Tweaking extremes (WARNING: rambling)

[greiswig]

I find it philosophically disturbing when I come to such a substantially different conclusion about a component value from a builder like HAD, or any of the rest of you experienced builders. So consider this a confessional of sorts: forgive me, it has been...well, never. Never mind.

The amp is a D'Lite, Bluesmaster PI, Skyliner stack. I changed the OT to one of Brandon's 50W models, and that or going over all the solder joints while I had the preamp board changed the tone substantially. This OT seems to have less extension in the high end, has tighter bass, and just generally seems more "in your face" than the stock D'Lite 22W OT did when using 6L6's. So many of the component tweaks I'd decided on before swapping OT's went by the wayside.

EXTREME #1: the overdrive entrance that has been recommended here of a 10M resistor to ground and a .02uF cap in series with the OD trimmer. Without the new OT, that seemed too thin now. Getting rid of it altogether was too muddy, though. So fine, I'll try a .05uF in there. Still not as tight as I'd like. I settled on a .033uF. Not too radical a departure, but a departure nonetheless.

Another one of the tweaks I put in my D'Lite was a pot to alter the global feedback resister. I started with a 500k pot in series with a 10k resistor (so 10k minimum), but pretty quickly realized that the sweet part of the adjustment was in a pretty narrow range on the pot, and it was indeed right around 100k or so, or else wide open (no feedback).

(...or at least that is the case without altering the R from the presence pot to ground...haven't changed that from stock 4.7k, and I don't know what effect that might have on the presence control. Anyone?)

Anyway, the Bluesmaster presence calls for a .1uF cap to ground. Perhaps because I am using single coils, there seems to be an upper-mid thing going on that is piercing in quality. This is through a G12-65 paired with an Eminence Legend 10. The piercing is particularly noticeable in OD, so I played with the snubbers there a bit.

EXTREME #2: I ended up kind of liking a 390pF snubber on V2a, and a 330pF on V2b. Most Dumbles seem to have 330pF snubbers in both places. I don't know whether the asymmetry matters...maybe I should try to get some 350pF caps, but I don't have any. I also actually liked the just slight overdrive sound better when the stock 270pF snubbers were in there: they let a bit more of the highs through and I liked that, but then when you turn up the OD more, it starts to get shrill. I wish I could have it both ways.

Next step to tame the piercing was a bit of a fluke: that spike "sounded like a presence problem" to me, and I kept finding myself wanting to turn the presence down more and more. So, what they hey...let's play with that cap.

EXTREME #3: I tried changing from a .1uF film cap to a .1uF ceramic, just to see what happened. According to my new capacitance meter, they were both within .02uF of one another. The film cap sounded better. Next, I tried going down in value on the presence cap, trying a .05uF in there. That seemed to help a bit, but just seemed to move the spike up in the frequency band, and made the presence control do less overall. Okay, just for kicks let's try going the other way: pop in a .47uF. Wow! The piercing spike is gone, and the control is pretty usable throughout the range. When the presence is turned up, there is real added punch in the mids to upper-mids. Great for clean tones on the Strat #2 and #4 positions, and adds some nice snarl to the bridge overdrive without being overly shrill. Turn it down, and everything smooths out without sounding thin. But it almost sounds like it's too much cap now...I need to get a .3uF or so and try that.

EXTREME #4: Bright caps. I have a 3-way switch there, and the bright circuit is disabled when the OD relay is tripped. Stock value is 120pF, but that extended down so far into the upper mids that I really didn't foresee using it. After numerous tries, I ended up with (!) two 33pF caps in there, so the first bright position is 33pF, the second one is 66pF. The first position just adds a nice sheen on the top of the tone, and the second one is what I would call bright but not overly so.

But, as I said from the start, it bothers me to think that I might be doing something "wrong." I know, do what sounds good. But am I trying to cover up something else in the amp that is faulty? Do I need to put the humbuckers back in my PRS to find the weaknesses in the tweaks that I'm making? Will I find that I've painted myself into a corner here? Anyone else find that their component tweaks go pretty far outside the mainstream?

[Fischerman]

FWIW, I found that I was having better luck/results, learning more, etc. when I stopped thinking 'inside' the D-box and just drew on what limited experience I had and did whatever I thought was appropriate.

One very simple example would be snubbers on V2b vs. increasing the grid stopper vs. a treble bleed circuit vs. a bypass cap across the plate load resistor. I had read many posts about all of those methods to reduce harsh high-end here except the bypass cap across the plate load resistor method (which is extremely common and well known...I just hadn't seen it mentioned here wrt ODS amps). So I tried all those other ways and didn't even try the Rp bypass cap until later...once I tried it I thought; "Why didn't I try this before? I KNOW it works and sounds good...so why didn't I try it?"

So I say just do what you think sounds good...try whatever you want...and whatever sounds best to you is what it's all about anyway. BTW, I've been putting .33uF and/or .47uF caps on Presence controls for years now...it makes the Presence actually useable for me. They pretty much stay locked on '0' otherwise.

[Structo]

I struggled with the presence control as well but have settled on this design.
Seems to give a good range of control.
I kept the stock values with a 390R and Tantalum 1uf.
I'm not sure if that cap needs to be a electrolytic or non polarized.
I'm still using the 6K2 resistor on the board too.

I have changed the bypass and plate resistors on V2.
I went with Rp of 150K/220K and the Rk of 3K3/2K2.
V1a bypass to 4.7uf and V1b still at 10uf
V2a,b bypass at 4.7uf.

PI Rp at 120K/110K

I wanted to try the OD entrance mod too but was put off by having to completely pull the main board to do so, so I didn't do that one yet.
Mine is the D44 so I have the 4K taps running JJ 6L6's.

I have changed the choke to 330R and the power tube grids to 3K3 and the screens to 470R.
Treble cap to 330pf.
Bass pot mod removed and cap changed to .001uf.
Haven't messed with the dropping string yet but the voltages aren't that far off.

I did the bypass resistors yesterday and really haven't had the chance yet to try it out at volume.
I also padded the PAB relay with a 10M resistor to try and cut some of the boost.

I think that is all the changes I have made so far.
I play mainly strats and teles. My favorite strat has a HB in the bridge and I may change the newer one to that configuration.
As much as I try to like single coils in the bridge, I just can't warm up to them.
I should add they are Area pups, since I can't abide the SC noise either.

[Funkalicousgroove]

Do you not like the OT? Your experience with it is quite unique, I use those all the time, I find that they make for sparkly chimey high's, and tight bass. I do agree that they are more "Explosive" sounding than the typical Fender/schumacher design, I think that is due to the lower primary Impedance.

I don't think anyone should be afraid to experiment with values and networks "Outside the box" there is no wrong answer, so long as you like the way it sounds.

[greiswig]

Do you not like the OT? Your experience with it is quite unique, I use those all the time, I find that they make for sparkly chimey high's, and tight bass. I do agree that they are more "Explosive" sounding than the typical Fender/schumacher design, I think that is due to the lower primary Impedance.

I do like the OT, and I suspect that what I am hearing in the highs might be due to something else I changed at the same time (see my other post today about grid stoppers?). Your OT tightened up the bass flab that I was having a hard time with.

I don't think anyone should be afraid to experiment with values and networks "Outside the box" there is no wrong answer, so long as you like the way it sounds.

I know this, but philosophically I wonder if I end up trying to turn my Dumble-esque amp into a Fender or something. If that's what I am doing, I think maybe I should just buy a Fender.

[greiswig]

(SNIP)I had read many posts about all of those methods to reduce harsh high-end here except the bypass cap across the plate load resistor method (which is extremely common and well known...I just hadn't seen it mentioned here wrt ODS amps). So I tried all those other ways and didn't even try the Rp bypass cap until later...once I tried it I thought; "Why didn't I try this before? I KNOW it works and sounds good...so why didn't I try it?"

Fischerman, thanks for this. The snubbers seem to be tricky for me. I think that they might be introducing a slight peak right where their knee frequency is, and maybe that's what I'm hearing? Also, I almost find myself wishing for less of a slope to the high cut that they introduce. Is this something that I might find more to my liking by using the plate bypass cap? If so, can you recommend a value range to try? E.g. a SWAG: maybe I'd be happier with the 270pF snubbers but a .001uF plate bypass cap on V2a?

[Fischerman]

Yea, try a .001uF and tweek from there. I'm pretty sure I have a 1000pF ceramic disk there. I put my amp away for a while and just pulled it out and blew the dust off last night (just to play...no tweeks until tonight)...so I'm not as familiar where I last left it as I should be.

LOL, I left it at the gates of midrange hell...that's where I left it.

[Funkalicousgroove]

Who cares what you call it, the point is that it makes the tone you want. I build Fenders all the time

[Tonegeek]

greiswig,
I went down this same road and had some of the same reservations you seem to be having. Basically, I wanted the D' tone but wasn't getting it going the normal route so I went my own way. It is all turning out OK for me (after a year of experiments) and ironically I have come full circle as my amp now has more accepted values and less of the stuff I added when I "went off the reservation" and it now sounds great (to me). Still I have done my own thing to an extent but I did it after finally building a solid foundation with known values (just not the known values I started with...) I learned a lot along the way about filtering and supply voltages, how gain and bias affect the sound, and especially about tone shaping. If I was a newbie doing it again for the first time, I would try to get "the sound" using the accepted values and with help from the senior members of this forum. If I had stuck with that approach early on it may have saved me a lot of time. I did not exactly give up, but I got frustrated and went my own way without asking for more help. However I still learned a lot, but I just wasn't methodical about it. Also, it wasn't until late last fall that I stumbled on the Bluesmaster bandwagon, and that with some other suggestions floating around got me going in a direction that worked for me. My feeling is the more you know, the better your amp will sound.

On a practical note, and as you already found out, the NFB/presence area is a good place to make changes that have big impact on the tone. I had my FB coming off the 4 ohm tap at one time and was getting some spikiness. When I moved it back to the 8 ohm tap, it went away because it needed more feedback to cure the problem. I suspect something similar is going on with your choice of pres. cap. Seems like a bigger cap lowers the knee so more lower frequencies are affected by the control (perhaps your spike is lower than the freqs. the .1 cap affected so .47 makes sense).
Good luck.

[heisthl]

No flames please but try going to the non-HRM 101 schematic values as posted in the files section (no cheating change everything, 220k/150k plates 270pf snubbers PI etc.). Use middle of the road shielded cable for the OD runs (read lossy) and even shield the OD trimmer to V2 run. No bleeders or mods required except use the old syle dropping string and size the FET simulator resistor for 305 volts on the B+5 node. If you have good iron it works every time.
The only tweaks needed to tweak to the iron/speaker choice would be possibly V2 coupling change to .02 and PI input coupler to .01 and PI output caps to .02. If you must tweak further a 10uf on CL2 bypass.

[Normster]

I have to agree strongly with heisthl. If you want a great sounding amp out of the gate, it's hard to go wrong with a non-HRM based on the "101" values. As Scott and others have stated many times, you must have a baseline.

However, the circuit is wide open to modification, even to the point of sounding NOTHING like a Dumble...if that's what you want. In the end, you should never build an amp to satisfy a forum member, you should build it to satisfy yourself. Now if you're building for a customer, that's a different story. As Scott will testify, my personal amp (4 x 6V6 BM) would probably never satisfy a Dumble clone buyer, but it works for me.

[Bob-I]

As Scott will testify, my personal amp (4 x 6V6 BM) would probably never satisfy a Dumble clone buyer, but it works for me.

I love my 4x6V6 amp. It sounds big and fat and you can crank it up without killing birds flying by.

True words, satisfy yourself. Each Dumble is a unique animal.

[RJ Guitars]

I find it philosophically disturbing when I come to such a substantially different conclusion about a component value from a builder like HAD, or any of the rest of you experienced builders... Anyone else find that their component tweaks go pretty far outside the mainstream?

George I find this to be a great thread... I've hung around the forum for quite a while now, but just recently got my "first ODS build complete" status - A clone of the D'Lite clone... I am far from an ODS guru, but at least capable of following the conversations to some extent...

First I had to debug a few build errors in my construction, then the amp was working. One thing I found immediately was that there are a bunch of knobs, a trimmer, and some switches and I had no idea where to set any one of them. I don't see too much discussion about this but it seems that there are some basic settings that really make the amp sound good or otherwise bad.

I've since started tweaking and my amp just seems to sound better all the time. What I can't discern is how much of that is tweaking and how much of it is grasping how to setup the amp. I have found that when I was struggling to get a certain sound, more often than not I had the knobs set all wrong.

I am growing to believe that one piece of being a "Dumble Guru" is learning what to listen for and how to dial things for a given sound. I'm convinced that most of you would have had great tone out of my amp in a few minutes with no solder iron needed... Not to say I don't believe in tweaking, but now it seems I'm after that last few percent of tone Nirvana when the stock build got me 95% of the way there.

For a while I really thought my amp needed major tweaks... then subtly I started to understand it and dial it in. I'm now convinced that the stock ODS 101 non HRM and/or the D'Lite as built are 95% of the battle and then it's tweak to personal taste after that? How can anyone else determine your personal taste in what sounds good? One thing I understand about HAD is that he tweaked every single amp for a specific customer. He was probably outside his own box on numerous occasions.

rj