestions.

leftwinger57

To DON73, I just went through a debate w/ people who are better off to explain why it's not a good idea to bridge your 555. The concecsus is it degrades the sound to which one would be quite upset at hearing mud from such a good amp. My advice from their advice is not to do it and leave well enough alone.I or we all thought bridgeing or doubling up would make this the best rig ever, it does not. As for a single gfa555 I could not ask for an amp to do any better,it never gets hot and plays all day and for $300 I'm a happy guy..LW

heiney9

leftwinger57 wrote: »

To DON73, I just went through a debate w/ people who are better off to explain why it's not a good idea to bridge your 555. The concecsus is it degrades the sound to which one would be quite upset at hearing mud from such a good amp. My advice from their advice is not to do it and leave well enough alone.I or we all thought bridgeing or doubling up would make this the best rig ever, it does not. As for a single gfa555 I could not ask for an amp to do any better,it never gets hot and plays all day and for $300 I'm a happy guy..LW

LW57, this thread would have answered your questions before you started another. That's what I'm talking about when I comment in your threads about using the search feature first. Just a heads up because at some point people get tired to repeating the same answers over and over and over.

H9

Joe08867

And over and over. Sorry got caught up in the post above.

Joe08867

Don I think you are missing the idea of Biamping. I placed a picture in this thread about the subject. This would be if you have two GFA555's. Your speakers would be seeing a lot more than 200 watts each. And would sound better.