Vox Escort Lead 50 repair/tone problems

[OwenM]

OK thanks...

Here you go, the ceramic disk caps on the top right of the component side and on the board underside are labelled 221g which I think is 220pf?

[dmeek]

Here it is

https://music-electronics-forum.com/...1&d=1561387226

[panzer6slayer]

[ATTACH=CONFIG]53958[/ATTACH][ATTACH=CONFIG]53959[/ATTACH][ATTACH=CONFIG]53960[/ATTACH][ATTACH=CONFIG]53961[/ATTACH]

Here's some shots, the wires and 100k resistor on the 'low' pot are off on these photos.The 'high' tip goes to the 10n chicklet and the 'low' tip goes to the 470n chicklet.

The 'high' channel seems to go through the 10n chicklet followed by the .022 green cap, the 'low' through a 470n chicklet then a 22k (I think?) resistor... then they meet...

So Hi there. I am new here. I bought a Vox escort 50 Lead 1 mount ego. It seems like potantiometer were changed. Also I would like to de-activate drive so I can use my pedals on a clean channel. Do you know what is RC4136DB? I don't understand electronics and in this point I need Your help to arrange clean tone for thıs amp. Please help me for that because there is nothing on internet for this amp.

[OwenM]

Hi there, there's no way to deactivate drive on this amp as far as I know, it has only one channel with the 'volume' control working much like a gain control on most other amps, and a master volume. The cleanest it will go is if you turn the volume knob down low and then compensate by turning up the master volume. I don't see how you could easily modify the circuit in any way to get it cleaner... But that said, my pedalboard sounds fine on it at these cleaner settings.

If you use a buffered pedal at some point in your chain that would be good, as it will avoid having to do the mod that I did to mine, in order to get a proper input impedance. When I tried mine with a buffer it sounded fine!

The IC RC4136DB is a chip (IC) containing 4 op amps. One of these op amps is used on the input volume, one on the master volume and the others for the eq and some other intermittent stage (see Dmeeks schematic, post #47).

[panzer6slayer]

Hi there, there's no way to deactivate drive on this amp as far as I know, it has only one channel with the 'volume' control working much like a gain control on most other amps, and a master volume. The cleanest it will go is if you turn the volume knob down low and then compensate by turning up the master volume. I don't see how you could easily modify the circuit in any way to get it cleaner... But that said, my pedalboard sounds fine on it at these cleaner settings.

If you use a buffered pedal at some point in your chain that would be good, as it will avoid having to do the mod that I did to mine, in order to get a proper input impedance. When I tried mine with a buffer it sounded fine!

The IC RC4136DB is a chip (IC) containing 4 op amps. One of these op amps is used on the input volume, one on the master volume and the others for the eq and some other intermittent stage (see Dmeeks schematic, post #47).

So thank you for answer. I made a little search about op amps and I see this is just a regular op amp but the companents arround this op amp actualy make the audio distorted. So need master look for calculation of output signal so I can find the correct companents to remove and I will have the clean audio I guess. I am hoping that I will find any solution otherwise I cannot use this amp normally. Or maybe I can craft a basic clean amp and plug it the original speaker. Thank you much and best regards.

[OwenM]

So, does your amp distort too much for you, even when the volume control is set to very low? There are only resistors (and pots), capacitors and opamps in the preamp. Resistors and capacitors don't 'distort' as such, they burn up if they are pushed too hard, but they don't cause any kind of audio distortion in normal circuits. It's the op amp distorting, and those other components are setting how the op amp is driven. You should be able to get the opamps working in it's clean range very easily by turning the 'volume' (the one that should be labelled gain) down. Removing other components (if you could find ones that gave the desired result) would just be achieving the same thing as turning the volume down, if you were lucky, but would almost certainly have other bad consequences! I can't see an obvious mod that would get the first opamp in it's 'non-distorted' range that would be any more effective than just turning down the volume. There are a tonne of others here who know many times more than me, however.

If your amp is still very distorted on a low volume setting (that's knob on the right, not the master volume on the left, this amp is all backward!), then I would suggest that something is wrong and it's time to think 'repair' rather than 'mod'.

[panzer6slayer]

So, does your amp distort too much for you, even when the volume control is set to very low? There are only resistors (and pots), capacitors and opamps in the preamp. Resistors and capacitors don't 'distort' as such, they burn up if they are pushed too hard, but they don't cause any kind of audio distortion in normal circuits. It's the op amp distorting, and those other components are setting how the op amp is driven. You should be able to get the opamps working in it's clean range very easily by turning the 'volume' (the one that should be labelled gain) down. Removing other components (if you could find ones that gave the desired result) would just be achieving the same thing as turning the volume down, if you were lucky, but would almost certainly have other bad consequences! I can't see an obvious mod that would get the first opamp in it's 'non-distorted' range that would be any more effective than just turning down the volume. There are a tonne of others here who know many times more than me, however.

If your amp is still very distorted on a low volume setting (that's knob on the right, not the master volume on the left, this amp is all backward!), then I would suggest that something is wrong and it's time to think 'repair' rather than 'mod'.

Actualy when the gain nob is on the 0 position the voice cut off like nothing. I don't know if the nob is broken or is the amp work like this way? Orange amps are working like this. One you shot it the voice muted. I am living such a good country for perfect restoration but I only had the chance to have a large amp. What if I us only the original speaker with another head amp? You know google and youtube are such a marketing place and there is not enough research materials in them. So If there is someone really understand the amps please help me with that. Otherwise I just wasted some money.

[OwenM]

It doesn’t sound like you’ve wasted any money just yet.

The amp being silent with the volume knob (input gain) being turned all the way down is normal behaviour.

Put this knob a quarter turn up, that should be clean, you’ve set the first opamp to be working away from the point where it starts distorting. You can try it a little
quieter and see if that gets cleaner still, you’ll need to adjust the master volume to compensate.

This is standard behaviour for guitar amps. With the volume knob on low that’s likely to be as clean as the amp will be, you won’t get it any cleaner by modding it. If it still sounds very distorted with the volume control on low then there’s probably some kind of fault and I would take it to someone who knows how these kinds of things work.

if it’s pretty clean when low, then it sounds like it’s working fine!

They are an odd design and one that didn’t stand the test of time, it would be no major loss to run the speaker from an external head.

as mentioned, if you stick with the original amp they sound a lot better with a buffered pedal in the effects chain.