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12-04-2023, 01:09 AM
Hi Guys
Yes, having larger main and subsequent filters will stiffen the supply apart from improving noise performance. I always take the performance improvement over preserving natural sag. In most cases, because I choose to use over-sized PTs to have lower transformer temperature rise, this improves the supply regulation and reduces EMI from the PT. I end up with a pretty stiff supply. To enhance hum reduction, I always have active hum filters. All of this goes against the economically-driven PSU design of traditional guitar amps.
How do you soften things up? Get some sag effect? But without altering the super-low-noise supply?
As TUTs illustrate, adding low-cost resistors here and there will give you all the sag you desire. Or, add electronic circuits to provide user-controlled sag. All of this is post-nirvana-providing-raw supply so there is no noise penalty with whatever we do.
Note that added resistors in series with supply feeds, say to the output transformer, will introduce a signal-dependent voltage drop that has fast collapse and recovery times - as fast as the signal. There are no caps to recharge, and thus, it will sound different compared to whole-supply sag. If you add a cap to ground after the R, you have an RC constant for the recovery BUT this will only sound proper for a given signal current range. This is what one of Randall Smith's patents was for, which was worthless on two counts: the effect is limited to playing the amp near full output; patents do not cover circuit values... yet the USPTO took his money anyway.
The solution is to have a means to proportion the sag effect to the power level you wish to use, the loudness, regardless of whether the amp is Power Scaled or not. For this, London Power offers the SUS Sustain kits. These are NOT like a BOSS Compressor-Sustain pedal. Instead, SUS only changes the attack of the note, which can sound like the supply sagging or at least running out of headroom to pass the transient part of the waveform. This is a compressor side-chain approach. SUS can control the output stage or be installed further back at the splitter, or a preamp stage. You have to use the correct kit for whatever circuit block you are tying it to.
Alternatively, you could have switched resistors to provide the range of effect for different current levels corresponding to different loudness levels. This would be entirely passive and understood by tinkerers of most skill levels.
An alternate to the SUS approach or the passive one is to use an RMX technique from TUT4, again active, and also continuously variable.
If you are tailoring an amp to your own playing situation, many of the decisions become simpler. You can decide on a power output that is around what you need, then add passive elements to fine tune it. this is okay for playing the same place every time BUT maybe sometimes you play much bigger places?
One approach is to simply mic your small rig through a larger one for the extra coverage. Another approach is to have a larger amp tuned like the small one. A further approach is to have oine amp that can be used both places at the two different power outputs required, which can be achieved in countless ways.
Yes, having larger main and subsequent filters will stiffen the supply apart from improving noise performance. I always take the performance improvement over preserving natural sag. In most cases, because I choose to use over-sized PTs to have lower transformer temperature rise, this improves the supply regulation and reduces EMI from the PT. I end up with a pretty stiff supply. To enhance hum reduction, I always have active hum filters. All of this goes against the economically-driven PSU design of traditional guitar amps.
How do you soften things up? Get some sag effect? But without altering the super-low-noise supply?
As TUTs illustrate, adding low-cost resistors here and there will give you all the sag you desire. Or, add electronic circuits to provide user-controlled sag. All of this is post-nirvana-providing-raw supply so there is no noise penalty with whatever we do.
Note that added resistors in series with supply feeds, say to the output transformer, will introduce a signal-dependent voltage drop that has fast collapse and recovery times - as fast as the signal. There are no caps to recharge, and thus, it will sound different compared to whole-supply sag. If you add a cap to ground after the R, you have an RC constant for the recovery BUT this will only sound proper for a given signal current range. This is what one of Randall Smith's patents was for, which was worthless on two counts: the effect is limited to playing the amp near full output; patents do not cover circuit values... yet the USPTO took his money anyway.
The solution is to have a means to proportion the sag effect to the power level you wish to use, the loudness, regardless of whether the amp is Power Scaled or not. For this, London Power offers the SUS Sustain kits. These are NOT like a BOSS Compressor-Sustain pedal. Instead, SUS only changes the attack of the note, which can sound like the supply sagging or at least running out of headroom to pass the transient part of the waveform. This is a compressor side-chain approach. SUS can control the output stage or be installed further back at the splitter, or a preamp stage. You have to use the correct kit for whatever circuit block you are tying it to.
Alternatively, you could have switched resistors to provide the range of effect for different current levels corresponding to different loudness levels. This would be entirely passive and understood by tinkerers of most skill levels.
An alternate to the SUS approach or the passive one is to use an RMX technique from TUT4, again active, and also continuously variable.
If you are tailoring an amp to your own playing situation, many of the decisions become simpler. You can decide on a power output that is around what you need, then add passive elements to fine tune it. this is okay for playing the same place every time BUT maybe sometimes you play much bigger places?
One approach is to simply mic your small rig through a larger one for the extra coverage. Another approach is to have a larger amp tuned like the small one. A further approach is to have oine amp that can be used both places at the two different power outputs required, which can be achieved in countless ways.
