Guitar Input // Echolette M40

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Dr_J

Well-known member
Joined
Jul 5, 2011
Messages
277
Location
Germany
Hi Guys,

just a short one.
What's the difference of using PIN 3 with R=1k to ground instead of PIN 2 direct ground on connecting a guitar?
I found some adapter schematics with bridging PIN 3 and 2? Does that make sense?

Thanks &
ROCK-ON!
 

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That jack is wired to accept many different things, including true balanced sources.

If you want to use it as a guitar amp, put in a guitar jack, and wire it to the grid the usual way.
 
Thanks for the reply,

so nothing special here, just the straight way - good to know.  :)

THANKS,
ROCK-ON!
 
I have one and it sounds realy good on manny things.
LF hum is huge on mine. Even with the inputs all down.
I looked at the filter caps but their values are allready bigger than what the rectifier datasheet states as maximum.

best,
S.
 
DerEber said:
LF hum is huge on mine. Even with the inputs all down.
I looked at the filter caps but their values are allready bigger than what the rectifier datasheet states as maximum.

Well, are they OK then? If not, replace them with original values (shouldn't exceed the ratings for the EZ81's, also a potential problem).
Have you checked bias? These machines are rather quiet when healthy.

I would also change all of those ERO coupling caps. They tend to be very leaky. Naturally, same goes for the small decoupling electrolytics.

I have had a couple of M40's. They can be nice, for sure, but are really crappy when it comes to build quality IMHO.
 
Hey.

Well the EZ81 datasheet says 50uF maximum and 2x 150-2x310 Ohm series protection resistors.
My M40 schematic says 2x 32uF and does not show series resistors.
I substituted with 2x47uF...... so I am literally over maximum. But well.... it still runs :D

I haven´t messed with the bias yet..... well tubes are quite old. It would anyway probably make only sense with a new set
of tubes.
Maybe new tubes mtach better and cancel out LF hum in the output transformer?

I also changed the other two filter caps to new ones.

I really like the sound of this amp, so I decided to leave any audio caps until they break down. Could happen any day.  ;)
Sometimes the unit powers up with big noise. After 10 Minutes it´s ready to go.
And it´s still fine for most recording situations. I remember only one time where I needed to use a 100Hz notch in the end.

I recorded some samples:
This is the noise sample:
https://soundcloud.com/dereber/m40-noisetest/s-ilx8V

And here is one with both, the wurlizer and the guitar, going to the M40
https://soundcloud.com/dereber/panorama-studiojam-05-track05

I could search the recording having the big hum.... but maybe this is enough.

best, Stephan
 
DerEber said:
btw. I need for a similar unit 500V 16uF with the same mount (M18?). I can´t get right F&T Caps from my store.
Any hints?

Hm, that might be something Frag´ Jan Zuerst (http://www.die-wuestens.de/) have in stock, but it might be a little more expensive.  :-\

I would check bias. Really. You sholdn't have any notable LF hum. Could be the decoupling electrolytic in the bias circuit. Well, anything really.
I take it you don't wanna mess around with it too much because you like the sound, but keep in mind that the ERO/EROID capacitors are well known trouble makers.
 
Hi,

good to see there are some M40 around here...

Sound is great! Paints a big  ;D on my face...

Well i wouldn't call my M40 dead quit, but it's ok so far. I just bought it a few weeks ago, so i'm still testing, e.g. building
a proper adapter wire. Next thing is to build one of these "magic loop cables" for more GAIN  ;D  ;D
For that i'm not sure what's the better way, using the tape out (back side) or the front side EINGANG/AUSGANG DIN Plug-in??
Maybe we can use this threat although for some discussion about that?!

@L´Andratté: If it's a one with 6.3 jacks and ptp, than it must be an earlier one than 1964?!

I friend of mine has a BS40, maintained by TONEHUNTER; great machine!! Definitely the next one I'll buy...

Currently I'm not sure if I'll bring my M40 to TONEHUNTER... I'll have to play it a bit more and then we will see...
Repairing tube-amps is no fun for me, so i'll leave that to a really pro one  ;D

ROCK-ON!  ;D
 
Oh man, time flies by...
Meanwhile I had my M40 @TONEHUNTER for a little maintenance. Ralf did a great job, now it's dead quiet, sounds great and is running fine.  Lot of fun to play :)

A few day ago I came back to my plan to build a "Overdrive Loop Cable" like this one:
https://youtu.be/nPSYoHquBlQ


On my first prototype I used the "Tape Out" bridging Pin 1 & 3 to Input Pin 1, which works so far.
On all examples I found, they did a loop back to 2 Input Channels.

Could I just split the output to 2 input channels? (Dotted lines)
Or is there something to take care of? (Adding resistors due to impedance?)

Any suggestions on using "AUSGANG III" instead of "Tape Out"?
What about using Pin 3 here? (or 4 / 5??)


ROCK-ON!

 
So,

i did some more little tests, using the BAND AUSGANG works (sounds) quit well.

Playing around with AUSGANG III was not satisfying.
Can anybody explain the pin out of AUSGANG III, what was it made for?

Would be great to know! Thanks!

ROCK-ON!
 
Dr_J said:
So,

i did some more little tests, using the BAND AUSGANG works (sounds) quit well.

Playing around with AUSGANG III was not satisfying.
Can anybody explain the pin out of AUSGANG III, what was it made for?

Would be great to know! Thanks!

ROCK-ON!

The „Ausgang III“ is made specifically for Echolette tape-echos like NG51/ E51. The pinning is differend from e.g. Dynacord`s. The signal is taken out from pin 4 and the echoed signal from NG51/E51 is taken back through pin 3. The dry signal(„original signal) is taken back through pin 5.
I agree, that the Band Ausgang sounds well, but the sound gets too noisy fror some reason.  I guess it`s due to the two amplification stages, because it surely is not a grounding issue, as I tried out all the possible options.  I havent tried for some time anymore, but my memory is, that Ausgang III was quieter, though not really quiet either. Splitting into two channels reduces the noise slightly too.  The issue is that you cannot turn the master-volume up much without getting too much noise. I would be happy if I would be proved to be wrong about that noise.
 
Thanks

alot panman for the reply!

Now AUSGANG III makes a bit more sense to me.
But i'll think there's a typo in your post concerning PIN 5, isn't it?
So i can take PIN 4 as an output and loop it back through EINGANG, can't I?

Talking about noise level, when using BAND AUSGANG there isn't much more or annoying noise on my setup. Well I just cranked up the loop input half (Master Volume @1/4 maximum: hell loud  ;D) and then there's a little floor noise of course, but it's ok (for me).

ROCK-ON.
 
Dr_J said:
What's the difference of using PIN 3 with R=1k to ground instead of PIN 2 direct ground on connecting a guitar?
I found some adapter schematics with bridging PIN 3 and 2? Does that make sense?
At the time, many microphones were bi-impedance; the low-Z was on Pin 3 and High-Z on Pin 1. With this connection, teh microphone is properly loaded, with 1k on its low-Z output, and the high-Z output is rightly connected to teh high impedance of the grid.
 
Dr_J said:
But i'll think there's a typo in your post concerning PIN 5, isn't it?
So i can take PIN 4 as an output and loop it back through EINGANG, can't I?

Ihave corrected the typo on my posting.
And  yes, Pin 4 as an output and back through Eingang should work. Well, that is if you don`t use the NG51/E51 connected to the Ausgang III. And don`t forget to pull out the original channel-button to switch on the Ausgang III.

The previous pinning was taken from "Service Manual Klemt Echolette M40. There is also some contradicting  pin-info for "Ausgang III"from "Bedienungsanleitung Klemt Echolette M40":

Stift 1+3=Original-und Echo-Signal für NG 51
Stift 2=Abschirmung/Masse
Stift 4=Originalsignal vom M40 zum NG 51(echo-send)
Stift 5=Echo-Signal vom NG 51(echo-return)

I don`t have time to check out which one is right, but maybe someone will do that.

 
THANKS a lot for the information.

I'll do some tests on AUSGANG III again as soon as i've got time.

@panman: Do you have the manuals as digitals?

ROCK-ON!
 
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