LAR/MAR PPIMV bypass pop noise?

[psychepool]

LAR/MAR PPIMV bypass pop noise?

I am reviewing the Ton King Imperial circuit.

This amplifier has a built-in attenuator, and there is an option to have the attenuator operate only on the lead channel when switching channels.
I think this is a very good idea. Since this is an amplifier without a master volume, there will be a volume difference between channels when switching using a footswitch, but I think this is the ideal way to solve this problem.

However, I think it would be difficult for me to build this system if I DIY. Instead, I want to insert LAR/MAR PPIMV and operate it only when it is the lead channel through switching.
I have a deluxe reverb clone with a 1-channel configuration, and I am using PPIMV quite satisfactorily. If I don't lower the master too much, the power saturation doesn't feel bad. Therefore, if I use it with an attenuator and I use PPIMV only to balance the channel volume, I will likely get quite good results. I think it would be even better since Imperial doesn't even use NFB or presence.

I looked up the reference and found this switching method.

Lar-Mar_PPIMV_Bypass.png

I think it is a simple switching method that uses as few contacts as possible.
The operation itself doesn't seem to have any problems, but I'm worried about popping noise since it's intended to be used when switching channels.

I'm not expecting completely silent switching, but I'm worried that the pops might be quite loud. If anyone has used a PPIMV bypass switch like this, can you tell me how loud the pop noise is?

[wpaulvogel]

That isn’t going to work because the grid can’t be lifted from a 220k leak to a 2M2 leak resistor no matter what. It has to retain the 220k resistance whether it’s a parallel of the MV control or a fixed resistor. It’s going to pop loudly also because it’s an open circuit while the contact switches. You’ll need a make before break switch.

[wpaulvogel]

Look into what Alexander Dumble did to switch between the overdrive channel and the clean channel. It’s how you do what you want to do.

[Roe]

those who have switched between two larmars have simply used two 500k stereo pots in parallell, which gives about the same resistance as single 250k stereo pot.

Instead of the 2m2 security resistors on the 250k you may need to adjust the value of the security resistor. but don't be too mechanincal, measure the pot since the values vary a lot. it needs to be fairly balanced.

anyway, the idea is to feed both pots with the signal from the phase inverter. for the signal that goes to the output tube pin 5's you switch between the viper of the two pots

[pdf64]

those who have switched between two larmars have simply used two 500k stereo pots in parallell, which gives about the same resistance as single 250k stereo pot.

Instead of the 2m2 security resistors on the 250k you may need to adjust the value of the security resistor. but don't be too mechanincal, measure the pot since the values vary a lot. it needs to be fairly balanced.

anyway, the idea is to feed both pots with the signal from the phase inverter. for the signal that goes to the output tube pin 5's you switch between the viper of the two pots

Consider that if one of those LarMars was set full CW, electrically, it would be equivalent to the schematic in post 1.

[martin manning]

That isn’t going to work because the grid can’t be lifted from a 220k leak to a 2M2 leak resistor no matter what. It has to retain the 220k resistance whether it’s a parallel of the MV control or a fixed resistor. It’s going to pop loudly also because it’s an open circuit while the contact switches. You’ll need a make before break switch.

In bypass, the 2M2 is paralleled with the pot's 250k element, maintaining 220k to bias voltage. It may well pop when switched. A large value resistor (another 2M2?) placed across the wiper and the input terminal of the pot might fix that.

Look into what Alexander Dumble did to switch between the overdrive channel and the clean channel. It’s how you do what you want to do.

Somewhat surprisingly, ODS channel switching does not have any anti-pop measures included. Mid-Boost and PAB (tone stack) do, however.

[pdf64]

... I'm worried that the pops might be quite loud...

Pop / thump noises are usually caused by -
a change in DC voltage
charging or discharging a cap (which causes a momentary change in DC voltage)

I don't think that a loud pop is likely to occur in that schematic, unless one of the output valves has excessive grid current.

The grid side of the coupling cap and grid always have a resistive path to the bias voltage.

Ideally the switching action (relay contacts) would be make before break (so that the grid was never relying on on the safety back up grid leaks, even momentarily during switching), but I've not seen any like that.

[pullshocks]

i recently wired up my 6V6 SE amp with the Imperial preamp as in the attached schematic. It sounds great, My amp has a master volume and I do not play loud enough for power amp overdrive to be a factor, unlike the real Imperial where power amp overdrive is a big part of the sound. But I like it for what it is.

I'm interested in adding a lead master. Since this is a SE amp, your PPIMV concept is not applicable. I have wondered about replacing R19 with a pot.

I havent tried this yet as I have been pleasantly surprised to get lead sounds I like without drastic volume differences between the channels. Rhythm volume on 6, lead volume on 4 , mid bite on 3. But turn the lead volume and mid bite way up and there would undoubtedly be a volume mismatch.

20th_Imperial_SC200HB_pg1 (2).pdf

[psychepool]

I thought this switching wouldn't break the amp at least, so I tried it on my Deluxe Reverb clone.

01.jpg

It works very well as expected.
Of course there is pop noise. But it's not as loud as I think.
By my standards, it feels like it is sufficient for the purposes I mentioned. (footswitchable channel switching)

The Imperial is a cathode bias amp and mine is fixed bias, but it probably won't make much of a difference in the results.
If you are thinking of making an Imperial clone, you can consider a configuration where PPIMV operates only on the lead channel.
Since Imperial does not have NFB, I think PPIMV would be a better fit than my Deluxe Reverb.


Actually, I am not a follower of Fender sound.
Of course, there is no one who dislikes Fender's clean tone. I also really like Fender's clean tone.
However, Fender's gain sound is not the tone I really want to pursue.
Basically, I consider the classic Marshall sound as my main focus, and I also like modern chug high gain.
I have built several high gain amps and enjoy it.
And was planning to build a Friedman Twin Sister based amp next time for low or medium gain.

However, when I recently repaired someone's 5E3 clone and listened to the sound, there was a texture that could not be replaced by any other amplifier.
I was quite intrigued by it, so I took out this Deluxe Reverb that I kept in storage and occasionally used as a substitute for a bass amp.
Of course, I made this amp for enjoy clean tones, but I realized 10 years after making it that it sounded really good when I turned on the overdrive.
And when I applied pedal drive to the amp overdrive, it was even more fantastic.
Through this experience, while looking for an amplifier that could use Fender Gain, I discovered the Tone King Imperial, and wondered whether I should make a Twin Sister or an Imperial.

It would be nice to disassemble and build it in this deluxe reverb chassis, but unfortunately, it was made in such a tight size that there is no room for more tubes.
I think it would be possible to add a one-tube reverb instead of the reverb circuit in the circuit diagram, but it would feel a bit disappointing.

02.jpg

03.jpg

[psychepool]

That isn’t going to work because the grid can’t be lifted from a 220k leak to a 2M2 leak resistor no matter what. It has to retain the 220k resistance whether it’s a parallel of the MV control or a fixed resistor. It’s going to pop loudly also because it’s an open circuit while the contact switches. You’ll need a make before break switch.

Unfortunately, I couldn't find a relay with the make before break specification. Of course, the dpdt toggle used in the test is not that specification too.
If it is not a make before break specification switch, could it cause problems with the amplifier? The grid leak of 2.2M is a fairly large value, but at least the grid is not floating, so I assumed there would be no safety issues.

Look into what Alexander Dumble did to switch between the overdrive channel and the clean channel. It’s how you do what you want to do.

Can you tell me what configuration should I refer to in the Dumble Circuit? Dumble's preamp and channel switching methods are structurally very different from Imperial's, and it does not use PPIMV, so I am not sure exactly what point to refer to.

Pop / thump noises are usually caused by -
a change in DC voltage
charging or discharging a cap (which causes a momentary change in DC voltage)

I don't think that a loud pop is likely to occur in that schematic, unless one of the output valves has excessive grid current.

The grid side of the coupling cap and grid always have a resistive path to the bias voltage.

Ideally the switching action (relay contacts) would be make before break (so that the grid was never relying on on the safety back up grid leaks, even momentarily during switching), but I've not seen any like that.

I read the thread and looked for the make before break relay for a while, but unfortunately I couldn't find it. I thought it was my lack of search skills, but it may be that such a product does not exist in the first place.
After testing, it wasn't a loud pop to bother me by my standards, so I think it would be okay to use a regular relay.

i recently wired up my 6V6 SE amp with the Imperial preamp as in the attached schematic. It sounds great, My amp has a master volume and I do not play loud enough for power amp overdrive to be a factor, unlike the real Imperial where power amp overdrive is a big part of the sound. But I like it for what it is.

I'm interested in adding a lead master. Since this is a SE amp, your PPIMV concept is not applicable. I have wondered about replacing R19 with a pot.

I havent tried this yet as I have been pleasantly surprised to get lead sounds I like without drastic volume differences between the channels. Rhythm volume on 6, lead volume on 4 , mid bite on 3. But turn the lead volume and mid bite way up and there would undoubtedly be a volume mismatch.

20th_Imperial_SC200HB_pg1 (2).pdf

https://el34world.com/Forum/index.php?topic=29297.0

I haven't checked the circuit of the SE amplifier you made, but I expect that if you install a master volume on the preamplifier, the overdrive will not work properly on the lead channel.
Seeing that there is an example of adding a master volume to a Champ like this, I think you can apply the same PPIMV switching to that position in your SE amplifier.