Hi:

I'm wondering if anyone has come up with any mods/upgrades for BC9500 and or BM8000

Are there any recommended tweaks for the BM8000 other than recapping the unit? Perhaps upgrading the resistors in the audio path to 1% metal film? I've always found it interesting and curious why B&O always used lower spec'ed electronic components. They over engineer the power supply of the BM8000 (gorgeous toroid and dual power supply) but yet would use low grade circuit boards and 10 - 20% tolerance parts like resistors.

As for the BC9500, I've been using mine with a pair of Rogers LS 3/5As. I've been very impressed with the sound quality. Its been criticized for
its rather low power "chip" amplifier however I've found it to perform admirably even when driving the complex 15ohm 3/5a load.

I do think thought that there is room for further improvement such as lower noise opamps. Has anyone taken an attempt at upgrading these units? Can we get more out of these units?

Thanks,

Derek
 

It's not really a mod, but you may wish to bypass the op-amps (which don't get a good write-up) by using a set of active speakers. You'll be able to get plenty of advice here on how to do that!

It might help if you are  clear in your own mind about what the problem is you are tryng to solve via upgrading. Is there anything in particulat about your current setup that you feel needs improvement?

Simon

auric:

Hi:

I'm wondering if anyone has come up with any mods/upgrades for BC9500 and or BM8000

Are there any recommended tweaks for the BM8000 other than recapping the unit? Perhaps upgrading the resistors in the audio path to 1% metal film? I've always found it interesting and curious why B&O always used lower spec'ed electronic components. They over engineer the power supply of the BM8000 (gorgeous toroid and dual power supply) but yet would use low grade circuit boards and 10 - 20% tolerance parts like resistors.

As for the BC9500, I've been using mine with a pair of Rogers LS 3/5As. I've been very impressed with the sound quality. Its been criticized for
its rather low power "chip" amplifier however I've found it to perform admirably even when driving the complex 15ohm 3/5a load.

I do think thought that there is room for further improvement such as lower noise opamps. Has anyone taken an attempt at upgrading these units? Can we get more out of these units?

Thanks,

 

Derek
 

Popular myth that the LS3/5A is difficult to drive. It is actually a very easy load. No really horrid low impedance drop. The problem is driving them to high volumes as they are not very efficient and besides, they just don't like going loud! I use mine with a BM4400 most of the time - fantastic speaker! I use AB1s as well to get at least some of the lower frequencies!!

The Linn Isobariks mentioned in another thread are a truly horrid load! Interesting that the BM2400 is decribed as driving them well but the BM4500 having problems. I imagine that the 9500 would probably not like them much either! Amplifiers have no problem with higher impedances though obviously the power output dropd in a linear fashion. It is low impedance which sorts out the men from the boys - look at the impedance against power output for the Beolab 5000 amplifier in the service manual to see what a good amplifier can manage! I'd love to see this sort of information for more of the range.

Upgrading a B&O device is not sooooo difficult. There is a system possible:

Almost every capacitor in the sound path is a small problem. The best solution is, not to use them at all, just eliminate them... if possible.

Otherwise replace them by better quality parts. The best price / quality ratio is with WIMA MKS-2-5 plastic capacitors, they can be used in almost every application.

Opamps like the NE4558, LM833 can be replaced by the audiophile OPA 2134 or OPA 2132, even smd is possible... OPA 2134UA.

Resistors are not the typical problem... if they are non magnetic, no problem. Especially the 1% resistors are worse than 5% or even 10% types, they have often real magnetic and induction problems... they consist of too much metal, lots of nickel. Sound and nickel doesnt work together...

 I dont have a BM2400... otherwise it would have been already modified ;)

The next Workshop is planned with the BM5500 and the BS2500 around Christmas. 

Martin  

My BM8000 is working fine. I do find it a bit noisy. When you turn it up you can hear a very faint hum and static like noise in the backgroud. Also when you adjust the volume control you can hear the "ticking."

I've AB'd the BM 8000 with other amplifiers including ones that I've built from magazine based designs. All in all it is not a bad sounding amp but I do find it lacks definition at the high end. Like all things "audio" its hard to explain but I get better high freq response on new amps. (It's also 25 yrs old so I'm sure that its not sounding like the day when it came out of the factory.

 Derek

Hi Martin:

National Semiconductor has a new line of audio grade opamps. LME49860NA

Do these modifications make a big difference? I'm tempted to give them a try... its too bad that the ICs are not socketed. I'm thinking where they would make the biggest difference is in the phono section.

Interesting how you say that metal film resistors actually sound worse. Why is it that the majority of high end equipment mfgs use 1 or 2% metal film resistors? I realize that when you get to swapping out these parts it may be a bit of black magic :)

Derek 

Peter:

In a small room the LS3/5As sound gorgeous. I can drive mine pretty loud on the 9500 but the amp will distort near 90-95% volume. It's one of the best sounding speakers I've heard. My pair unfortunately are loaners so they at some point will have to go back to the owner.

Derek 

The tolerance itself is no problem with resistors, 1% or 10%, it wont make a big difference. Maybe one channel can be louder or something like that, but the sound itself is the same.

5% or 10% resistors consist of coal, the only disadvantage is some noise that can be heard at very high volumes.

But the main problem is: some of the resistors are magnetic... and this is what you can hear!

Some or most of the coal 5%/10% types have copper wires and connectors, they are non magnetic. Only some noise, but really good sound!

Metal film 1% types have (sometimes) a real metal wire inside, they are the worst what you can do for the sound, the sound is distorted because of inductions... it's like a coil. Very, very bad. And lots of Nickel inside, also magnetic

Metal oxide is better, just the caps can be Nickel, sometimes copper. If it is copper, ok, use it, they have low noise and no distortions.

The simple test is with a magnet: magnetic => dont use it !!!

Non magnetic :)

Quite the same is with capacitors: magnetic types have a worse sound...

Martin