massygt6 wrote:
I'd like to remove some "honkiness" and darkness form the clean channel of my clone, it has a lower B+ than the standard values, around 420V.
it's better to work on tonestack, or should I lower the value of the anode resistors to let more voltage come into the preamp stages?
Voltage in itself has no effect on frequency response. Look instead for places where treble is being lost (and then prevent it) or where bass can be cut (smaller coupling cap maybe...)
Also the tone stack of course.
Merlinb wrote:
Voltage in itself has no effect on frequency response. Look instead for places where treble is being lost (and then prevent it) or where bass can be cut (smaller coupling cap maybe...)
Also the tone stack of course.
Well, since I've got a pretty lower voltage (ca.175v-180v) in the preamp section than the usual 185v-190v, and this kind of amp is all about finding a pretty narrow sweetpot for every tweak point, I thought that raising the preamp voltage could give back a brighter tone.
I mean, I have a killer OD tone, very "brown" and creamy, but the amp is definitely lacking that sparkly fendery clean tone I've heard in other clones.
On the subject of the tone stack itself, I have a question. PAB has been a bit of a mystery to me. Looks like the treble cap winds up passing all the frequencies through it when bottom of the treble pot gets lifted - makes sense if you think of that part of the circuit as a high pass filter, when the resistance to ground becomes infinite, the cutoff frequency goes to 0 HZ. If this is the case, then the mid switch should have no effect in PAB mode, since everything is already passing through the treble cap - yet when I toggle the mid switch in PAB mode I hear the mids change. I must be missing something here? It would also seem to me that the PAB implementation is a non-obvious trick - something where I wonder if this was true genius at work, or whether HAD discovered it by accident, powering up and amp with a missing or broken connection on the treble control and having an "ah-ha" moment. I, not being a genius, would have tried to re-route the signal around the whole stack with the relay, in stead of just lifting the treble/bass pot connection, had it even occurred to me that this would be an interesting thing to try.
Bill
Tony, in your recent use of the NOS CTS pots, did you find out where the break point is timewise, i.e. before 19XX is good, after 19XX is not good, or is it more of a range, eg before 19XX good after 19YY bad, in between a crapshoot?
I seem to get enough range on the bass for me, since things are pretty well balanced I don't need a ton of range - it's usually set somewhere between 10 and 2 - most often more towards 10. I wired my amps all in permanent rock mode, and then use the rock/jazz switch as an alternate lift to get somewhere between normal and full PAB. Why do you ask?
Bill
massygt6 wrote:Great post, thanks for the practical and clear explanation!
I'd like to remove some "honkiness" and darkness form the clean channel of my clone, it has a lower B+ than the standard values, around 420V.
it's better to work on tonestack, or should I lower the value of the anode resistors to let more voltage come into the preamp stages?
Thanks!
You don't want to alter the plate resistors to change the voltage.
those along with the cathode resistors set the bias point of the tube.
You would want to adjust the dropping string resistors located at the power supply to change the B+ voltages to the various stages.
massygt6 wrote:Great post, thanks for the practical and clear explanation!
I'd like to remove some "honkiness" and darkness form the clean channel of my clone, it has a lower B+ than the standard values, around 420V.
it's better to work on tonestack, or should I lower the value of the anode resistors to let more voltage come into the preamp stages?
Thanks!
I tried a Mallory 150 on the PI input and it made the amp sound less dark and honky. It was nice for the clean channel, but the orange drop is definitely needed for the right OD tone. So it might be worth switching in a Mallory just for when using the clean channel.
LPSGME wrote:I tried a Mallory 150 on the PI input and it made the amp sound less dark and honky. It was nice for the clean channel, but the orange drop is definitely needed for the right OD tone. So it might be worth switching in a Mallory just for when using the clean channel.
Orange Drops can be polypropylene (SBE 715P, 716P series) or polyester. Mallory 150, Mallory PVC, 6PS series are polyester with the PVC and 6PS being the Orange Drops used in Trainwreck and Dumble amps respectively. So a 150 and a polyester Orange drop are going to be very similar in tone, albeit probably a slight difference for those with finely tuned hearing. Just wondering which ODs you might be referring to for that position.
LPSGME wrote:I tried a Mallory 150 on the PI input and it made the amp sound less dark and honky. It was nice for the clean channel, but the orange drop is definitely needed for the right OD tone. So it might be worth switching in a Mallory just for when using the clean channel.
Orange Drops can be polypropylene (SBE 715P, 716P series) or polyester. Mallory 150, Mallory PVC, 6PS series are polyester with the PVC and 6PS being the Orange Drops used in Trainwreck and Dumble amps respectively. So a 150 and a polyester Orange drop are going to be very similar in tone, albeit probably a slight difference for those with finely tuned hearing. Just wondering which ODs you might be referring to for that position.
Actually I tried replacing the .1 rather than the .02 input. The amp pretty much follows the 101 non HRM schematic.
