New API 525 build thread.

[emrr]

yep you're right, the same.  Back to my original comment; I was looking at Peter's schematic, which ain't right. 

 

[jplebre]

Does anyone know if Ed made a run of transformers for this new version of the 525? He said he had done enough transformers for the ones that bought the v1 of the Peter board.

Where can I get trafos in the UK? I know Jeff @ classic API sells them but was trying to avoid postal charges and the likes

J

 

[zayance]

Does anyone know if Ed made a run of transformers for this new version of the 525? He said he had done enough transformers for the ones that bought the v1 of the Peter board.

Where can I get trafos in the UK? I know Jeff @ classic API sells them but was trying to avoid postal charges and the likes

J

If you check the mainboard BOM, on first page, it says you can use 2X SOWTER 9935, don't know if that will be cheaper than Jeff at the end?


T.

 

[jplebre]

Yeah, last case scenario I was considering that.
But when I spoke with Peter he said "use Ed's have no idea what he has"

.... You know, the ever helpful Peter

 

[jplebre]

Question about the input trafo. The original has no input trafo, am I correct?
For the people that did go for the input trafo, is there really a benefit? I mean the unit is coloured enough (at least the original ones) is it worth to fork out those £40 on a Lundhall?

Pardon my noobiness if the original has in fact a trafo input. (never actually opened one, but the pictures I've seen only had the o/p and sidechain trafo)

 

[901]

The original has two transformers, but one is the output transformer and the other is used to generate the voltage that goes to the FET. No input transformer.

I built mine with the line receiver as proposed by Peter. Works fine for me.

 

[jplebre]

The original has two transformers, but one is the output transformer and the other is used to generate the voltage that goes to the FET. No input transformer.

I built mine with the line receiver as proposed by Peter. Works fine for me.

Thank you 901. As expected, I guess.

 

[jplebre]

Does anyone know if Ed made a run of transformers for this new version of the 525? He said he had done enough transformers for the ones that bought the v1 of the Peter board.

Where can I get trafos in the UK? I know Jeff @ classic API sells them but was trying to avoid postal charges and the likes

J

in the end, getting Ed's transformers from Jeff in the US was still cheaper for than the sowters (UK folks).
Grayhill 71BDF30-02-1-AJS in stock at RS 2508966576

 

[jplebre]

any HFE requirements? I have tons of under 400-450hFE BC184
I guess I could also use the BC550. I saw on another post they should be matched, not a problem there (Q1 and Q2)

 

[peter purpose]

Just match the input pair.

 

[jplebre]

are 1/8w ok for the miniature resistors? I've used ohms law for worse case scenario (+16v to ground) and it did give 0.250w
But I don't think in both cases it's "signal" to ground so that shouldn't matter.

I wanted to avoid carbon and the only ones I found were either 1/8w or carbon.

What are you guys getting?

Cheeeeeers

 

[jplebre]

Hey guys

What exactly is CG and RG?
Since it has a weird naming convention decided to look up but couldn't find on original schemo.

Is this a remnant from the old build?

Is this optional, or necessary for either the A4 or Lundahl?

I'm going A4 so I skiped XR1 and XR2. but I'm confused with CG/RG

 

[peter purpose]

Cap ground & resistor ground. They join power and audio grounds through 10R & 10pF... Don't ask.

 

[jplebre]

will 2k make a difference for R75 (2.2k?) having a hard time finding the right ones for the right footprint.

is it just setting impedance for the rail supply?

 

[jplebre]

Big Pete

in the first page of the thread you posted a pic with PRV6 lin as i/o? was this only for the picture or>

 

[jplebre]

2Q

is it normal that the sidechain opamp (a3) big trannies run slightly hotter than the rest? (eg. almost too hot to the touch?)
and:

Anyone else see the meters going full on when engaging true bypass?


EDIT: did the same mistake as 901 with the sidechain trafo I'll try and fix it later but that should be the end of it.. nothing to see here move along

 

[901]

Yes, bypass lights the whole meter.

 

[jplebre]

in normal conditions also does it? or just because i have the trafo mounted wrong?

 

[901]

No, the wrong trafo connection does not affect that behaviour.

 

[jplebre]

Yes, bypass lights the whole meter.

Odd! I thought that the switch was simply a 4pdt. 2 poles for the + and - copy of the signal or the trafo out, and then the extra pole used for the bi-colour LED.

Signal should still go through the whole circuit. O/p trafo still sees the 600ohm load is still there, nothing else changes in the circuit so why does this happen?

I feel like some probing and trace cutting coming on just need to understand what else is being affected

(not having a go in anyway, just want to learn more