ours sound like the 2*5*2*0?

[strangeandbouncy]

dear All,

I've just completed my first 2520 RC v1. it works beautifully in my home-brew API 553-based passive-eq (with switchable frequencies). I haven't tried it in a high gain application, 'cos i don't have one - Yet!

Let me give you the values I used.

Q1/2 - hfe 530 matched
Q3/4 - hfe 460 matched
R1 - 150k
R2 - 100R
R3 - 82k
R4+R5 - 82k('cos I can't add up! Should be 90k . . . )
R6 - 3k9
R7 - 3k3
R8/14/15 - 1k
R9/13 - 56R
R10 - 800R
R11/12 - 5R6
R16 - 47k
C1 - 1000pF
C2/3 - 47pF
C4 - 39pF
C5 - 10pF
D1 - 2xIN4148
D2/3 - IN4148

All caps ceramic, All resistors - 1/8th Watt, except R11/12 - 1/2 Watt.

Next one finished tonight, testing tomorrow - must have STEREO Eq's after all ! . . . I have 6 positions in the HF - I guess@10kHz-22kHz-ish. I am waiting to order Inductors from Sowter, but no money at the 'mo . . . I changed feedback cap around 2520 from 180pF to 150pF - again, by mistake! When I corrected them to 180pF the eq sounded "smeary" especially on the upper settings, so i put 150pF bach again. Much sweeter than my original API 553. Maybe it needs re-capping(?) It has a "Melville" 2520. When I dropped my new 2520 in on the old unit, it sounded remarkably similar, definately API, but a tad more detail in the top end. I also noticed a distinct difference between using polystyrene caps and polyester in the passive eq. Never really noticed this phenomenon before. Polystyrene is much "richer" sounding. Polyester still sounds fantastic, tho'. Can't wait to build second unit and try phase reversing one with polyester to see what the difference is . . .

Gawd Blimey! This is so much FUN!!!!!!!

- Fabio, You are the greatest! This IS the eq I have always wanted - SO SWEET! - and i have only made the HF part so far! I want to try 3 frequencies in the LF(Shelf) and no mid-range.

ps - BTW, should I change feedback cap on Melcor to 10pF too?
:guinness: :sam: :guinness: :green: :grin: :green:

Andy-"Loadsa-Sweet-Top-End-Now!"-P

 

[Bauman]

COOL! I´m in love with those little blocks... :grin:

my home-brew API 553-based passive-eq (with switchable frequencies).

:shock:
schematics?

cheers!
Fabio

 

[strangeandbouncy]

dear Fabio,

i have scemo, but no scanner . . . . actually I have LOADSA schemos, and no scanner!

i'll try to see if my wife can scan it for me! it is virtually the same as the op-amp labs circuit, which i don't know how to paste here . . . .HELP! - How do I attach something?

Edit :- I have posted the op-amp labs eq diagram on my .mac acount

go here :- http://homepage.mac.com/strangeandbouncy

Api 553 uses Profile 2503 tx and 1 Henry inductor, and 0.033uF in HF. HF to low for me, so I have used 22nF, 10nF, 6n8, 4n7, 3n3, and 2n2. i am going to try Sowter Neve type inductor tapped at 2H/1,2H/and0.45H. Should give me@40Hz, 80Hz, and 180Hz(?dunno?).

 

[pmroz]

Strangeandbouncy, great news! Congratulations... thanks for link.
With all these spare DOA boards (ave Fabio!!), i was going to make all-discrete tacobell drive-thru talkback amp, utilizing 12 DOAs (finally they would get my order right!), but your idea looks way cooler.

Gus, try those for input pairs? I'm game, i'll see if i can find them.

 

[Bauman]

all-discrete tacobell drive-thru talkback amp

:grin:

I´d trade more opamps for some Tacos right now... haha


:guinness:
Fabio

 

[pmroz]

I´d trade more opamps for some Tacos right now... haha

maybe not ones from 'the bell'. Bottom of taco barrel. You need good Brazilian tacos!

 

[deveng]

Strangeandbouncy wrote:

I changed feedback cap around 2520 from 180pF to 150pF - again, by mistake! When I corrected them to 180pF the eq sounded "smeary" especially on the upper settings, so i put 150pF bach again.

The feedback (compensation) cap should be determined by the value of the feedback resistance and the upper rolloff required. Typically you would set the cap for a 1 or 1.5us RC. For example, if you are shooting for 1.5us amp and the feedback resistor is 20k, then the feedback cap would a 50pf. If your feedback resistor is more than 20k and you're using even a 150pf cap, you could be starting to roll off the high end.

Regards,
Jeff

 

[strangeandbouncy]

Jeff,

Feedback resistor on original 553 is 10k, and I have used the same in my eq.

AndyP

 

[Flatpicker]

[quote author="strangeandbouncy"]...i have scemo, but no scanner . . . . actually I have LOADSA schemos, and no scanner![/quote]Should we take up a collection to buy Andy a scanner? :wink:

 

[daArry]

Whereabout are ya in London Andy?

I got a scanner and would be happy to scan some bits up... :thumb:

 

[strangeandbouncy]

Da ARRY,

I work at Grey's Inn Rd/Chancery Lane. Live currently in Edmonton (TEMPORARY accomodation til my flooded flat is rebuilt AGAIN!)

Where abouts are you,Sir?

Andy P

My wife has a scanner at her work . . . . .

 

[daArry]

I'm in W9, just of the Harrow Rd...

 

[strangeandbouncy]

How Bizarre!

- So's my flooded flat . . . . Malvern Rd, me . . . . . behind Chippenham pub.

Andy p

 

[fum]

Is that a scanner I hear warmin up? :grin:

 

[strangeandbouncy]

Fum,

By the pricking of my thumbs, something schematic this way comes!

BTW, your Profile 4808 are Rockin' in my API 553-based passive eq's with switchable Frequencies . . . . only built HF so far, cos I aint got no inductorzzzz. Sounds AMazing! Thanks!

 

[fum]

Good to hear! =) I'll be interested to see this, as I am largely without outboard eq at present, and will be starting my eq building fest in T minus 4 mic pre projects, and counting

Ya gotta post some pictures, too!!

Regards

ju

 

[daArry]

Small world indeed Andy - Malvern is just like 2 turns from me (I'm on Portnall) :thumb:

 

[Bauman]

Oh man, you guys are neighbours? come on!!!

 

[strangeandbouncy]

This is just like internet dating, but without the embarassment . . . (Blush Blush Blush)

 

[daArry]

:shock: just the schems man...just the schems!! :thumb: