I had a nice visit with #94 today until...

[Charlie Wilson]

Structo, the 152k was measured from wiper to ground with the amp on and in OD mode. I just don't think you can get an accurate measurement of the overall resistance of the trimmer while it is in the circuit. I think that is why with #124 the trimmer was removed and measured. If that is the case, then even the measurement from wiper to ground with the amp on and in OD mode is not an accurate measurement of the actual resistance. It is different than the measurement with the amp off but not accurate. I hope this makes sense. I also notice that the 100k level and drive pots measure lower in the circuit than the actual resistance.
CW

[Structo]

Yep, there is a lot more than meets the eye with these amps.

[lovetone]

I measure the resistance to ground with the valve pulled out as that way the wiper is not connected to the valve.

I have now found that with the amp on standby the reading to ground is about 1.5m ohm although I have just measured the resistance to ground with the standby on and the reading is correct, I did try this before but did not trust the reading. ( Valve In )

I think the resistance values that Charlie measured are correct as my resistance reading with the valve in place and the standby on are the same with standby off and the valve out.

Geoff

[jam-mill]

[snip]
Oh yeah, the HT taper cap is a .o2.
CW

Well it turns out that a bright or harsh OD issue in my amp was just solved with the installation of a HF taper consisting of 500K -> .01u. This completely smoothed out the sound of the amp with the OD engaged. In fact, the bleeder cap value may have to be reduced a bit or, perhaps the OD snubbers could be reduced from 330p to 270p.

' Was initially reluctant to install such a large cap, based on expert opinions tendered previously in older threader, but this tweak was exactly what was needed in my amp. It was seeing the information about #94's HF taper that lead me to try a larger cap.

So, for Single Coil Strat players, installation of a HF taper circuit should not be overlooked if an amp seems unusually bright; provided that all else is okay with the amp. My 2p (from a rookie perspective with hours upon hours of reading here and a fair bit of experimentation).

Hope this is helpful to someone.

BTW, with such a large cap in #94, seems like this amp may have been pretty bright...

Regards,
-jack

[vibratoking]

So, for Single Coil Strat players, installation of a HF taper circuit should not be overlooked if an amp seems unusually bright; provided that all else is okay with the amp. My 2p (from a rookie perspective with hours upon hours of reading here and a fair bit of experimentation).

IME, the Strat 'problem' is not related to too much brightness. It's that there is no chime or there is an apparent lack of brightness. The other problem, IMO, is that there is not enough output from the pickups, which causes the amp to sound a bit lifeless. Or have less life compared to HBs. I always use the FET input with a Strat and it helps quite a lot, but still lacking the great chime of say a good Super Reverb.

[aflynt]

IME, the Strat 'problem' is not related to too much brightness. It's that there is no chime or there is an apparent lack of brightness. The other problem, IMO, is that there is not enough output from the pickups, which causes the amp to sound a bit lifeless. Or have less life compared to HBs. I always use the FET input with a Strat and it helps quite a lot, but still lacking the great chime of say a good Super Reverb.

I think the "lifeless" thing is maybe more of a heaviness weighing down the feel of the amp imparted by the thick, focused voice of the ODS style circuits. I kind of like that myself, even with the Strat. I've had other Strat players tell me it's an uninspiring feel, though. Pulling out low mids and adding presence seems to make it sound right, but not necessarily "feel" right if you have more of a "Fendery" frame of reference.

-Aaron

[bluesfendermanblues]

IME, the Strat 'problem' is not related to too much brightness. It's that there is no chime or there is an apparent lack of brightness. The other problem, IMO, is that there is not enough output from the pickups, which causes the amp to sound a bit lifeless. Or have less life compared to HBs. I always use the FET input with a Strat and it helps quite a lot, but still lacking the great chime of say a good Super Reverb.

I think the "lifeless" thing is maybe more of a heaviness weighing down the feel of the amp imparted by the thick, focused voice of the ODS style circuits. I kind of like that myself, even with the Strat. I've had other Strat players tell me it's an uninspiring feel, though. Pulling out low mids and adding presence seems to make it sound right, but not necessarily "feel" right if you have more of a "Fendery" frame of reference.

-Aaron

@Vibroking & Aflynt, Aaron
I don't agree with you regarding the ODS amps not being Strat friendly - the Dumble's amps are Fender derived designs - Super, Vibro, Twin or whatever blackface or silverface. And even the Skyliner is not that far sound wise from a blackface amp. (dial the mid control to 8 0'clock and it sounds like a Fender - only with rounder treble and rounder bass.). And we agree that Silver and Blackface Fender's are good with both Strats, Tele's and HB guitars don't we?

IME many players start by playing the OD channel (I did) and dial the knobs to facilitate a great OD sound, and once they engage the Clean, it can sound dull or limited or whatever. IME it's imperative that you focus on getting the Clean right first and once you like the clean you move to the OD, that may be a bit bright and you may want to trim off some highs, like the HF trimmer can do. I wan't the OD to sound like the clean channel only with a more bluesy gain. I want the OD to be an extension of the clean channel so to speak.

It cannot said be too often. Don't paint by numbers, expecting a 1:1 clone of #102 (and they are never alike anyway, too much tolerance in many parts) to sound like the real #102.

Build one of the well documented amps with external or built-in Dumbleator and tweak it to your own taste. That's what HAD did back in the day. Rather than expecting a certain Dumble design to fit your taste and guitar, we've got to tweak those things.

[Synchu]

Can't agree more with the above. I am tweaking a BM HRM for the past few months, until collecting parts for the next build and from what I considered passable sounding amp, it turned to a great sounding piece.
Tweaking is the key with these designs.
Niki

[jam-mill]

In general, I concur with 'bluesfendermanblues' regarding tuning this amp; although, I don't completely understand what 'paint-by-numbers' means.

The post I made previously identified a specific problem with my particular d-style amp and described a modification with its results that were found to be pleasing to my ears. The post mentioned nothing about "the strat problem" because I don't know what that is. It was merely a suggestion to other players of the same/similar instrument faced with a similar "problem".

As mentioned by 'bluesfendermanblues' these amps seem to require a certain amount of tweaking to accommodate the individual players' technique, the speaker and its cabinet, the 'iron', the various tubes, the component tolerances, and what each player wants to hear.

Regards,
-jack

[aflynt]

@Vibroking & Aflynt, Aaron
I don't agree with you regarding the ODS amps not being Strat friendly - the Dumble's amps are Fender derived designs - Super, Vibro, Twin or whatever blackface or silverface. And even the Skyliner is not that far sound wise from a blackface amp. (dial the mid control to 8 0'clock and it sounds like a Fender - only with rounder treble and rounder bass.). And we agree that Silver and Blackface Fender's are good with both Strats, Tele's and HB guitars don't we?

IME many players start by playing the OD channel (I did) and dial the knobs to facilitate a great OD sound, and once they engage the Clean, it can sound dull or limited or whatever. IME it's imperative that you focus on getting the Clean right first and once you like the clean you move to the OD, that may be a bit bright and you may want to trim off some highs, like the HF trimmer can do. I wan't the OD to sound like the clean channel only with a more bluesy gain. I want the OD to be an extension of the clean channel so to speak.

It cannot said be too often. Don't paint by numbers, expecting a 1:1 clone of #102 (and they are never alike anyway, too much tolerance in many parts) to sound like the real #102.

Build one of the well documented amps with external or built-in Dumbleator and tweak it to your own taste. That's what HAD did back in the day. Rather than expecting a certain Dumble design to fit your taste and guitar, we've got to tweak those things.

My point was not that they aren't "Strat Friendly" but that they're just not some people's cup of tea feel-wise with a Strat. I happen to really like my Strat through all my ODS style amps, but I've run into people that don't. It seems to boil down to a somewhat intangible "feel" thing in my experience. Not sure if it's the D'Lator compression or the low preamp plate voltages or what, but the notes all have this perceptible "weight" to them that some people (like me) totally love, and some people don't really like. I'm sure that it could tweaked to not have that feel, but to me that's part of it's charm.

I totally agree with all your points about tweaking the amps, not painting by numbers and making the OD an extension of clean, though.

-Aaron

[bluesfendermanblues]

.........
My point was not that they aren't "Strat Friendly" but that they're just not some people's cup of tea feel-wise with a Strat. I happen to really like my Strat through all my ODS style amps, but I've run into people that don't. It seems to boil down to a somewhat intangible "feel" thing in my experience. Not sure if it's the D'Lator compression or the low preamp plate voltages or what, but the notes all have this perceptible "weight" to them that some people (like me) totally love, and some people don't really like. I'm sure that it could tweaked to not have that feel, but to me that's part of it's charm.

I totally agree with all your points about tweaking the amps, not painting by numbers and making the OD an extension of clean, though.

-Aaron

Gotcha regarding the 'feel'/weight thing probably stemming from the D-lator and lower pream voltages...The SSS is a different animal, pedal friendly and to be used without d-lator and it suited SRV's taste better. He didn't like the ODS.

Maybe it comes down to how hard you hit the strings.

SRV used a lot of force in picking his strings, tried an ODS, but ended up with a SSS. ODS users, Robben Ford and Larry Carlton on the other hand have dynamic and varied picking attacks with a lot of soft strokes, allowing the amp 'breathe' more. (Even though Larry calls the D-lator a piece of S***t )

[aflynt]

Gotcha regarding the 'feel'/weight thing probably stemming from the D-lator and lower pream voltages...The SSS is a different animal, pedal friendly and to be used without d-lator and it suited SRV's taste better. He didn't like the ODS.

Maybe it comes down to how hard you hit the strings.

SRV used a lot of force in picking his strings, tried an ODS, but ended up with a SSS. ODS users, Robben Ford and Larry Carlton on the other hand have dynamic and varied picking attacks with a lot of soft strokes, allowing the amp 'breathe' more. (Even though Larry calls the D-lator a piece of S***t )

The D-Lator feel discussion made me remember somebody's suggestion to try disabling the LNFB on the loop return to bring back the dynamics. I just tried it and the amp really does feel a lot more "Fendery" now. You lean into the notes and it screams instead of compressing... Gotta play it more to see if it messes with the higher gain OD sounds, but so far I like it a lot. Oddly I DIDN'T like disabling V1B LNFB, though.

-Aaron

[Structo]

Are you talking about the NFB circuit that includes the presence control?

I have mine on a switch, I like it off sometimes for lower volume playing.

[aflynt]

Are you talking about the NFB circuit that includes the presence control?

I have mine on a switch, I like it off sometimes for lower volume playing.

No. Haven't messed around with that yet. I'm talking about the local negative feedback network on the recovery amp of the Dumbleator: Grid (pre 220k/500pF) -> 10M -> .22uF -> 10M -> Plate. Breaking that network seems to open the amp up feel-wise.

-Aaron

[Structo]

Ah, sorry misunderstood.

I haven't played around with that.