Technical question about Hipower and tone frequency

DLC86

DLC86

Fractal Fanatic
Hi, as title says I'd like to have clarification on the tone frequency setting on the hiwatt model, if I select hipower normal it defaults to 350 Hz, while for the brilliant and jumpered model it goes up to 700 Hz. I think there's something wrong with this cuz in the real amp the only difference between the two channels is the highpass filter at the input stage (set by the coupling cap at lug 2 of the channel volume pot and by the bypass cap on the cathode) so the tonestack shouldn't be affected by the channel selection. Comparing it to the real dr504 that I have, and listening to how the tone controls behaves, I think the right setting is 700Hz (or near that) even for the normal channel, but I get more usable tones setting it to 350 or little more (but maybe this is just a matter of finding the right IR). So what's the "right" setting? Thanks in advance
 
Note for Cliff: I have the schematic for the linked inputs mod that Pete Cornish did on Gilmour's heads, if you want to try it I can send it to you, would be nice to have the jumpered model based on that, it's just a few components swap, let me know
 
DLC86 said:
Note for Cliff: I have the schematic for the linked inputs mod that Pete Cornish did on Gilmour's heads, if you want to try it I can send it to you, would be nice to have the jumpered model based on that, it's just a few components swap, let me know
Click to expand...

this sounds interesting.
 
But if the mod simply jumps the inputs don't we already have that? I don't have the schematic but it sounds like it's a convenience mod so Gilmore could simply plug in w/o having to use a patch cable.
 
No it's not only an internal jumper of the inputs, he also changed a few components around the first tube of the preamp. I'll post the schematic as I get home, if it's not a problem
 
DR_PreLinkedInput_Cornish.jpgOk, here it is, this schematic has been created from some internal photos of a gilmour's head sold a few years ago on ebay. Beyond linking the inputs he changed the grid stopper resistors from 68k to 2,2k, this lets way more high frequencies get into the first stage of the preamp, then put out the bypass cap on the brilliant channel giving it the same gain of the normal channel thus eliminating the highpass filter that this creates, but it's compensated by the change of the coupling caps near the channel volume pots, 10nF for the normal instead of 22n (this only cuts out a small amount of low frequencies) while for the brilliant channel hasn't been possible to see the value in the photos, but with 470pF it should set the cutoff frequency about the same to the original schematic so I'd start from there.
Anyway I think it's already possible to emulate this mod in the axe: select hipower jumpered amp, put a 2nd order highpass filter at the input of the amp set to 34Hz (this simulates the 10nF cap on the normal channel), then, in the tone page of the amp set lowcut at 720Hz (this simulates a 470pF on the bright channel, you can experiment with this) and highcut at 20000. I still have to understand how to emulate the 2,2k grid stoppers, I think increasing the definition control or using the character knobs could be useful, I have to try various combinations. And that's it!
 
I also add that in the speaker page, at least according to the transformer specs found at hiwatt.org, should be correct to set xformer lowcut at 10hz, xformer hicut at 40000 and xformer drive at 0.09. These are valid for all 3 hiwatt models, not only for the jumpered one.
If someone is interested I can post a few floydian patches I've created, even if I'm an axe fx newbie I think I've now got very good results and everyday I spend with it I get more and more excited with this beast!
 
DLC86 said:
Hi, as title says I'd like to have clarification on the tone frequency setting on the hiwatt model, if I select hipower normal it defaults to 350 Hz, while for the brilliant and jumpered model it goes up to 700 Hz. I think there's something wrong with this cuz in the real amp the only difference between the two channels is the highpass filter at the input stage (set by the coupling cap at lug 2 of the channel volume pot and by the bypass cap on the cathode) so the tonestack shouldn't be affected by the channel selection. Comparing it to the real dr504 that I have, and listening to how the tone controls behaves, I think the right setting is 700Hz (or near that) even for the normal channel, but I get more usable tones setting it to 350 or little more (but maybe this is just a matter of finding the right IR). So what's the "right" setting? Thanks in advance
Click to expand...

I don't know anything about Hiwatts, but your post says you have a DR504. The model is based on a DR103, which may explain some of the differences.
 
Tubiflex said:
Very interesting information ! I would certainly like to try your patches
Click to expand...
I'll share them.. soon :D
SarasotaSwing said:
I don't know anything about Hiwatts, but your post says you have a DR504. The model is based on a DR103, which may explain some of the differences.
Click to expand...
Both have the same exact preamp and I've made the comparison based just on that, preamp vs preamp going direct to the power amp of my head
 
You must log in or register to reply here.
Back
Top Bottom