What's the purpose of R105 in the Hot Rod Deluxe 2 tone stack?

[isaac]

I've thought about dueling the mid pot to vary the slope resistor in a small range, and use the mid pot like usual. I'd just have to reduce the value of my pots to make both pots reasonable values. But I'm very familiar with reducing pot values with resistors. Oh yea, tweed? That's interesting. Now what if I try this... Think twin reverb preamp, right before the 250pf and the 100k meet, between there and the plate of the tube, i actually in one design have a .047 cap, it was just to keep the plate voltage away from the tonestack, in this one particular design it just needed it, not for the bass though, but what if I put a cap after the volume control to reduce bass a little overall if the slope mod is too much. (still on a twin reverb type preamp.) It's not a fender amp, its a custom something or other i built, but thats the idea.

[freefrog]

That resistor in the tonestack is probably what others have said about it, but you mentioned, after you took it out, it sounds like a fender...

There are other issues with the tonestack that aren't fender styled... SO if you care, I'll point them out. The slope resistor (130k) to be like a BF twin would be a 100k. the mid pot would be a 10kl wire like this: jumper the wiper of the mid pot to the top of the mid pot (like on the bass pot) remove the 200k (like you already did.) and the .022 cap on the mid pot, is wrong, unless you want a super reverb tonestack, because only on the super reverb did they put a .022 cap to the mid pots. The twin and the deluxe etc. , had .047. The .022 will give you a good amount more low-mids than a .047. Try it in the TSC. Hope this helps. Again, the biggest mod out of all these ones I just pointed out, would be the 220k (but you already did that) and the jumper from the wiper and the top of the mid pot, it will get a way more fendery response and tone. Even without the other value changes. Also with a 100k slope resistore vs 130k you will get more bass and mids than before which might be nice, which you can always roll back a little bit more than before anyway.

Thx to you and Leo_Gnardo for your helpful replies!

I understand what you say and I agree. Simply, the 130k slope resistor + the 22n mid cap appear to give the same curve than a Fender tone stack with a few adjustments.

As an attached file, I post a picture about it. Green curve= typical Fender tone stack, all controls @ noon. Orange curve = BMT controls @ 6, 3, 6 with the HRD tone stack as I've modified it for the moment (jumper on the mid pot, 220k additional resistor removed, all other parts intact). As you can see, TSC draws a similar spectrum although the settings and components are different. It's "good enough for me" right now.

I'll jusst have to try the amp in rehearsal, in order to decide if it requires further mods or not to my ears. :-)

[isaac]

Ok, you did you do the jumper wire on the mid pot. Big difference huh? If you wanted it to be the most fenderesque you could go crazy and blackface the amp... at least in the clean channel, but i haven't heard of anyone doing that... Anyway, Hope you like it, and make sure you tell us how it has worked out for you.

[Leo_Gnardo]

Thx to you and Leo_Gnardo for your helpful replies!

I'll just have to try the amp in rehearsal, in order to decide if it requires further mods or not to my ears.

Thanks for the mention AND the chart!

Keep us posted, LG.

[Tone Meister]

Yeah, I'm also interested to know what you think of these changes after playing the amp a while. What mid cap did you end up with?

[isaac]

The .022 will give you more mids in general, also a little more low mids than before, as compared to the regular mid increase. I'm tempted to put a second .047 in parallel with my first one so I'd get kinda about .022, but when I do it, put a dual pot on so I can control the mids, but Also control how much that cap is paralleled in so the more I increase the mid pot, the more the mids actually increase. But yes, Tonemeister, he should be getting a very blackface style tone. Should sound very close. Please make a youtube or sound clip where we can hear it. Hopefully you have a clip from before the mods.

[Tone Meister]

The .022 will give you more mids in general, also a little more low mids than before, as compared to the regular mid increase...

I presume that you mean with the R105 220K resistor removed, because the stock value for the C6 mid cap is 0.022 uF. I've been using an 0.015 here, and recently an 0.02 when I ran out of the 0.015. I'm always interested in hearing what others are doing in these amps and why.

Isaac, can you elaborate a bit more on your comments?

[Tone Meister]

Additionally, I'm looking for a way to increase headroom reasonably in the clean channel without having to perform major surgery.

[52 Bill]

I'm tempted to put a second .047 in parallel with my first one so I'd get kinda about .022, but when I do it, put a dual pot on so I can control the mids, but Also control how much that cap is paralleled in so the more I increase the mid pot, the more the mids actually increase.

Check your theory here about paralleled caps.

[isaac]

Sorry 52 bill, I meant series caps with a pot to bypass it. And Tonemeister, I forgot that the standard value was .022, but I was talking mostly if you use a BF twin tonestack and then mod from there. Sorry for confusion guys. And Tonemeister, I'll look at the full schematic see what headroom helps I might be able to direct you to... For clean channel headroom... Some tweaks, Change the first cathode cap to a 25uf instead of 47uf. Replace volume pot with 1MA, and you may want to take out the bright circuit on the second cathode cap. And reuse the switch for a regular bright cap on the volume control, you'll probably want it on the clean channel volume. then replace that cathode circuitry with a 820 ohm resistor in parallel with probably around a 5-10uf cap. You could go lower if you think it's too bassy. Also, I've never actually tried one of these amps, but I hear that the drive channel is really dark and unusable. In which case I'll take a small peak at that... try removing the 250pf cap and the 1M resistor that are in series at the grid of the third stage. and change the .047 cap at the master volume in the drive channel for a .022 and then get rid of the 390pf cap on the master. Now again, I've not tried this amp, nor have I worked on one, but I know many people say they have bad drive channels, so these are theoretical mods. Also the schematic you posted above says the PI is standard blackface type so two 1M resistors, a 22k and a 470 resistor right? Does the amp have a 12ax7 or 12aT7. If its a 12ax7, try a 12aT7 that should help, with headroom, and maybe even overall tone. Hope some of this helps.

Once more, I haven't worked on or tried this amp, its theoretical, although the clean channel is pretty basic and I've worked on so many other ones, but I haven't worked on many drive channels. I've done several but not many, so please forgive me if something doesn't sound good, or it didn't work out.

[alga]

Hello Freefrog. Real nice and interesting post. I have just registered to this Forum just to know more about the mod you mentioned (clipping R105)

I already have done the jumper mod to the mid pot, I leaved the R12 130K, changed the value of C1 to 2,2 uf and I am very interested in clipping R105, but I would like to know if you have new info about this mod?

This amp is HONKY sounding and I suspect this could be a remedy.

Also you mentioned something about the .022 uf tone cap,which I imagine is the mid cap. Did you tried the .047 uf in there? Do you think a .033 uf (half way between .022 and .047) would be a good idea in order to achieve a more BF sound with less mids?

I´m writing from Venezuela, your answer is very important for me.

Thanks in advance

[alga]

I presume that you mean with the R105 220K resistor removed, because the stock value for the C6 mid cap is 0.022 uF. I've been using an 0.015 here, and recently an 0.02 when I ran out of the 0.015. I'm always interested in hearing what others are doing in these amps and why.

Isaac, can you elaborate a bit more on your comments?

Hello Tone Meister

When you used the 0.015 uf cap and later the 0.02 uf for the mid cap,what did you noticed? more mids, less honky sound, more BF sound?

Thanks in advance

[alga]

Additionally, I'm looking for a way to increase headroom reasonably in the clean channel without having to perform major surgery.

I think using a 12AY7 in the V1 will help o a lot. Also it seems to me that changing the C1 value from 47uf to 22 or 10uf will help.

[freefrog]

Hello Freefrog. Real nice and interesting post. I have just registered to this Forum just to know more about the mod you mentioned (clipping R105)

I already have done the jumper mod to the mid pot, I leaved the R12 130K, changed the value of C1 to 2,2 uf and I am very interested in clipping R105, but I would like to know if you have new info about this mod?

This amp is HONKY sounding and I suspect this could be a remedy.

Also you mentioned something about the .022 uf tone cap,which I imagine is the mid cap. Did you tried the .047 uf in there? Do you think a .033 uf (half way between .022 and .047) would be a good idea in order to achieve a more BF sound with less mids?

I´m writing from Venezuela, your answer is very important for me.

Thanks in advance

Hi alga and welcome !

Removing R105 adds some bass but as I said above, it also tends to change the "openess" of the curve IME. Pic below.

Yes, the amp is naturally honky.

Yes, I've tried a 47nF mid cap. It works but makes it a bit too qwacky IMHO/IME if other mods are not done... Paradoxically, a 15nF mid cap wouldn't necessarily be worse if the goal is to have less honk (questions of clariity aside). I've never tried a 33nF in this position.

FWIW, one of the most useful things that I've done with the tone stack of the HRD has been to put a 220k switchable resistor in parallel with the treble pot, lowering its overall value to 117k (IOW, I've somehow moved R105 elsewhere, in order to control other frequencies). It opens the curve more than simply clipping R105, by taming the high mids.

I'll share other measurements and tricks ASAP... Life is busy for me right now.

In the meantime, see the measurement below: it's the EQing curve of the HRD (clean channel) captured from the FX loop with R105 (white curve) then without it (black curve), measured a few years ago...




Hope to be useful. :-)

[alga]

Hi alga and welcome !

Removing R105 adds some bass but as I said above, it also tends to change the "openess" of the curve IME. Pic below.

Yes, the amp is naturally honky.

Yes, I've tried a 47nF mid cap. It works but makes it a bit too qwacky IMHO/IME if other mods are not done... Paradoxically, a 15nF mid cap wouldn't necessarily be worse if the goal is to have less honk (questions of clariity aside). I've never tried a 33nF in this position.

FWIW, one of the most useful things that I've done with the tone stack of the HRD has been to put a 220k switchable resistor in parallel with the treble pot, lowering its overall value to 117k (IOW, I've somehow moved R105 elsewhere, in order to control other frequencies). It opens the curve more than simply clipping R105, by taming the high mids.

I'll share other measurements and tricks ASAP... Life is busy for me right now.

In the meantime, see the measurement below: it's the EQing curve of the HRD (clean channel) captured from the FX loop with R105 (white curve) then without it (black curve), measured a few years ago...

[ATTACH=CONFIG]48543[/ATTACH]


Hope to be useful. :-)

Hello Freefrog

Thanks for the welcome. I´m so happy and excited you answer me.

I saw the chart and hope to see more difference on the curve with and without R105.

Yes I found this amp honky and dont like that. I think that Fender amps has 2 traditional and characteristics sounds (black face and tweed) BF are mid scooped and tweed mid humped. I found the Hot Rod Deluxe and Deville are more toward the tweed sound but maybe with way more mid hump than Bassman, bandmaster etc etc

My goal with this amp (maybe will sound crazy) will be to reduce or eliminate the honkyness which will somehow resemble a bassman sound. After acheiving that would like to know if its possible to make a mod with 1 or 2 switches for blackfacing the Hot Rod taking out lot of mids. The final outcome will be a very versatile Fender amp with a terrific mid humped sound (without honkyness) and on the other hand at least an aproximation to the BF scooped sound, I know technically is impossible to obtain 2 different circuits from just one, but with an aproximation to the BF I´ll conform.

If what I said is somehow possible and makes sense, from your experience what should be the first step? I´m eager to hear the tricks you mentioned and also more details of the 220K in parallel with treble pot and the relocation of R105 etc etc

So so grateful with your help

Thanks in advance