Johnny D's 700 Adventure

[soundude]

Re: Phase Linear 400

laatsch55

Should still have the 555's, some are nsc, and nec. alos have the original PL branded 909's. I can tell by your quest there is some intrest there!!! 555's, they work in the 400, indistructable little things they are, and you have some 400's too!

I understand your confusion with some amps sounding different. I believe it component..when I build a amp every component is top grade audiophile even tubes are chose super clean rated so on the mass produced corners are cut and usually degrades the sound. Alos I have been surronded by some really retarded engineers so they rely on test equiptment to gade sound instead of the human ear...the best sounding amp I know of is built by the user for the user.
Anyway after dinner I'm going to swap the driver transistors from left to right and listen again and if the fuzz moves I know where to stop.

 

[soundude]

Re: Phase Linear 400

Got a chance to look at the schematic for the 700b and there are no bypass caps on the rails so they must of omitted them, should be there to drain off any PS ac...don't get it.

 

[laatsch55]

Re: Phase Linear 400

They were omitted on the schematic but not in production. I've worked on more with them than without. In this case they were put there to filter any stray RFI, and EMI the output wires picked up because of how long they were.

At one time I had 16 400's and 8- 700's of varying pedigrees. Not counting my Specs, or the Cary SLM 100's I sold to Larrt.
The 2SD555's are a wonderful output. they have been going strong in my Spec 2's for 35 years, and I have not been gentle with them.

And btw-there are no none "NEC" 555's.

 

[soundude]

Re: Phase Linear 400

well my 700b must be special, there are no trace of them on the plane and I had this amp forever and I did all my own repairs.
swapped drivers and noise still there in process of moving one bank of outputs over...
again I must have special transistors some are NEC's probably rebranded but clear as day, black and silver....lol
going to do outputs and if still noise going to unsolder d9 and d10 from the channel.
if that doesnt do it change all the crappy carbon resistors...

 

[laatsch55]

Re: Phase Linear 400

I was about to say that the carbon comp emitter resistors can be a noise source also. Not a bad idea to change them anyway.

About the 2SD555's if they ARE NOT stamped NEC, then they aren't real 2SD 555's.NEC had that one right. Still a hot rod today.
There are a lot of 2SD555 counterfeits around was what I was getting at. There may be some NOS NEC 2SD555's in existance, but it would be pure luck to get a genuine one. That's why i always break out in a big smile when i open the back of a just unpacked 400 or 700 and see nothing but 2SD 555's everywhere.

 

[soundude]

Re: Phase Linear 400

Does the NEC had a groove on the underside that follows the shape of the case?
The stamp and lettering look pretty original to what there logo looked like back in the 70's..
so I moved a bank over and still noise, moving the other bank over now, let you know what happens.

 

[laatsch55]

Re: Phase Linear 400

Yep they had the groove.

 

[laatsch55]

Re: Phase Linear 400

Does your 700 still have the ground wire going from, the RCA inputs to the left speaker out ground???????

 

[soundude]

Re: Phase Linear 400

ok switch other bank still have noise, do I unsolder d9 and d10 or just one of the diodes leg?

 

[soundude]

Re: Phase Linear 400

yes got heavy gauge wire soldered to copper buss of input grounds going to left channel ground and then jumps over to right speaker ground.

 

[laatsch55]

Re: Phase Linear 400

WHOA!! , we got to straighten out this ground thing . See Joes thread in the PLWO archive, that addresses this issue. Do this before anything else. I thought when you said "per Joe's instructions" you had done this. Itt makes a LARGE difference in the noise floor and can have collateral effects. Like shitty sounding channel.

 

[soundude]

Re: Phase Linear 400

basically what needs to be done? cut the ground off the input channels?

 

[laatsch55]

Re: Phase Linear 400

Basically, I can not explain it better than Joe. the connection between the RCA ground plate and the speaker outs need severed. A separate ground wire to the common point of the PS caps from the RCA ground plate, ands 2 separate grounds running from the negative speaker outposts to the same common ground point between the PS caps. Then the 5L,5R grounds from the board need to go to that same point, IF you have the jumpers on the back of the board, you only need to run one wire to the star ground(between the caps).

 

[soundude]

Re: Phase Linear 400

do I keep the normal/direct switch at the inputs? Or does it go bye bye??

 

[laatsch55]

Re: Phase Linear 400

Personal preference on that one.

 

[laatsch55]

Re: Phase Linear 400

Ok, another explaination on that one. t The direct/normal switch cut the low freq response to eliminate subsonics, and in non-audio applications a DC response start was desired.

 

[soundude]

Re: Phase Linear 400

so basically for audio lose the switch?

 

[laatsch55]

Re: Phase Linear 400

I don't know, ya like the earth to move??

 

[soundude]

Re: Phase Linear 400

ok noise is gone in one channel but when I add the second channel comes back......its in both channels now when I play stereo..got a 10lb sledge waiting in garage for it!!!!!!!
HATE F*%)in transistors

 

[laatsch55]

Re: Phase Linear 400

Ah------="Frustrations Galore" as they said in Princess Bride. It can be a hair puller.What do you mean when you say"add the second channel comes back" ?? In mono mode out of your pre can you select L, R, or L & R ??