EHX - Big Muff Pi 2007  [schematic]

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Post by Bernardduur »

Today I got a 2007 EHX Muff in and yes, again, they differ from all the before models :)

So, for the persons who like to complete their collection, here's the schematic

Linkie

Transistors are BC550's; diodes are 1N4148's
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Post by analogguru »

It´s funny that after more than 35 years of BigMuff history it appears that the people at EH can´t stop to tweak around with this circuit....

But because it is Christmas I will tell you a "secret":
The 2007 Version is nothing else than "back to the roots" and the component values are the same as used one the first prototype(s) Triangle-Muffs which were build on perfboard. You have seen the guts ?

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Post by Bernardduur »

analogguru wrote:It´s funny that after more than 35 years of BigMuff history it appears that the people at EH can´t stop to tweak around with this circuit....

But because it is Christmas I will tell you a "secret":
The 2007 Version is nothing else than "back to the roots" and the component values are the same as used one the first prototype(s) Triangle-Muffs which were build on perfboard. You have seen the guts ?

analogguru
Cool!

The build quality was OK although I really disliked the solder used and the ribbon cable that connected the switch with the PCB; that was the reason it came to me as these points were damaged
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Post by bumblebee »

my favorite muff is the current (06 PCB) model, its probably the same as this.

i dont like the rams head,its muddy,or the russian,its weak and poorly made.
one fault i find with EH TH PCB's is that the trace is very thin and breaks easy if you wana mod it,my bmp looks more like its been built on perf with all the repairs ive done to the traces due to modifying it.

the SMD PCB's look and feel real good though!

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Post by Meanderthal »

Hey, this does look different. This is the new NYC version? I haven't seen those 0.47uf decoupling caps at the input and the in of the last gain stage before... interesting. I wonder if that's enough to tame the usual mud... probably for some amps... and all those 10k resistors remind me of the Russian ones... mid notch shouldn't be too extreme with those tonestack values.

Thanks!

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Post by Bernardduur »

I also wondered about the 500k log pot as the volume pot; would this change anything when compared to a 100k log pot there (as in all the other versions)??
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Post by bajaman »

I also wondered about the 500k log pot as the volume pot; would this change anything when compared to a 100k log pot there (as in all the other versions)??
It will roll off some more highs - less fizzy sounding :wink:
bajaman

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Post by Bernardduur »

bajaman wrote:
I also wondered about the 500k log pot as the volume pot; would this change anything when compared to a 100k log pot there (as in all the other versions)??
It will roll off some more highs - less fizzy sounding :wink:
bajaman
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Post by Zztop128 »

I've a BMPi from 2004 and all pots are 100k, so it would be interesting to replace the volume pot with a 500k.... Another mod to do 8) 8)
But first I'm working on my LDO and SHO clone :D

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Post by patafix »

bajaman wrote:
I also wondered about the 500k log pot as the volume pot; would this change anything when compared to a 100k log pot there (as in all the other versions)??
It will roll off some more highs - less fizzy sounding :wink:
bajaman
I think it would be the opposite !!!!

As in guitars, the higher the value, the higher the output level and the highs.

Maybe I'm wrong ???
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Post by bajaman »

think it would be the opposite !!!!

As in guitars, the higher the value, the higher the output level and the highs.

Maybe I'm wrong ???
yes you are wrong - because you will unlikely be running the output level on full and the larger series resistance will roll off more highs in conjunction with the input capacitance of the proceeding stage.
Try turning your guitar volume 500k pot down to half way and listen to the loss of highs (unless you have a treble bleed bypass capacitor fitted to your poti). :wink:
bajaman

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Post by Pippuz »

But this not change with other pedal in the audio chain?
It's not better to filter off some highs with a capacitor from output to ground?

Another question... I have a small clone and it have a 47ohm resistor between the - of the power jack and circuit ground..

can be this the definitive cure for ground loops problem?

bajaman wrote:
think it would be the opposite !!!!

As in guitars, the higher the value, the higher the output level and the highs.

Maybe I'm wrong ???
yes you are wrong - because you will unlikely be running the output level on full and the larger series resistance will roll off more highs in conjunction with the input capacitance of the proceeding stage.
Try turning your guitar volume 500k pot down to half way and listen to the loss of highs (unless you have a treble bleed bypass capacitor fitted to your poti). :wink:
bajaman

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Post by Dirk_Hendrik »

bajaman wrote:your poti
Since when did you change over to German terminology !!?? :shock:
Sorry. Plain out of planes.

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Post by bajaman »

Since when did you change over to German terminology !!??
:slap: :lol:
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Post by Bernardduur »

YES! They do it again! The 2008 model??? Again one with changes from the 2007 model

Linkie

Transistors are BC550C's, diodes 1N4148's....... all caps ELCO's except for the tone stack which are ceramics

Sounds even worse :)
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Post by AL »

Bernardduur wrote:Sounds even worse :)

:lol:

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Post by Rocket Roll »

Just in case, here's the board:
IMG_0002.jpg
IMG_0008.jpg
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Post by cctsim »

I have this one too. Totally useless. I had to change all 1uF electrolytics to 0.1uF ceramics to remove all the excessive bass.
Now it sounds ok-ish.

The pcb is for sure not suitable for modifications, even with moderate heat I managed to damage it.

There are also a few electrolytic caps (2 220uF and one 2.2uF) that I have not seen in previews schematics.

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Post by bumblebee »

The schematic of this is already posted in this forum some place.
Thanks for the pics though, this is the onyl modern muff i dont yet own.

BTW, some of these come with a blue PCB.

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Post by cpm »

i dindnt have much problems when soldering on the board, not great quality, but not terrible.

some 1uFs must be changed into 100n definitely.
those 2 100R+220uF filters dc nicely

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