gato

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #20 on: October 04, 2016, 08:09:54 AM »
so this point is mute, or moot, depending on which dictionary you use, Webster or AES.

lol!


Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #21 on: October 04, 2016, 08:16:33 AM »
700 turns on the primary will give you the same inductance as the original Neve mic input and will add 3 db input level, 1.4 v-rms means 2700 Gauss on a core that will handle 5000. That core you bought off evilbay has two errors on the spec page, 1)-49 Ni will handle 12 KGauss and 2)-if you do an inductance test, you will find that what he sold you is actually 80 Ni with a max level of 5 KG, however, you want 80 Ni for a mic input and 50/50 for line input,

So your saying that the lams I've got should be good with 5000 right?

I'm wanting to use this as a mic input transformer.

Regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

CJ

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #22 on: October 04, 2016, 04:37:31 PM »
DCR means signal loss in a mic input, so you use as few primary turns as possible,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #23 on: October 13, 2016, 12:54:49 PM »
right guys,

i have some results, havent tested transformer yet but inductance looks ok, on PRI winding its about 7H on SEC winding its over 20H as my cheap inductance meter only goes up to 20H.
this is with 2000 turns on SEC and 1000 turns on PRI.
will plug in now and listen and put sinewave through and look at waveform on scope to see if frequencies look alright throughout.

regards

Spence
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #24 on: October 13, 2016, 05:02:07 PM »
waveform looks good from 20hz to 20khz with sinewave and scope, time to plug it in and give it a listen!!!
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

CJ

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #25 on: October 13, 2016, 11:17:51 PM »
inject a 20 Hz sine wave at 1 volt

measure AC current by putting DMM set to ma-AC in series with signal source,  no load on secondary

what is the AC current at 1 volt?

we can get a 20 Hz - 1 V  AL number for that core at 1000 turns,

then we can get the perm of that core and determine what alloy it is,



If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #26 on: October 14, 2016, 02:36:35 AM »
Hi CJ,

Just to check I'm getting everything right, the sinewave signal at 1v should this measure at 1.228v ac?
Or should it be 0.775v ac?

Regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #27 on: October 14, 2016, 04:56:12 AM »
HI CJ,

not exactly sure that i'm doing this right but i'll explain how i've interpreted what you've said.

ive got a stage cube speaker checker which i use as a signal generator, i have measured output at approx 0.775v ive then connected this to the PRI and measured the AC volts which is slightly higher now at 0.800v ive then measured the SEC and i have 1.580v.

does this help?

regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #28 on: October 14, 2016, 07:13:35 AM »
well i just tested against an input transformer out of a voodoolabs preamp with an M marked on it and it sounds better than that!!!
clear as you like!!! no distortion, unless i push the preamp gain of cause.
would be interested in working out what i've done!!!!

regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

gyraf

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #29 on: October 14, 2016, 08:10:22 AM »
Quote
would be interested in working out what i've done!!!!

Very good.

It all starts here, now.

Jakob E.
..note to self: don't let Harman run your company..


Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #30 on: October 14, 2016, 08:14:09 AM »
sound wise it sounds much more defined bottom end, better low mids, more mid forward in general, clear top end.
this was compared with the EZ1290 with carnhills on output transformers and sowter input transformers.

regards

Spence.

gonna take this 10468 and get it tested and the transformer place down the road!!!!
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #31 on: October 14, 2016, 08:42:56 AM »
Congrats Spence :)

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #32 on: October 14, 2016, 01:34:43 PM »
Dont want to start celebrating yet, i do need to check something out.
on my EZ1290 i get nice transients, on this other 1073 (BA284 and BA283AV) i'm not getting very big transients at all?
would this be more to do with the circuit or transformer?

regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #33 on: October 14, 2016, 03:28:22 PM »
Right, I've sat down printed out both the ez1290 and the 1073 schematics and I'm comparing what I've done.
Can see some changes I need to do with caps c7 c8 I can replace for a 4400uf rather than only having 1000uf.
I notice the 1290 only uses two gain stages and the 1073 uses four, so this must be where I'm loosing transients.
I'm going to disconnect the 2nd and 3rd gain stages on the ba284 Pcb, then gain stage wise both preamps should be the same.
I will check the transistors then hopefully both preamps will sound closer.

Regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #34 on: October 15, 2016, 04:12:43 AM »
right,

ive done a couple of screen shots of the S/N and you can clearly see the 1073 version has bump at 50hz, 100hz, 200hz, 300hz, 500hz.
where as the 1290 has much lower 50hz then bump at 150hz, 250hz, 350hz but also has much better signal to noise level.

I did have two 10k resistors on the 1073 the ones marked R31 and R32, i have taken them out as im now going to disconnect E, M and D and L from the BA284 and then look at transients.
I havent changed C7, C8 yet for 2 x 2200uf (4400uf)

regards

Spence.
« Last Edit: October 15, 2016, 06:55:56 AM by Spencerleehorton »
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #35 on: October 15, 2016, 06:56:37 AM »
this is the 1073 one.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #36 on: October 15, 2016, 08:09:56 AM »
must be output transformer wiring now i'm thinking, as i've changed the 1073 to two gain stages now and apart from being different tonally the transients and output level are just the same.
is it better to have a bit of clipping or not now im thinking? as i can squeeze a fair bit more level out of this 1073, just would like to at least work out how to get the transients and output level the same, at least then i can put it back to how it is now!!!

regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #37 on: October 15, 2016, 01:42:19 PM »
right, i think ive sussed it now, output transformer was wired back to front!!!
ive now pretty much got exactly the same S/N and output levels as my 1290 now from this 1073.
now to put the other gain stages back in.

regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

CJ

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #38 on: October 15, 2016, 04:13:33 PM »
800 mv at how many micro-amps AC?

ohm law, if we know current and voltage then we know AC ohms=reactance=innductance
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Spencerleehorton

Re: Making Neve Style Input Transformer for 1073/1290 preamp
« Reply #39 on: October 16, 2016, 06:38:22 AM »
I will test again CJ as I didn't put DMM in series, I put it in parallel on the terminals.
So could you verify I'm setting up correct please?

Sinewave at 0.775ac volts into PRI but with DMM in line on the positive side

Is this correct?
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!