I have a Engl 530 preamp.
It's a 4 channel guitar preamp with 2 ecc88 tubes inside.
The first 2 channels have a "fender type" eq before the main distortion tubes, the other channels have a "marshall type" eq after the distortion tubes.
What I don't like is the sound of the high gain stage. And imo it can be made a lot more versatile.
So what I've done is changed the high gain stage. It was a normal anode follower with 330k anode resistor and 3k3 kathode resistor bypassed with a 20uF cap. It's the 3th stage in the schematic (the schematic is only a very rough guide to what it really is!) I've changed it to a 120k anode resistor and a 1k kathode resistor bypassed with a 20uF cap. This is a place where you can experiment a lot, so it suites your taste.
An other thing I've done is use both eq's for the higher gain channels. This makes it way way more flexible in sound sculpting for distortion sounds.
It's just a wire from the output of the first eq to the gain pot of the higher gain channels, and I had to remove a 100k resistor between the first and second stage that is not in the schematic.
To do: Set the marshall type eq behind the cleaner channels. This is more difficult to do as there are 2 relay's and 2 circuitboards for this.
Any suggestions?
P.s. somehow I couldn't add the schematic and picture of the mods I've done, but it's not difficult to figure out (even I could do it).
It's a 4 channel guitar preamp with 2 ecc88 tubes inside.
The first 2 channels have a "fender type" eq before the main distortion tubes, the other channels have a "marshall type" eq after the distortion tubes.
What I don't like is the sound of the high gain stage. And imo it can be made a lot more versatile.
So what I've done is changed the high gain stage. It was a normal anode follower with 330k anode resistor and 3k3 kathode resistor bypassed with a 20uF cap. It's the 3th stage in the schematic (the schematic is only a very rough guide to what it really is!) I've changed it to a 120k anode resistor and a 1k kathode resistor bypassed with a 20uF cap. This is a place where you can experiment a lot, so it suites your taste.
An other thing I've done is use both eq's for the higher gain channels. This makes it way way more flexible in sound sculpting for distortion sounds.
It's just a wire from the output of the first eq to the gain pot of the higher gain channels, and I had to remove a 100k resistor between the first and second stage that is not in the schematic.
To do: Set the marshall type eq behind the cleaner channels. This is more difficult to do as there are 2 relay's and 2 circuitboards for this.
Any suggestions?
P.s. somehow I couldn't add the schematic and picture of the mods I've done, but it's not difficult to figure out (even I could do it).
I've done some more experimentations.
And I've got my hands on the correct schematic. As far as I could check it, this is the correct one. Thank you Mr Gishian!
In the attachments are the mods.
Everything in red is what I've settled on with my experimentations.
It now has 2 EQ's on every channel. This is what makes IMO the biggest difference, being able to control how much bass mid and treble go into the distortion stages is so useful/versatile that I now wonder why not every instrument amp has it.
The other major improvement was the 1nF bypass cap to the 3th stage. This is the high gain stage and that sounded really thin to me.
The other mods are optional IMO, I don't have a guitar and use line level signals. These mods are there so the bypass levels are the same as the processed levels. If you use guitar, these mods may not be useful.
What did I try and didn't make it in the final mods:
For the third stage I tried the JCM800 100k anode and 10k non bypassed cathode resistors. The SLO100 with the 39k cathode resistor didn't make it either. The standard 100k/1k5 combo with bypass caps didn't work.
So I finally settled on the original setup, that sounds good enough for me.
If someone has any suggestions, please let us know.
Best Bill.
And I've got my hands on the correct schematic. As far as I could check it, this is the correct one. Thank you Mr Gishian!
In the attachments are the mods.
Everything in red is what I've settled on with my experimentations.
It now has 2 EQ's on every channel. This is what makes IMO the biggest difference, being able to control how much bass mid and treble go into the distortion stages is so useful/versatile that I now wonder why not every instrument amp has it.
The other major improvement was the 1nF bypass cap to the 3th stage. This is the high gain stage and that sounded really thin to me.
The other mods are optional IMO, I don't have a guitar and use line level signals. These mods are there so the bypass levels are the same as the processed levels. If you use guitar, these mods may not be useful.
What did I try and didn't make it in the final mods:
For the third stage I tried the JCM800 100k anode and 10k non bypassed cathode resistors. The SLO100 with the 39k cathode resistor didn't make it either. The standard 100k/1k5 combo with bypass caps didn't work.
So I finally settled on the original setup, that sounds good enough for me.
If someone has any suggestions, please let us know.
Best Bill.
Attachments
I don't use this thing in a life situation.
But if I did, I would add an resistor between the 680pF cap and RE1.1, as the 3th channel is louder in level as the high gain channel.
But if I did, I would add an resistor between the 680pF cap and RE1.1, as the 3th channel is louder in level as the high gain channel.
Lowering the second stage's plate to 82k cleans up the lead channel without reducing the gain. as for the 330k 3k3 stage, I'd reduce it to 220k with a different cathode resistor.
Thanks.
I'll try the 82k anode resistor.
I did experiment a lot with stage 3, including what you mentioned, but the original configuration sounds best to me.
I'll try the 82k anode resistor.
I did experiment a lot with stage 3, including what you mentioned, but the original configuration sounds best to me.
The 82k is a keeper.
There's more balance between the channels, going from clean to relatively high gain.
Question:
Can you replace the 1nF cap I used in the 3th stage with a 1M pot, so you can adjust the amount of bass going into it?
There's more balance between the channels, going from clean to relatively high gain.
Question:
Can you replace the 1nF cap I used in the 3th stage with a 1M pot, so you can adjust the amount of bass going into it?
I was sure you'd liked it, every Engl I modded never came back to 100 kOhm in that place, for the exact same reason you wrote.
Yes, just connect the pot like a rheostat and ground it. Then connect the cap from 3rd stage's anode to the pot. This way you'll decide how much highs you want to cut.
IMPORTANT: this way the 1 nF snubber is connected to ground (for safety reasons), but for the ac signal it's exactly the same as being connected to B+, but for you... touching a grounded potentiometer is... safer! 😀
One final tip from me, I don't have anymore to give:
The 530 has 2 solid state power amps in it, 2.5Watt each. And you can set a frequency compensation in and out of those channels. (They are after the tube section and there's an output just after the tube section).
These are great for driving 8 Ohm primary winding reverb tanks (higher impedances work to, there's a vast amount of headroom). The only downside is that there's no volume level for this, so be careful not to blow the primary windings. The upside is that you can drive them harder, this gives a nice twang from the tank.
The 530 has 2 solid state power amps in it, 2.5Watt each. And you can set a frequency compensation in and out of those channels. (They are after the tube section and there's an output just after the tube section).
These are great for driving 8 Ohm primary winding reverb tanks (higher impedances work to, there's a vast amount of headroom). The only downside is that there's no volume level for this, so be careful not to blow the primary windings. The upside is that you can drive them harder, this gives a nice twang from the tank.
Thank you Bill,
never thought about that, I've always had my Lexicons for that, but it's a very good and creative tip!
never thought about that, I've always had my Lexicons for that, but it's a very good and creative tip!