Hello all, new to the forum! I've recently been building my own custom all tube preamps that I run into the effects loop of a DSL 40C. The first I built was based a JMP 2204 (I used mustard caps, Vishay CMF60 metal film resistors, Vishay 470pf in the treble peaker spots and EQ with a 33k slope resistor) so to me it sounds like a typical 2204 (bright, not kverly gainy and cuts through well).
However, I decided I wanted something similar to a 2204 with more gain, little more bottom end but still retain the 2204's ability to cut through. I used Mallory 150's (0.022uf's throughout, Vishay CMF60 MF resistors, 2200Pf treble peaker going to the gain pot, 470pF on 470k/470k divider) but I added and 4th gain stage by adding a 12ax7 after the first 10k cold clipper. 220k/220k voltage divider, a 100k plate load, .022uF coupling cap, no treble peaker, 10k cathode before the original (3rd stage in original 2204). Also, for reference this 2nd build uses a 36k slope resistor, 560pF treble cap, and typical Marshall .022uF mid and bass caps. All Pots are typical 2204 value (1M gain, 220k Treble, 22k Mid, 1M Bass, 1M Master volume)
The first issue I ran into was some high frequency oscillation which I added a 470pF on V1A and a 220pF on V1B to fix. I usually run the master on 3-4 (I made another voltage divider using the master volume 470k/1M Gain pot to cut volume) before the effects loop return of my DSL.
However, the issue I'm having is the amp is still super bright. I know 220k plate load on V1A increased the gain at 10khZ from the stock marshall of 35.5dB to around 37dB. But, it also raised gain at 60hZ from 28dB to about 39dB, so it increased both the highs and lows. My question is would it be better to increase my cathode bypass on V1A to get more lows or increase the coupling cap at V1A from .022 to .047. to increase lows? Both would achieve my end result, as a larger cathode bypass would let more frequencies through, and a larger coupling cap would as well. However, would one way be more beneficial then the other? I know I could just try it, but I still like learning and hearing others approaches as I learn more and more.
Now, for the most important part, I do practice safety first. I discharge my filter caps (50uF, 33uF, 33uF on each preamp I build) prior to anything. Speaking of that, would increasing filter cap size also be beneficial to getting mofe lows? I know the filter caps in a 50-Watter vs 100 seem to play a role in bass.
However, I decided I wanted something similar to a 2204 with more gain, little more bottom end but still retain the 2204's ability to cut through. I used Mallory 150's (0.022uf's throughout, Vishay CMF60 MF resistors, 2200Pf treble peaker going to the gain pot, 470pF on 470k/470k divider) but I added and 4th gain stage by adding a 12ax7 after the first 10k cold clipper. 220k/220k voltage divider, a 100k plate load, .022uF coupling cap, no treble peaker, 10k cathode before the original (3rd stage in original 2204). Also, for reference this 2nd build uses a 36k slope resistor, 560pF treble cap, and typical Marshall .022uF mid and bass caps. All Pots are typical 2204 value (1M gain, 220k Treble, 22k Mid, 1M Bass, 1M Master volume)
The first issue I ran into was some high frequency oscillation which I added a 470pF on V1A and a 220pF on V1B to fix. I usually run the master on 3-4 (I made another voltage divider using the master volume 470k/1M Gain pot to cut volume) before the effects loop return of my DSL.
However, the issue I'm having is the amp is still super bright. I know 220k plate load on V1A increased the gain at 10khZ from the stock marshall of 35.5dB to around 37dB. But, it also raised gain at 60hZ from 28dB to about 39dB, so it increased both the highs and lows. My question is would it be better to increase my cathode bypass on V1A to get more lows or increase the coupling cap at V1A from .022 to .047. to increase lows? Both would achieve my end result, as a larger cathode bypass would let more frequencies through, and a larger coupling cap would as well. However, would one way be more beneficial then the other? I know I could just try it, but I still like learning and hearing others approaches as I learn more and more.
Now, for the most important part, I do practice safety first. I discharge my filter caps (50uF, 33uF, 33uF on each preamp I build) prior to anything. Speaking of that, would increasing filter cap size also be beneficial to getting mofe lows? I know the filter caps in a 50-Watter vs 100 seem to play a role in bass.
