the legendary tg12412

[drask]

Maybe sowter could make the inductors for whoever won't have the balls to DIY.

By the way, what kind of core are you going to use? Toroids? EI? Permalloy? Iron?

Yes I can make inductors by sowter. But the project will more expensive, not necessary a problem.
But I'would like try to make inductors myself. If the resuslt it's not good, I'll make inductors by sowter.

For the core I don't know exactly yet. A tech who use a MK4 tell me the core of inductors is like this :
http://cgi.ebay.fr/10x-RM8-Pot-Core-Ferrite-Bobbin-Philips-Epcos-Coils-/140529385536?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item20b8344040
I know the TG12410 and the MK4 it's not the same console. But inductors it's maybe the same core.
What do you think for this rafa?

 

[abbey road d enfer]

For the core I don't know exactly yet. A tech who use a MK4 tell me the core of inductors is like this :
http://cgi.ebay.fr/10x-RM8-Pot-Core-Ferrite-Bobbin-Philips-Epcos-Coils-/140529385536?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item20b8344040

These cores are based on N26 material, which is not produced anymore; it was in the low-performance category. Al2900 is a lot for such a small core as an RM8. The drawback is that the gap is very small, resulting in high tolerance (-20/+30%). This, combined with the low quality material will make the coils sensitive to level, with risks of saturation. You really need to check the material and the size of the core. I've never used smaller than RM14 in low frequency applications (f<1kHz).

 

[drask]

For the core I don't know exactly yet. A tech who use a MK4 tell me the core of inductors is like this :
http://cgi.ebay.fr/10x-RM8-Pot-Core-Ferrite-Bobbin-Philips-Epcos-Coils-/140529385536?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item20b8344040

These cores are based on N26 material, which is not produced anymore; it was in the low-performance category. Al2900 is a lot for such a small core as an RM8. The drawback is that the gap is very small, resulting in high tolerance (-20/+30%). This, combined with the low quality material will make the coils sensitive to level, with risks of saturation. You really need to check the material and the size of the core. I've never used smaller than RM14 in low frequency applications (f<1kHz).

Thank's for the information.
Wich core do you advice me for make the inductors, you have a idea?

 

[warpie]

Can someone suggests a way to drop the Voltage from 28V to 24V?
I'm using a PSU that outputs 28V and then the voltage it's being dropped to 24V with a resistor (as per original design).

However, I believe that by changing some resistors it is possible to use a PSU with +/-24V.

I just can't figure out the exact resistor values...  :

 

[abbey road d enfer]

Can someone suggests a way to drop the Voltage from 28V to 24V?

You mean drop the voltage requirement, I guess...

However, I believe that by changing some resistors it is possible to use a PSU with +/-24V.

R64 & R62 are the voltage droppers. Since the intended working voltage for the circuitry is 24V (except the output stage), you would need to short R62. But you would also need to make sure your +24 supply is extremely clean and robust, because this resistor, in combination with C103, helps cleaning PSU noise. For the output stage, the voltage is regulated at 23V by the Zeners D2 & D3. The actual current through R64 is about 70mA. To maintain the same current for 24V operation, R62 should be ca. 14 ohms, but the risk is that if your 24V PSU goes up to, say, 25V, the current would double, putting R62 and the Zeners in danger. OTOH, if the PSU goes down to 23V, there will be no current through the Zeners, meaning no regulation.
You could replace the Zeners with lower voltage ones, but that would reduce the headroom.
Ther is no simple answer to your question. If I was you (but I'm not) and hard-pressed for going 24V, I would make sure the PSU is superclean, take off the Zeners and short R64.

 

[warpie]

R64 (56Ohms) gets very hot although I'm using 2W resistor (which according to my maths it's well above the limit).
Oddly enough, I've noticed that this doesn't happen always. I've breadboarded two circuits
and it happens on both so there must be something else. Any idea?

I'm using a 2x0-25,50VA transformer (RS Stock No.540-5242) with a KLM PSU JLM Power Supply kits

 

[abbey road d enfer]

IR64 (56Ohms) gets very hot although I'm using 2W resistor (which according to my maths it's well above the limit).
Oddly enough, I've noticed that this doesn't happen always. I've breadboarded two circuits
and it happens on both so there must be something else. Any idea?

you must check the voltage on both sides of the resistor.

 

[leadbreath]

ive been meaning to try making my own inductors for quite a while now, maybe this will give me the incentive to finally go ahead with it...

 

[abbey road d enfer]

That's correct, so the dissipation is about 0.3W.

 

[warpie]

Exactly, that's what I initially tried but the resistor was getting very hot.
Now I use a 2W resistor and it still gets hot.

 

[abbey road d enfer]

Exactly, that's what I initially tried but the resistor was getting very hot.
Now I use a 2W resistor and it still gets hot.

Now, we're getting into philosophical debate: How hot is hot?
Anything below 50°C is considered perfectlysafe.

 

[abbey road d enfer]

Well, there are not many possibilities: either the input voltage gets higher - but your 28V supply is regulated, isn't it? - or the the 23V rail goes down. So I suggest you measure these two voltages when the res gets too hot.

 

[abbey road d enfer]

Are you sure the resistors measures effectively 56ohms?

 

[etheory]

I just whacked the whole schematic into LTSpice, and it's a really cool circuit.
Simulates perfectly - as is.

I tell you what though, it would be pretty expensive (in terms of what I can afford for DIY anyway, especially with those 5P5T and 1P21T switches and inductors) to put together as is, but a cut-down version, where you choose which of the LOW, BL, MED, SH and HIGH curve types you want per band (i.e. fix it to one option for each of the 4 bands), could be quite affordable, especially considering the lack of iron and simple transistors that are still available (I would probably sub BC177 for BCY71) and it would be an amazing thing to have around....

Very very very cool - this is going on my long term list of crazy projects to build.... Thanks so much for posting the original info, I LOVE the curves of the plug-in, but to have a physical version would be even better.  I might even have to build a version with just that high band - it's such a nice curve shape and set of frequencies for adding sparkle.

 

[etheory]

How does it sound?
Looks like you have built some very cool boards - congratulations!
Did you use the discrete two-transistor amplifier circuit from the original schematic, or replace it with an opamp configuration?

 

[etheory]

Oh cool, that's awesome.
Which transistors did you end up using for the BC109 and BCY71?  Or did you have stock of original parts?

 

[abbey road d enfer]

Or the diodes keep the voltage at 23V regardless?

Yes, the Zeners are regulators.

 

[drask]

I just whacked the whole schematic into LTSpice, and it's a really cool circuit.
Simulates perfectly - as is.

I tell you what though, it would be pretty expensive (in terms of what I can afford for DIY anyway, especially with those 5P5T and 1P21T switches and inductors) to put together as is, but a cut-down version, where you choose which of the LOW, BL, MED, SH and HIGH curve types you want per band (i.e. fix it to one option for each of the 4 bands), could be quite affordable, especially considering the lack of iron and simple transistors that are still available (I would probably sub BC177 for BCY71) and it would be an amazing thing to have around....

Very very very cool - this is going on my long term list of crazy projects to build.... Thanks so much for posting the original info, I LOVE the curves of the plug-in, but to have a physical version would be even better.  I might even have to build a version with just that high band - it's such a nice curve shape and set of frequencies for adding sparkle.

Hie Etheory,

You're right, it would be little expensive, but it's a great EQ. And have it in physical, will be great.
Your solution it's good too, but we can find a 5P5P for a correct price.
I think I find. Need to check again for to be sure.

 

[drask]

It sounds good. Well, it sounds passive... 

The main board is exact copy of the original. Nothing changed.

That's the main board. You'll see on one side it has 4 molex connectors. These are for the filter boards.

http://s688.photobucket.com/albums/vv242/warpy/Tongue%20Control/?action=view&current=IMG_2143.jpg#!oZZ2QQcurrentZZhttp%3A%2F%2Fs688.photobucket.com%2Falbums%2Fvv242%2Fwarpy%2FTongue%2520Control%2F%3Faction%3Dview%26current%3DIMG_2143.jpg

Hie Warpie,

I would like listen your version
If you have demo files. You can send me on my email

Thank's friend.
regards

 

[abbey road d enfer]

My other concern is that this resistor is located next to the 470uF cap (c101) on the PCB. Is there any danger that the cap will dry out faster due to the heat from the resistor?

Yes, it is a problem. You have to find the cause. You tell me the voltages are correct, I can only suspect the resistor value is not correct, or there is something near it dissipating heat.