View Full Version : 3155 L-Pads

Dr.db

07-27-2015, 11:53 AM

Hey folks,

I´d like to swap the original L-pads in the 4355 to some fixed resistors.

Which values would I need to reach the +4db setting of the L-pad for the HF and UHF section :confused:

Thanks a lot,

Olaf

Challenger604

07-27-2015, 05:40 PM

Hey folks,

I´d like to swap the original L-pads in the 4355 to some fixed resistors.

Which values would I need to reach the +4db setting of the L-pad for the HF and UHF section :confused:

Thanks a lot,

Olaf

Take the value at +4 on your L-Pad and you'll have it. But I believe that if you have it at +4 it's like you don't have any. (L-Pad)...

I would disconnect it...

cheers!

Dr.db

07-28-2015, 04:03 AM

Thanks for your help :)

Actually I haven`t got the oppertunity to measure the values, sorry. But you think I could simply bypass the L-Pads!?

3155 has two L-pads. One 16 ohm and one 8 ohm.

Remove L-pad will affect the crossover frequency.

Set L-pad to +4, disconnect cables and measure the value between the legs.

Dr.db

07-28-2015, 12:53 PM

"Here is what I get measuring an L-Pad." (Quote:4313B (http://www.audioheritage.org/vbulletin/member.php?15-4313B))

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=1153&stc=1&d=1066931501

http://www.audioheritage.org/vbulletin/showthread.php?999-Modeling-networks

This is what I found for the 8ohm L-Pad. But I´m not shure how to read this.... :dont-know:

The "series resistor" (3 to 2) varies from 7.2ohms to 0 ohms, so I guess I could simply cancel this resistor!?

But which value does the remaining "parallel resistor" has to be ?

4313B

07-28-2015, 02:36 PM

If you can find my 3155 charge coupled schematic it should have the fixed resistor values in it.

Dr.db

07-28-2015, 03:01 PM

Thanks for the hint :)

So it would be none series-resistor and a 100giga-ohm in parallel ?

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=46834&stc=1&d=1280446056

4313B

07-28-2015, 03:58 PM

No, the 16 ohm L-Pad measured 8 ohms in series and 22 ohms in parallel at the 0 position and the 8 ohm L-Pad measured 4 ohms in series and 22 ohms in parallel at the 0 position.

grumpy

07-28-2015, 07:41 PM

I'd say to make sure the 100Gig ohm resistor is non-inductive

and that 1% might sound better, but someone might take me seriously.

(a -really- poor idea)

Sometimes including non-physical parts (particularly DC resistive paths to ground)

help electrical simulations run properly.

Dr.db

07-29-2015, 02:17 AM

No, the 16 ohm L-Pad measured 8 ohms in series and 22 ohms in parallel at the 0 position and the 8 ohm L-Pad measured 4 ohms in series and 22 ohms in parallel at the 0 position.

That is for the "B-position" and is the 0 position setting as you mentioned.

But I´m looking for the +4db setting.

I thought this would be the "A-position" without a series resistor and just the 100gig ohm parallel resistor?

berga12

08-02-2017, 09:05 AM

No, the 16 ohm L-Pad measured 8 ohms in series and 22 ohms in parallel at the 0 position and the 8 ohm L-Pad measured 4 ohms in series and 22 ohms in parallel at the 0 position.

So, If I decided to run at 0db without variable Lpad I've absolutely to place in the crossover an 8/22ohm for the 2441 and a 4/22ohm for the 2405, otherwise it changes crossover point?

Dr.db

08-21-2017, 02:21 AM

So, If I decided to run at 0db without variable Lpad I've absolutely to place in the crossover an 8/22ohm for the 2441 and a 4/22ohm for the 2405, otherwise it changes crossover point? I would agree, but I´m not really a technician to ultimatly varify it ;)

berga12

08-21-2017, 02:36 AM

Ok I purchase them :) lets try!

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