Simple Attenuators - Design And Testing

Gene Ballzz

Well-Known Member
Joined
Feb 19, 2013
Messages
3,952
Reaction score
4,881
Location
Las Vegas, NV
Hi pietro, I reckon the case should not be grounded, and with the plastic Cliff jacks that we recommend, then the case is not in circuit at all.


@JohnH ,

I have a "proposed" guess as to why we've encountered issues when the jacks get "grounded/connected together" through the metal enclosure. The speaker signal passing through this unit is AC and what we are considering to be "negative" (at the sleeves of the jacks) actually becomes "positive" for a portion of the full form of the wave cycle. Please correct my thought process, if I am full of Doo-Doo?

On another, yet possibly related note: I'm not sure "phasing" of the signal from stage to stage or input to output has ever been discussed?

Oh, and wait till you see Pietro's so far STELLAR 100 watt build! He's got some skills! He's been the "guinea pig" for my 100 watt drilling template and layout. It seems to work quite well! Now that he has "proven" it, I'd be happy to share with anyone interested! It is, however, centered around the use of the resistors from "chinesiawanoreanam!"

Thanks, As Always!
Gene
 
Last edited:

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
Post 1 updated

I've just given the first post on page 1 an update do-over, with the latest M2 schematic and discussion. I've also kept the original M design there, and reposted my sound samples, now from Soundcloud.

Nothing really new, but hopefully a bit clearer for new readers.

cheers
John
 

Gene Ballzz

Well-Known Member
Joined
Feb 19, 2013
Messages
3,952
Reaction score
4,881
Location
Las Vegas, NV
Post 1 updated

I've just given the first post on page 1 an update do-over, with the latest M2 schematic and discussion. I've also kept the original M design there, and reposted my sound samples, now from Soundcloud.

Nothing really new, but hopefully a bit clearer for new readers.

cheers
John

NOICE!
 

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
@JohnH has anybody figured out how to add an effects loop to your attenuator?

Thanks for your message. Effects loops for attenuators only work in designs with active re-amplification, but not with a purely passive attenuator such as our designs, which deal with speaker signals. If you take a line-out, that could go to an FX loop and then you need another power amp if you want to feed that to a speaker. Units like Boss TAE or Ox work that way..
 

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
M4 Attenuator - all the bells and whistles

In Post 1, first page of this thread, you can see the latest basic design for an M2 attenuator, then with a few additions such as line-out and correction for different speaker Ohms.

But there's several other ideas that have been developed and tried over the last couple of years, so this diagram puts them together, and I'm calling it M4. Mostly, its M2 with a series of extras that can be added, or not, as wanted. I'm hoping that by showing the basic design and then the first couple of add ons in Post 1, it will help to follow what is added.

M4 221119a.gif

Stage 1 - Bass resonance circuit

This has been referred to as M3. An iron-cored coil L2 and capacitor C1 are added in series with the air-core inductor L1. This shows the amp the bass peak and makes it track the tone slightly more accurately. From a few builders, the concensus to date is that if just for attenuating a guitar speaker, the circuit works perfectly ok without this bass circuit, since the real speaker replicates the peak, interacting with the attenuator. But it may improve the response when using a line-out without a speaker. If it's included, the parts are fairly bulky and the best capacitor may be two or more in parallel, using large non-polarized film caps for very low dissipation.

Whether of not the bass circuit is used, no other parts are affected and it could be added later if wanted.


Stage 1 -3.5/-7db switch

The M2 provides attenuation from -7dB down to -31.5dB, in small equal steps of -3.5 dB. This will cover most needs, but for some, particularly those gigging or using small amps, a -3.5dB setting may be useful. So this switch changes resistances in Stage 1 to provide that option, with full reactive tone. The intention (for best tone) is that this is only used when that small -3,5dB setting is needed, and to go to the next step down, it is returned to -7dB as usual. However, it is safe to use it in any switch arrangement, such as -3.5 in stage 1 and other stages engaged too.


Stage 2 - Three resistors

Stage 2, which is -14dB, usually has just 2 resistors, but to go with the amended Stage 1 with the -3.5/-7dB switch above, it needs one more resistor to fix the correct impedance, since it can be electrically a bit closer to the amp when Stage 1 is set at -3.5.


Line out

For this diagram, I've shown a 1k pot with resistors, so that the output is nominally max 1/10th of the amp voltage. This should allow a good level to be found with most amps, depending how they are driven. It is intended to go into an unbalanced line-in on a mixer or similar. A cab-sim or IR box will be needed to get a reasonable speaker-like tone in a recording or PA feed. But you may not need a line out, some devices such as Redbox by H&K or Mooer Radar go between amp and load, with a direct pass through. You can also take a signal from a spare output on the attenuator, if a speaker is plugged in.

If using the line out with no speaker, set all attenuation stages to max. If you don't have the bass circuit discussed above, you might add a bit of low EQ down-stream, eg slight bass boost with cut below 100 hZ which is setting that I've found works quite well.


Multiple outputs

The basic circuit is optimised for speaker ohms = attenuator build = amp output. But so long as the attenuator version matches the amp, you can plug different speakers into it safely since the Ohm miss-match amp to speaker, is adequately corrected by the attenuator. But the base tone may be a bit bright or dark, so the added outputs correct for this. Otherwise, a 16 Ohm speaker into an 8 Ohm attenuator will be a bit dark, and a 4 Ohm speaker will be brighter.

Out 1 and Out 2 are in parallel, useful to plug two 16 ohm cabs into an 8 Ohm attenuator for an 8 Ohm load. Out 3 corrects for a single 16 Ohm cab in an 8 attenuator, and Out 4 is for speaker Ohms < attenuator. Its to do with the impedance and damping seen by the speaker. Just build what you need. eg, if you build for 16 Ohm, you just need Out 1 and Out 4 to deal with a 16 speaker, or an 8, or two 16's.


Full bypass switch

Many people may feel that this is needed but don't actually use it. ie, if you don't want to attenuate, then don't connect the attenuator. With a bypass switch, you need to be very careful to always match speaker to amp, and never operate it unless the amp is 'off' or on 'standby' . But it could be useful at a gig, where it becomes necessary to engage or disengage the attenuator later to control volume, without fully rewiring. Ive shown it here so that it should be safe with any of the outputs, but to get the attenuator fully out of circuit, use just out 1 or out 2.


Footswitch

Depending how you like to play, a small boost or cut for rhythm may be useful. This circuit puts another -3.5dB stage in a remote footswitch box. It is wired with a 3 core cable, using a TRS jack with switch contacts. The switch contacts for tip and ring bypass it when not plugged in and they are crossed over in parallel.

Also included is an LED, to light up in the louder setting. The switch can be a 3PDT, such as used on stompboxes. Two contacts in parallel give redundancy for the rmain signal. The cable could be made from 3 core 5 Amp mains flex, I suggest it is wired fully into the foot switch box so its not confused with any normal cable.


Overall, few will need all these features. There is a huge advantage in keeping builds as simple as possible, to build, and also in use. But I hope that some of this will be useful and interesting too!.
 
Last edited:

ellipsis

New Member
Joined
Oct 18, 2022
Messages
15
Reaction score
7
Location
London, UK and Riga, Latvia
After having the previous few weekends pre-empted by other obligations, I've finally put together my first M2 over the past 24 hours. I've done an 8 ohm M2 with bypass switch and line out, and it's going to live in my office/workshop, attached to both a 1 x 12 cab under the desk and an audio interface.

M2 - 1.jpeg
I'm quite happy with myself that I've apparently wired and soldered everything properly, because upon first try all of the switches and knobs and jacks do what they're supposed to, and the amp I used to test it didn't go up in smoke.

First impressions: I like it, a lot. I've always had a use for good attenuation, and I've owned various options over the years, and sold them because they weren't quite it - Dr. Z Brake Lite, Jet City Jettenuator, Swart Night Light Jr., Tone King Ironman II. This M2 really does what it's designed to do - delivers multiple usable playable volumes without sacrificing tone at the lower and lowest volume settings.

The line out works just fine as well. I used a 5k (well, 4.7k, since that's what I had available) resistor and a 5k pot, from a @JohnH schematic from a couple of weeks ago. The output is pretty hot, I don't get much past 9 o'clock on the pot before the signal is too much for the interface. With the cab disconnected and max attenuation (using it as a silent load), it sounded pretty good just slapping a generic cab sim on the signal in a DAW. I suspect it would sound much better if i put some thought into it (use a good plugin and tweak etc.). I must say it feels like there's "something" missing in the bass, but I don't know if I'm just telling myself that because I know that I want to build one of these boxes with the bass resonance circuit. A quick EQ-ing helped things a bit, and it'd probably get better if I spent more that 30 seconds on it, but I'll probably build an M3/M4 to satisfy my curiosity.

I still have a UAudio Ox, Two Notes Captor X and Fryette Power Station PS-2A strewn across the couple of places I live and have gear. The Ox and Captor X will be going up for sale, because the M2 has made them obsolete/superfluous. I am keeping the Fryette, though, because it is an excellent tool, and an entirely different level of functionality than the boxes on this thread - integrated tube power amp, fx loop etc.

Here's my new unit in its new home, in the upper right hand corner:
M2 - 2.jpeg

Once again, many thanks to @JohnH and @Gene Ballzz for all of their efforts here.
 

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
Hi @ellipsis , congrats on getting that together. It looks like a great build and thanks for all that feedback! May I ask what amp you have tried with so far?


On line-out, You can cool it down with a resistor across the pot outer legs, and I might change the M2 diagram to show thst explicitly.



We are deeply honoured by your 'for-sale' list!
 

ellipsis

New Member
Joined
Oct 18, 2022
Messages
15
Reaction score
7
Location
London, UK and Riga, Latvia
May I ask what amp you have tried with so far?

An Acme Silvertone 1484 - 2 x 5881 push-pull, which is the most powerful amp I have with me here in the UK. It also happens to be one of my favorite amps in general (https://www.acmeverb.com/home) and much better sounding and more reliable than the actual Silvertone 1484 I used to own and subsequently sold.

As I may have mentioned earlier in this thread, my amp collection is generally low wattage (2 x 6V6, 2 x EL84, SE 6V6), so I wanted to first try the M2 with the amp with the most juice and see what happens. All good - after nearly an hour of playing the amp nearly dimed, I can't say the M2 was even particularly warm. I didn't want to drill holes in the top unless I needed to (I don't like the aesthetics), and apparently I don't need to. I do have a few holes in the side and in the base.
 

Gene Ballzz

Well-Known Member
Joined
Feb 19, 2013
Messages
3,952
Reaction score
4,881
Location
Las Vegas, NV
After having the previous few weekends pre-empted by other obligations, I've finally put together my first M2 over the past 24 hours. I've done an 8 ohm M2 with bypass switch and line out, and it's going to live in my office/workshop, attached to both a 1 x 12 cab under the desk and an audio interface.

View attachment 119528
I'm quite happy with myself that I've apparently wired and soldered everything properly, because upon first try all of the switches and knobs and jacks do what they're supposed to, and the amp I used to test it didn't go up in smoke.

First impressions: I like it, a lot. I've always had a use for good attenuation, and I've owned various options over the years, and sold them because they weren't quite it - Dr. Z Brake Lite, Jet City Jettenuator, Swart Night Light Jr., Tone King Ironman II. This M2 really does what it's designed to do - delivers multiple usable playable volumes without sacrificing tone at the lower and lowest volume settings.

The line out works just fine as well. I used a 5k (well, 4.7k, since that's what I had available) resistor and a 5k pot, from a @JohnH schematic from a couple of weeks ago. The output is pretty hot, I don't get much past 9 o'clock on the pot before the signal is too much for the interface. With the cab disconnected and max attenuation (using it as a silent load), it sounded pretty good just slapping a generic cab sim on the signal in a DAW. I suspect it would sound much better if i put some thought into it (use a good plugin and tweak etc.). I must say it feels like there's "something" missing in the bass, but I don't know if I'm just telling myself that because I know that I want to build one of these boxes with the bass resonance circuit. A quick EQ-ing helped things a bit, and it'd probably get better if I spent more that 30 seconds on it, but I'll probably build an M3/M4 to satisfy my curiosity.

I still have a UAudio Ox, Two Notes Captor X and Fryette Power Station PS-2A strewn across the couple of places I live and have gear. The Ox and Captor X will be going up for sale, because the M2 has made them obsolete/superfluous. I am keeping the Fryette, though, because it is an excellent tool, and an entirely different level of functionality than the boxes on this thread - integrated tube power amp, fx loop etc.

Here's my new unit in its new home, in the upper right hand corner:
View attachment 119529

Once again, many thanks to @JohnH and @Gene Ballzz for all of their efforts here.

Hi @ellipsis , congrats on getting that together. It looks like a great build and thanks for all that feedback! May I ask what amp you have tried with so far?


On line-out, You can cool it down with a resistor across the pot outer legs, and I might change the M2 diagram to show thst explicitly.



We are deeply honoured by your 'for-sale' list!

Very nice job sir! And yes indeed, that "for sale list" speaks VOLUMES (pun definitely intended ;)) about John's design!

Just Noticin'
Gene
 

ellipsis

New Member
Joined
Oct 18, 2022
Messages
15
Reaction score
7
Location
London, UK and Riga, Latvia
As I now consider building another attenuator, this time with the bass resonance circuit, can anyone enlighten me on why it would be preferable to use a huge and expensive film/polypropylene capacitor (or a pair of 100uF ones to get to a 200uF capacitance) instead of a seemingly more sensible bipolar electrolytic? Thanks in advance for any insight.
 

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
You might be ok with the bipolar electros, or you might not. The resonance happens at about 110hZ, and above that frequency (ie almost the full spectrum), most of the amp power has to pass through the capacitor. Hence a low loss and high ripple current is needed or else the capacitor may heat up.

Electrolytics have a much higher dissipation factor. So apart from the heating and current issues, the Q of the bass resonance will be better.

But I'd suggest maybe a test. You could add the bass circuit as an external test to your current build. Just add it in series with L1. And since you can monitor, you could do this with the iron-core coil and a set of electrolytics in parallel. Try it with and without and you'll see if it's making a difference and how it heats up, If it does.

I thought about the big film caps from a thread on TGP on load boxes:

 

luxspring

New Member
Joined
Jan 12, 2022
Messages
12
Reaction score
0
Background

Passive attenuators are wired between the amp output and the speakers. Their function is to absorb most of the output power of the amp, feeding a smaller amount to the speaker itself. This allows the amp output stage to run at higher power, letting the glorious tone of a good valve output stage develop, but without excessive volume.

The attenuator must present a load to the amp that is similar to a speaker and also maintain the tone as volume is reduced. It needs a consistent tonal and dynamic response from low attenuation, down to sub-bedroom level. This is where the simplest designs can be inferior, and the best commercial designs get expensive.

With feedback and testing by others I think we have a design that achieves this. For about $100-$120, anyone with workshop skills and the ability to follow a circuit schematic can build this. I want to thank everyone who has built one of these or contributed to this thread, with a special thankyou to @Gene Ballzz who was the first to see the potential and has been a great source of insight and practical help for everyone.

An important point:

Anyone who builds it does so at their own risk, and takes responsibility for working out their own wiring for their own private, non-commercial use, and completing it safely


Summary: November 2022

This thread focusses on the design of reactive attenuators for DIY building using simple construction and inexpensive parts. It started with just a few resistors and then developed into multistage resistive and reactive designs. The latest designs work much better than I’d first expected and have been built and tested successfully by many others. The design continues to evolve but the main principles have been constant for several years. This 1st post shows the current basic design M2, and a few possible additions to it.

View attachment 118594

It must be matched to the output tap of the amp, eg 8 Ohm or 16 Ohms. Component values for both are given, which differ by a factor of two:.

There are 4 attenuation stages, engaged or bypassed by switches.

Stage 1 is the key reactive stage and includes an inductor coil. This stage on its own, reduces power by a factor of 5, or -7db, reducing a 50W amp to 10W. The inductor coil is configured so that the impedance presented to the amp is similar to that of a real speaker (values based on various Celestions), particularly how impedance rises with frequency.

After Stage 1, three more stages are provided. These can be mixed and matched, but the design shown is based around additional -3.5db, -7db and -14db stages. By combining these switches in combination, and with Stage 1, reductions of up to -31.5db can be achieved in small, equal steps of -3.5db, at which point a 50W amp, at full power, is playing quietly at about 35mW.

On pages 111 and 112 are two construction layouts which may assist (designs are very close to above, not identical though). I recommend studying the diagrams above to understand the connections and then adapt the layouts to suit your needs. Further features can be added, discussed in the thread, such as bass resonance circuit, foot-switchable stage, variable input impedances, bypass switch etc.

If you'd like to see a schematic with most of these further add-ons, go to Page 158, post 3146 from 19/11/2022.


Component values and power ratings

The table above shows the recomended power ratings for each resistor, based on up to 50W amps. The component ratings need to have a good margin above the actual power. I use a factor of at least 3 for case-mounted aluminium resistors, bolted (using thermal grease) to a heavy metal chassis or heatsink , and a factor of 5 or more for air-cooled resistors. These values fit with the spec in the schematic diagram above and also allow for overdrive of the amp.

Wire for hookup and also the winding of air-cored inductors should be 18 gage for 50W attenuators, and this is also OK for a 100W one, if built to the 16 Ohm values. For switches, use at least 5A rating (at 125V ac) for a 50W 8 Ohm build. The best jacks are plastic Cliff jacks, TRS (ie stereo type) which grip the plugs better than mono jacks.


Cooling

With amps > 30W at high power, the unit will heat up as it dissipates power. A good size die-cast aluminium case is best. Once components are positioned, then a number of additional large vent holes should be drilled, in the top and in the base, with feet to raise up the base. This will help to promote good convective flow of air out through the top, replaced by cool air at the base. The best colours for cooling are dark. For amps more than 50W, a fan should be added

Mount the coil without using a ferrous bolt, with a few mm timber or plastic spacer off the case surface.



Thanks for reading. If you are interested, and since this is a long thread, I suggest to read this post, look at the layouts and the most recent few pages, then make a post yourself and we'll be happy to discuss what would work best for you.

For nice collection of completed builds, see this thread:





Attenuator M ( January 2019)

The following is the original reactive design M which I built myself, with sound samples. M and M2 are closely related and perform the same, although M has two coils. It also has a bypass switch and a -3.5dB setting.

The build was in a case 170 x 120 x 55mm of thick aluminium:





Simplified version M-Lite

This was the same design, omitting the bypass switching and the 3rd output. Minimum attenuation is -7db. Its an easier build and it should still meet most needs.



Performance

In the schematic above, there is a graph showing a calculated frequency response at each attenuation level from 0 to -31.5 db. These use a spreadsheet to calculate the signal at each stage of the circuit, as a series of voltage dividers, using complex number theory to assess magnitudes and phase angles. The speaker was represented, for analysis, by an equivalent load model, by Aiken:

http://www.aikenamps.com/index.php/designing-a-reactive-speaker-load-emulator

...adjusted to match the measured performance of a G12M 4x12 cab. The plots are based on small signals, with the amp output impedance assumed to be 20 Ohms, for an 8 Ohm tap, based on measurements of my VM2266C. These calcs were used to adjust the values in the design.


Sound Samples

The ideal is for volume to reduce, but with no change in tone or feel. This is best tested with a consistent loop, with attenuated sounds then normalised back to equal volume:

Attenuator M: Max attenuation to non-attenuated:


Attenuator M: Normalised:


It’s a simple looped riff, played twice at each attenuation setting from -31db up to full unattenuated in 3.5db steps. The second file is based on the same recording, with each stage normalised for volume so you can hear any differences in the tone.

My VM2266c amp was on LDR mode, body at 6, detail at 9, master vol at 6, tones and presence at 6, using my LP bridge pickup, miced off a speaker.


The plots are taken from the sound sample posted above. The lower set of data are the basic plots, from full volume down to -31db (db scale is arbitrary, but relative db's are right).

The upper plots are intended to show the differences between responses. I took the -7db recording as the base case, so this is shown as a flat line. The others are the various other settings, with the -7db trace subtracted. The ideal for these traces is therefore also a flat line. And for all the traces below -7db down to -31db, this is what is happening, there is virtually no further tonal change at all as you attenuate down as far as you want. It measures as consistent.

Hi guys. I’m sure this question has already been asked but is it safe to connect an 8ohm amp speaker output to a 16ohm version of the johnh attenuator ?
Thanks a lot
Paul
 

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
Hi guys. I’m sure this question has already been asked but is it safe to connect an 8ohm amp speaker output to a 16ohm version of the johnh attenuator ?
Thanks a lot
Paul
EDIT: I may have miss-read the question - see posts below

Yes its perfectly safe with an M2, 3 or 4. The fixed stage 1 which is always on, separates the speaker enough from the amp so the amp still sees close enough to 16 Ohms.

The tone may be a little brighter, a bit like turning up a presence and also a resonance knob, if you had one. On page 1, the second diagram has an extra output jack Out 4 that compensates for this, But its only a tone tweak, no safety or miss-match problem.

If however, you have a full bypass switch, then to use that, amp ohms must match speaker ohms
.
 
Last edited:

Gene Ballzz

Well-Known Member
Joined
Feb 19, 2013
Messages
3,952
Reaction score
4,881
Location
Las Vegas, NV
Hi guys. I’m sure this question has already been asked but is it safe to connect an 8ohm amp speaker output to a 16ohm version of the johnh attenuator ?
Thanks a lot
Paul

Yes its perfectly safe with an M2, 3 or 4. The fixed stage 1 which is always on, separates the speaker enough from the amp so the amp still sees close enough to 16 Ohms.

The tone may be a little brighter, a bit like turning up a presence and also a resonance knob, if you had one. On page 1, the second diagram has an extra output jack Out 4 that compensates for this, But its only a tone tweak, no safety or miss-match problem.

If however, you have a full bypass switch, then to use that, amp ohms must match speaker ohms.

@JohnH,

As the wording was a little odd, you may have misunderstood the question from @luxspring ? I think he was asking if it is OK to plug a 16 ohm attenuator out of an 8 ohm amplifier output. I don't think he meant using an 8 ohm speaker, although that may also be the case. I've re-read the question a couple of times and still am not quite sure?

I've noted that some folks get confused by the direction of signal flow, especially when dealing with a combo, as they assume the speaker to be part of the amp.

To be more clear, if the amplifier's "output" jack is only 8 ohm, this should only feed the "input" of an 8 ohm load (either attenuator or speaker), but the "output" of the attenuator cares a little less whether it is feeding a 4 ohm, 8 ohm or 16 ohm speaker load, except for the tonal aspects that you mentioned.

AMPLIFIER OUTPUT>ATTENUATOR INPUT/ATTENUATOR OUTPUT> SPEAKER INPUT

Simply Attenuatin'
Gene
 

luxspring

New Member
Joined
Jan 12, 2022
Messages
12
Reaction score
0
@JohnH,

As the wording was a little odd, you may have misunderstood the question from @luxspring ? I think he was asking if it is OK to plug a 16 ohm attenuator out of an 8 ohm amplifier output. I don't think he meant using an 8 ohm speaker, although that may also be the case. I've re-read the question a couple of times and still am not quite sure?

I've noted that some folks get confused by the direction of signal flow, especially when dealing with a combo, as they assume the speaker to be part of the amp.

To be more clear, if the amplifier's "output" jack is only 8 ohm, this should only feed the "input" of an 8 ohm load (either attenuator or speaker), but the "output" of the attenuator cares a little less whether it is feeding a 4 ohm, 8 ohm or 16 ohm speaker load, except for the tonal aspects that you mentioned.

AMPLIFIER OUTPUT>ATTENUATOR INPUT/ATTENUATOR OUTPUT> SPEAKER INPUT

Simply Attenuatin'
Gene
Hi again guys. Gene nailed it there, so sorry for how I worded it.

So in that case , why can we not do a one way mismatch with the Amp to attenuator connection like we can normally do with an amp direct to a speaker (no attenuator) ?
I.e. 8 ohm out of the amp direct to a 4ohm or 16ohm speaker.
 

JohnH

Well-Known Member
Joined
May 31, 2008
Messages
5,177
Reaction score
3,449
Location
Wilton NSW
Thanks Gene - yes I see now!

@luxspring - you must indeed match the output of your amp to the ohms rating of the attenuator. If you missmatch, that is at your risk, but its not recommended
 

luxspring

New Member
Joined
Jan 12, 2022
Messages
12
Reaction score
0
Thanks Gene - yes I see now!

@luxspring - you must indeed match the output of your amp to the ohms rating of the attenuatoOR
Thanks for the reply John , so that is loud and clear then.
Which leads me to ask, is there any possibility of another version (M5?)with a selectable amp input impedance ?

Thanks
Paul
 

Latest posts



Top