DR: OT @ 2 Ohms/ 10" spkr Q.

[g1]

Have you tried shorting out the 1R yet?
If it is now working "exactly as it should", then the problem is in how we are defining "normal volume". Are you talking about conversation levels? How loud would you define someone playing an acoustic guitar hard?
As Chuck said, "If you can raise your voice to talk with someone in another room, you should be able to crank your DR into this attenuator". Is this the type of volume we are talking about?
Look at the numbers Dave H used "Are you trying to be really quiet? With the 1R resistor in the attenuator the DR will be attenuated to about 0.35W which will be about half as loud as an unattenuated Champ (assuming 1/10 power is half as loud)."
.35W doesn't sound like much does it? Well, consider that guys who build 1/4W micro-amps for apartment use say they are too loud, probably half that power would be good. I think this is the type of volume you are calling normal, conversation level that won't wake the baby in the next room maybe?
Anyway, what is the result with the 1R bypassed?

[Sea Chief]

Yes I think normal volume for us here, often with folks in close proximity perhaps more pften than yous, is perhaps much less. Someone playing acoustic gtr hard is what Id term for a room "nearing loud" and what maybe Im trying to get to with the attenuator.

Ok bypassing the 1R seems to work: at DR 6.5 and max attenuation I can hear the OD, albeit some fizzyness to notes. I wouldnt call it a great sound and its not the richness of the Champ OD (with the 1R).. but Im getting somewhere.

The attenuator gets very hot after 15 mins.. so I'll have to re-route the wires next to the R's as Im worried the heat might melt the insulation & short them to the box.

So would the idea now be to consider a fat R between 0 and 1R.. is that the idea?

Thanks SC.

[Chuck H]

The 1R is an unnecessary part of the design. It won't reduce heat to have it or any other value below 1R in there. It was only there to minimize the glitchiness of the rheostat at the terminal end of it's rotation. If you decrease attenuation a tad you should still have the same tone for your Champ that you did with the 1R installed. I'm surprised yours gets that hot. I suppose it's hard to know the exact temperature. If you can put your finger to it and hold it there then the wires are fine. Of course... If you play a lot and have asbestos fingers that may not be an accurate enough gauge. You be the judge. If you can widen the holes and insert a heat resistant sleeve that should be as good as anything. Heat resistant gasket material from an auto parts store is a good cheat if you don't want to wait for an order of silicone grommets.

[Sea Chief]

Ah ok Chuck. I think it must be fact that I played with it for 20 mins then, not the 5 mins before at vol 6.5 with the 1R in- it wasn't even warm then. So why I heard no OD before and its there now at same vol I wonder.. I even backed off the attenuator slightly (as you say damn glitchy- one tiniest notch nr max end and boom the vol increaces hugely) the 2nd time w'out the 1R.

Anyway it is extremely hot- far too hot to hold fingers on the Rs (or the housing tbh too- 1,2.. ouch hot) so much so the wire insulation is slightly pliable.. so I'll just re-route round back of the box. Idea is its a temprorary housing until I see something else.. but I cant say I'll find anything better tbh. Is this very high heat of any concern? or is that simply to be expected & the whole idea of the oversize heavy-duty design of the rheostat & the R's?

Gratefully, SC

[Chuck H]

Well... A DR does put out a little more than my 2xel84 amp. And that's my main gauge for how hot these things get. When I built one in a 4xel84 I doubled all the ratings.

If you get a bigger chassis to build in it should be fine. Obviously any extra space should be used to separate the rheostat and the bigger power resistor. Those are the components dissipating all the watts. I've use mine with a 50W amp for limited time periods (maybe 10min) without incident and it did get very hot, but not so hot I couldn't pick it up. There are two others a lot like yours (Ohmite rheostat, aluminum housed resistors, small chassis) on 2xel84 amps and they're working just fine after several years. Perhaps those players aren't attenuating all the way, all the time. That IS the hottest way to run them. These are also rear mounted types on the bent aluminum that I showed earlier. So the rheostat would be exposed to free air. Oh well... My point is just that the units have proven quite durable. So you just need to get the heat under control. Until you come across a bigger chassis to mount the parts in, maybe just leave it on it's side and blow a small fan on it when you're going to play for an hour.

[Sea Chief]

All very interesting, & understood ChuckH. I suppose the fallible bits are the plastic switch housing & wire coating esp. Is that solid core cloth stuff perhaps a better bet? maybe higher current (a bit thicker iirc) heater guage stuff? (although if my logic is correct its not high current here that's causing the heat, or it'd be dangerous housed/ open as it is, so erm therefore its watts.. which is not current but.. erm.. p o w e r/ heat.. erm).

Interesting it should work so well on the 4 Ohm Champ. Even if its duties lie solely with this its a valuable addition: as I said playing that true OD 'brown' sound I last experienced nr 30 yrs ago at school.

Hugely grateful again Chuck.

[Chuck H]

All very interesting, & understood ChuckH. I suppose the fallible bits are the plastic switch housing & wire coating esp. Is that solid core cloth stuff perhaps a better bet? maybe higher current (a bit thicker iirc) heater guage stuff? (although if my logic is correct its not high current here that's causing the heat, or it'd be dangerous housed/ open as it is, so erm therefore its watts.. which is not current but.. erm.. p o w e r/ heat.. erm).

Interesting it should work so well on the 4 Ohm Champ. Even if its duties lie solely with this its a valuable addition: as I said playing that true OD 'brown' sound I last experienced nr 30 yrs ago at school.

Hugely grateful again Chuck.

Hugely sorry for losing patience. Too bad you can't get more volume going. It gets better. Once you play through some cranked up tube amps it's hard to go back to stomp boxes. Well, unless your a metal head and that's your sound I suppose. Otherwise... Yes, it's less refined and yes, it's got distinctly UN-pretty things going on like spikes, crossover distortion and some slurred bottom end. But somehow it's still just better That's why we love our tube amps

[Sea Chief]

Not at all Chuck- I understand. For some reason tube amps don't perform with me, your annoyance is a fraction of mine. But I will persist you see until I get a result. Turning the 5F1 up (2x when both n'bors out) does not get me the brownsound your attenuator does, its harder/ less harmonic with no "sag"/ no urge to keep playing. Why? christ knows. And why the DR got into some brownsound at vol 4 with no attenuator with an unmounted p12Q on a table, at loudish room levels.. christ knows too. I might take to same guy & demand to try again to find out as I'm mystified. Its like these amps laugh at me! thanks, SC

[Sea Chief]

Ok b*llocks to the DR, Im not sure Im going to get my brown mojo sound from this. Its a nice clean amp with great reverb and tremolo: thats what it shall be. But, Ive got Champlove for the 1st time! its brown & it oozes mojo; I tried at vol 12 & ok it sounds flubby & OTT/ unuseable (whether this is the attenuator robbing treble, or actually how it sounds at 12 I'd be interested to know) .. but hang on.. turn gtr vol down to clean it up (one thing Ive been puzzling over in what situation this works -properly/ exactly like this- for donkey's years) and bingo! the brown sound appears! by god you have to search for it.. in my case a bewildering & perplexing road, but its paid off thanks to Chuck's gadget. And it remains barely warm too.

Two small things I dont understand. Ive read XYZ about the general gtr rule of 'turn gtr vol down & the treble diminishes', & all about wiring methids to counter etc. So why does the opposite happens with my tele and £20 strat-with-upgraded £30 p/ups? (sounds as good as the tele- I kid you not) IE turning the fat unuseable raucous OD at 12 down to 1/2 via the gtr vol and it brightens beautifully (& bingo! Ive found my mojo/ brown/ the goodies sound Ive been striving so many years for.. spankingly good.. a fluke as Id settled on Champ be good up to vol 8, but no good at all after).

Is this brightening usual??

And 2ndly.. assuming the SG is ok (it is, it must be/ the p'ups just cant be bad, & Ive re-wired it to 50's wiring with small but good benefit/ a tad brighter overall but same ballpark sound- daaaark) why when I turn the vol(s) down & it cleans up like the single coil gts above, the tone doesn't brighten? is this a humbucker thing?

Thanks, SC

[Dave H]

And why the DR got into some brownsound at vol 4 with no attenuator with an unmounted p12Q on a table, at loudish room levels.. christ knows too.

You don't have to be Jesus to figure that out. An unmounted speaker is way less efficient than one in an enclosure especially at the low end. That fact was explained at the time so pay attention at the back then we won't have to keep repeating ourselves

[Sea Chief]

Patronising post.

I cant recall anything at all mentioned about this spkr's efficiency being lowered by its placement, or its efficiency being altered whatsoever.

If you cant contribute without being demeaning- just dont bother please.

[Dave H]

Cheer up Chief. I was only pulling your leg. We are trying to help you know. I think the speaker efficiency post was in a earlier thread.

[Sea Chief]

Cheer up Chief. I was only pulling your leg. We are trying to help you know. I think the speaker efficiency post was in a earlier thread.

Yes I think it might be too Dave H...............

[eschertron]

Two small things I dont understand. Ive read XYZ about the general gtr rule of 'turn gtr vol down & the treble diminishes', & all about wiring methids to counter etc. So why does the opposite happens with my tele and £20 strat-with-upgraded £30 p/ups? (sounds as good as the tele- I kid you not) IE turning the fat unuseable raucous OD at 12 down to 1/2 via the gtr vol and it brightens beautifully (& bingo! Ive found my mojo/ brown/ the goodies sound Ive been striving so many years for.. spankingly good.. a fluke as Id settled on Champ be good up to vol 8, but no good at all after).

Is this brightening usual??

shhhhh..zzz...ip! The sound of a can of worms being opened

There's about as many opinions about bright caps as there are IP addresses in the known universe. Start by searching for that term, and see what I mean. But a general rule of thumb; the bigger the cap value (in pF) the more 'brighness' it will let past the vol knob as it turns down.

[Sea Chief]

shhhhh..zzz...ip! The sound of a can of worms being opened

There's about as many opinions about bright caps as there are IP addresses in the known universe. Start by searching for that term, and see what I mean. But a general rule of thumb; the bigger the cap value (in pF) the more 'brighness' it will let past the vol knob as it turns down.

oops well Id best not go there then.

What I was meaning is not the minutiae of X vs Y caps.. but the bigger picture was so 'two camps': seemingly the single coil gtrs (fenders) getting slgnificantly brighter compared to A) the gibson, which remained as bright whatever gtr vol.. and B) compared to what I had envisaged that being the more the gtr rolls down the mpre treble is lost.

Have I got magic guitars then?