WOPL 400 1st time build

[George S.]

Got it. Currently both my 400 WOPLs are dead silent, but I'll incorporate the "continuous improvements" this winter or next time I open them. Easy enough to do. Just rerouting and shortening the AC leg.
I have the 700 WOPLs AC run equidistant between the backplanes and control board. Guess I need to push it back closer to the backplanes after pulling it out.

 

[Gepetto]

Got it. Currently both my 400 WOPLs are dead silent, but I'll incorporate the "continuous improvements" this winter or next time I open them. Easy enough to do. Just rerouting and shortening the AC leg.
I have the 700 WOPLs AC run equidistant between the backplanes and control board. Guess I need to push it back closer to the backplanes after pulling it out.

George if you are successful, no need to alter it.

 

[gene french]

George if you are successful, no need to alter it.

wouldnt the same ac canceling field be present over and around the back planes as long as to and fro lines are cable tied together??
asking for a friend ...

 

[Gepetto]

wouldnt the same ac canceling field be present over and around the back planes as long as to and fro lines are cable tied together??
asking for a friend ...

Yes

 

[gene french]

whew!!!
dodged that bullet!!!
or my friend did, rather...
lol

 

[mr_rye89]

Mine’s quiet enough, I think I can hear the faintest little hiss with my ear against the the 811 horns on my Altecs

 

[mlucitt]

faintest little hiss

That might be air leaking out of your 811 horns... Actually, it is called "Idle hiss" and it is always present but disappears when the music is playing. Think of it as the noise in the ratio of "Signal to Noise" (S/N). We call it amplifier residual noise when we short circuit the inputs and measure the db level at the speaker jack. It can be accentuated by a preamp with a lot of gain, by an amplifier with low input sensitivity (like 0.8V), and with high efficiency speakers (you likely have two out of three).
Our Phase Linear amplifiers have average sensitivity (1.75V for full output) and have excellent S/N ratios (greater than 100db) and even better after the White Oak Audio upgrades. So just don't put your ear up against your 811 horn and you will have no problem.

The 60 Hz hum is unmistakable at 120 Hz. Listen to it here:

 

[mr_rye89]

Yep those Altecs are probably around 104db/1w/1m. I could never get the filament hum from my 300b amp low enough not to hear it

 

[mlucitt]

Bob Carver told me an interesting story. He was called by Clair Bros. Audio to build several PL700 amplifiers for their sound reinforcement business, but they wanted a demo first. Bob said they had this huge speaker box you could walk into. With the amp hooked up, you could hear a hiss inside the speaker box, Bob said it was magnetic resonance from the transformer and you cannot avoid it. The Clair dude said get rid of it or no deal. So he took the demo amp back and installed a "hiss generator" out of phase with the amplifier feedback loop and it eliminated the hiss during his second demo.
He got the contract. Many years later, the Clair dude was cleaning out the dusty amp and saw the small circuit board. He called Bob and asked him what it was for. He said, "You got me." But the Clair dude laughed it off because the amplifiers were so successful for them.

 

[plex]

I have finished most of the backplane wiring and now moving on to the Watts Abundant wiring. Exactly which resistors/capacitors do I have to cut off to disable the Zoebel network on it? Thanks

 

[George S.]

R1, R2, C8, C9. I carefully remove them with desoldering equipment and fill the holes.

 

[plex]

R1, R2, C8, C9. I carefully remove them with desoldering equipment and fill the holes.

Thanks George

 

[Mohawk]

It is neater to route it this way, lower noise too... View attachment 67851 View attachment 67852 View attachment 67853

Morning Joe,

Have you experimented with somehow mounting the thermal switches and wiring outside the chassis ?

Wouldn't that give the best possible separation AC / DC ?

M

 

[Gepetto]

Morning Joe,

Have you experimented with somehow mounting the thermal switches and wiring outside the chassis ?

Wouldn't that give the best possible separation AC / DC ?

M

Hi Matt

Only on my own design which runs only DC to the thermal switches instead of AC.

To run line level AC outside the chassis would create a safety issue that would need to be dealt with. Complicated.

 

[Mohawk]

Well then, do elaborate !

M

 

[gene french]

can you still get those thermal switches??

 

[e30m3mon]

can you still get those thermal switches??

Sniff posted this comment to the WOPL Parts Database ... last page. Lots of good reference material and part numbers, but you'll want to scroll each page as you make up your shopping list for parts inventory

#124

I just ordered some of these from Mouser:
https://www.mouser.com/ProductDetail/682-1NT01L-7941

 

[gene french]

R1, R2, C8, C9. I carefully remove them with desoldering equipment and fill the holes.

I have finished most of the backplane wiring and now moving on to the Watts Abundant wiring. Exactly which resistors/capacitors do I have to cut off to disable the Zoebel network on it? Thanks

get george to explain how to connect meters after dc protect...helps prevent meter damage should you.get dc in output...

 

[Gepetto]

can you still get those thermal switches??

Absolutely...

Selco OA-190-QC

 

[Gepetto]

get george to explain how to connect meters after dc protect...helps prevent meter damage should you.get dc in output...

You won't get meter damage but you may get pegged meters. The dropping resistor in series with the meter protects the meters (unless you are in the -20dB position on a PL700B and you peg them for a duration).

Meter damage comes from mechanical shock.