SAE Preamplifier Equalizer Mark IXB

[audiomachines]

Hi all,

Anybody knows the inductor values of an SAE Preamp Mark IXB eq section? or service manual, I am currently restoring one and i am trying to wound my own coil using EPCOS P26 cores. Any info would be highly appreciated.Thank you.

 

[RJM1]

Inductors usually do not go bad. Especially in low current applications. What makes you think that they need to be replaced?

 

[audiomachines]

well this is a 40 year old preamplifier. my multimeter says open even my LCR meter say so

 

[Mark Tillotson]

What is it like? Could you count the turns and measure the AL value(*) for its core? Or reuse its core, come to that.
(*) AL value [Encyclopedia Magnetica]

 

[rayma]

my multimeter says open even my LCR meter say so

Same in both channels? It's very unlikely the inductor is bad.

 

[audiomachines]

Well somebody did messed up the board before i got the preamplifier, He tried to clean it with a brush not knowing that the inductors are torroid wound with a very fine wire (AWG 37), Yes it would be possible to count windings but its gonna take a long long time (the inductors were the torroid type) plus i dont have access to a torroid winder that is why i am using epcos pot cores. Most of these LC base eq (pre-Gyrator designs) are using 5-3 Henry on the 30z-50Hz band thats a lot of winding to cound. I did try to wound an inductor on a EE25 core with AL values of 1950 i got 3.5H for a 1400 turns gapped due to the adhesive.

 

[rayma]

Then if only one channel is damaged, measure the inductor in the good channel,
and replace both inductors with new ones. Don't try to wind 1400 turns yourself.

 

[audiomachines]

Then if only one channel is damaged, measure the inductor in the good channel,
and replace both inductors with new ones. Don't try to wind 1400 turns yourself.

i got a motorized winder with counter but not a torroid winder well all the inductor were damage

 

[rayma]

i got a motorized winder with counter but not a torroid winder well all the inductor were damage

If it's a simple LC circuit, read the associated capacitor value and the frequency on the front panel.
Then use the formula: f = 1 / ( 2 x Pi x sqrt (L x C) ) to find L.

 

[audiomachines]

yes I did do the math, but you need to also know the DCR value of the inductor so you could estimate the Q of the LC ckt

 

[rayma]

yes I did do the math, but you need to also know the DCR value of the inductor
so you could estimate the Q of the LC ckt

Measure the wire gauge, then calculate the coil resistance from the estimated wire length.

 

[llwhtt]

The Service Manual lists no inductor info other than the frequency that it is used.

Craig

 

[PRR]

> DCR value of the inductor so you could estimate the Q

You know C and F, which gives L. Using F and either C or L you can compute Q. We don't know the design Q but if this is a 10-band I would start with 1.3 to 2.8. Comparison of peak boost to factory spec may refine this value.

 

[audiomachines]

it is a 7 band eq with non ISO center freq 40hz, 120hz, 320hz, 960hz, 2500hz, 7500hz, 15khz i love the sound of inductor eqs similar to those manley passive eq, pultec amd rupert neve designs for me thisnis the real tone control before the simulated inductor become mainstream aka gyrators

 

[Rolox]

Hi all,

Anybody knows the inductor values of an SAE Preamp Mark IXB eq section? or service manual, I am currently restoring one and i am trying to wound my own coil using EPCOS P26 cores. Any info would be highly appreciated.Thank you.

I used to have a Mark 1B fully restored. Still regret having sold it

 

[llwhtt]

If I hadn't blown up my LCR meter, forgot to discharge a capacitor, I would take my IXB apart and measure the inductors for you.

Craig

 

[Mark Tillotson]

it is a 7 band eq with non ISO center freq 40hz, 120hz, 320hz, 960hz, 2500hz, 7500hz, 15khz i love the sound of inductor eqs similar to those manley passive eq, pultec amd rupert neve designs for me thisnis the real tone control before the simulated inductor become mainstream aka gyrators

Gyrators simulate ideal, linear inductors, which is a struggle for real inductors to achieve. I'd worry you think there's some magic present, when the magic is in the performance of gyrators, cheaper, better, more precise.

 

[llwhtt]

My friend worked at SAE at the time the IXB was designed and he designed the inductors. I've asked him if it's OK to give you his email address.

Craig

 

[llwhtt]

audiomachines,

I sent you the email address of the man that designed the inductors in IXB.

Craig

 

[Martin P]

it is a 7 band eq with non ISO center freq 40hz, 120hz, 320hz, 960hz, 2500hz, 7500hz, 15khz i love the sound of inductor eqs similar to those manley passive eq, pultec amd rupert neve designs for me thisnis the real tone control before the simulated inductor become mainstream aka gyrators

Dear,

I bought a SAE Mark IXB that had/has some issues. Some wiring needed to be replaced, some switches were broken, etc. I found 2nd hand switches and replaced the defective ones. The only thing that still doesn't work is the equalizer (the switch to turn the EQ on/off is okay). I do not know what the cause can be (no schematic). Would you be so kind to help me out and ask your friend, who knows the product really well, for advice? Thank you very much.

Kind regards,

Martin