Unstrap those amps for your SDA's

I see your tubes listed, but what brand amp/pre are you running?

In addition to your new awesome sound, from your pic I'll bet the candles and mood lighting help the WAF:rolleyes:

joeparaski wrote: »

Could someone make this real simple and provide a "strapped" diagram please? And what is an AI-1 cable? How does it differ from the stock cable?

Oh, and I'm bi-amping my SRS's...so anything different with this "strapping".?

Joe

Cheap Diagram coming up.

Strapped Amps look like this.
Amp 1's Ground
_____________] Strap to connect amps together to make common ground.
Amp 2's Ground

AI-1 Cabled SDA's Look Like this.
Amp 1 to Speaker 1
_________________@}@ AI-1 Cable instead of SDA Cable to connect grounds
Amp 2 to Speaker 2

Two I'll tell you about right off the top

Telefunken ECC81 (euro designaton of 12AT7; exact same tube) are superb sounding and very neutral with great 3D imaging and last forever.

1950's Raytheon 6414 3-mica black plate with D or Horseshoe getter are also excellent they add a little warmth and have a very nice top end and very nice soundstage. They are a little lower gain than the typical 12AT7/ECC81.

For 6SL7 I have fallen in love with the 1950's Sylvania JAN CHS 6SL7WGT (tall or short brown base) black plate w/square getter. The soundstage is unbelieveable the high are very vivid and sparkly but never a hint of harshness........makes you feel like you are right in the music. Called "Chrome Domes"

1940's Tung Sol 6SU7GTY (black glass, brown base) these are basically 6SL7's but the triodes are very, very tightly matched from the factory and were for critical Military installations. These tend to be rare because not a lot were made. I have a reliable source, but they have become very pricey since stock is drying up. These are a very close 2nd to the Sylvania's above. Simply sublime tubes.

****, you know me I could write pages about the tubes I've rolled. So I'll stop for now

Something for you to chew on Larry and yes, they will make a huge difference; you think those amps sound good now..............

H9

P.s. I can tell by the photo's those are 80's Sylvania's and CV4024's. Not the best amongst what's available, but better than current production stuff, IMO

So one other thing that has not been mentioned in this thread that needs mentioning is:

1) not all non-common ground amps can have their negative term strapped

2) not all SDA's can use the AI-1, actually only a few select models.

H9

TOOLFORLIFEFAN wrote: »

That is True!!!!

Is there a list of SDA's that can use the AI-1 cable??

I have the SDA1.2tl's/ SDA1C's/ CRS+'s. are these OK?? I know the 1.2/1.2tl's are OK but not sure on the others..

I'd have to check when I get home, but those sound OK for the AI-1, except only certain serial # 1C's can use it. With regards to 1C's and the early model serial #'s there is a work around but you have to contact Polk to see how that works.

Just wanted to mention it since these types of threads are used as reference sometimes.

H9

P.s. I believe only the CRS+'s with pin/blade (1989 model) can use AI-1, but I'd have to check my notes for sure.

ben62670 wrote: »

All pin/blade SDA's can use the A1. Some of them do need to have the blade connected to the ground terminal in the cabinet. As for the BB SDA's I would also like to know what speakers can use the A1. There should be a sticky in the vintage speaker section of the forum.
Merry Christmas
Ben

Not so sure that is true Ben, but I'll check when I get home and post the definitive (if there is such a thing) list later tonight.

Actually I've posted the info about the 1C's atleast twice before.

H9

heiney9 wrote: »

So one other thing that has not been mentioned in this thread that needs mentioning is:

1) not all non-common ground amps can have their negative term strapped

I disagree,if it's common ground(a non differential/ bridged output stage) there should be no issue strapping the negative terminals.There are some amps that have a small amount of resistance added between the grounds of the two channels (to provide some isolation) but these can and must be strapped.Otherwise potental high ground currents might cause those resistors to fail.

heiney9 wrote: »

Hmmm............I was told by NP under no circumstances should I strap any of the Pass X series amps when I asked specifically about this.

Because the X series amps are a balanced differental/bridged output stage,not common ground.

heiney9 wrote: »

Also there have been members who did strap a non-common groundand had lowered output vs. the AI-1 because of the resistors. Not sure I can find the thread/posts

H9

If you re-read my first post I was specifically saying common ground.

FTGV wrote: »

If you re-read my first post I was specifically saying common ground.

But you disagreed when I stated "non-common" ground, then you confirmed what I stated. :biggrin:

Why would anyone strap a common ground amp for use with SDA's? That's why I was confused. I never said not all "common ground amps....."

:biggrin:


H9

heiney9 wrote: »

But you disagreed when I stated "non-common" ground, then you confirmed what I stated. :biggrin:

Why would anyone strap a common ground amp for use with SDA's? That's why I was confused. I never said not all "common ground amps....."

:biggrin:


H9

Se above.

ben62670 wrote: »

Some Adcom's that are common ground do have resistors between the channels. If you don't strap them the little resistors will blow.

Yep the wire effectively bypasses the resistors so they don't see the large currents that could cause them to fail.The amps with the ground isolation resistors aren't truly common ground ,but when strapped they become common ground.

The use of the A1 negates the need for strapping,so I guess the improvement your hearing is purely the result of using it.