Simple EQ for Neve 1290

[Spencerleehorton]

Very nice info, ok I think I’m all set now to wind at least the AL400 version with 0.12mm wire.
Will do 2000mh (2H) with taps at 200mh, 450mh, 1000mh.

Have ordered a couple of 4.2UH cores and will wind the 10000 (10H) version with taps at 7H, 3H and 1.3H.

These two inductors should give me what I need!?

We will see!!!

 

[alexc]

Excellent  ..  and one needs to consider the 'measurement of the frequencies and curves'  and so on  .. 

There is/are a body of experience that speak  of the parameters of 'merit' for filters ..  and so on  ..

I would think that the 'curves' are out 'there'  such that a bod could get some comparitive data ? Maybe even 'REW' them ?

 

[Spencerleehorton]

just done a test wind on a bobbin and can fit 1800 turns of 0.1mm max before a problem getting core on.

So will have to look at RM6 AL=630 and do 1781.7 turns to get 2H, with taps at 563.4 turns (200mh), 845.2 (450mh) and 1259.9 (1H)

then the other i will have to get FERRITE CORE RM 10 N97 AL=4.2uH and do 1543 turns for 10H, 1291 turns for 7H, 845.2 turns for 3H and 556.3 turns for 1.3H.

I will then screen with copper and then shield with mumetal.

 

[Spencerleehorton]

Not entirely sure how to implement the eq on/off switch, I can see that part of the circuit but a bit confused as normally P to L on the ba283 has the 5k there to adjust the output, on the 1073 schematic P goes through a 22uf cap then a resistor then a break switch ?
Can I use a SPST or DPDT switch here?
Wouldn’t this stop the output at this point?

 

[Spencerleehorton]

Here is my crude drawing attempt!!!
I haven’t drawn in the 5k pot but I would assume the output pot replaces the 5.1k resistor.

 

[Spencerleehorton]

The only concern now is getting fairly close with DCR to other figures if they are way off on first wind I’m gonna worry!!
I’m going to use 0.1mm and see what I get, if the DCR is way over I’ll try going up to 0.12 or 0.14.
I have 0.16mm here as well but I don’t think it’ll be that bad.

 

[Spencerleehorton]

well total miscalculation on RM6, only can get 900 turns on with 0.1mm at 45R and 540mH measured at 100hz!

going to look at RM12 gapped AL1000 and RM12 non gapped AL6000, hopefully this will be better!!

 

[Spencerleehorton]

Have ordered some p18 n48  2.8uH cores and bobbins first.
845 turns for 2H.

Also some P18 N30 should be better for the large inductor.
Giving 5.9uH.
1414 turns to get 10H at 85ohms so would give Q of 148  at 1khz.
Which I’m led to believe is pretty good.

 

[Spencerleehorton]

Just wound the first two inductors and DCR and inductance seems pretty close, measuring at 100hz I get : 216,mH, 512mH, 1.01H, 2.03H.
will see how these sound and if needed i'll take 10-20 winds off each winding.

Just waiting for the higher inductance ferrite cores now!!

 

[Spencerleehorton]

switched pots done, will start with wiring up tomorrow

 

[Spencerleehorton]

Could someone confirm that if the 450mH winding is used please?

I can’t see it being used?

 

[Spencerleehorton]

In studying the 1073 schematic I thought something was wrong!!!
The BA211 pcb has 8 positions for switched pot but on the main schematic it only shows 7?
I’ve got the frequencies as 360hz, 700hz, 1.6khz, 3.2khz, 4.8khz, 7.2khz.
Along with the off position that’s 7, what frequency is the 8th and why is the schematic wrong!!!!!

 

[Spencerleehorton]

Stuffing it all in there too see if it fits, need to wind other inductor once other gauge wire arrives then can finish the wiring.
Front panel a bit cramped but it’ll be fine for the time being!

 

[Spencerleehorton]

Bit confusing these errors in the schematic, I was under the impression that the higher capacitance would be lower frequency, but this pot on the ba211 pos J is 22nf and pos H is 100nf?
On the main schematic it shows the switch the other way!!?
Would like some clarity on this if anyone can help please?

 

[alexc]

No help here for your serious endevours, but when you get 'there', I could go a 'pair' 

Good going with your works!

 

[Spencerleehorton]

Well I’ll be there along with a few other projects as I’ve got some time off this December!!
Need to wind the other inductors tomorrow, then wire in one channel and test where it’s at, I always get problems so expecting this to take while!!
Also need to finish headbaskets to my fet47 and U47fet bodies but need to build a good heater for my nickel playing goo!!
Also going to make several 2254 pcbs and start that next year!!

 

[alexc]

Machina !

 

[Spencerleehorton]

Wound all inductors now and got fairly close to 1.3, 3, 7 and 10H,  Mine was 1.4, 3.4, 7.9 and 11H, also DCR nice and low!
Will finishing wiring tomorrow and then test!!!

 

[Spencerleehorton]

2 x 22uf tants off testing!!!

Hopefully tomorrow I’ll put some  power through along with a sign wave!!

 

[alexc]

Your enthusiasm for the 'diy' is very gratifying just to read on  

Reminds me of the young engineers at my last work place ...  they were early 20s type of young people, 'full of beans'  and really could be hugely productive when full 'engaged'.

Almost makes me wish I was back in the 'great game'  [tech eng] 

But not quite.