still plugging away at my ceriatone HRM 50, done a few small mods which for me have mproved the overall sound, the deep switch is gone and has become the standard bright switch with typical dumble values(ish), slope resistor is currently about 80k and the treble cap somewhere between 0.01 and 0.005 The NFB switch got disconnected briefly then reinstalled as i quite like the extra dimension it adds . I have some more bits coming from musikding in germany includeing a 33k dale resitor to try out as a slope resistor plus some 1meg alphas to replace the switched pots i used in the original build.
But back to the title, the HRM is bypassed and in my humble opinion the drive is now more like what i would have expected, anyone else feel that maybe non hrm is easier to work with and sounds better.
I,m toying with the idea of making the HRM switchable and would appreciate any input on it.
I put the ground from the Mid Pot to the HRm board on a Switch (Changing the OD Level POT to a push/pull). This lifts the HRM stack giving you Non-HRm OD.
boldaslove6789 wrote:I put the ground from the Mid Pot to the HRm board on a Switch (Changing the OD Level POT to a push/pull). This lifts the HRM stack giving you Non-HRm OD.
This a smart mod I would try, but I never would want to loose the HRM voice.
All this does is lift the Ground to the board so you won't sacrifice any OD tone by this mod. The HRm OD will sound the same still. Kinda acts as a Pre-amp boost for the OD.
boldaslove6789 wrote:All this does is lift the Ground to the board so you won't sacrifice any OD tone by this mod. The HRm OD will sound the same still. Kinda acts as a Pre-amp boost for the OD.
Sorry Greg, I didn't post that correctly, the part about loosing the HRM voice was meant generally, like I would never completely disconnect/bypass the HRM board.
Although, you did clarify it even more. Thanks.
aren't the hrm od triode stages biased and bypassed differently then the non hrm od stages?
that's going to affect things more then whether or not the hrm is in the circuit or not, especially that 1uf cathode bypass cap as opposed to the 4.7uf in the non hrm circuit.
since having to totally rewire my amp the HRM has been reinstated, still toying with the idea of making it switchable but the volume increase by defeating it makes it harder to control the OD master, i'll be having a play and let you all know what happens
diagrammatiks wrote:aren't the hrm od triode stages biased and bypassed differently then the non hrm od stages?
that's going to affect things more then whether or not the hrm is in the circuit or not, especially that 1uf cathode bypass cap as opposed to the 4.7uf in the non hrm circuit.
HRM can be high or low plate. It is much more common to be high plate though.
jestaudio wrote:since having to totally rewire my amp the HRM has been reinstated, still toying with the idea of making it switchable but the volume increase by defeating it makes it harder to control the OD master, i'll be having a play and let you all know what happens
Instead of lifting the ground totally, try switching in about 70k to ground, and see if that gives you more the behavior you are looking for.
diagrammatiks wrote:aren't the hrm od triode stages biased and bypassed differently then the non hrm od stages?
that's going to affect things more then whether or not the hrm is in the circuit or not, especially that 1uf cathode bypass cap as opposed to the 4.7uf in the non hrm circuit.
HRM can be high or low plate. It is much more common to be high plate though.
what part of the plate is connected to the cathode bypass capacitor chris? what part of the plate resistor controls the high frequency roll off of the cathode capacitor chris?
jestaudio wrote:since having to totally rewire my amp the HRM has been reinstated, still toying with the idea of making it switchable but the volume increase by defeating it makes it harder to control the OD master, i'll be having a play and let you all know what happens
Instead of lifting the ground totally, try switching in about 70k to ground, and see if that gives you more the behavior you are looking for.
I,ll give a a try tomorrow and get back with the results
diagrammatiks wrote:aren't the hrm od triode stages biased and bypassed differently then the non hrm od stages?
that's going to affect things more then whether or not the hrm is in the circuit or not, especially that 1uf cathode bypass cap as opposed to the 4.7uf in the non hrm circuit.
HRM can be high or low plate. It is much more common to be high plate though.
what part of the plate is connected to the cathode bypass capacitor chris? what part of the plate resistor controls the high frequency roll off of the cathode capacitor chris?
Bypass caps have no relavance to the bias point of the stage AcousticMirror. Stop trying to be a smart ass.
HRM vs. non-HRM has nothing to do with high plate/low plate or biasing. I was just saying HRM seem to generally be high plate.
Also the plate is connected to the cathode via the snubber cabs on V2
The NFB switch got disconnected briefly then reinstalled as i quite like the extra dimension it adds . I have some more bits coming from musikding in germany includeing a 33k dale resitor to try out as a slope resistor plus some 1meg alphas to replace the switched pots i used in the original build.
