I wanted to test out different plate resistors for v1 and v2 in my recent build (https://ampgarage.com/forum/viewtopic.php?f=4&t=36323) and I thought if I was going to the trouble, then I might as well document it and post the results here for the community. First and foremost, this was an attempt at a reasonably controlled test. It is certainly not a perfect test and not up to snuff for a scientific paper. I am sure there will be mixed opinions on the results, but I am really curious to hear everyone's thoughts. Depending on interest level, I will wait a bit to upload a key of which clips belong to which sets of resistors tested.
Methodology
My amp was recorded with these settings for all of the tests. The OD trigger wiper reads 25.2K to ground with the amp on and in OD mode. When building the amp, I installed 18 gauge solid core wire connected to an alligator clip where each end of a plate resistor would normally go. This allowed for relatively quick swapping of components between recordings. Obviously the circuit constants with this arrangement are not exactly the same as a resistor soldered to the board. Does that actually matter? I have no clue
I am running the amp through my Dumbleator, but without any effects in its loop. This is how I will use the amp, so it is how I wanted to run the tests. Some may have preferred no active loop. With the amp system setup this way it is quite loud. Certainly keep up with a drummer small gig loud. I was wearing earplugs while making the recordings.
The amp's power cord is connected to my variac, then to my power conditioner. My DMM was connected to the amps IEC jack throughout the tests. I adjusted the variac before each clip was recorded to ensure the AC input to the amp was 121.5vAC and did not drift more than +/- 0.3vAC throughout the clip. I recorded 2 guitar clips, one into Loop 1 (clean) and another Loop 2 (drive) of my TC Electronic Dittox4 looper. Every clean and drive recording are these loops being played back into the Normal Input of the amp with the appropriate channel selected. All gain staging through the Ditto was not touched between clips. The guitar was an epiphone les paul ultra model with a chambered body and two humbuckers, Seymour Duncan SH2-N Jazz Neck pickup and Screamin' Demon Bridge pickup. These are a little hotter than a vintage PAF style pickup. The Clean clips are the bridge position. The Drive clips are the Neck position.
The amp is running through am 8 ohm EVM-12L open back Dumble style cabinet. The cab was mic'd with an SM58 just off-center. The mic position was not changed between any clips.
The mic is going to my Universal Audio Volt 476P interface. The only input being used to record is input 4. The gain on this channel was not changed during recording. The interface is not using the built-in discrete compressor or the "vintage" circuitry. My DAW is Reaper. I am using it to simply record each clip, I have adjusted the volume in Reaper of all the Clean tracks and all the Drive tracks the same for each group to obtain a peak of -4.5 to -3.2 for each set of clips respectively. Once rendered, then the .wav files were renamed to numbered clips with a "Clean" and "Drive" designation and uploaded here.
Resistor GroupsI tested mostly metal film but a few sets of carbon film resistors as well, some NOS, mostly not. Here are the pictures and the info. If anyone can't read my handwriting, let me know and I can type out these details. As you can see every plate resistor position is not the same exact nominal resistance value. But they are pretty close imho.
The resistor groups are labeled with letters A-J. The clips are labeled with numbers 1-10. I randomly assigned clip numbers to the resistor groups, so for instance, Group A is not what is recorded in clip 1, and so on. -Dan
