Vox ac15tb > ok with a 16ohm spkr?

[Chuck H]

Well here's a "layout". Which is what I think you were interpreting a diagram to be? I will say I just drew it up how it made sense to me and this doesn't represent a 7x5x3 case. But I know it would fit in that case with room to spare front to back. There is no significance to lead color other than trying to be sure the connections were clear. Since there is nothing to actually mount the inductors and capacitor to, on my own unit I just drilled holes in the bottom of the box and secured them with zip ties. Add screw on rubber feet to the bottom for clearance on the resistor mount screws and zip ties.

Estimated cost is about USD $100. It occurs to me you could easily buy a used "Hot Plate" for that, but it wouldn't sound as good

[vintagekiki]

About speaker attenuators

https://www.tdpri.com/threads/reactive-loadbox-attenuator.806311/

https://www.thegearpage.net/board/index.php?threads/suhr-reactive-load-i-r-reviews-and-amp-compatibility.2019071/

Weber MASS Attenuators

https://guitar.com/guides/diy-workshop/diy-workshop-build-your-own-attenuator/

http://guitarprojects.weebly.com/diy-attenuator.html

https://forum.allaboutcircuits.com/threads/speaker-attenuator-aka-power-soak.167344/

https://merwinmusic.com/2020/08/12/how-to-build-a-guitar-amp-attenuator/

[g1]

Well here's a "layout". Which is what I think you were interpreting a diagram to be?

Chuck, you've went way 'above & beyond the call' on this and I know you've posted about it before. Your efforts are greatly appreciated.
Here's a zip for you (schem/layout/notes) to save some time in the future. You can edit, delete, rename as required, or make a pdf so it can't be edited (or I would be happy to do that for you).

[Chuck H]

Chuck, you've went way 'above & beyond the call' on this and I know you've posted about it before. Your efforts are greatly appreciated.
Here's a zip for you (schem/layout/notes) to save some time in the future. You can edit, delete, rename as required, or make a pdf so it can't be edited (or I would be happy to do that for you).

Edit indeed! I've seen more than one error in some of the work I've posted (even as recently as this thread)

Thanks for collecting it all in one place

[Bloomfield]

Chuck, thanks for all the info on your attenuator; I think I might build one one of these days. Does it have its own thread somewhere? I have a couple questions and some additional info, but this thread has already run long and off-track.

[Sea Chief]

Edit indeed! I've seen more than one error in some of the work I've posted (even as recently as this thread)

Thanks for collecting it all in one place

Hi Chuck, you are a real gentleman to post that layout up for us.. superkind of you. Even colour coded for idiots like me so its 'fun' too & I dont get bored. No I probably cant get that chassis sent, but with a code/ part no. I can search away over here, we get the eddy types ok. Muchos gratias sinior Chuckos. SC

[Sea Chief]

vintagekiki thanks for those links/ internal photos too.. very useful indeed.

[Chuck H]

Chuck, thanks for all the info on your attenuator; I think I might build one one of these days. Does it have its own thread somewhere? I have a couple questions and some additional info, but this thread has already run long and off-track.

I don't remember a devoted thread. But I designed and built this thing twelve years ago, so who knows.?. I'm sure the layout I posted is correct. The error in this thread was that I had the 22r and 33r resistors swapped for position. Not a huge deal, but...

In the link posted by vintagekiki (#66) for the stomp box forum member Manfred posted a very early image of the schematic (at least ten years old) that has two errors. And he posted it only a year ago! Where did he get this? I think I'm going to join the forum just so I can post a correction.

[Bloomfield]

I found a source in Canada for the inductors: https://qcomponents.ca/McBride-CO-12...keep_https=yes and https://qcomponents.ca/McBride-CO-12...keep_https=yes

They don't have .25mH, just .2 and .3. Would it be better to use 2 x .2mH, 2 x .3mH, or one of each?

[Chuck H]

I'd use .3mH
I always figured there was some inductance value lost in the "sandwich" due to mutual inductance between the coils. I just never had the ability (or maybe knowledge of how to use what I have to to do it?) to test for the actual value in the constructed unit. Using .3uH seems like the smartest error direction to me since odds are any error in the actual design could be low from ideal.

[Sea Chief]

I plan to get round to this build idea once I've ironed-out a few gremlins on my AC15, so I'll come back to this thread.

In meantime I think I need a new ('vox gremlins') thread tbh, so if anyone could have a read- Id be grateful.

Thanks Chuck & to vkk for info on here. SC

[Sea Chief]

Chuck H Chuck could you advise: I built a small attenuator (Im not sure if if wasn't from a design on here.. cant think how else Id have made it) which has a few things might be of use. The rheostat.. now around its edge I read 25r (good) but as to wattage it gives no indication.

It says " RHS 25r.. 25 ohms.. 1.0A...List 214 L...IND.CONT.EQ... FOR USE AS SERIES RESISITOR ".

Any ideas?

[Chuck H]

RHS is the Ohmite series code and means 25W. 25r is the value code. Together (RHS25r) they make the model number. Simply looking it up would have given you your answer. That rheostat will be fine. I know it says "for use as series resistor" but it's the same one I have in my own attenuator and so far so good.

[Sea Chief]

RHS is the Ohmite series code and means 25W. 25r is the value code. Together (RHS25r) they make the model number. Simply looking it up would have given you your answer. That rheostat will be fine. I know it says "for use as series resistor" but it's the same one I have in my own attenuator and so far so good.

Ok great thanks (sorry I thought the RHS was just the makers name: unless you know what to look up, it's all a minefield of numbers & letters.. 25r I got ok).

So what amps have you used yours with, & do you use it as a way of fully cranking your amp.. or just into the sweet spot as it were?

[Chuck H]

My personal amp puts fifteen clean watts. Not sure how much when cranked and overdriving, but it's more than that. I've used my attenuator with that amp cranked into it A LOT. Over 500 hours for sure. Maybe a thousand. It only ever gets warm. And mine is literally jammed into a much smaller chassis than the layout I put together for you. Meaning the unit you build will dissipate heat better (good). I've also used my attenuator a few times with fifty watt (ish) amps but only for short duration amp testing purposes. No failures.