butwhatif wrote:Thanks Ayan, for posting on this subject, as I have never liked the grainy
sound of the clean with the biased hi cathodes. And I'm sure that your experience with these amps and in the clone community, the idea will be received with renewed thought. The larger plate resistors can make for a robust difference in tone, I think, to taste, but the higher biased cathodes get too dry and 'hard' for my ear. I think that the 1.5k resistor places the tube in it's warm working range, imho. I like these in OD1 and OD 2 also, but more care needs to be done here to get a good sound. Also, the power supply for the amp can be tweaked for varied sound, as well. I have a Mesa Mk III that has been rebuilt for a clone sound, and the nice thing with these is there's a platform for a d'ator already inside, although it needs much rework as the original wiring of it sounds not well. This internal interface also can be tweaked for variations of tone, and done right can really add to the overall sound.
I did start another post (after this one went astray) in which I reported my experience with the 100K amp live. I loved it, and still do, it is a keeper.
Very bold of you to mod a Mark III. I owned all Marks at some point or another, and except for my Mark Is, I only modified my IIC+ slightly (changing a cap here and there), but never really dared to "get in there" and do serious work in those amps.
A Mesa Mk III is not the easiest thing to mod, although I have worked on all the Mk series amps, and am quite familiar with them. With all the components in such close proximity, there is hardly such a thing as 'lead dress' and whatnot. But all the clone circuitry is practically on the tube sockets, so lead dress isn't much issue. I've never liked the sound of a stock Mk III, although I like the Mk II's a lot, and worked on many. Hard to believe I can get this huge sound, and bottom, out of this old III.
butwhatif wrote:With all the components in such close proximity, there is hardly such a thing as 'lead dress' and whatnot.
Ain't that the truth? If I am not mistaken, the Mark IV had so much switching (some of it useless: switching between one bad tone and another...) that it sported some double-decker LDRs, right? If not, I should patent the idea -- pun intended.
I just had a IV in my studio a month ago, and was surprised at the tone we got from it, but that's in a studio, I can't imagine trying to play one live-
Fischerman wrote:Would going to 180k/120k on CL1/2 and then having the 220k/150k on OD1/2 (all with the 'corresponding' Rk values) be any sort of happy medium?
I was thinking the same thing, only with the 100k on CL1/2 and 220k/150k on OD1/2.
It would also be interesting to see how low values in the clean section and high values in the OD section would compare with "in between" values in both.
This one hasn't been revisited in awhile. Did anyone ever try these combinations to see if there was a good balance between the low-plate cleans and the high-plate OD?
heisthl wrote:If you go "off the reservation" you can get some benefit from using 100k plate 25uf bypass on CL1 and keep CL2 at 150K/5uf with a .02 coupler.
Interesting. Can I get you to expound a little? What are the changes that you heard?
Also, the higher Rp values always seem to be on the first stage of either preamp tube. What is the effect of reversing this as you suggest? And I've never seen any references to these amps having over 10uF as a Ck cap. How did you arrive at that?
Last edited by greiswig on Mon Feb 25, 2008 9:39 pm, edited 1 time in total.
Fischerman wrote:Would going to 180k/120k on CL1/2 and then having the 220k/150k on OD1/2 (all with the 'corresponding' Rk values) be any sort of happy medium?
I was thinking the same thing, only with the 100k on CL1/2 and 220k/150k on OD1/2.
It would also be interesting to see how low values in the clean section and high values in the OD section would compare with "in between" values in both.
This one hasn't been revisited in awhile. Did anyone ever try these combinations to see if there was a good balance between the low-plate cleans and the high-plate OD?
I tried that lineup in my most recent (non-HRM) build. I tried it with varying combinations of K bypass caps from 4.7 to 10uF. (I had some spring clips installed on my preamp board on loan from Mark to facilitate component chages, so over a period of weeks, I tried tons of combinatons). With 10uF on the V1A and 5.6uF on V1B (4.7 on each of the OD) I was pretty happy.... it almost stayed.
BUT, the amp ended up as a 220(4.7)/150(5.6)/220(4.7)/150(4.7). This is where I was happiest overall. But I need to also mention that this amp has a built in D-lator loop which is permanently in the circuit, I was using EL34s, Bassman replacement iron and it was a 50 watter, so YMMV.
"Let's face it, the non HRMs are easier to play, there, I've said it." - Gil Ayan... AND HE"S IN GOOD COMPANY!
odourboy wrote:(SNIP)This is where I was happiest overall.
Thanks for the response. I'd sure like to hear more about *why* you settled where you did, and what you thought the effects were of trying those lower Rp/Rk pairs and the various Ck's with them.
To summarize, Gil Ayan had suggested that the cleans were better on a lower plate V1, but that this compromised the control over the overdrive section. This "somewhere between 220k/180k and 100k/100k" compromise had been suggested, but nobody ever followed up with any level of detail if they had tried it out.
heisthl wrote:If you go "off the reservation" you can get some benefit from using 100k plate 25uf bypass on CL1 and keep CL2 at 150K/5uf with a .02 coupler.
Interesting. Can I get you to expound a little? What are the changes that you heard?
Also, the higher Rp values always seem to be on the first stage of either preamp tube. What is the effect of reversing this as you suggest? And I've never seen any references to these amps having over 10uF as a Ck cap. How did you arrive at that?
I was going more for the "Fender on 10" sound - the OD does suffer in that there was no longer the ability to get those "OD on but doesn't sound like it is" tones.
The 100k on CL1 seems to add some warmth(dirt) to the clean sound and doing 100K on CL2 even more so, but at the expense of the OD (unless you want to do major tweaks). I found the 150K on CL2 made it work with no changes to the OD section. Depending on the amp 10uf on CL1 may work better than a 25uf.
heisthl wrote:If you go "off the reservation" you can get some benefit from using 100k plate 25uf bypass on CL1 and keep CL2 at 150K/5uf with a .02 coupler.
Interesting. Can I get you to expound a little? What are the changes that you heard?
Also, the higher Rp values always seem to be on the first stage of either preamp tube. What is the effect of reversing this as you suggest? And I've never seen any references to these amps having over 10uF as a Ck cap. How did you arrive at that?
I was going more for the "Fender on 10" sound - the OD does suffer in that there was no longer the ability to get those "OD on but doesn't sound like it is" tones.
The 100k on CL1 seems to add some warmth(dirt) to the clean sound and doing 100K on CL2 even more so, but at the expense of the OD (unless you want to do major tweaks). I found the 150K on CL2 made it work with no changes to the OD section. Depending on the amp 10uf on CL1 may work better than a 25uf.
Great info. Were all these changes made with the stock LNFB loop (44M, .05uF)? I'm sure you've tried disabling the loop, since IIRC you edumacated me about how to do so without a large volume gain. How would you compare the disabled LNFB against the lower plate resistor on V1a?
odourboy wrote:(SNIP)This is where I was happiest overall.
Thanks for the response. I'd sure like to hear more about *why* you settled where you did, and what you thought the effects were of trying those lower Rp/Rk pairs and the various Ck's with them.
To summarize, Gil Ayan had suggested that the cleans were better on a lower plate V1, but that this compromised the control over the overdrive section. This "somewhere between 220k/180k and 100k/100k" compromise had been suggested, but nobody ever followed up with any level of detail if they had tried it out.
I don't think I'm going to be able to provide the answer you are looking for; I didn't make recordings and do direct A-B comparisons between each component change, so i can't tell you exactly what I heaerd between say - a 4.7 uf byapss on CL2 and a 10. (But I can say, the specific changes were often extremely subtle.) My objective was to find the combination with the least number of sonic tradeoffs using my two most often played guitars (a PR HBII and a Deluxe Fat Strat with SCN noisless) with emphasis on OD lead tones - played into an EVM 12L. My method was simply to try a particular combination of plate resistors and cathode resistors and caps - play for several minutes to several days (depending on how much I liked a particualr combination) lookig for flaws and overall tone, keeping track of which combination I liked the best and continue to A-B over a perod of weeks until an overall favorite emerged.
I did find that the cleans on the low plate version were indeed excellent - much like Gil described (which gave me confidence in my build and method).
"Let's face it, the non HRMs are easier to play, there, I've said it." - Gil Ayan... AND HE"S IN GOOD COMPANY!
heisthl wrote:If you go "off the reservation" you can get some benefit from using 100k plate 25uf bypass on CL1 and keep CL2 at 150K/5uf with a .02 coupler.
I've got another question about this. Messing with the Pr is going to change the plate voltages. In a D'Lite with standard value plates the sweet spot for voltages seem to be:
220/150 on V1 with 190V, 150/120 on V2 with 200V
If you end up tweaking to basically switch the plates around, do the same target voltages still apply for each stage? In other words, if I set the amp up as suggested above, do I want to see this?
100/150 on V1 with 190V, 220/150 on V2 with 200V
...or should the voltages be reversed as well? And for those of you who have tried these tweaks, did you go back and redo your dropping string?
Make the change and let the voltages fall where they may. The 100K plate will be higher and looking at my notes, the last time I did this I had 205 on CL1 and 189 on CL2, 194 and 198 on V2.
