Passive preamp for speaker protection

[whaardahl]

Hi, I have WiiM Pro Plus that is connected directly to a Buckeye NC502MP amp via RCA to XLR cables + a trigger cord. I'm very happy with this setup; but with more than one person using the system via more than one device, I'd like to protect my speakers from volume spikes. Would a passive preamp between the WiiM and amp be a good solution? Stepped attenuator? Any suggestions for specific devices and considerations? Thanks for any help!

 

[unpluggged]

passive preamp

Is a misnomer.

Stepped attenuator?

This should do the trick. Or a switchable attenuator such as the JTS MA-123 or the Shure A15AS.

 

[whaardahl]

Is a misnomer.


This should do the trick. Or a switchable attenuator such as the JTS MA-123 or the Shure A15AS.

Thanks. I need a rotary knob with more settings vs. a switchable attenuator. It's hard to find reviews/recommendations + other questions arise, e.g. will the 2volt output of my WiiM be passed through the volume attenuator and onto the amp as 2volts? And will the RCA to XLR cables work between the volume attenuator and the xlr inputs on the amp? I am ignorant re: such issues and need counsel

 

[unpluggged]

will the 2volt output of my WiiM be passed through the volume attenuator and onto the amp as 2volts?

If the attenuator has 0 dB setting, it will.

And will the RCA to XLR cables work between the volume attenuator and the xlr inputs on the amp?

It depends on the attenuator, the amp, and the cables in question.

 

[wadude]

My passive step attenuator is located after a Wiim Pro Plus and before a Buckeye 252 amp so you must admit, it is “pre-amp.”

I tried using the touch controls on the Wiim for a while but feel more secure with the passive preamp, plus I just like it better!

I use RCA interconnects from the Wiim to the attenuator and the Hypex spec’ed RCA to XLR type cable between the attenuator and the amp and it works very well.

The attenuator raises and lowers the voltage to the amp input, which raises and lowers the volume level.

After trying a Monoprice cable, which worked fine but looked and felt stiff and cheap I ordered an RCA to XLR cable made by Redco Audio. They do good work.

Have fun with that rig! The eq on the Wiim is great!

 

[whaardahl]

Thanks, wadude. Helpful to hear from someone with a similar setup. I have the RCA-XLR cable from Blue Jeans Cable, which also does good work. I'm using the WiiiM's room correction, which applies parametric eq and it seems to bring + results. Would you mind sharing which brand and model of passive step attenuator you are using? Can't find many options for products let alone recommendations/reviews.

 

[rdaow]

I'm using the silver one from Audiophonics, it costs about 50€. But is it any good? I don't know.

 

[whaardahl]

Have you tried taking it out of the box?

 

[rdaow]

yeah.. I guess you know I meant to say "I don't know how it measures". Audibly - it's good for me.

 

[Waxx]

A passive preamp brings in a new set of disadvantages or problems, one is the vairable output impendance as the pot meter usre resistance to reduce the volume. So you need or a buffer or a multitap transfo to keep the output impendance of the preamp like the amp expect. A buffer is fairly simplle to make yourself even and the best solution.

 

[Mort]

I have the same setup and instead limit the Wiim output.

Not the same as a passive preamp but let's face it, one doesn't often need 2V for a 500w amp unless you have some really unusual needs or setup.

Also look for the Buckeye integrated when it's released.

 

[whaardahl]

yeah.. I guess you know I meant to say "I don't know how it measures". Audibly - it's good for me.

I understand; just couldn't resist. I saw that one on Audiophonics and will have another look. Thanks for the suggestion!

 

[whaardahl]

A passive preamp brings in a new set of disadvantages or problems, one is the vairable output impendance as the pot meter usre resistance to reduce the volume. So you need or a buffer or a multitap transfo to keep the output impendance of the preamp like the amp expect. A buffer is fairly simplle to make yourself even and the best solution.

Thanks very much; I'm not much of a DIY guy re: electronics but will bear the impedance issue in mind as I shop.

 

[Sokel]

Thanks very much; I'm not much of a DIY guy re: electronics but will bear the impedance issue in mind as I shop.

I would advice some attenuators such as you have the level you'll ever need (including peaks) and be done with it.
(don't ask me which ones,it's probably the simplest audio thing out there and the hardest to find at decent quality.I have yet to measure a ready-made cheap one who doesn't add noise)

 

[audio_tony]

Thanks very much; I'm not much of a DIY guy re: electronics but will bear the impedance issue in mind as I shop.

If you keep the cables from the preamp to the power amp reasonably short (0.5M to 0.75M) the impedance won't be an issue.

In simple terms what happens is this; Depending on the position of the volume control, the output impedance can be high enough to interact with the cable capacitance which causes a very slight reduction i nthe to pend frequencies.

With any decent cable (even Amazon basics), so long as you keep the length short this won't be an issue.

However - ideally you want an attenuator that's no higher than 10k ohms in value. 22k ohms would be just about ok.

Something like this would work well. https://www.amazon.co.uk/TENEALAY-Passive-Preamplifier-selector-FV2-Black/dp/B0BWN5XR3P

The other thing to be mindful of is the quality of the actual potentiometer used - some can result in uneven channel balance at various positions.

This is why people tend to recommend a stepped attenuator, however you need to ensure that you get one that operates in 1dB steps, otherwsie it can be tricky to get the volume level right (can be too loud or too soft depending on which step is selected).

Good quality stepped attenuators also tend to be expensive.

 

[somebodyelse]

A passive preamp brings in a new set of disadvantages or problems, one is the vairable output impendance as the pot meter usre resistance to reduce the volume. So you need or a buffer or a multitap transfo to keep the output impendance of the preamp like the amp expect. A buffer is fairly simplle to make yourself even and the best solution.

It isn't usually a problem unless you have an unusually low input impedance on the amp, or a high cable capacitance, say from a long cable between the attenuator and the amp.
Edit: Should have refreshed the tab before replying - @audio_tony got there first with more detail.

 

[Deleted member 71304]

I use this, don't knoe if it measures fine but subjektive-acustically it doesn't change anything
Besides: great small company with fantastic customer support even in the EU

OL Switcher _ Shop JDS LABS

OL Switcher is the solution to your input/output woes, enabling you to route your audio where needed, without fumbling with cables. OL Switcher is a 2 input, 2 output, passively attenuating preamp. Connect a DAC, connect a DAP, connect a headphone amp, and your speaker system.

jdslabs.com

 

[whaardahl]

If you keep the cables from the preamp to the power amp reasonably short (0.5M to 0.75M) the impedance won't be an issue.

In simple terms what happens is this; Depending on the position of the volume control, the output impedance can be high enough to interact with the cable capacitance which causes a very slight reduction i nthe to pend frequencies.

With any decent cable (even Amazon basics), so long as you keep the length short this won't be an issue.

However - ideally you want an attenuator that's no higher than 10k ohms in value. 22k ohms would be just about ok.

Something like this would work well. https://www.amazon.co.uk/TENEALAY-Passive-Preamplifier-selector-FV2-Black/dp/B0BWN5XR3P

The other thing to be mindful of is the quality of the actual potentiometer used - some can result in uneven channel balance at various positions.

This is why people tend to recommend a stepped attenuator, however you need to ensure that you get one that operates in 1dB steps, otherwsie it can be tricky to get the volume level right (can be too loud or too soft depending on which step is selected).

Good quality stepped attenuators also tend to be expensive.

Very helpful; thanks!

 

[whaardahl]

It isn't usually a problem unless you have an unusually low input impedance on the amp, or a high cable capacitance, say from a long cable between the attenuator and the amp.
Edit: Should have refreshed the tab before replying - @audio_tony got there first with more detail.

You reinforce @audiotony's response, so thanks.

 

[OMas]

Hi, I have WiiM Pro Plus that is connected directly to a Buckeye NC502MP amp via RCA to XLR cables + a trigger cord. I'm very happy with this setup; but with more than one person using the system via more than one device, I'd like to protect my speakers from volume spikes…Thanks for any help!

Hey there whaardahl,

No need for anything additional…I own the Wiim Amp and, in their WiiM Home mobile control app, there is a setting for max gain; Devices > Gear Icon > Audio Settings > Volume Limit. A setting around 70% will result in plenty of gain without killing any transducers.