[How-To] McIntosh EF-1208I Sub Gain Mod

Detailed descriptions of how to do things to your Liberty.

Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby Monkey » Fri Oct 18, 2013 8:46 pm

Cheers for that. I presume your box is in the boot? What 8" sub did you go with? What power amp?

The pic I posted is from another forum member in a different thread (viewtopic.php?f=22&t=13828&hilit=kenn) and I think he said it was about 15L. Probably doesn't matter too much - a sealed enclosure with a sub 3.5x the max RMS rating over the stock Clarion (70w vs 250w); and an amp feeding 15x the RMS power over the stock McIntosh amp (30w vs 460w) should be infinitely better!! :D
But then I think why not find a 10" 300w RMS....? I'd love to hear a 8" boot install if someone has one.
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tom_kauf » Sat Dec 21, 2013 7:50 pm

I have just taken my McIntosh Amp (in my 08 GT SpecB Wagon) apart and noticed it is a EF-1259I, not 1208 or 1080. Do you think the mod would work here too?

R519 is in the same spot, and mine is 10k (labelled 103) just like suggested in the write-up for Wagons. So unless someone knows that it won't work, I'll go ahead with it?

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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tony_m » Sun Dec 22, 2013 9:04 am

I am pretty sure mine was different also. The resistor was in a slightly different position, but still labelled R519 & "SUB".
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tom_kauf » Sun Dec 22, 2013 10:35 am

Ok, cool. I did the mod yesterday. All went well, except the trimpot legs broke. I'll get another one today, and finish it.
I couldn't close the lid with the capacitor where the guide put it. But I just moved it to another earth point.

EDIT: Actually, I might redo it with the shield intact until the end, and run the shield from R519 like the guide says. Less noise that way....
Either way, the mod all went well :)

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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby BATMAN87 » Tue Jul 08, 2014 2:48 pm

Hi all,
I have this planed for tomorrow night.

With the shielded wire that you ground one end using 100nf cap, Is the other side of the shielded wire supposed to be connected to anything at all? Or does it just stay unexposed on one end?
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tom_kauf » Tue Jul 08, 2014 3:32 pm

I only connected one end of the shield. There are as many 'experts' on the internet recommending connecting both ends, as there ones recommending one end only.

I was taught at Uni to connect one end only. It depends on type of cable, and what you want to shield against (coaxial vs twisted pair, rf vs audio frequency noise).

But also because it's such a short wire (picks up less noise than a long one), and it's hard in our case to fit a return wire (very tight fit). So more reasons to just shield one end.

But if you do connect it to anything, connect it to ground (earth). It's going to be well shielded inside the metal case of the amp anyway, so you probably won't notice either way.
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby BATMAN87 » Tue Jul 08, 2014 3:50 pm

Cool, thanks for that mate.

I get kinda get what it’s there for now. Did you put a 10k resistor before the trimpot ?

So I diagram with kind of look like:

Amp – red wire – resistor – trimpot right pin
Amp – white wire – trimport middle pin
Amp ground – 100nf cap – shieldwire
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby BATMAN87 » Wed Jul 09, 2014 8:02 pm

Wow fmlll didn't now how small the welding spot was until I had the amp open. Might leave this to the guys who now how to weld :assassin:
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tony_m » Thu Jul 10, 2014 9:08 am

It's pretty intense. That mod was my first time soldering too. I have no idea how I didn't short out everything in a 2cm radius. The heart was pounding upon reinstallation and testing :lol:
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tom_kauf » Sat Jul 12, 2014 8:33 pm

Yes, the resistor goes in line with the trimpot (either before or after). It's there so the minimum valie of the circuit doesn't go to zero, even if you turn the trimpot fully to zero.

Lol, yeah surface mount stuff is small. You need a steady hand, and a mall soldering tip. I've been soldering since I was a little kid, but even I would struggle with some of the fat soldering iron tips I see people use.
Last edited by tom_kauf on Sat Jul 12, 2014 8:37 pm, edited 1 time in total.
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tom_kauf » Sat Jul 12, 2014 8:34 pm

Double post...
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby kane2785 » Wed Oct 08, 2014 9:01 pm

I have come up with an additional Mod. for the factory McIntosh amps also.

According to this site http://jeremy.geek.nz/2010/06/17/mcintosh-ef-1080i-information/, and my own observations, the amps are based on ST TDA729* series amplifiers. These can do up to 60W music power (for the TDA7296). However this does depend on the voltage available to the amplifier.
McIntosh has set the internal supply rails to +/-26V. This is on the safe side of the amplifiers, and as the maximum is +/-35V (TDA7296).
I have increased the voltage to the amplifiers, to 29.5V. This allows more 'Swing' on the output before clipping, and allows additional power output.
The mod is very simple. A 50k ohm resistorhttp://www.altronics.com.au/p/r7599-51k-0.25w-metal-film-resistor-pk-10/ between pins 1&7 of IC601 as found in this service manual:https://nzlamb.files.wordpress.com/2010/06/ef-1080i-c.pdf
I used 2 100k resistors in parallel. A 47K resistor will be ~30V, 51K ~ 29V
I don't think the power supply will be able to do much more than +/-30V with a battery voltage below 13V. The OEM configuration could not maintain +/-26V below 12.5V input.
Bench testing on PSU duty cycle doesn't change much from the original.

The increased voltage available to the amplifiers will mean that they dissipate more power. Power= Heat=Bad. So if you want to run the amplifier with this mod continuously, buy a bigger after market one. However if your music has a large dynamic range, and you were clipping in the louder sections, this might mean you will not risk destroying the speakers due to clipping.
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby tom_kauf » Wed Oct 08, 2014 11:55 pm

kane2785 wrote:I have come up with an additional Mod. for the factory McIntosh amps also.

According to this site http://jeremy.geek.nz/2010/06/17/mcintosh-ef-1080i-information/, and my own observations, the amps are based on ST TDA729* series amplifiers. These can do up to 60W music power (for the TDA7296). However this does depend on the voltage available to the amplifier.
McIntosh has set the internal supply rails to +/-26V. This is on the safe side of the amplifiers, and as the maximum is +/-35V (TDA7296).
I have increased the voltage to the amplifiers, to 29.5V. This allows more 'Swing' on the output before clipping, and allows additional power output.
The mod is very simple. A 50k ohm resistorhttp://www.altronics.com.au/p/r7599-51k-0.25w-metal-film-resistor-pk-10/ between pins 1&7 of IC601 as found in this service manual:https://nzlamb.files.wordpress.com/2010/06/ef-1080i-c.pdf
I used 2 100k resistors in parallel. A 47K resistor will be ~30V, 51K ~ 29V
I don't think the power supply will be able to do much more than +/-30V with a battery voltage below 13V. The OEM configuration could not maintain +/-26V below 12.5V input.
Bench testing on PSU duty cycle doesn't change much from the original.

The increased voltage available to the amplifiers will mean that they dissipate more power. Power= Heat=Bad. So if you want to run the amplifier with this mod continuously, buy a bigger after market one. However if your music has a large dynamic range, and you were clipping in the louder sections, this might mean you will not risk destroying the speakers due to clipping.

Sweet!! :D Love it - I'll be doing this on top of the other mod I've done. Because even though my custom 10" sub box will help with the lack of bass, I've always turned the volume up to over 75% of its maximum to get decent volume (and that's not even loud, that's just a medium level at highway speeds).
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby Ric B » Wed Oct 15, 2014 10:34 pm

Great Work!

I found this very informative and will give the sub mod a go.
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Re: [How-To] McIntosh EF-1208I Sub Gain Mod

Postby wastegate » Mon Nov 24, 2014 9:34 pm

I managed this mod on the weekend.

Amp is a EF-1208l out of a '06 SpecRB Wagon, the R519 resistor is a 6.8K. I used a 10k resistor base with the trim pot anyway. Even with just the 10k there is noticeable gain increase. Don't want to go too high as it's still only the stock sub.
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