EH Electric Mistress volume drop

CB Amp · 08-25-2009, 02:45 PM

Hello,

I've got an original Electro Harmonix Electric Mistress (1980). I love its sound, but I hate the volume drop when the effect is ON.

I had a look on the web to learn more about it, but I did not find anything. I know that Howard Davis offers this mod, but I'd prefer to do it myself (I live in Europe, shipping is complicated and expensive).

Does anyone knows the mod which can increase the effect volume ?
Thank you.

CB Amp · 08-25-2009, 02:46 PM

Here is the schematic :

cbarrow7625 · 08-25-2009, 08:01 PM

There has to be a gain adjustment in that SAD 1024 somewhere (he says without really knowing if that is true). Here is a link to the data sheet, maybe you (or someone else here) can have a look and figure out how to do it:

http://www.synthdiy.com/files/2003/SAD512-1024.pdf

cjlectronics · 08-27-2009, 03:57 PM

I'm not sure what Howard does to increase the gain, but in other SAD1024 circuits, there is a gain stage (op amp) after the BBD. Looking at the spec sheet for the SAD1024, the gain is based on the load resistance. This makes me think that whatever you're using after the Electric Mistress (this particular circuit) will affect the volume.
The easy answer maybe to put a boost pedal after the EM like an MXR Micro Amp.
The more involved answer would be to wire in a single op amp gain stage.
The in between answer would be to change one of the 10k resistors on the output stage and see if this makes a difference.

This sounds like fun CB Amp... let me know what you find out.

CJ

CB Amp · 08-27-2009, 08:55 PM

Thanks for your replies.
As a matter of fact, the deluxe EM has an op amp stage after the SAD1024...

I tried to change the 10k and 13k resistors (I used trimpots to adjust the level). It increases the volume a bit, but not significantely... It more changes the spectral response, giving it more mids and high mids.

I wonder whether I can increase the gain before the SAD1024, at the second part of the 4558... ?

cjlectronics · 08-28-2009, 01:45 PM

Yes, the Deluxe EM has a gain stage after the BBD and this is one reason I mentioned wiring an op amp stage after it. Just copy the circuit from the deluxe.

You could probably increase the signal going into the BBD a little but be careful not to drive the SAD1024 into distortion. The spec sheet for the SAD1024 should tell you the maximum signal level it'll handle before clipping occurs. My guess is its already close to the maximum.

I've repaired a few EM's just like yours and they all had a low volume problem...or I should say that has been the complaint.

Jilka · 11-11-2009, 05:56 PM

Quote:

Originally Posted by CB Amp

Hello,

I've got an original Electro Harmonix Electric Mistress (1980). I love its sound, but I hate the volume drop when the effect is ON.

Does anyone knows the mod which can increase the effect volume ?
Thank you.

I just fixed standard non-deluxe electric mistress.
It was completely damaged, without any jacks, wires, switches.
I replaced all IC's and re-wired whole stompbox.
I noticed not only the volume drop but also a low frequency drop.
It's almost impossible to use with a fuzz or big muff...
Is it common for all non-deluxe electric mistresses?

Thanks, Alexander

CB Amp · 11-12-2009, 10:30 AM

Hi Alexander,

There is no low freq drop with my EM. On the contrary, it has a full rich sound, especially in the lower range...

Since my firsts posts on this thread, I've found some other EM and vintage EH pedals (Deluxe EM, Echoflanger, Polyphase, Clone Theory...). And for me, the vintage EM (non deluxe) has the best flanger effect, and the deeper one.
I read that some people try to mod the Deluxe models to have more trebble, as in the standard ones. It's true that the deluxe has different treble, but also less bass...

Anyway, there is perhaps a problem in one of your components. And I also saw that there was some different circuits for the standard EM, with a few components changes. Are the input and output capacitors ok ? they do a lot on the range.

Cyril.

Jilka · 11-12-2009, 11:00 AM

Cyril,

Thank you very much for reply!
Yes, exactly, I saw many versions of the green 18v non-deluxe mistress...
I have schematic for version that I own, it looks exactly like this:

http://img357.imageshack.us/img357/5...tressukhq5.jpg

So, input capacitor is 0,1 uF. Could you please tell me what is your version?
I just worry that i made a mistake somewhere...

By the way, you can see very strange bypass wiring, that goes from pin 6 and 7 of jrc4558 through 10 uF cap. I decided to use DPDT Switch for true bypass straight from input to output without connecting this 10 uF cap.

CB Amp · 11-12-2009, 01:41 PM

Be careful !! you have to connect this 10µ cap !
It stops the DC voltage that comes out of the buffer. If there is no cap, you feed the amp or the next pedal with DC voltage, which is not good.

The bypass wiring is not strange, this is a normal buffer. The signal passes throught it in bypass or non-bypass mode (this is why it's not a true bypass switching). There is not gain in it (= 1), that's a part of the problem of the volume drop.

My first pedal (1980) has the same circuitry, with a 0.1µ input cap. There should be another problem in your wiring or PC board...

Jilka · 11-12-2009, 02:36 PM

Cyril, no didn't remove that cap. I wired dpdt switch like this:

i think I'm gonna wire it as the original, non true bypass.
no need to mess up with the historical stompbox...

CB Amp · 11-12-2009, 09:41 PM

hmm, your schem is strange... you have to wire the switch this way :

It means :

Input cap (0.1µ) <----o o<----- (13K+10K+470)
____ Input jack >-----o o------> Output jack
___________________ o-o

The arrows represent the path of the signal, the underscores are just here to line up the 6 lugs of the switch on the drawing...

Jilka · 11-16-2009, 10:15 PM

thank you, Cyril!

I tried to use with my friend's mistress with es-335 and it's okay, sounds really good!
I think my strat is too bright to use with it...

now i'm ready to build my own electric mistress...

Jilka · 11-30-2009, 12:19 PM

Blonde Graimey posted a new vid about Standard Electric Mistress.

And explained mod to solve volume drop problem

YouTube- Electro Harmonix Electric Mistress Vintage

08-25-2009, 02:45 PM	#1
CB Amp Junior Member Join Date: Feb 2009 Location: France Posts: 9	EH Electric Mistress volume drop Hello, I've got an original Electro Harmonix Electric Mistress (1980). I love its sound, but I hate the volume drop when the effect is ON. I had a look on the web to learn more about it, but I did not find anything. I know that Howard Davis offers this mod, but I'd prefer to do it myself (I live in Europe, shipping is complicated and expensive). Does anyone knows the mod which can increase the effect volume ? Thank you.

11-12-2009, 02:36 PM	#11
Jilka Junior Member Join Date: Nov 2009 Location: Moscow, Russia Posts: 8	Cyril, no didn't remove that cap. I wired dpdt switch like this: i think I'm gonna wire it as the original, non true bypass. no need to mess up with the historical stompbox... Last edited by Jilka; 11-12-2009 at 03:12 PM.

11-16-2009, 10:15 PM	#13
Jilka Junior Member Join Date: Nov 2009 Location: Moscow, Russia Posts: 8	thank you, Cyril! I tried to use with my friend's mistress with es-335 and it's okay, sounds really good! I think my strat is too bright to use with it... now i'm ready to build my own electric mistress... Last edited by Jilka; 11-16-2009 at 10:27 PM.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Help with my new Electric Mistress	moses20	Guitar Effects	4	12-05-2008 11:44 PM
I try to repair my EH Electric mistress Flanger please help	fjgaston	Guitar Effects	0	07-15-2008 09:35 PM
Electric Mistress?	drewl	Guitar Effects	2	09-05-2007 01:47 AM
EHX Electric Mistress Repair	spiritquest	Guitar Effects	0	06-09-2007 12:42 PM
Component question on Electric Mistress	Neal	Guitar Effects	7	06-23-2006 06:21 PM

08-25-2009, 02:46 PM	#2
CB Amp Junior Member Join Date: Feb 2009 Location: France Posts: 9	Here is the schematic :

08-25-2009, 08:01 PM	#3
cbarrow7625 Senior Member Join Date: Mar 2007 Location: Philadelphia suburbs Posts: 366	There has to be a gain adjustment in that SAD 1024 somewhere (he says without really knowing if that is true). Here is a link to the data sheet, maybe you (or someone else here) can have a look and figure out how to do it: http://www.synthdiy.com/files/2003/SAD512-1024.pdf

08-27-2009, 03:57 PM	#4
cjlectronics Supporting Member Join Date: May 2006 Posts: 182	I'm not sure what Howard does to increase the gain, but in other SAD1024 circuits, there is a gain stage (op amp) after the BBD. Looking at the spec sheet for the SAD1024, the gain is based on the load resistance. This makes me think that whatever you're using after the Electric Mistress (this particular circuit) will affect the volume. The easy answer maybe to put a boost pedal after the EM like an MXR Micro Amp. The more involved answer would be to wire in a single op amp gain stage. The in between answer would be to change one of the 10k resistors on the output stage and see if this makes a difference. This sounds like fun CB Amp... let me know what you find out. CJ

08-27-2009, 08:55 PM	#5
CB Amp Junior Member Join Date: Feb 2009 Location: France Posts: 9	Thanks for your replies. As a matter of fact, the deluxe EM has an op amp stage after the SAD1024... I tried to change the 10k and 13k resistors (I used trimpots to adjust the level). It increases the volume a bit, but not significantely... It more changes the spectral response, giving it more mids and high mids. I wonder whether I can increase the gain before the SAD1024, at the second part of the 4558... ?

08-28-2009, 01:45 PM	#6
cjlectronics Supporting Member Join Date: May 2006 Posts: 182	Yes, the Deluxe EM has a gain stage after the BBD and this is one reason I mentioned wiring an op amp stage after it. Just copy the circuit from the deluxe. You could probably increase the signal going into the BBD a little but be careful not to drive the SAD1024 into distortion. The spec sheet for the SAD1024 should tell you the maximum signal level it'll handle before clipping occurs. My guess is its already close to the maximum. I've repaired a few EM's just like yours and they all had a low volume problem...or I should say that has been the complaint.

11-12-2009, 10:30 AM	#8
CB Amp Junior Member Join Date: Feb 2009 Location: France Posts: 9	Hi Alexander, There is no low freq drop with my EM. On the contrary, it has a full rich sound, especially in the lower range... Since my firsts posts on this thread, I've found some other EM and vintage EH pedals (Deluxe EM, Echoflanger, Polyphase, Clone Theory...). And for me, the vintage EM (non deluxe) has the best flanger effect, and the deeper one. I read that some people try to mod the Deluxe models to have more trebble, as in the standard ones. It's true that the deluxe has different treble, but also less bass... Anyway, there is perhaps a problem in one of your components. And I also saw that there was some different circuits for the standard EM, with a few components changes. Are the input and output capacitors ok ? they do a lot on the range. Cyril.

11-12-2009, 11:00 AM	#9
Jilka Junior Member Join Date: Nov 2009 Location: Moscow, Russia Posts: 8	Cyril, Thank you very much for reply! Yes, exactly, I saw many versions of the green 18v non-deluxe mistress... I have schematic for version that I own, it looks exactly like this: http://img357.imageshack.us/img357/5...tressukhq5.jpg So, input capacitor is 0,1 uF. Could you please tell me what is your version? I just worry that i made a mistake somewhere... By the way, you can see very strange bypass wiring, that goes from pin 6 and 7 of jrc4558 through 10 uF cap. I decided to use DPDT Switch for true bypass straight from input to output without connecting this 10 uF cap.

11-12-2009, 01:41 PM	#10
CB Amp Junior Member Join Date: Feb 2009 Location: France Posts: 9	Be careful !! you have to connect this 10µ cap ! It stops the DC voltage that comes out of the buffer. If there is no cap, you feed the amp or the next pedal with DC voltage, which is not good. The bypass wiring is not strange, this is a normal buffer. The signal passes throught it in bypass or non-bypass mode (this is why it's not a true bypass switching). There is not gain in it (= 1), that's a part of the problem of the volume drop. My first pedal (1980) has the same circuitry, with a 0.1µ input cap. There should be another problem in your wiring or PC board...

11-12-2009, 09:41 PM	#12
CB Amp Junior Member Join Date: Feb 2009 Location: France Posts: 9	hmm, your schem is strange... you have to wire the switch this way : It means : Input cap (0.1µ) <----o o<----- (13K+10K+470) ____ Input jack >-----o o------> Output jack ___________________ o-o The arrows represent the path of the signal, the underscores are just here to line up the 6 lugs of the switch on the drawing...

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)