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add balanced inputs to power amp bryston or adcom Monitor Controllers
Old 5th September 2008
  #1
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add balanced inputs to power amp bryston or adcom

hi all

i wanted to know if its possible / feasible to add balanced xlr or trs inputs to an older bryston 3b or 4b, and to the adcom 555 amps. everything im running is xlr or trs balanced and im in the market for a new power amp. i been eyeballing the brystons and the adcom amps from recommendations i read here on GS. most of the older brystons and adcoms i see are all rca.
Old 6th September 2008
  #3
That's not a problem with the Adcom 555. Just ground the low side (ring or pin 3) if the driver circuit is transformer coupled or electronically cross coupled outputs. If they are inverter balanced outputs, float pin 3 or the ring. The Adcom's use a 2 wire AC cable so grounding loops are avoided. I've installed Adcoms in many rooms with many consoles and monitor output circuit designs. There is always an easy way to integrate the two.

Jim Williams
Audio Upgrades
Old 11th September 2008
  #4
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xlr and no rca

hi

thanks for the input

the jensen box looks nice.

but what i was thinking was drilling out some holes on the back of the unit and put xlr inputs on there. i guess i would have to bypass the rca inputs and use the same wires to the xlr connectors. but what would i have to add to make it +4 balanced? i assume there would only be 2 wires attached to the rca connector on the inside of the amp. i contacted adcom and bryston and they both said they use electronically balanced inputs on their amps.

the outputs feeding the amp would either be: pro tools interface into the coleman tb4, then into the power amp. OR ill be using the control room output on a console (which i dont own yet...thats later on down the road) that will feed into the amp.
Old 11th September 2008
  #5
I have set up several rooms with Coleman boxes into 555's. Easily done, works great, no mods to the amp designs.

Sounds like a solution looking for a problem to me. Anything in between is another filter between you and your music.

Jim Williams
Audio Upgrades
Old 12th September 2008
  #6


You could get the transformers only and mount them in the box (if there's room).



-tINY

Old 12th September 2008
  #7
That would work, one would need to place them far away from the large power transformer. Consider that this would change the sonics of the monitor path and perhaps take it sonically away from the tape output path. Last thing you want is the monitor path to have different sonics to the mix path. That will lead to mixing to the amp rather than matching the monitor path to the mix path so sonic suprises are eliminated. It's far easier to mount an RCA plug on the end of your cable and call it a day.

Jim Williams
Audio Upgrades
Old 12th September 2008
  #8


Sure. But if you have to have balanced inputs, a pair of Jensen isolation transformers is a low-risk way to get them without coloring the sound....

Other transformers - not so much.




-tINY

Old 14th September 2008
  #9
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how long is too long?

so you think 50ft is too long to have the unbalanced connection? that is about how long it is from the interfaces, to the snakes, patchbay, coleman and then to the amp.

but here is what i dont get. .. i dont understand the point of having all the way at the back end of my setup, the connection to the amp be unbalanced? i mean high quality mics, cable, pres, all connections to the patchbays be balanced, all outboard be balanced, coleman monitor system balanced...but then run it all out to the amp on unbalanced cable lines.

how much does the jensen unit go for?

i appreciate the input/info. i even contacted adcom about modifying the amp to have xlr balanced inputs and they said the same thing jim was saying "why bother? just use rca connectors." i guess i might just do that. cause the price on those adcom amps used is cheap. and rca connectors are cheap as well.
Old 14th September 2008
  #10
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Quote:
Originally Posted by Dirty Gear Pimp View Post
so you think 50ft is too long to have the unbalanced connection? that is about how long it is from the interfaces, to the snakes, patchbay, coleman and then to the amp.
You can try with a balandced cable with a semi-balanced connection first, if it's all ok and you don't have hums and ground noises you can use your Adcom in unbalanced mode
Old 14th September 2008
  #11
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Jim knows, listen to him! Any transformer has a color, and balanced is not automatically better unless you have a noise problem. Guess what goes on inside many amps? The signal is unbalanced anyway at some stage. You can mount an XLR on your amp and wire it as Jim suggested, they are good and solid connectors compared to many others. RCAs and plugs are a PITA.

Martin
Old 18th September 2008
  #12
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looking for a power amp

Since you don't already own a 555 or an older Bryston, restrict your search to amps with balanced input.
Adcom GFA-5800 has both rca and XLR inputs (switched). Adcom is a lot of amp for your money in the top models.
Old 16th April 2011
  #13
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initself's Avatar
Quote:
Originally Posted by Jim Williams View Post
That would work, one would need to place them far away from the large power transformer. Consider that this would change the sonics of the monitor path and perhaps take it sonically away from the tape output path. Last thing you want is the monitor path to have different sonics to the mix path. That will lead to mixing to the amp rather than matching the monitor path to the mix path so sonic suprises are eliminated. It's far easier to mount an RCA plug on the end of your cable and call it a day.

Jim Williams
Audio Upgrades
I just got an Adcom 545 II and an SM Audio M-Patch 2, concurrently. The M-Patch 2 has balanced XLR outputs, the Adcom unbalanced RCA inputs.

I've got a couple of XLR Female to TRS Male cables. Can I just get a simple adapter to make the TRS an RCA? I'm not worried about keeping the signal balanced, I just want to plug it in properly.

Thanks,

mb

Old 16th April 2011
  #14
Old 16th April 2011
  #15
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many important facts

in random order:

The vast majority of power amplifiers ever made have unbalanced connections.

The vast majority of ALL audio gear is unbalanced internally.

This is normal, and is not an indication of inferiority.

Even amplifiers with XLR connectors are usually NOT balanced input.
The XLR is often just wired in parallel to the 1/4 connector. Check the specs of the amp to be sure.

There is nothing inherently wrong with unbalanced, sonically it is "superior" to balanced, it just has the inconvenience of not working as well over longer distances. Some of the finest mastering facilities in the world have a 100% unbalanced setup.

In order for ANY audio device to have balanced ins or outs, it MUST have one of these things added to the design: a transformer OR additional circuitry/components. For people who are purist about audio reproduction, BOTH of these may be considered a "compromise"

SO usually we all overlook this and take advantage of our balanced connections, where available. And things sound good, even when connected over long distances, and we usually don't regret the decision to include all that extra circuity and transformers in all our gear.

BUT, the amplifier is somewhat unique, in that since it IS at the end of the chain, it does NOT feed another electronic device. It feeds a MECHANICAL device known as your-speaker-air-ear. Since all it does is produce enormous gain, with as low noise as it can manage, it does not need a balanced input. A well-designed power amp will try to take WHATEVER you feed its front end, and try to give it to you LOUD and with low noise, subject only to your mood/volume knob position. There really is no "unity gain" out at the end of the monitoring chain. In your living room, the proper gain structure is "as loud as I want" with "as little hiss as possible".

Also, many of the finest amps for the studio are unbalanced because they are also the kind of amps that were sold to audiophiles/hi-fi, and those customers may not appreciate balanced connections.

SO your choices are:
1. move stuff closer and hook up unbalanced (be prepared to experiment a little with best grounding/shielding/terminating)

2. BUY transformers (many awesome ones already mentioned)

3. BUY some sort of quality circuit box.

4. BUY amplifier with true balanced input (not just XLR)

5. wait and buy amplifier with lightpipe input

BTW the fine Bryston company DOES offer a factory mod to put balanced connections on Bryston amps. Not sure if its just 2 pin- XLRs (not truly balanced) OR if its some kind of transformer.
Old 16th April 2011
  #16
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JohnRoberts's Avatar
 

Quote:
Originally Posted by TRJanuary View Post
in random order:

The vast majority of power amplifiers ever made have unbalanced connections.

The vast majority of ALL audio gear is unbalanced internally.

This is normal, and is not an indication of inferiority.

Even amplifiers with XLR connectors are usually NOT balanced input.
The XLR is often just wired in parallel to the 1/4 connector. Check the specs of the amp to be sure.

There is nothing inherently wrong with unbalanced, sonically it is "superior" to balanced, it just has the inconvenience of not working as well over longer distances. Some of the finest mastering facilities in the world have a 100% unbalanced setup.

In order for ANY audio device to have balanced ins or outs, it MUST have one of these things added to the design: a transformer OR additional circuitry/components. For people who are purist about audio reproduction, BOTH of these may be considered a "compromise"

SO usually we all overlook this and take advantage of our balanced connections, where available. And things sound good, even when connected over long distances, and we usually don't regret the decision to include all that extra circuity and transformers in all our gear.

BUT, the amplifier is somewhat unique, in that since it IS at the end of the chain, it does NOT feed another electronic device. It feeds a MECHANICAL device known as your-speaker-air-ear. Since all it does is produce enormous gain, with as low noise as it can manage, it does not need a balanced input. A well-designed power amp will try to take WHATEVER you feed its front end, and try to give it to you LOUD and with low noise, subject only to your mood/volume knob position. There really is no "unity gain" out at the end of the monitoring chain. In your living room, the proper gain structure is "as loud as I want" with "as little hiss as possible".

Also, many of the finest amps for the studio are unbalanced because they are also the kind of amps that were sold to audiophiles/hi-fi, and those customers may not appreciate balanced connections.

SO your choices are:
1. move stuff closer and hook up unbalanced (be prepared to experiment a little with best grounding/shielding/terminating)

2. BUY transformers (many awesome ones already mentioned)

3. BUY some sort of quality circuit box.

4. BUY amplifier with true balanced input (not just XLR)

5. wait and buy amplifier with lightpipe input

BTW the fine Bryston company DOES offer a factory mod to put balanced connections on Bryston amps. Not sure if its just 2 pin- XLRs (not truly balanced) OR if its some kind of transformer.
Nice list but you missed another important data point... the vast majority of Hifi system wiring is unbalanced, so there is little benefit from using balanced input circuitry in those systems.

That said power amps typically boost the audio signal voltage before sending it to a loudspeaker so there is merit in keeping the interface clean since any input noise will get boosted too. These days most professional sound reinforcement amplifiers use balanced input.

If Bryston offers a factory mod, that seems like a good plan.

JR
Old 20th April 2011
  #17
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chet.d's Avatar
 

Quote:
Originally Posted by Jim Williams View Post
That's not a problem with the Adcom 555. Just ground the low side (ring or pin 3) if the driver circuit is transformer coupled or electronically cross coupled outputs. If they are inverter balanced outputs, float pin 3 or the ring. The Adcom's use a 2 wire AC cable so grounding loops are avoided. I've installed Adcoms in many rooms with many consoles and monitor output circuit designs. There is always an easy way to integrate the two.

Jim Williams
Audio Upgrades
Jim would you say the same is true for the Adcom 535 ?

I'm trying create a scenario wherein my Adcom 535 can accept balanced input from Shadow Hills Equinox
( and Lavry DA10 )
As well, hoping to create a headphone output via some resisters.
Thanks for your take.
Old 20th April 2011
  #18
Quote:
Originally Posted by TRJanuary View Post
Even amplifiers with XLR connectors are usually NOT balanced input.
The XLR is often just wired in parallel to the 1/4 connector. Check the specs of the amp to be sure.


For professional amps, I have not found this to be true. The XLR are wired in parallel to the 1/4" phono jacks, but those are TRS, not TS.




-tINY

Old 21st April 2011
  #19
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Ike Zimbel's Avatar
 

Quote:
Originally Posted by tINY View Post


For professional amps, I have not found this to be true. The XLR are wired in parallel to the 1/4" phono jacks, but those are TRS, not TS.




-tINY

+1!
Old 21st April 2011
  #20
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I can't speak for all sound reinforcement amps, but older than 15-20 years or so ago, the The Peavey amp XLRs were wired unbalanced, but they offered optional transformer PL cans, so you have transformer balanced as a plug in accessory.

Newer than around 15 years ago the XLRs are wired to active balanced inputs.

JR
Old 21st April 2011
  #21

I guess Peavy was improved after the 80's...




-tINY

Old 21st April 2011
  #22
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Quote:
Originally Posted by tINY View Post

I guess Peavy was improved after the 80's...




-tINY

I was aware of many improvements in my 15 years working there, and I won't bore you with the full arguments against adding electronic balanced inputs prior to that, but Peavey was successfully managing power amp interfaces without active balanced inputs for decades by the time I showed up in the mid '80s. The transformer balanced option was more than many amp sellers perceived as more professional offered back then.

By the time the conversion to active balanced took place, low cost opamps were good (quiet and fast) enough that they wouldn't degrade the overall amp performance (not to mention Peavey was also dealing with a legacy pin 3 hot issue, around that time that was made incorrect by the later adoption of a pin 2 hot standard).

While I am surely biased by my experience working there, Peavey was (and is) IMO routinely underestimated for the value delivered, because they don't advertise as aggressively as other manufacturers.

JR
Old 21st April 2011
  #23
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All of the older Yamaha amps, like the NS series (including the venerable P2200) are examples of amps that have XLR's but are NOT balanced input.
Old 21st April 2011
  #24
Quote:
Originally Posted by JohnRoberts View Post
I was aware of many improvements in my 15 years working there, and I won't bore you with the full arguments against adding electronic balanced inputs prior to that, but Peavey was successfully managing power amp interfaces without active balanced inputs for decades by the time I showed up in the mid '80s. The transformer balanced option was more than many amp sellers perceived as more professional offered back then.

By the time the conversion to active balanced took place, low cost opamps were good (quiet and fast) enough that they wouldn't degrade the overall amp performance (not to mention Peavey was also dealing with a legacy pin 3 hot issue, around that time that was made incorrect by the later adoption of a pin 2 hot standard).

While I am surely biased by my experience working there, Peavey was (and is) IMO routinely underestimated for the value delivered, because they don't advertise as aggressively as other manufacturers.

JR


No slight to Peavy on the product delivered to the consumer, but they were always the budget choice. I haven't played with any of their products since the mid 80's when compromises had a lot more consequenses than today.

Of course, back then, phase controlled dimming was pretty exotic, so at a typical small gig, the balanced inputs weren't needed. It makes sense to save the money on the base product in that case.


-tINY

Old 22nd April 2011
  #25
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Quote:
Originally Posted by TRJanuary View Post
There is nothing inherently wrong with unbalanced, sonically it is "superior" to balanced,
Sound depends on things like frequency response, noise and distortion. Unlike some humans, electrons and sound waves are pragmatic when it comes to topology. :-)

Some of the best performing amps are balanced.


Quote:
In order for ANY audio device to have balanced ins or outs, it MUST have one of these things added to the design: a transformer OR additional circuitry/components. For people who are purist about audio reproduction, BOTH of these may be considered a "compromise"
Wrong thinking if the design is made balanced from scratch.

The purist with some insight realize that balanced topologies potentially means 1) cancellation of asymmetric nonlinearities 2) avoidance of dynamically loading the power supply (=no caps in signal path) 3) higher output level for a given type of device and power supply.

AFAIK the lowest distortion (and basic noise floor) microphone preamp is balanced (Earthworks ZDT). The lowest distortion power amp is balanced (Bruno Putzeys ExtremA).

Yes it's fully possible to design very high performance unbalanced audio electronics but there are clear advantages in the balanced route.

The idea of simple constructions with few devices and stages is born out of ignorance, otherwise why not use only one transistor between your CD player and speaker?

Quote:
Also, many of the finest amps for the studio are unbalanced because they are also the kind of amps that were sold to audiophiles/hi-fi, and those customers may not appreciate balanced connections.
Such as?


Quote:
5. wait and buy amplifier with lightpipe input
Why wait, there are amps with digital inputs today.. but OP is talking about analog interfacing now.


/Peter
Old 8th June 2011
  #26
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Appreciate any suggestion re; a mod for the Adcom 535 so that it can accept balanced input (in my case from the all balanced Shadow Hills Equinox).
Considering the Jensen though it's a bit pricey.

As it is now it sounds very good though there is a low level hum I would be happy to eliminate.
Thanks.
Old 22nd July 2011
  #27
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chet.d's Avatar
 

Quote:
Originally Posted by chet.d View Post
Appreciate any suggestion re; a mod for the Adcom 535 so that it can accept balanced input (in my case from the all balanced Shadow Hills Equinox).
Considering the Jensen though it's a bit pricey.

As it is now it sounds very good though there is a low level hum I would be happy to eliminate.
Thanks.
Just giving this question a bump.

Maybe Jim or ? can chime in on a plausible solution for using the Adcom with a balanced input.
I am however a bit reluctant to add a transformer to the monitoring path.

Much thanks for any insights.
Old 22nd July 2011
  #28
Let me guess, if you pull the plug out of the power amp, the hum disappears?

The amp is not the problem. Check with Shadow Hills on the design of their balanced output circuits. There is a way. Either you float or ground pin 3. Either you ground or float pin 1. Rane has some nice interfacing notes on their website for y'all to read through. Time to get some educatin'.
Old 22nd July 2011
  #29
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chet.d's Avatar
 

Quote:
Originally Posted by Jim Williams View Post
Let me guess, if you pull the plug out of the power amp, the hum disappears?

The amp is not the problem. Check with Shadow Hills on the design of their balanced output circuits. There is a way. Either you float or ground pin 3. Either you ground or float pin 1. Rane has some nice interfacing notes on their website for y'all to read through. Time to get some educatin'.
Thanks Jim.

Peter's a SH is a good guy though not always easy to track down.

I'll have to try to track down what's floating and what's grounding where.
Old 23rd July 2011
  #30
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Hi
An unbalanced signal can be 'quieter' than balanced although this depends on the details of the design and I am referring to the noise of the actual circuit (hiss), not the 'junk' that is dragged in by external cabling.
Leave the amp as it is then when you get bored with it it will have a resale value.
Matt S
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