The Workbench

Re: Building a powerlink to line pre amp

Puncher — Tue, 22 May 2007 08:42:47 GMT

Had a mooch around the 'net at lunchtime perusing the current state of "serious" audio opamps. The LM4562 from National Semiconductor would appear to be King of the Hill at the moment and although it's still not readily available in the UK from the usual sources (RS, Farnell) yet, it is available here for approx. £5.

Re: Building a powerlink to line pre amp

Beobuddy — Wed, 16 May 2007 13:44:50 GMT

Hi guys,

About the volume difference.

My old man (still) has a BM2000. The one with the big tuning wheel. He bought that one in the early '70's.

It's still a nice piece of design and techique.

As I remember, he had it modified to cope with the nowadays used Line Level audio.

The modification was done by official B&O technician.(wrong spelling?)

In the early days, the signal strenght was according to Din Level. And that is a lower level signal compared to Line.

He made the modification to make it possible to use it with a modern cd-player. So it works fine now. So that could be the difference you're talking about.

But some years ago there were, and there still are, complete amplifiers modules.

I bought also 2 modules of 60 Watt each. I used it with my Beovox S60 or 55, can't remember.

These where connected to my Avant 50Hz from 1995. These modules where directly connected to my powerlinkconnectors on the dolby unit. There was no kind of volumeadjustment on the module. To avoid plop's or other anoying sounds the module had a mute relay when the module was swithed on.

That worked well for 3 years. But now have a pair of penta's so I don't use them anymore.

Re: Building a powerlink to line pre amp

Kevin — Wed, 16 May 2007 13:39:23 GMT

Great off I go then

Any chance of getting some of your work on here?

I would say the BM7000 conversion would be very well recieved.

Thanks ,

Kevin

Re: Building a powerlink to line pre amp

Puncher — Wed, 16 May 2007 13:34:06 GMT

Die_Bogener:

Try an Burr Brown 2134 or 2132. There is a huge difference to the LF353.
I have used these Burr Brown opamps in different modifications on my BM7000/CD7000 and BC2500. This chip in pincompatible and has distortions less than 0,00008%. More than 1000x times better than the LF353 :)

Agree - I would start with a trip to Burr Brown, Linear Technology or Analog Devices websites.

Re: Building a powerlink to line pre amp

Die_Bogener — Wed, 16 May 2007 13:24:11 GMT

Try an Burr Brown 2134 or 2132. There is a huge difference to the LF353.

I have used these Burr Brown opamps in different modifications on my BM7000/CD7000 and BC2500. This chip in pincompatible and has distortions less than 0,00008%. More than 1000x times better than the LF353 :)

Re: Building a powerlink to line pre amp

Kevin — Tue, 15 May 2007 07:48:44 GMT

yes I believe it is the pro gear that ends up nearer the 2v level while standard gear at about1.2v.

Most of the older amps have an input circuit where some adjustment can be made to balance the inputs between the various sources, tape deck, record deck etc.

Anyway do yo have a chip in mind for the pre amp? As you will have gathered this is meant to just up the signal cleanly but not to audiophile quality so I would see some of the more expensive chips as really not worth while.

I'll probably try the 353 anyway to see what it sounds like.

Re: Building a powerlink to line pre amp

Puncher — Tue, 15 May 2007 07:26:44 GMT

Kevin:

I've tried it with 3 amps. A BM4400, a BM3000 and a BM2000. The ones I'll probably be using are the BM200 and a BM2200 (not working, Yet!).
I'm probably missing something here but if you effectively double the strength of your signal surely that means your main amp circuit has a lot less to do.

Agreed - if the volume difference is there then its there. The reason for question was that most "pro" gear operates with higher i/o levels than consumer stuff and I was wondering if you were using a "pro" amplifer (that would explain the volume difference). Which leaves us back at the beginning

Re: Building a powerlink to line pre amp

Kevin — Tue, 15 May 2007 07:07:48 GMT

I've tried it with 3 amps. A BM4400, a BM3000 and a BM2000. The ones I'll probably be using are the BM200 and a BM2200 (not working, Yet!).

I'm probably missing something here but if you effectively double the strength of your signal surely that means your main amp circuit has a lot less to do.

Re: Building a powerlink to line pre amp

Puncher — Tue, 15 May 2007 05:34:10 GMT

Which amp are you intending to use to drive the passive speakers?? If the difference is as pronounced as you say it seems unlikely that is just down to a signal difference of a factor of 2 (6db).

Re: Building a powerlink to line pre amp

Kevin — Tue, 15 May 2007 05:13:22 GMT

Nicely collated we could maybe work that into an FAQ of sorts?

I'm a great believer in try it and see if it works.

Using the powerlink outputs from my Avant it requires the amp being used to be at almost full volume in order to get an equivalent sound to the Avant . that includes upping the output on the speaker adjust in the Avant and trying the two speaker types.

The 0-600mv comes from Solderon29 as was on the old site.

Re: Building a powerlink to line pre amp

Puncher — Tue, 15 May 2007 03:57:30 GMT

I've had a bit of a poke around on Beocentral and Beotech and it would appear

Powerlink is single ended and has a signal level of 1Vrms max., while

Audio Aux is again single ended and also has an output spec of 1Vrms max, 1 KOhm and an input spec of 0.25 - 2 Vrms max., 47 KOhm.

Speakerlink connects at loudspeaker level and so would need attenuating to preamp or line level ib order to use active speakers (not really a good plan as it will then have been amplified twice).

Masterlink is the only balanced connection system which will account for the ability to use very long cable runs with out noise or interference issues.

I apologise if this is old news to you but I myself didn't understand the differences and so I list them here for others like me.

From the above however I ask the question - have you tried direct connection without the need for a preamp - it seems to me it should work fine.

Re: Building a powerlink to line pre amp

Kevin — Tue, 15 May 2007 00:02:14 GMT

Searching questions

powerlink is 0-600mv so I'm looking for a gain of x2 x2 1/2 there is a trimmer in the circuit to allow some variance in the gain.

The idea is to take the powerlink signal and feed it into a standard amp line in to power passive speakers.

Could also be done by using the phono in and filtering out the RIAA but the gain is high and would mean having to reduce the input only to have to bring it back up again. Higher chance of introducing noise into the circuit.

Not sure.

cheers,

Kevin

Re: Building a powerlink to line pre amp

Puncher — Mon, 14 May 2007 13:45:02 GMT

Kevin:

Some interesting alternatives. Thanks for the links
BTW I went for the 353 because it seems to be the one B&O use in their signal line and reviews I've read on the net favour it's clean sound especially when only 1 channel is used (apparently less noise that way).
The supply voltage I'm working to is +/-12v and surface mount is really not an option.
cheers,
kevin

No probs

What are the relative signal levels of powerlink versus standard line level?? (i.e what gain are you aiming for)?? Also is Powerlink a balanced or single ended connection?

Re: Building a powerlink to line pre amp

Kevin — Mon, 14 May 2007 09:57:35 GMT

Some interesting alternatives. Thanks for the links

BTW I went for the 353 because it seems to be the one B&O use in their signal line and reviews I've read on the net favour it's clean sound especially when only 1 channel is used (apparently less noise that way).

The supply voltage I'm working to is +/-12v and surface mount is really not an option.

cheers,

kevin

Re: Building a powerlink to line pre amp

Puncher — Mon, 14 May 2007 02:47:43 GMT

I think I'd use something a little more up-market than the 353, obviously any noise or distortion you add is then amplified by your Beolabs.

I would start here

http://www.go-dsp.com/selection-tool/audio/tool.htm

http://focus.ti.com/analog/docs/amplifiersandlinearhome.tsp?familyId=57&contentType=4#