Balanced input on amplifier with Lundahl LL1540

audiorado

Member
Paid Member
2009-02-25 12:16 pm
Maribor
I need a little help about this.Just build amplifier AB on Lm3886 module with balanced input 48Kohm.My source is tube cd player with single ended/unbalanced output and 275 ohm output impedance.I become from my friend Lundahl LL1540 pair of input transformers.So now I look at the schematic for Lundahl and I see that first picture scheme is what I must use.But I will know what value must have parts in this schematic for my diferential 48Kohm input in amplifier,or is the Lundahl ll1540 wrong transformer for this job??I will build the transformer in amplifier enclosure so it will be as near as posibile to amplifier pcb.;)
 
Actually your best bet is to put the transformer at the CD player end of the cable, to take advantage of the noise
cancellation in the differential/balanced line on the amplifier.

You would hook up to the RCA connectors with the transformer primary, then run a 2 Conductor + Shield microphone cable from the secondary over to your amplifier and hook up with either a TRS or XLR connector, depending which your amp has.

Properly done, you should not need any extra components.
 

Attachments

  • Capture3.JPG
    Capture3.JPG
    28.1 KB · Views: 213
  • XLR Pinout.jpg
    XLR Pinout.jpg
    26 KB · Views: 209

audiorado

Member
Paid Member
2009-02-25 12:16 pm
Maribor
Hi guys,thanks for answers.So now I have at home my friends anawiev D class amp with symetrical(balanced imput )only.My cd player is Tjoeb with tube output and 275ohm output impedance.For anawiev input impedance it is stated 2,5Kohm.So now for conect Lundahl LL1540 from cd player(unbalanced)to amplifier (balanced) input,where is the best choice to have the transformers,inside cd player or inside power amp.This amp is power amp without volume control,I have volume control on my cd player.So what about now the parts value must be to become bedt results from lundahl ll1540?
 
From the spec sheet for the transformer...

Connect pin 2 to pin 4
Connect pin 6 to pin 8

Connect the RCA+ from your player to pin 1
Connect the RCA ground from your player to pin 3

Connect the balanced shield to pin 6/8
Connect the balanced hot line to pin 5
Connect the balanced cold line to pin 7

Run the balanced (2+shield) wire over to your amp and follow the hook up directions for the XLR connectors.

Dupilcate this on the other transformer, for the other channel.

No other parts should be required.
 

Attachments

  • lindall.JPG
    lindall.JPG
    18.3 KB · Views: 165