T Pad Attenuator Supplier

[opacheco]

Hi again!

Here I am with these rare question again!....I am looking for some Audio (no RF) Variable (no fixed) T Pad 150 Ohms input and 150 output (constant impedance) for 40dB attenuation at least.

Do someone knows where I can find a Supplier for that units (or similars units)?

Opacheco.

 

[gridcurrent]

http://www.shallco.com/attenuators.html

 

[opacheco]

http://www.shallco.com/attenuators.html

Dear gridcurrent let me to check it!!
Thanks
Opacheco

 

[lassoharp]

I wonder who Shallco's biggest clients are these days.  Maybe Lock-Weed Martin buys thousands of them at 5K per unit and just warehouses them.


You can always build one on a rotary switch.  NYDave has a schematic for them somewhere in the Gallery.

 

[opacheco]

Another one knows where I can find other supplier for these kind of the Constant Impedance T attenautor???....I am searching something like DAVEN, TECH LABS or Cinema Engineering Co. Attenuators.

Thanks,
Opacheco.

 

[lassoharp]

I am searching something like DAVEN, TECH LABS or Cinema Engineering Co. Attenuators.

There are no current suppliers for these exact attenuators.

You have to shop them down on ebay or other open markets.  Sometimes surplus places like Surplus Sales of Nebraska gets them in but they go lightning quick because too many people chase them and hoard them.

They probably will cost as much as new ones from Shallco, if they will even sell them in small quantities.


If you just want something functionally equivalent = similar, just buy this:

http://www.hairballaudio.com/shop/index.php?cPath=27&osCsid=4abefa64014d757379654bffdb165bfc



 

 

[opacheco]

Dear lassoharp,

Are these T pad constant impedance attenuators?

That is the most important for me in the part substitution.

Thanks a lot
Opacheco

 

[lassoharp]

Dear lassoharp,

Are these T pad constant impedance attenuators?

That is the most important for me in the part substitution.

Thanks a lot
Opacheco

Yes.

They will work on all tube gear outputs like Altec 436, tube mic pres etc.

 

[opacheco]

Nice to know that!!......these constant impedance 600 ohms T new attenuators pads are the only ones commercially available I believe!!. I can't see anyone in the net for sell. The another's ones ere vintage used units available in eBay.

Thanks a lot for your information and help!
Opacheco.

Dear lassoharp,

Are these T pad constant impedance attenuators?

That is the most important for me in the part substitution.

Thanks a lot
Opacheco

Yes.

They will work on all tube gear outputs like Altec 436, tube mic pres etc.

 

[lassoharp]

You're welcome Opacheco - Good luck in your builds!

 

[ilfungo]

Dear lassoharp,

Are these T pad constant impedance attenuators?

That is the most important for me in the part substitution.

Thanks a lot
Opacheco

Yes.

They will work on all tube gear outputs like Altec 436, tube mic pres etc.

Sorry for a stupid question
I've 2 Tpad that I want to use with VK1 comp ( similar to altec 436)
The T pad are unbalanced?
I must use another transformer to rebalance the signal after ?
Trafo - Tpad -Trafo?
Thanks!!!

 

[lassoharp]

Dear lassoharp,

Are these T pad constant impedance attenuators?

That is the most important for me in the part substitution.

Thanks a lot
Opacheco

Yes.

They will work on all tube gear outputs like Altec 436, tube mic pres etc.

Sorry for a stupid question
I've 2 Tpad that I want to use with VK1 comp ( similar to altec 436)
The T pad are unbalanced?
I must use another transformer to rebalance the signal after ?
Trafo - Tpad -Trafo?
Thanks!!!

For an output transformer on a tube circuit your biggest concern is keeping a constant impedance load on the secondary and maintaining a constant source impedance from the pad's output, which the T-pad does a good job of.  Technically the T network is unbalanced, but so is the transformer strictly speaking - if you are defining balanced as each leg balanced to ground.  Transformer outputs on tube amps for audio use are virtually never ran that way, which would mean using a center tap on the secondary connected to ground.  Without the center tap, they are considered "balanced floating" and this is the way all of the common tube audio amps are ran.  So, to answer your question, no, you do not have to add another transformer after the T pad.  The T-Pad does not upset the performance of the floating balanced output from the OT secondary in any way that degrades the audio.

If you search the forum there are a number of discussions on T-Pads and Ladders and Bridged-Ts that hash out the details in much depth.

 

[emrr]

Opacheco, why 150?  What for?

 

[ilfungo]

Thanks lassoharp!!!

 

[opacheco]

Opacheco, why 150?  What for?

emrr,

This is for not overload and not to get out from the distortion spec. of the unit.....this unit output is very sensible to the load and I want to be secure to be in that impedance all the time.

600 ohms is well number for this unit too but the another unit after this need to be 150 ohms too!.

Opacheco.

 

[fobee]

http://www.ebay.com/itm/Mallory-T250-250-ohm-Audio-Attenuator-/360944916926?pt=Vintage_Electronics_R2&hash=item5409fe59be

 

[opacheco]

fobee,

Thanks for the link!!....but I Will need to searching for 3 more like this, although I prefer Daven type T Pad for durability and noise issues.

Opacheco.

http://www.ebay.com/itm/Mallory-T250-250-ohm-Audio-Attenuator-/360944916926?pt=Vintage_Electronics_R2&hash=item5409fe59be