Is it possible to replace the output transformers on master section of mixer?

[PhilipMarlowe]

Hey there,

I'm curious if it was possible to replace the output trannies on this mixer with better ones. I have compared the monitor output, that goes through the identical output path, but emits the transformers. This path seems to leave the lowend more intact, whereas the transformers for whatever reason reduce the punch and heft of the lowend.


Anyhow, I was wondering if it was possible to replace the output transformers if I have the schematic. Unfortunately I'm not yet experienced enough to determine if they are correctly labeled in this schematic, and the schematic has been a bit corrupted. The end of the output stage should say XLR/LEMO

Thanks for the help.

 

[rock soderstrom]

I'm curious if it was possible to replace the output trannies on this mixer with better ones. I have compared the monitor output, that goes through the identical output path, but emits the transformers. This path seems to leave the lowend more intact, whereas the transformers for whatever reason reduce the punch and heft of the lowend.

Yes, in general this is possible, although it may be that the supposedly better OPT also produces similar limitations in direct comparison with the direct output.

What kind of transformer is installed? Any Photos?

To be honest, I have never heard an output transformer that sounded better than the comparable direct line signal (especially in the frequency range you mentioned). But I haven't heard all the OPTs in the world either, so this is a statement with a limited basis and of course completely subjective. YMMV. Transformers are often glorified in this position, just like additional boxes with transformers in them that are supposed to refine line signals. I haven't heard anything that would have convinced me at this point either.

Anyhow, I was wondering if it was possible to replace the output transformers if I have the schematic.

Sure, technically that's not a problem.

 

[Newmarket]

Hey there,

I'm curious if it was possible to replace the output trannies on this mixer with better ones. I have compared the monitor output, that goes through the identical output path, but emits the transformers. This path seems to leave the lowend more intact, whereas the transformers for whatever reason reduce the punch and heft of the lowend.


Anyhow, I was wondering if it was possible to replace the output transformers if I have the schematic. Unfortunately I'm not yet experienced enough to determine if they are correctly labeled in this schematic, and the schematic has been a bit corrupted. The end of the output stage should say XLR/LEMO

Thanks for the help.


View attachment 121769View attachment 121769

Do you particularly require the galvanic isolation provided by a transformer coupled output ? If not then it seems a solid state solution would be preferable.

 

[timtom]

Which console is it? Maybe there is even a transformerless version of the console.

 

[ruffrecords]

It is possible that the reduction in low frequencies is deliberate, for a broadcasting application for instance. A better transformer, with better low end performance would nee a larger primary inductance and that means either more turns of thinner wire or/and a larger core.

Cheers

Ian

 

[OneRoomStudio]

Interesting that the two secondaries are loaded differently. It looks like there are two outputs. If the lower one is the XLR/main out, what is the upper one for?

 

[PhilipMarlowe]

Interesting that the two secondaries are loaded differently. It looks like there are two outputs. If the lower one is the XLR/main out, what is the upper one for?

The mixer has two outputs. Both are transformer balanced but one is +6dbu and the other is +15dbu.

It is possible that the reduction in low frequencies is deliberate, for a broadcasting application for instance. A better transformer, with better low end performance would nee a larger primary inductance and that means either more turns of thinner wire or/and a larger core.

Cheers

Ian

Hey Ian, this is probably exactly it! This is a broadcast (mobile) mixer. It is Austrian and is based closely on the 169 Studer.
Which transformers could be used? I particularly like running the mixbus hot for the glue and transformer saturation.

Which console is it? Maybe there is even a transformerless version of the console.

It is the Acousta P100, based on the Studer 169 and it features Haufe in and output transformers.
Unfortunately I found no information on the internet on this particular output tranny.

 

[rock soderstrom]

AFAIK, the output transformers are Haufe RK605. RK stands for "Ringkern" or toroidal core. I am curious to see what they will be replaced with and how much better the low end will be afterwards

 

[NOON]

The 220uF output capacitor could be a bit on the low side, especially if it's dried out and lost capacitance. Try replacing it with a fresh 470uF cap before playing with the transformers.

 

[PhilipMarlowe]

AFAIK, the output transformers are Haufe RK605. RK stands for "Ringkern" or toroidal core. I am curious to see what they will be replaced with and how much better the low end will be afterwards

Yes, that's exactly it!

The 220uF output capacitor could be a bit on the low side, especially if it's dried out and lost capacitance. Try replacing it with a fresh 470uF cap before playing with the transformers.

Great! You mean C25, right? I did not know that. I will do and report back. Maybe the capacitors dried out, but they looked healthy from a visual point of reference ( no bulging or acid leaking)

 

[NOON]

Yes, C25 between the output driver and transformer. Most don't bulge or leak electrolyte, they just slowly lose capacitance and/or become electrically leaky (turn into a resistor) over the years.

 

[Matt Syson]

An output capacitor that low in value (before it is actually failing) will probably give a low end peak ( resonance) before really rolling off. Broadcast gear usually intentionally rolled off the extreme low and high (above 15KHz) because it would embarass MW and FM transmitters. Whether the transformer would perform any better with changed capacitors can only be determeined by trying it.

 

[PhilipMarlowe]

Update: I replaced the C25 Output Cap with a 470uf 40v one ( those were kind of tricky to find, maybe not manufactored anymore?). This improved the headroom somewhat but didn't change the frequency response. The low end and transient response was still lacking somewhat. Interesting enough it did increase the point of choking the board with low end, probably due to higher headroom?
After trying this, I tried to replace the Haufe output transformer with the Lundahl 1539s I had lying around. I first did this with one channel of the master output.

I connected the 1539s as follows:

"Input Board hot LL1539 pins 1+6
Input cold/gnd LL1539 pins 2+5
connect LL1539 pins3+4

LL1539 pin 12 XLR pin 2
LL1539 pin 8 XLR pin 3
LL1539 pin 10 local ground and XLR pin 1
LL1539 pin 11 + 7 connect"

Is this the recommended way to connect it? I recall shooting Per Lundahl an email, and he was explaining this was the standard 1:1 wiring. Maybe I interpreted it wrong? I attached the data sheet of the 1539.



Anyway, with this configuration the mod worked surprisingly well and easy- I did plenty of testing with only the one modded Lundahl master channel inside the mixer. The low end response was drastically better, and it just sounded like a whole new mixer- really punchy and didn't choke in a bad way. However, after modding the second channel and powering them both up, one channel's resistor started glowing and smoking lol. Luckily enough I saw and smelled it early enough to avoid further damage.

I'm unsure if it was just physical short from lack of space ( this setup is very DIY and was only meant to be temporary to check if the Lundahl's 1539 actually worked). So maybe the legs of the transformer accidentally touched a contact of the second channel and shorted something? Or was it the voltage needed from two channels making a resistor overload and smoke? Unfortunately the html coding of the schematics seems to have scrambled some of the resistor values. So I'm not sure what exactly or where the r45 that started smoking is located in the schematic.

Could someone kindly walk me through this? I guess I'm out of my depths, as I didn't think simply replacing the output tranny could result in physical danger lol. I'd like to be sure I'm not permanently destroying this channel, but so far the burn on the resistor seem repairable. I really like the sound of the 1539s on the outputs, it would be great to make this a reality without blowing anything.

Thank you!