What would be a recommended method of including a switch for different levels of gain to the ACP+? An older post from Mark J. (Amp Camp Pre+Headphone Amp - ACP+) suggested switchable gain, but I didn’t see a follow up or implementation.
Edit: Another question: Would it be feasible to implement switched gain options off-board (official pcb), or would this require a different layout?
Thanks in advance!
Edit: Another question: Would it be feasible to implement switched gain options off-board (official pcb), or would this require a different layout?
Thanks in advance!
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it can be done with aux switch, changing value of feedback resistor going from output node
best if made as one fixed resistor (highest value, highest gain) and switching resistors in parallel
best if made as one fixed resistor (highest value, highest gain) and switching resistors in parallel
Thank you, ZM! That makes sense.
I could use some coaching on what kind of switch would work. I think 3 positions would be enough.
In theory:
Switch in parallel to highest resistor.
Position 1: open (just the installed resistor)
Position 2: parallel resistor 1 (total resistance 1/2 way between stock and installed resistor)
Position 3: parallel resistor 2 (total resistance = stock resistor value)
I could use some coaching on what kind of switch would work. I think 3 positions would be enough.
In theory:
Switch in parallel to highest resistor.
Position 1: open (just the installed resistor)
Position 2: parallel resistor 1 (total resistance 1/2 way between stock and installed resistor)
Position 3: parallel resistor 2 (total resistance = stock resistor value)
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Rumor has it that parts kits for the ACP+ are going to arrive in the store reasonably soon!
And now we can have more controls on the front. Gain and headphone matching....um, not included in kit
And now we can have more controls on the front. Gain and headphone matching....um, not included in kit
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yup
easiest to use Lorlin rotary switch (make before break/ shorting) - 3 sections/4 positions
even if you can use 2 sections/6 positions - they have indentation washer , so you can set it to 3 positions easily
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One could use my fave switch, DPDT on-off-on. Center position would be “installed resistor”
HOWEVER ZM’s point about out make before break seems smart. I just don’t know how big a “click” we’re talking about....don’t want speaker cones across the room...
HOWEVER ZM’s point about out make before break seems smart. I just don’t know how big a “click” we’re talking about....don’t want speaker cones across the room...
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Yes, so I don’t know how the circuit would respond to live switching. Make before break would in theory lead to lowest resistance when switching, so lowest gain ‘between’ clicks? I confess I’m a total layperson on circuitry.
MBB is safe bet when these things are in question
however, Mark has it right - these small switches are cute
you can try that way and - if there are no pops, use it
however, Mark has it right - these small switches are cute
you can try that way and - if there are no pops, use it
You mean “lots of small switches are cute, and cheap too!” I may add a phase switch also to see if I can tell the difference.
Is what I am hearing a phase issue
Mark, playing thru my record collection a fair number of recordings sound as if I am listening from the wrong side of a curtain hanging between me and the musicians. Just somehow......"attenuated".
These are big name artists, so I know they got the benefit of a good recording. Wrong phase?
Edit: Maybe I should switch the output and find out!!
Mark, playing thru my record collection a fair number of recordings sound as if I am listening from the wrong side of a curtain hanging between me and the musicians. Just somehow......"attenuated".
These are big name artists, so I know they got the benefit of a good recording. Wrong phase?
Edit: Maybe I should switch the output and find out!!
Thing is, I have no idea if I can even detect it! I am pretty sure it’s a very subtle effect. That’s why I want the switch, so I can see.(I mean hear!) And I think it’s legit to wonder if the phase is maintained throughout the recording process on all recordings. So if I can detect it, it would be fun to have that option on the “remote I may sometime add to the preamp...”
Your problem sounds like it would take the fun out of HiFi. So it’s serious no doubt. I suspect it’s not phase...
Your problem sounds like it would take the fun out of HiFi. So it’s serious no doubt. I suspect it’s not phase...
The VFET amp "front end" cards Marauder and Bulwark include a DPDT switch on the PCB, that lets you select between inverted and not-inverted polarity. Could be fun to play around with.
I've included a link to the schematics of all four boards, below. Please feel free to have a look, and decide whether they do or don't meet your requirements. The grand total power supply voltage between VsupplyPos and VsupplyNeg is 36V in the VFET amp, because that amp runs off a 36VDC SMPS made by Mean Well. However, you can study/analyze the front end circuits themselves, to decide whether they'll probably work with "X" volts total, (X not equal to 36), in a legacy amplifier application.
edit- here's a picture of the switches
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edit- here's a picture of the switches
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Attachments
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Nelson has always wanted to have mix and match front ends and output stages.
(See Burnimg Amps) But now it ‘s really going to happen on a decent scale!
I know Mark doesn’t like spoon feeding people, but a thread with a post for each front end option, each with a standard list of relevant specs including Mark’s and the old BA-1,2,&3, and the new Pass VFET front end, etc., etc...would eventually eliminate a lot of questions over time. Then if there were post for each of various output stages and their requirements, (there aren’t really that many) over time, questions as to what gain stages are appropriate for which output stage would be a lot less.
But it could include opinions on various combinations and their characteristics too.
(See Burnimg Amps) But now it ‘s really going to happen on a decent scale!
I know Mark doesn’t like spoon feeding people, but a thread with a post for each front end option, each with a standard list of relevant specs including Mark’s and the old BA-1,2,&3, and the new Pass VFET front end, etc., etc...would eventually eliminate a lot of questions over time. Then if there were post for each of various output stages and their requirements, (there aren’t really that many) over time, questions as to what gain stages are appropriate for which output stage would be a lot less.
But it could include opinions on various combinations and their characteristics too.
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This helps my lazy butt who have been putting-off for too long sitting down and ordering part for part. I want to build this first before the Sony P-VFET.
Just ordered... that does make things easier for sure. We are fortunate to have the option with these projects.
ACP+ Kits are In The Store!
Hi folks,
ACP+ kits are available in the diyaudio store!
ACP+ (Amp Camp Pre-Amp + Headphone Amp) – diyAudio Store
If you do get one and have feedback please do post either here or DM me as I am always looking to improve.
I want to thank Jason Donald, 6L6, Richard Dortch and of Papa Pass for helping me put this together as this was actually my first kit I put together. I learned a heck of a lot having to scrutinize parts, consider how they would be used and everything in between and look forward to more awesome projects!
Cheers,
--Tom
Hi folks,
ACP+ kits are available in the diyaudio store!
ACP+ (Amp Camp Pre-Amp + Headphone Amp) – diyAudio Store
If you do get one and have feedback please do post either here or DM me as I am always looking to improve.
I want to thank Jason Donald, 6L6, Richard Dortch and of Papa Pass for helping me put this together as this was actually my first kit I put together. I learned a heck of a lot having to scrutinize parts, consider how they would be used and everything in between and look forward to more awesome projects!
Cheers,
--Tom