Parallel effects loop for Marshall style amps
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Re: Parallel effects loop for Marshall style amps
Hello Larry, as noted before, the problem was infront of the amp, i just want to confirm my mistake and make sure i'm correcting it right - i have found i've switched Va with Vb on the schematic, BUT i've mixed my wires on pin's 6 and 1, so would this swithc accountfor a very highly compressed scooped mids and really overdriven sound i got? that almost seems to be independant of the send/ return levels and hihgly dependent on the master volume?
ps can you send me the schematic with the serial/ parallel switching if you have it?
Thank you!
edit: the effects of my mistake make sense to me since it seems the output of the loop came straight after a single gain stage from the amp with only the master volume and send level....
ps can you send me the schematic with the serial/ parallel switching if you have it?
Thank you!
edit: the effects of my mistake make sense to me since it seems the output of the loop came straight after a single gain stage from the amp with only the master volume and send level....
Evgeny N.
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Re: Parallel effects loop for Marshall style amps
Nice that you've found your bug!
But I can't send a schem in a PM, so you know, what still to do.
Larry
But I can't send a schem in a PM, so you know, what still to do.
Larry
The fault almost always is sitting in front of the amp
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Re: Parallel effects loop for Marshall style amps
Hello Larry,
I have put this loop in a Sovtek Tube Midget amp and it works, except for a slight hum so I must check everything again.
I have 370 Volt after the 4k7 resistor is that to high ? You mention 310 to 330 V in previous posts.
Is it necessary to shield the wire to the B+ (Uc)?
Niklas
I have put this loop in a Sovtek Tube Midget amp and it works, except for a slight hum so I must check everything again.
I have 370 Volt after the 4k7 resistor is that to high ? You mention 310 to 330 V in previous posts.
Is it necessary to shield the wire to the B+ (Uc)?
Niklas
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Re: Parallel effects loop for Marshall style amps
Grounding! Shielded signal cables!hammeron wrote:I have put this loop in a Sovtek Tube Midget amp and it works, except for a slight hum so I must check everything again.
Woo-hoo! What voltage is at the PI? Over 400V?hammeron wrote:I have 370 Volt after the 4k7 resistor is that to high ? You mention 310 to 330 V in previous posts.
So better try a 10K instead of the 4.7K, to at least come below 350V
No!hammeron wrote:Is it necessary to shield the wire to the B+ (Uc)?
Larry
The fault almost always is sitting in front of the amp
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Re: Parallel effects loop for Marshall style amps
Larry, I have gone through the loop and everything looks fine, all signal cables are grounded and I have increased the value of the 4K7 resistor and the voltage is now ok.
But I still have a very annoying hum in the amp and when I knock on the 22n coupling cap of V3b I hear the knocking sound in the speaker, all other components are quiet.
Is this normal ?
I have changed the cap and tried different tubes but no luck.
Any ideas ?
Niklas
But I still have a very annoying hum in the amp and when I knock on the 22n coupling cap of V3b I hear the knocking sound in the speaker, all other components are quiet.
Is this normal ?
I have changed the cap and tried different tubes but no luck.
Any ideas ?
Niklas
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Re: Parallel effects loop for Marshall style amps
Yes, all signal caps are more or less microphonic, ceramic caps sometimes even terrible microphonic - but this is normal!hammeron wrote:But I still have a very annoying hum in the amp and when I knock on the 22n coupling cap of V3b I hear the knocking sound in the speaker, all other components are quiet.
Is this normal ?
If your hum issue wasn't before the loop, then you've built in a ground loop in the loop circuit!
The loop related grounds have to meet all at the same spot! Grounds from the jacks & pots, from the additional filter cap, from the mixer area and from the tube's cathodes. Have you done it different?
Larry
The fault almost always is sitting in front of the amp
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Re: Parallel effects loop for Marshall style amps
Yes everything is grounded at the same place, the only thing left is that I maybe built the loop too compact, Sovtek Midget 50H is a very tiny amp so maybe the wires are to close to each other, and I have to face the fact that it never get quieter than this.
Thanks Larry
Thanks Larry
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Re: Parallel effects loop for Marshall style amps
I'm not sure which look you used, but you could try lifting the ground on the send jack by puting a 10ohm resistor from the ground tab of the jack to chassis ground. Of course for this to work the jack has to be a Cliff or other insulated jack.
I also don't know if this has been mentioned, but the shield of the FX cables should only be connected at one end.
I also don't know if this has been mentioned, but the shield of the FX cables should only be connected at one end.
Richard Johnson
Playing an instrument doesn't make you a Musician ... Listening does...
Playing an instrument doesn't make you a Musician ... Listening does...
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Re: Parallel effects loop for Marshall style amps
Hi Larry. Is it too late to request a schematic?
Thanks!
Thanks!
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Re: Parallel effects loop for Marshall style amps
No, not too late.Just Mike wrote:Hi Larry. Is it too late to request a schematic?
But I can't send a pdf file in a PM
Larry
The fault almost always is sitting in front of the amp
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Re: Parallel effects loop for Marshall style amps
Larry
Can I get a copy? PM sent.
Russell
Can I get a copy? PM sent.
Russell
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Re: Parallel effects loop for Marshall style amps
Russel, hope the following will answer your request. It's written in the 1-st post of this topic.
Larry
Sorry, but too many have joined here in the past, just to request the schem - and after they got it, they never were seen again on the board.novosibir wrote:Yes - it's for Metro board members only!
The only I'm expecting from you is:
- a Metroamp membership of at least 3 months
- a minimum post count of 10
- that you keep it for your personal use
- and that you don't forward the schematic to anybody else
Larry
The fault almost always is sitting in front of the amp
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Re: Parallel effects loop for Marshall style amps
Larry, I was registered at a forum to receive the FX loop scheme which here so praise. I simply read before.
I from Russia. It is very difficult to me to communicate as I badly know English language. I know technical English language is even worse.
At a forum basically copies are discussed. And almost nobody tries to make something new. For example a theme from me http://forum.metroamp.com/viewtopic.php" onclick="window.open(this.href);return false;? f=7&t=29444 has not caused interest and discussions.
On asked by a question in a theme about a FX loop the scheme is almost clear.
The rest can be found out by means of personal messages. Asking a question: "Can it is necessary to increase the condenser to 2 µF?" And further questions of the same maintenance.
On the basis of answers of participants it is possible to restore the scheme completely. I think, it will be not fair in relation to you and your work. I do not wish to make a detour to try new realisation of a FX loop in the amplifiers.
Yours faithfully, Evgenie.
I from Russia. It is very difficult to me to communicate as I badly know English language. I know technical English language is even worse.
At a forum basically copies are discussed. And almost nobody tries to make something new. For example a theme from me http://forum.metroamp.com/viewtopic.php" onclick="window.open(this.href);return false;? f=7&t=29444 has not caused interest and discussions.
On asked by a question in a theme about a FX loop the scheme is almost clear.
The rest can be found out by means of personal messages. Asking a question: "Can it is necessary to increase the condenser to 2 µF?" And further questions of the same maintenance.
On the basis of answers of participants it is possible to restore the scheme completely. I think, it will be not fair in relation to you and your work. I do not wish to make a detour to try new realisation of a FX loop in the amplifiers.
Yours faithfully, Evgenie.
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Re: Parallel effects loop for Marshall style amps
Hi! I installed the Larry loop (using Rockstahs layout) to my JTM45 clone and it works perfectly! This is a really great loop! Now I tried to install it to my SLOclone as well but I´m having problems. I want to install the loop between tone stack and master volumes. Here´s a picture where and how I installed it: http://s51.photobucket.com/albums/f358/ ... ysloop.jpg" onclick="window.open(this.href);return false;
I tried the loop but I get a huge amount of hum when having treble pot at 1-9. At 0 and 10 there isn´t any hum and the loop works perfectly. Do I have a ground problem or something else?
Thanks for the help!
-Matti
I tried the loop but I get a huge amount of hum when having treble pot at 1-9. At 0 and 10 there isn´t any hum and the loop works perfectly. Do I have a ground problem or something else?
Thanks for the help!
-Matti
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Re: Parallel effects loop for Marshall style amps
First you should remove the orig. Soldano loop entirely.
Then run from V3A's cathode directly into the tone stack - from beyond R25!
Remove C12 - go directly from the cathode into the tone stack.
And then you must run all grounds of the loop section to the ground connection of that filter, from which the loop's tube is fed - and your hum probably will disappear.
Larry
Then run from V3A's cathode directly into the tone stack - from beyond R25!
Remove C12 - go directly from the cathode into the tone stack.
And then you must run all grounds of the loop section to the ground connection of that filter, from which the loop's tube is fed - and your hum probably will disappear.
Larry
The fault almost always is sitting in front of the amp
Larry's Website now with included Pix's Gallery
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