V1B Cathode Resistor - 2.7k vs 820

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Elad E
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V1B Cathode Resistor - 2.7k vs 820

Post by Elad E » Tue Oct 31, 2017 5:11 pm

In my never ending search for "a better tone" (which normally leads to more tone chasing) I revamped my 100 watter with a V1B .0022 plate bypass cap, .68 V2 bypass cap and Super lead tonestack (with low '68 filtering) only this time I replaced the 820 V1B resistor with a 2.7k and I felt like I finally struck the balance I wanted between crunch, firm low end and dynamics (basically, going from clean to mean with the vol knob).

that being said, the restless tweaker in me had to see if this was some "trick of the mind" so I changed it back to 820r played it some 30 minutes with and without pedals, then added a 250uF "fat cap" to V2 (parallel to the .68 bypass cap) - played it some more and then went back to the .68 alone and the 2.7k on V1B.

my impressions thus far:
Late '68 specs (2.7k/.68, .0022, .68 on V2) - great picking dynamics, maximum gain roll off with volume knob, low-end holds together great but is not super compressed, the high end is open and rounded - not an ounce of harshness in there. great with pedals and for edge of break-up tones.

820/.68 - sounds kinda mushy and muffled but gets super aggressive when the volume is dimed. pinch harmonics are a breeze and the overall feel is very responsive and easy to play yet saggy</t>
cleanup with the volume knob with either a Strat or LP left a lot to be desired...

820/.68 & 250uF (Suhr SL68) - feels pretty much like the 820/.68 combination but with a fuller mid range.
frankly I found the same configuration sans the 250uF to better nail the EVH 1 tone (which to me is bright, saggy and "harmonically" rich) but this configuration was a little a bit more versatile, worked better with my pedals and cleaned a little a bit better, albeit considerably less than the 2.7k/.68 config.

bottom line, I put the 2.7k back in and yanked the 250uF electrolytic "fat cap" and while the inherent crunchiness is not on par with the two other configurations the amp is overall better sounding to me, has cleaner and clearer top end and a tighter low end lending to a more a bluesy - starting to break up tone which I love, not unlike a Superbass but with ultra clear high end and more mids.

next step - putting a DPDT switch to toggle between two of the configurations (and building another 100 water, just because...).
Last edited by Elad E on Sun Nov 05, 2017 1:56 am, edited 1 time in total.

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Re: V1B Cathode Resistor - 2.7k vs .820

Post by Roe » Fri Nov 03, 2017 2:20 pm

I like hotter bias with low output pickups (e.g. strat) and colder bias with hotter pickup
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neikeel
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Re: V1B Cathode Resistor - 2.7k vs .820

Post by neikeel » Sat Nov 04, 2017 6:29 am

I did the same as you (back and forth)
Then compromised on one build with 1k5 Piher. I generally like (or have got used to ) the 0.68uF on V2a and relatively tight NFB (47k/8ohm minimum and really like 27k/16ohm too).
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bill bokey
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Re: V1B Cathode Resistor - 2.7k vs .820

Post by bill bokey » Sat Nov 04, 2017 12:56 pm

I usually go with 1k2 minimum (byppassed by a 680nF cap) but I guess it depends on the amp. The JMP50 I just built sounds better with 820 (I tried 820, 1k2, 1k5 and 2k7), even with HBs.

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by Elad E » Tue Nov 07, 2017 6:26 pm

interesting.
so what should I expect with a 1n2 or a 1n5 as opposed to the 2n7?
I'm guessing more compression and dirt?

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by neikeel » Wed Nov 08, 2017 8:04 am

You need to swap some n for some k in your note above!
820 gives more gain but can be fuzzy with hot humbuckers.
2k7 is a bit crisper but quite a commonly used value with a 0.68 cap.
Neil

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by Elad E » Wed Nov 08, 2017 4:21 pm

oops, my bad...

anyway, I noticed 820 was too mushy and fuzzy and 2.7K is crisper, just wondering what 1.5K or 1.2K will do to the tone.

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by neikeel » Thu Nov 09, 2017 7:32 am

Try it!
Neil

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by Elad E » Fri Nov 10, 2017 10:55 am

I'll try it but if it indeed lowers available headroom it won't be what I'm looking for as I really dig what I'm getting with the 2.7K.

that being said, I wonder what I'll get from putting 1K-1.5K on both V1A and V1B cathodes...

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by neikeel » Sat Nov 11, 2017 6:12 am

You can do that but I suggest dropping the v1a cap to 25uF or smaller
Neil

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Re: V1B Cathode Resistor - 2.7k vs 820

Post by Elad E » Sat Nov 11, 2017 12:05 pm

ok, I tried 1.5K and 1K.
for the record, the 2.7K I had on V1B was a CF resistor and the ones I tried were CC so this may also account for the differences. V1A was left untouched (820 Ohm).

beginning with the 1.5K (actually a 1.2K that measured 1.49K)- sounded pretty much the same as 2.7K with more compression and less high-end but not much gainier.

next I put 1K (measured 1.04K) which was still not much gainier than 2.7K, pretty much the same compression as the 1.5K and still cleaned very nicely with the volume knob but the tone was punchier and tighter.
with humbuckers it sounded great - just the right amount of treble, very much the epitome of Marshall tone IMO - tight low mids with crunchy highs and no fizz or graininess at all. very thick tone, almost 10-series like, that also worked very nice with pedals and with the PPIMV on 50% and still pretty good even on 25%.
with single coils however the sound is too dark and nowhere as fuzz-friendly as with the 2.7K.

for the time being I left the 1K in there, may just put it and a 2.7K on a switch though the tonal difference doesn't justify that.
bottom line - if I played mostly with the PPIMV out of the circuit I'd probably leave the 1K in there but for home noodling at moderate volumes 2.7K seems to yield the best results.

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