Check this out. No LFNB. 250pF snubbers.
https://www.youtube.com/watch?v=wx7TR7C ... e=youtu.be
Fender Evil Twin modified to #102.
Moderators: pompeiisneaks, Colossal
Re: Fender Evil Twin modified to #102.
Is that your amp? Any more details?
I don't know if you ever saw the threads but I did something similar to a Fender Super Twin Reverb a few years ago. Based on #124 circuit.
https://www.youtube.com/watch?v=NvkB2wE ... dLyXgWMoYw
I don't know if you ever saw the threads but I did something similar to a Fender Super Twin Reverb a few years ago. Based on #124 circuit.
https://www.youtube.com/watch?v=NvkB2wE ... dLyXgWMoYw
"You feel like you're floating on a football field filled with marshmallows." -Dumble
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jazzyjoepass
- Posts: 192
- Joined: Wed Feb 15, 2006 4:23 am
Re: Fender Evil Twin modified to #102.
It's a mate's amp.
I always thought it was worthy of being modified.
Looking at the schematics, it had the right signal path for a clone with pseudo dumbleator and reverb to boot.
Yes I did see the threads on the Super Twin.
I always thought it was worthy of being modified.
Looking at the schematics, it had the right signal path for a clone with pseudo dumbleator and reverb to boot.
Yes I did see the threads on the Super Twin.
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dcribbs1412
- Posts: 1386
- Joined: Wed Jun 11, 2008 6:56 pm
- Location: Arizona Desert
Re: Fender Evil Twin modified to #102.
Sounds great!
congrats
D
congrats
D
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jazzyjoepass
- Posts: 192
- Joined: Wed Feb 15, 2006 4:23 am
Re: Fender Evil Twin modified to #102.
Thanks, D. The real thing sounds better than on video and my chops aren't up to scratch..
IC-racer,
Problem with the Evil Twins is that they r LOUD. The amp became controllable once I stuck a 250kA volume pot in the FX loop. When I did that, I was able to crank the preamp end up and it sounded better and I could hear lots of potential in the amp. The Clean channel was typical Fender vibe - clean that can be sterile, bright chimey high end and bassy low end, scooped mids - think John Mayer. Although the OD did start to sing, it was not very usable and lacked character and harmonics - very bland, flat and one dimensional. So I changed the values in the PCB to mimic the #102 circuit as much as possible in there and put in a set of tubes that were strong and the voltages dropped right where it should be on the 200V mark. I did not rip out the PCB to do a PTP version.
In the Evil Twin schematic, there were no pots where they should be on the #102 - i.e. Content level and internal trim pot. I noted how RF usually set his amp, and simulated them with a voltage divider. Some other pots were also of wrong values as they were Push/Pull type and were hard to source. On the Mid pot, I lifted the ground and added a few more kiloohms (27k to 39k) to simulate the 250kA mid pot at noon. Even though the Bass pots weren't the correct values, it still sounded great stock. The Ratio level was left as 250kA. The series resistance before the Ratio pot was kept at 68k.
Some other features of the amp was Reverb and FX loop, which was much missed in the real Dumbles and I was able to use them fully.
The reverb was crap - thin and weak. I removed some of the series resistance (ie. two 100k) in the reverb path and copied the well known reverb circuitry from the Twin Reverb. Wile doing that I noted that Fender forgot a 500pF/1Mohm combo at the grid of the 12AT7 reverb driver.
Up to this stage, I've been using a 250kA pot inserted between the FX loop. That meant I had to routinely plug that in when I wanted to use the amp. I certainly was looking at the possibility of converting the loop into the Dumble-ator and using it to control the volume of the amp like what many users have been doing. But that meant that I'd have to mess around with the switching arrangements for the Send/Return levels and look for space on the chassis to put in the Send, Return and Output pots.
I decided to leave the FX Loop mostly stock. I noticed that there was a 0.0022uF coupling cap to the Send stage which probably would thin out the signals so I beefed up the coupling cap to 0.047uF. I noted that the Dumble-ator had a 250kA Output pot at the plate of the Return stage driver, coupled by a 0.1uF coupling cap. Following suit, I inserted the 0.1uF and 250kA and coupled that to a 0.022uF to the PI of the amp. I drilled a hole next to the Preamp Out jack and stucked that pot there. It works a treat.
The Plate voltage on the 6L6 tubes was 480V thereabouts, so I biased them at about 30mA. The PI was also changed to 1Mohm grids and 820R cathode. The plates were also changed to 110k and 120k. I took out the 9.1k on the PI plate. The 12AT7 PI tube was replaced with a matched section 12AX7.
The amp sounds really unbelievable now. It's got that chewy harmonics that changes according to your pick dynamics. Probably the best clone I've heard so far.
Mike
IC-racer,
Problem with the Evil Twins is that they r LOUD. The amp became controllable once I stuck a 250kA volume pot in the FX loop. When I did that, I was able to crank the preamp end up and it sounded better and I could hear lots of potential in the amp. The Clean channel was typical Fender vibe - clean that can be sterile, bright chimey high end and bassy low end, scooped mids - think John Mayer. Although the OD did start to sing, it was not very usable and lacked character and harmonics - very bland, flat and one dimensional. So I changed the values in the PCB to mimic the #102 circuit as much as possible in there and put in a set of tubes that were strong and the voltages dropped right where it should be on the 200V mark. I did not rip out the PCB to do a PTP version.
In the Evil Twin schematic, there were no pots where they should be on the #102 - i.e. Content level and internal trim pot. I noted how RF usually set his amp, and simulated them with a voltage divider. Some other pots were also of wrong values as they were Push/Pull type and were hard to source. On the Mid pot, I lifted the ground and added a few more kiloohms (27k to 39k) to simulate the 250kA mid pot at noon. Even though the Bass pots weren't the correct values, it still sounded great stock. The Ratio level was left as 250kA. The series resistance before the Ratio pot was kept at 68k.
Some other features of the amp was Reverb and FX loop, which was much missed in the real Dumbles and I was able to use them fully.
The reverb was crap - thin and weak. I removed some of the series resistance (ie. two 100k) in the reverb path and copied the well known reverb circuitry from the Twin Reverb. Wile doing that I noted that Fender forgot a 500pF/1Mohm combo at the grid of the 12AT7 reverb driver.
Up to this stage, I've been using a 250kA pot inserted between the FX loop. That meant I had to routinely plug that in when I wanted to use the amp. I certainly was looking at the possibility of converting the loop into the Dumble-ator and using it to control the volume of the amp like what many users have been doing. But that meant that I'd have to mess around with the switching arrangements for the Send/Return levels and look for space on the chassis to put in the Send, Return and Output pots.
I decided to leave the FX Loop mostly stock. I noticed that there was a 0.0022uF coupling cap to the Send stage which probably would thin out the signals so I beefed up the coupling cap to 0.047uF. I noted that the Dumble-ator had a 250kA Output pot at the plate of the Return stage driver, coupled by a 0.1uF coupling cap. Following suit, I inserted the 0.1uF and 250kA and coupled that to a 0.022uF to the PI of the amp. I drilled a hole next to the Preamp Out jack and stucked that pot there. It works a treat.
The Plate voltage on the 6L6 tubes was 480V thereabouts, so I biased them at about 30mA. The PI was also changed to 1Mohm grids and 820R cathode. The plates were also changed to 110k and 120k. I took out the 9.1k on the PI plate. The 12AT7 PI tube was replaced with a matched section 12AX7.
The amp sounds really unbelievable now. It's got that chewy harmonics that changes according to your pick dynamics. Probably the best clone I've heard so far.
Mike
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jazzyjoepass
- Posts: 192
- Joined: Wed Feb 15, 2006 4:23 am