PL400/PL 700 speaker connections

[marcok]

10 amps seems a little light....

At present there are two fuses beetween PL 700 and Allison Ones .
The value is 3,15 A ( fast blow ) , calculated using Phase Linear's formula ,
assuming that the speakers are disegned for 375 W for 1s .( declared by Allison )
So the margin factor is 3 times . For me is good , but......
Since I have studied very well Mark's video ,
I have seen , that he uses a special type DCP for PL 400 from mechnical point of view ,
which is the right type that you use for PL 700 B ?
I hope it's suitable also for PL 700 .
I have searched in the forum and in the web ,
but I can't find anything .
Ciao Marco

 

[laatsch55]

Don Imlay, wattsabundant, makes a nice DCP board for the 700. I have used a lot of them and work as advertised...every 700 I've built has a Don Imlay DCP, EXCEPT, Larry's 700 which had an AMPSLABS dcp, which required it's own external 24 volt secondary transformer.

 

[laatsch55]

DCP ratings should take into consideration the current involved when an output shorts....and it's much harder for a relay to "break" DC current than AC....

 

[marcok]

You are perfectly right .
Infact I always ask when I have doubts .
Ciao
Marco

 

[laatsch55]

I have plenty of those to, thank God for Joe...

 

[marcok]

Lee,
I have seen the specs of relays used by Don :
10 A for 400 and 20 A for 700 .
The kit by Vellemann uses 15 A .
For me it's o.k , considering also that the relay used by Don has no 15A type . ( or 10A or 20 A )
Vellemann kit is easier to install and to test and it's equipped with a 230 V transformer .
Now I have only to decide.
Today I have replaced the single short banana plugs with dual type in my father's PL 700 :
perfect !!!!! Two anchorage points are better than one .
There is only a limitation : max AWG 13 .
Ciao
Marco

 

[laatsch55]

On the 700 DCP of Dons, there are 2----20 amp relays....

 

[marcok]

True , Lee .
But also Valleman has two relays . ( one per channel )
I was talking about the type of relay ,
in particular the specs of relays used by these two
manufacturers .
Normal misunderstandings due to the language and probably due
to "cultural approach ". Sorry .
Anyway Don's design is tailored on PL 400/ PL 700 .
and Valleman's design is for every amp.
Ciao
Marco

 

[laatsch55]

Amen Marco....

 

[ksrigg]

I use these:

http://www.monoprice.com/product?p_id=2944

and these:

http://www.monoprice.com/product?p_id=2943

Both types of Banana plugs work well and are very affordable.

 

[marcok]

They are O.K., but for me they are dangerous ,
because they are not completely isolated .
PL 400/ PL 700 aren't toys .
I have investigated only PL , Hafler and Dynaco use small banana sockets.
Probably this kind of sockets were designed for instruments.
A little suggestion :
In case you want to locate DCPs by Watts Abundant on PL 400/ PL 700 ,
replace original banana sockets with big banana sockets ,
because in any case you have to replace them .
Anyway thank you and ciao
Marco

 

[wattsabundant]

Pardon the late comments here...

The way the relay is used is as important as the type/current rating of the relay. The objective here is to protect the speaker in event of amplifier failure. Most any economical relay out there has a contact rating of 28VDC and 250VAC. It is likely going to weld the contacts when trying to disconnect a failed 700 that is putting out 100VDC. Therefore when the relay disengages from the amplifier output it has to also has to crowbar (short across) the speaker terminals. This also assures the fuses in the amplifier open. So in order for the relay to do it's job it has to have a normally open and a normally closed contact with a common connection. This is known as a form C contact.

Most or the relay boards out there use a form A contact which is normally open. "Normal" is shelf state/de-energized. I've repaired amplifiers where the relay didn't disconnect and melted the contacts. My Marantz 140 did that which is probably why the guy sold it to me blown.

The traces on my relay boards were made as large as possible assuming that there would be a very high fault current. I assume the relay is expendable if it protects the speakers. I'm guessing that most of the relay boards found on ebay etc are intended for lower power receivers and amplifiers.