525 build thread

[peter purpose]

OK boys, I'm taking a week off.. :thumb:

 

[king-rb]

anyone know a produkt# forthe vcr2 sockets at farnell=?

thanks

 

[louder]

alo
farnell p/n:177128
best regards
pedro

 

[kazper]

[quote author="peter purpose"]OK boys, I'm taking a week off.. :thumb:[/quote]

I think you need it!

Enjoy...

 

[peter purpose]

Quick wiring dagram.
This does not mean I'm back..!!

Large version...
http://www.twin-x.com/groupdiy/albums/userpics/525wiring.jpg

 

[king-rb]

wow thanks ..thats what i deeded!

 

[capnspoony]

cheers peter...

I opted for this...

You deserve a present for all your hard work Peter! whatchoo want

--Richie

 

[peter purpose]

[quote author="capnspoony"] whatchoo want [/quote]

A week off.

 

[king-rb]

moin! on which voltage should i run the 525...
ther are 3 990opamps integrated

 

[peter purpose]

As standard, the 525 wants to see +&-15V.
If you have 990Cs, then they really want to see +&-24V(I think).
The upright opamp can also handle 24v, so it really depends on how brave you are.
I'd start out at standard voltage and push on up until your sphincter puckers up tight.

 

[king-rb]

yeahahh!!! first channel finished and it works.. haha
3x 990opamp stable with psu voltage 20V

now i have to build the other 3 ... haha
and a 19" case...

 

[chester]

[quote author="king-rb"]yeahahh!!! first channel finished and it works.. haha
3x 990opamp stable with psu voltage 20V

now i have to build the other 3 ... haha
and a 19" case...[/quote]

pictures please!! :wink:

 

[peter purpose]

Bigun.. http://www.twin-x.com/groupdiy/albums/userpics/built525.jpg

 

[king-rb]

wow.... this is a good looking one!

 

[shabtek]

I know I saw some discussion of this but I could not find it on this thread.

What is the gain of the upright op-amp? I have not traced it out to see what the resistor network is.

I think I want to bal->unbal the input with a trafo...1:1 hi.z input...?

Somebody had mentioned doing this before.

 

[peter purpose]

It's a differential input. So, balanced or unbalanced. Amplifying only the difference.
Here's the schematic of the op amp.

If you're sticking a transformer on the front, bring the secondary signal to the point marked RB1.
Leave out....
CD1-6
RD1-4
A4 and the two unmarked caps
CB1
RB1

peter

 

[babyhead]

[quote author="king-rb"]yeahahh!!! first channel finished and it works.. haha
3x 990opamp stable with psu voltage 20V

now i have to build the other 3 ... haha
and a 19" case...[/quote]

Watch out for DC across the primaries with the 990c's. Every application on the JH website calls for DC blocking on the output... you could slowly fry the output iron.

Am I correct?

Otherwise congrats!

 

[shabtek]

many thanks again peter.

babyhead: i believe the xfmrs ought to be gapped, if there is DC offset on the DOA out, it should not cause a winding to burn open...if ungapped there is always a possibility...and frequency response will suffer as the core could be saturated by the DC

 

[babyhead]

[quote author="peter purpose"][quote author="babyhead"]
It is either that the 2623 is DC capable or the DC output of the 2520 negligible. [/quote]

The latter.[/quote]

I'm going by this...

 

[CJ]

thats a steel core, so dc will not be a problem as with the Ni alloys, but turns are low, so any dc will go right thru the xfmr, so make sure your offset is low enough so that you dont burn up your op amp. it will do as its told, if this means pumping dc thru the output transconitinentals, so have your nearest tech buddy standing by with a soldering iron.

What happens to DC offset during the rise of an 8 hz sqaure edged bass note?


I mean, if the dc is really ac, but still sucks amps, do we consider it?

Measure DC offset while you play music thru it, and you will see what I mean.

People who bypass the output cap are either askin for trouble, or from the UK. Near London probably.
Hopefully not Twekesbury.