Dumble Serial number 006X OD50WX

[Mr. dB]

Hello Tony, yes, I am well aware that Boogie used Tantalum bypass caps in their Mark series amps...

Wet tants or dry?

[talbany]

Hello Tony, yes, I am well aware that Boogie used Tantalum bypass caps in their Mark series amps...

Wet tants or dry?

Solid electrolyte

Tony

[talbany]

Originally, my logical thought process was that the plate resistors are most critical, the grids have some impact too but the cathodes (being bypassed with a capacitor) should be less noticeable. I've since changed my mind. Dumble seemed to really like the old light gray molded IRC MEB's in this spot for a number of years and I suspect he ran out of inventory at some point in time and moved on to different brands. I do agree, however, that the difference in the voice of an amp with the MEB's versus some other NOS military type RN65 resistor is, however, subtle. I personally like the CGW NA65's in this spot but these are just as hard to find as the IRC MEB's. Anyway, having played around with the Dumble High and Low Plate circuits now...I understand much better how his combination of specific components build out the sonic signature of his various circuits. So now I do feel that the cathode resistor brand/type matters. It isn't an overly dramatic difference...but everything works together to build out the basic voice of the amp. That said, I still hold to the reality that the plate resistors matter the most and color the sound the most.

Gabe

This is cool that you can hear a difference between "types/brands" of RN65 military resistors in bypass. As someone who is fascinated and can usually tell a difference between different types and brands of some components can you (if you can) describe what it is you are hearing between these resistors you prefer. Things like frequency response harmonic content or character of overdrive (distortion) enhance sustain etc etc. If you could possibly help direct my ears to how these resistors influence the amps timbre so hopefully I can hear it too.That would be great.

I couldn't agree more! A big part of the sound of those early amps resides in those old hard to find parts!. IMO the difference between a good sounding amp and a fascinating one.
Thanks again!!

Tony

[GPD]

Tony Wrote: (if you can) describe what it is you are hearing between these resistors you prefer. Things like frequency response harmonic content or character of overdrive (distortion) enhance sustain etc etc. If you could possibly help direct my ears to how these resistors influence the amps timbre so hopefully I can hear it too.That would be great.

Hello Tony,

I took the family to the nations capital for spring break...kids got to experience DC in the spring and my parents who never get to see them got to spend quality time with them...a win win except for the cost of the trip part

Giving you specifics on the differences between different cathode resistor brands is a long conversation. First question, do you have a spectrum analyzer at your disposal? If so, then you can definitely see the differences between each brand of part and then you can remove your subjective "ears" from the equation. Obviously, you have a tremendous variation of clean and dirty tones on tap with any ODS type circuit so you have to limit your settings for rationality sake. I start by building two pre-amps as close to one another as possible (same parts and same tolerances of the same parts). This is important as some parts (like 6PS caps have a substantial tolerance and simply having the same part but with a wide variation in capacitance makes a substantial impact on the basic voice of the amp. Pots are difficult too, again, for tolerance reasons so you have to use your scope to get the levels identically set. One of the pre-amp boards I have rigged quick disconnect style (I like small alligator clips soldered into the eyelets though I have used spring retainers in the past for similar experiments. This allows for the direct comparison. The two pre-amps are run into the same power amp and you switch back and forth. It is tedious and time consuming but the only sure way to confirm whether your ears are really hearing differences or if you mind is wanting your ears to hear something different. You can drive yourself crazy with the combinations and pick apart the fundamental and harmonic structure of what the signal looks like on the analyzer...but you'll see differences if you start isolating components and measuring.

Anyway, what I've concluded with my experiments is that the old military parts, particularly those that were diamond wheel trimmed, tend to perform more to my own personal liking than the parts that were laser trimmed. This isn't exactly new news...the Hi-Fi world has known about this reality for decades now. David Hafler explained this to me, in detail, back in the 1980's. He also explained how different resistors leave their own sonic signature in how the electrons flow through them which is directly tied to materials and construction type. Leads, end caps, how they were soldered, coatings, etc. all have some impact according to the late great Hafler. I also have a good friend who's a PhD physicist who has spent decades studying audio circuits and tube circuits in particular. He has also concluded that at the quantum level of resistors there are phenomenon going on that most pragmatists don't wish to believe.

I used to be a skeptic to all this speak but over the decades I've come to change my mind. I do believe the construction and type of component matters. It might not make a gigantic impact in all cases but if you are expecting to build an amp that performs as close as possible to one of Dumble's original creations...you don't really have a choice, you have to find and employ the right parts...many of which are "unobtainium" today.

That said, at this juncture, there are significant volumes of Dumble clones out there that use modern parts and they actually sound quite pleasing and perform and react in a similar fashion to what they are copied from. But the devil is in the details and if you are looking for the exact same response to an original Dumble amp or as close as possible...the right parts actually do matter.

Looking back at the Dumble clone explosion...there were two clear leaders in this market. Andy Fuchs and Two Rock, both dating back to the late 1990's. Before this, there were surely some Dumble clones out there but not in the volumes that Fuchs and TR made them available. Andy's amps are obviously 100% modern parts and he's built a great reputation using modern parts. Some TR's are a little closer to what Dumble was building Krinard surely built his share of amps using NOS amps (though in small quantities). Since then, those in this space have pushed the envelope trying to get as close to the original as possible and even offering NOS upgrades. I personally think this is great...not practical but really inspiring to see people trying to push towards offering an affordable alternative to amps that the average Joe couldn't buy unless they won the lottery.

Sure, I know, HAD is not pleased with the industry that has grown up around his designs but it was inevitable that it would. Supply and Demand...plain and simple. Besides, HAD never asked Leo Fender or any of the other amp designs he borrowed heavily from? Did he?

I doubt it

In general, there are a multitude of characteristics that each of these old brands/types of resistors possess which is likely why/how HAD ended up selecting them in the first place. Trial and error, for certain. I think at first, he was trying to cut down on noise levels and then he stumbled across the different flavorings each brand brought to the equation. He obviously liked 1970's vintage Dale's on the V1 plates. He obviously liked Electra MF6's on the V2 plates. It is clear that he liked the Piher CF's in various signal handling spots for a number of years then got excited about the Draloric (Sprague Q-Line Flame-Proof) parts once he got into the early 1980's. The IRC MEB's...Cathodes for a lot of years...he clearly liked them in this spot. Later he got excited about Resista/Roederstien MK3's and NT MF's and so on.

Best Regards,


Gabe

[Max]

Max what is your opinion or speculation on the “How” a very earlier style ODR was built and assigned the serial number of #008X in 1978 yet #0057, #0058, #0059 and #0060 all have substantially lower numerical serial numbers relative to it yet seem to all appear to have later version ODR features? I can confirm, without a doubt, that #008X was ordered in 1977 and delivered in 1978. Every single component in this amp has date codes that predate 1977 too. So when do you suspect #0057 was built? And #0058? And #0059 and #0060? And why do they all have such relatively low serial numbers? Or I suspect the better question is, why does #008X have such a high serial number?

Hi Gabe,

IMO the serial number of a Dumble amp was usually fitted to its chassis before the installation of its circuit. So IMO - especially in regard to the rare Dumble amps (ODR, SSS, Dumbleland, etc) - there's only a rather loose correlation between the serial number and the date of completion and delivery to the first owner.

All the best,

Max

[Mr. dB]

In general, there are a multitude of characteristics that each of these old brands/types of resistors possess which is likely why/how HAD ended up selecting them in the first place. Trial and error, for certain. I think at first, he was trying to cut down on noise levels and then he stumbled across the different flavorings each brand brought to the equation. He obviously liked 1970's vintage Dale's on the V1 plates. He obviously liked Electra MF6's on the V2 plates. It is clear that he liked the Piher CF's in various signal handling spots for a number of years then got excited about the Draloric (Sprague Q-Line Flame-Proof) parts once he got into the early 1980's. The IRC MEB's...Cathodes for a lot of years...he clearly liked them in this spot. Later he got excited about Resista/Roederstien MK3's and NT MF's and so on.

I wonder how much of this was due to selection and how much just availability?

[GPD]

Max wrote: IMO the serial number of a Dumble amp was usually fitted to its chassis before the installation of its circuit. So IMO - especially in regard to the rare Dumble amps (ODR, SSS, Dumbleland, etc) - there's only a rather loose correlation between the serial number and the date of completion and delivery to the first owner.

Hello Max,

I think that is a good speculative generalization but I guess digging a little deeper...did he stamp the bare chassis' in batches and keep them in inventory and consume them over time? Or did he stamp them right before he decided to assemble the amp? I realize you are referring primarily to ODS's, however, it is rather interesting that there are several ODR chassis' with sequential serial numbers making one contemplate that he very well may have stamped them and let them sit...doesn't seem plausible that he knocked them all out within a short duration. Also, with the great variation of what is going on inside some of these ODR's is a bit of a head scratcher too. BTW, reached out to a customer of mine that has direct access to Rick Vito and he passed on some of my questions. Many, he couldn't really answer as he did not recall the specifics, however, he did confirm that his amp was indeed given to him by Jackson Browne during the 1982-1983 window of time. It was one of JB's amplifiers and when Lindley left and Vito stepped in it became his. His understanding is that the amp was built in the late 1970's...not certain what year in the late 1970's but he was told it was built for Jackson along with others in the late 1970's...that was his recollection.

We see some Q-Line Flameproof Dralorics inside of the JB/Vito amp. You could surely purchase these parts all over the USA as far back as 1976...though I know of no ODS, ODR or any other Dumble made in 1975 with the Dralorics. Sprague also packaged and sold non-flameproof carbon film resistors which turn out to be made by who? Yep, you guessed it...Piher. Sprague was selling these in the mid 1970's...again, available in anywhere USA back in those days. We also know that the JB/Vito amp and #0060 were not gooped...so this also gives us better clues as to the relative earliness of their construction...or maybe not? Hard to say for sure.

So I'm still a bit puzzled about a slide switch early incarnation ODR wearing a serial number of 008X, built in 1977-1978 and then 3 different sequentially numbered ODR's (mini-toggle chassis) built sometime in the late 1970's wear serial numbers in the 006X range. Yes, I know, you have a disclaimer for ODR's but it still doesn't make much sense to me understanding that ODS and ODR amps shared the same master serial number range.

Right? See what I'm getting at? He's working off a singular master serial number range...makes very little sense that there is an outlier ODR built between the years of 1977-1978 with a serial number of 008X. Yet it was...

Coming up with a logical explanation is challenging.

Best Regards,


Gabe

[GPD]

Mr. dB Wrote: I wonder how much of this was due to selection and how much just availability?

A great question and something I've contemplated quite a bit. I know that many of these parts were available during the 1970's and 1980's for positive in Southern California where the aerospace industry was quite substantial. You could find them in other parts of the country as well...that's for positive. Some military designated parts would have been harder to source than others...such as Texas Instruments, KDI/Pyrofilm, Continental Wirt (CWE), Jeffers, Angstrom, Clarostat and many other military/aerospace used brands. Personally, many of these other brands are of equal (or higher quality) than the brands Dumble used but would have been much harder for a civilian to get his hands on. I personally love T-I and Pyrofilm resistors and I use them quite often along with Holco's which I'm quite fond of too. He obviously had access to a number of high quality military/industrial metal film parts in the 1970's and 1980's. You'll find EKC/Electra, CGW, Dale, and IRC parts over these two decades...the IRC's are molded and almost always date to the 1960's...definitely surplus by the time he used them. The EKC's are molded too...also dating to the 1960's...again, surplus in the 1970's. the MF6 and MF7 Electra resistors he used generally seem to be 1960's construction as well...dare I say it? Yep, surplus in the 1970's and 1980's.

Of course, could he find all the values he was after in surplus...I'd say maybe...maybe not. That's the nature of surplus.

The Piher CF's were readily available in the Sprague Q-Line display racks and catalogs...they hung in electronics stores all over the USA during the 1970's into the early 1980's. You could buy them in bulk too if you needed. The flame-proof Draloric made carbon film parts were similarly readily available...he seemed to like both but obviously gravitated to the Draloric made parts during the 1980's and 1990's...and I totally get the "Why" he did this. He would also supplement in Archer/Radio Shack Asian made carbon films in certain spots of some amps.

Anyway, hard to say how Dumble arrived at his component choices but I suspect he surely liked the sonic qualities of those Dale's on the plates of V1...they are rather warm sounding for a metal film resistor. He liked those MF6 Electra's because of their aggressive coloring of V2...no doubt about it and he surely noticed a difference between using MF6's in that spot versus MF7's.

So I think there was a lot of trial and error experimentation going on during the 1970's and 1980's and he found what he liked best over time.

Best Regards,


Gabe

[Charlie Wilson]

Gabe,
I am curious about your reference to MF6 on V2 and Dales(I assume the brown rn65c) on V1. All the amps I have seen that have Dales on V1 also have them on V2. Am I missing something? Maybe you mean the PI plates in the 2nd generation amps?
CW

[GPD]

Charlie Wrote: I am curious about your reference to MF6 on V2 and Dales(I assume the brown rn65c) on V1. All the amps I have seen that have Dales on V1 also have them on V2. Am I missing something? Maybe you mean the PI plates in the 2nd generation amps?

Hello Charlie, you are not missing anything…I should have qualified what I stated as I was referring to the Electra MF6’s Dumble employed for V2 of ODR #0060. Which I’m quite positive he did on purpose…and I’m also positive that he elected to use MF6’s in this spot instead of MF7’s. This is one of the few amps that does not have the 1975 vintage Dale RN65’s on the V1 plates, instead there are the obscure silicone-oil-filled, hermetically sealed military RN70 size carbon film resistors. I’d love to know how he arrived at this decision…quite interesting. You can find these in many old signal generators…maybe that influenced his choice? I don’t know and would never claim to know

But you are spot on…he liked the Dale RN65’s on V1 and V2 plates for certain…and not just any Dale RN65’s…he was using the early construction parts for positive which were diamond wheel trimmed. The bulbous end caps are a dead giveaway without even reading the datecodes. And like I pointed out previously, these are warm sounding for metal film resistors. I suspect that was what influenced his selection of these parts. Plate resistors for V1 and V2 have a gigantic impact on the voice of any amplifier.

Now, going a bit earlier in his career during the 1970’s, he seemed to like to run the Electra’s. You do not see the Dale’s until time progresses through the 1970’s. As I also recall, ODS #0018 has Electra resistors on the plates of V1, V2 & V3, I believe ODS #0033 does too and I recall seeing another ODS in the #003X range with Electra’s on all the plates of each pre-amp tube. Yet, I have seen another ODS in the #003X range that had the Dale’s on V1 & V2.
That said, I still think he was very deliberate in what combination of brand/type resistors he used inside his amps of the 1970’s and into the 1990’s. There are definite patterns or trends he was employing.

Sorry for the confusion.

Best Regards,

Gabe

[Charlie Wilson]

Thanks Gabe, I was wondering if you know something about the Piher resistors that Dumble used. I have been told that there were several locations that made the resistors. The ones everyone has been getting on Ebay don't look the same as the ones I have seen in his amps and I have been told don't sound the same. I did a little research and found out that Piher only started making resistors in the 70s. I will attach a photo of #54 to show the Pihers. I was lucky enough to play that amp for several weeks.
CW

[GPD]

Charlie Wrote: I was wondering if you know something about the Piher resistors that Dumble used. I have been told that there were several locations that made the resistors. The ones everyone has been getting on Ebay don't look the same as the ones I have seen in his amps and I have been told don't sound the same. I did a little research and found out that Piher only started making resistors in the 70s. I will attach a photo of #54 to show the Pihers. I was lucky enough to play that amp for several weeks.

Hello Charlie,

I really like the 1970's ODS's...I like the OD content quite a bit...raw and aggressive when you get them dialed in that way. Not nearly as smooth as the later amps but smooth gets a little boring after a while

I have a great source to talk to in the U.K. that worked for a big Piher distributor from the very beginning of Piher...he's a wealth of knowledge on the subject of Piher resistors. You are right in that Pihers of different vintages have a different look. I'll have to dig you out some NOS Sprague Q-Line Pihers that I have and get you some good close-up pix and dimensions. I'm of the opinion that the Pihers you find in many of those 1970's Dumble amps came out of those little hanging Sprague packages with the plastic boxes taped to the card stock. Having had some real Dumble specimens in-hand and having a nice inventory of NOS Pihers (including the Sprague packaged Pihers)...it sure looks to be the case. Makes sense...he likely bought these along with all the other Sprague parts he liked to use and these were readily sourced locally by him back in the 1970's and early 1980's in either Santa Cruz or down in SoCal when he relocated to the Jackson Browne family estate:
http://pasadenamag.com/bohemian-masonry/

Plenty of electronics shops stocking and selling these Sprague parts in those days.

Best Regards,


Gabe

[Charlie Wilson]

Gabe, I found this in my Piher bag. I ordered 1k8 NTE from a guy and this is what he sent me. Maybe this is the Q-Line little plastic box you mentioned?
CW

[GPD]

Charlie Wrote: Gabe, I found this in my Piher bag. I ordered 1k8 NTE from a guy and this is what he sent me. Maybe this is the Q-Line little plastic box you mentioned?

Hello Charlie,

I would say yes...that looks to be an old Sprague "Filmistor" Q-Line plastic container. These were generally taped to a piece of card stock printed on the face and back. Here is a catalog page...I think this is from the Q-Line 1978 catalog:

Sprague_Filmistor.jpg

Now, check the two pictures below. This is a couple of different 1/2 Watt packages, front and back. You can see they had a couple of different variations on the card die cut but they generally ended up taping the plastic container in place.

IMG_4533.jpg

IMG_4534.jpg

It doesn't take Sherlock Holmes to realize these are 1970's vintage Piher CF resistors. On top of that you can clearly see the country of origin printed right on the back of the package:

IMG_4535.jpg

Close-up of one of the 1/2 Watt resistors...very obviously a 1970's Piher part:

IMG_4536.jpg

Now, think about it...

In the 1970's, Dumble was sharing a rented cliff home in Santa Cruz with his then buddy, Jack Smith. Jack had a Hi-Fi business and Dumble was repairing, modifying and building instrument and power amplifiers. Doing so as a 1-man show would have economically challenging on many levels. He likely couldn't afford to purchase new components in bulk and likely didn't need to...he didn't really have the bandwidth to handle much volume. Like I said before, in literally any-town, USA, you could buy high quality Sprague branded/packaged parts quite readily and they were generally packaged up neatly just like these resistors. Not just these Pihers but the Draloric Flame-proof 2% parts. Also in the same type of packaging you could get Sprague 6PS Orange Drops and Sprague Atom Electrolytics, and Sprague Ceramic Disc Capacitors and even Silver Mica capacitors (Quite often Sangamo's in the Sprague Q-Line packaging). All high quality parts for a reasonable price hanging on a display.

It isn't too hard to connect the dots...Dumble very likely sourced many of the above mentioned components in this type of packaging back in those days.

Buying them in bulk would have required volumes of parts he likely didn't need given his slow throughput...seems very plausible to me.

I could be wrong...but it sure seems like the path of least resistance for what he was doing during the 1970's and maybe even into the 1980's...I remember these displays still existing for a number of years...I myself bought a ton of these Q-Line parts starting in the 1970's and into the 1980's. It just didn't make any sense not to.

Best Regards,


Gabe

[GPD]

Charlie,

A few more pix of Sprague Q-Line "Filmistor" 5% Resistors for your perusal. Pay close attention to the 1/2 Watt 1.2R's...note they are definitely not Pihers!!! You can see right on the packaging that their country of origin is Japan. I believe the reason for the different source has to do with the reality that Piher couldn't supply all the values Sprague likely needed so they used a secondary source. I've seen quite a few of these Japanese parts not only in the Sprague Q-Line packaging but also in some of the "Archer" Radio Shack assortments of the 1970's. The other packages are for 1 Watt and 2 Watt parts which you can clearly see are Piher and their country of origin on the packaging is appropriately marked.

IMG_4537.jpg

IMG_4538.jpg

IMG_4539.jpg

IMG_4540.jpg

Another interesting tidbit to note is sometimes the resistors are bulk/loose but other times they clearly came on a ribbon. I spoke with an old Sprague salesman many years ago and he confirmed that Sprague did all the packaging in-house. They either manufactured or purchased the components and then handled the entire packaging operations in a few different locations.

Anyway, there you go...

I think I have some NOS Q-Line packages with Sprague Atoms, Sprague 6PS Orange Drops, Some Sprague Ceramic Disc Capacitors and quite a few with Silver Mica capacitors. The Silver Mica's appear to be either Sangamo or CDE parts.

Best Regards,


Gabe