Dumble Clone Break-In Issues

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kevster
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Location: Hutchinson Island, Florida

Dumble Clone Break-In Issues

Post by kevster »

I actually think "wear-in" sounds more appropriate. I just don't like the term "break".

I have a Ford-esque Dumble clone that is now up and running on the bench and I've put about 6 hours in it. What a change, or series of changes, those 6 hours make. I'm using the Dumbleator as is common/recommended. Here's the progress so far:

Fire-up: After I got it going (thanks to Todd for the assist), I had two overdrive channels. Literally, both channels were overdrives. I started out without the Dumbleator in the loop, but even with it both channels were overdriven. I had the "Volume" on the clean channel at minimum and still getting the OD above about 5 on the guitar volume. The OD channel sounded best with the (external, on back) OD Trimmer on about 2:00.

Two-Three Hours: The loop has been added and I've got all the knobs in the 9-11 range. I can turn the "Out" to 5:00 for more volume, but no need (I'm married... :D ). Starting to see some harmonics coming out, and the clean channel is losing the "overdrive". The overdrive is becoming "grittier" and I'm backing down the OD Trimmer.

Five-Six Hours: I have a clean channel. I turn it up to max and I get cleans until the guitar volume knob is above 7, and above that it is all about pick attack. The break-up is minimal. The OD is gaining in harmonics and I now have the Trimmer at about 9:00...

I'm using Magnetic Component trannies and the PT has an extra 15V on the mains, but I don't know if this is normal or not. I don't know for sure that there is a real normal... Anyway, my plate voltage is 458V and 468V respectively. I haven't touched that yet as it isn't too far off optimal (1.5%) My bias is at 37.x and 38.x with my bias pot at minimum, but at fire-up it was more than double that. I don't know how to get it below that without modding the amp.

My test speaker is a 4 Ohm Crate speaker in a combo SS amp my wife bought for $20 at a yard sale. Obviously, this is not an optimum speaker for a D-style amp, but I'm just testing at low volumes right now and it is nothing more than a functional test speaker.

I'm using two Winged C 6L6GC's (matched), a JJ 12AX7 Long Plate Gold Pin in the PI, and two Sovtek 12AX7s in the V1 and V2. I couldn't go NOS right off the bat...

So, anything sound abnormal here? Is the Plate Voltage a big issue? I'd like to get the bias down to about 35mV, but I wouldn't think the extra 10% should be too bad.

I will say that this amp's clean channel is probably on par with my best Fender right now and still improving fast. The OD is the "sound" I go for with a Zen and a Fender, but I'm looking for more harmonics and bloom as it continues to evolve. I feel like the burn-in is still ongoing and significant changes as each hour progressed. I know that 25+/- hours has been stated here numerous times, so it may still be a while.

Does the description sound "typical" for these amps?

Thanks guys for all the info that helped make this a reality!!!
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Structo
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Re: Dumble Clone Break-In Issues

Post by Structo »

Why do you figure you didn't have a clean channel at start up?

When I had a similar problem I found my preamp volume pot was defective.

Strange that the power tubes are 10v apart.
Especially for matched Winged C 6L6, those are usually closer together.

So you are biased now around 70%?

You may like it better down around 55-60%.

With the Dumbleator I like to keep the pre-volume at around 1:00 and the same for the Master, then control the volume with the Output pot on the Dumbleator.
Tom

Don't let that smoke out!
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greiswig
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Re: Dumble Clone Break-In Issues

Post by greiswig »

Although I've only had experience breaking in one amp, the magnitude of the changes you seem to describe is way over what I experienced. The part about the clean channel not cleaning up initially, in particular, caught my eye. Definitely not my experience.
-g
kevster
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Re: Dumble Clone Break-In Issues

Post by kevster »

Structo wrote:Why do you figure you didn't have a clean channel at start up?

When I had a similar problem I found my preamp volume pot was defective.

Strange that the power tubes are 10v apart.
Especially for matched Winged C 6L6, those are usually closer together.

So you are biased now around 70%?

You may like it better down around 55-60%.

With the Dumbleator I like to keep the pre-volume at around 1:00 and the same for the Master, then control the volume with the Output pot on the Dumbleator.
The readings I posted were taken at start up. I don't know if they might change slightly with some burn in time. I have the bias pot at MINIMUM. 37mV-38mV is the LOWEST I could get it at start up... Like I said, if things change after some burn-in time, that may be different now.

The clean channel was overdriven at first and has cleaned up SIGNIFICANTLY as I've put time in. I only really used the NORmal input. I'll try FET at some point.

Should I tweak the PI Trimmer to balance the voltages? Would that help the sound of the amp or the bias current/voltage?

I won't have any "tweaking time" until late this week or the weekend. I'm going out of town for a couple of days to testify in a retail center foreclosure case...

I'll also hav some sreious playing time on Sunday...
kevster
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Re: Dumble Clone Break-In Issues

Post by kevster »

Thread Resurrection Time!!!

Old post, same amp, but new questions...

So, I've got a number of years on my Ceriatone OTS50 ME w/C-Lator now (through a custom Thiele w/EVM-12L), and it's time to break it open again and get this thing REALLY right.

I've moved to a condominium, so I play at conversation volume only at home. I had the rig out this weekend for a gig, where it performed flawlessly, but it inspired me to get this thing BLOOMING as a Dumble clone should. The nature of the amp changed almost not at all between the house and the stage. The tone, the response, even the EQ, all required very little attention at all.

There is some bloom there, just limited at EITHER volume... Certain notes bloom a bit, while others only marginally. Since I've FINALLY gotten around to constructing a Treble Bleed w/12-way switch for the OD Channel, I need to install it, I figure I'll recheck the PI balance and see what else I can do while this thing is in the cradle. Since, the few spare tubes I have are packed up and in storage, and since they are only new production 12AX7's, I need to "go" shopping. I'm currently using the same two Winged C 6L6GC's (matched), a JJ 12AX7 Long Plate Gold Pin in the PI, and two Sovtek 12AX7s in the V1 and V2. The amp chassis was built and I installed the Magnetic Component trannies and tubes... Very little that I would have done to impact the dress of the internal wiring, so I think it is the tubes and the PI adjustment are the areas that need to be changed and tweaked.

FYI: I run my #102 clone very similar to how RF sets up his amp (EQ, OD Level/Ratio, etc. Also Compressor and Zen Drive in front, and a delay (on an X-Blender) and reverb in the loop.), with MV a bit higher at 2:30 - 3:00 or so, Rock/NO Bright/Deep (sometimes), and the C-Lator is: In @ 3 o'clock; Drive @ 10 o'clock (set where I BARELY get any break-up with a Humbucker); and OUT as my MV. Lastly, with the cap cables for the loop...

I've got hundreds of hours on the amp, and it sounds as good or better now than ever, but...

First question: What tubes should I consider for increasing harmonic bloom? I may spend a couple/few hundred $$$ on tubes now that this is a test-proven amp. Which tubes? V1 and V2? These two are $15 tubes, so they are not top-shelf... Would it be better to look at new tubes for V4 and V5?

Second question: Are the tubes the best place to focus? If not, where?

Thanks any and all!!!!

Kevster
Charlie Wilson
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Re: Dumble Clone Break-In Issues

Post by Charlie Wilson »

Hello, my opinion is V3 is the money tube. Also study the lead dress of some of the real Dumbles and well done replicas.
CW
Charlie Wilson
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Re: Dumble Clone Break-In Issues

Post by Charlie Wilson »

[quote="Charlie Wilson" post_id=375418 time=1500587456 user_id=15218]
Hello, my opinion is V3 is the money tube. Also study the lead dress of some of the real Dumbles and well done replicas. Also, and this may be not the opinion of most. I think chasing the controlled feedback/bloom thing is a bit overrated. I can get my amp to do that by unbalancing the PI trimmer but I don't love the overall clean/overdrive sound of the amp. Again, just my opinion. :D
CW
Charlie Wilson
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Re: Dumble Clone Break-In Issues

Post by Charlie Wilson »

Deleted, oops.
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ToneMerc
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Re: Dumble Clone Break-In Issues

Post by ToneMerc »

Charlie Wilson wrote: Thu Jul 20, 2017 9:50 pm Hello, my opinion is V3 is the money tube. Also study the lead dress of some of the real Dumbles and well done replicas.
CW
I agree with starting at the PI. I have often said that these amps are the sum of the small things and IMHO, the PI is one of them.

http://ampgarage.com/forum/viewtopic.php?f=4&t=18048

This is the Gospel according to Gil.

TM
kevster
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Re: Dumble Clone Break-In Issues

Post by kevster »

Thanks guys!

So... Favorite/best PI tube? That's where I'll start.

BTW... I can get some bloom clean or OD with the rig as it is, so it is pretty close to where it needs to be. I just read up on the JJ 12AX7 Gold Pin that's my current PI tube, and it wasn't particularly glowing (sorry for the pun :roll:). I'm going to spend the money to get a good $50-$100 PI tube.

Thanks again!

Kevster
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ToneMerc
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Re: Dumble Clone Break-In Issues

Post by ToneMerc »

kevster wrote: Fri Jul 21, 2017 4:40 pm Thanks guys!

So... Favorite/best PI tube? That's where I'll start.

BTW... I can get some bloom clean or OD with the rig as it is, so it is pretty close to where it needs to be. I just read up on the JJ 12AX7 Gold Pin that's my current PI tube, and it wasn't particularly glowing (sorry for the pun :roll:). I'm going to spend the money to get a good $50-$100 PI tube.

Thanks again!

Kevster
I have amps with NOS tubes but I typically use a $15-16 balanced Sovtek LPS and migrated to using Gil's PI technique. Why do you feel the need to spend up to $100 on a PI tube?

TM
kevster
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Re: Dumble Clone Break-In Issues

Post by kevster »

ToneMerc wrote: Fri Jul 21, 2017 7:56 pm
kevster wrote: Fri Jul 21, 2017 4:40 pm Thanks guys!

So... Favorite/best PI tube? That's where I'll start.

BTW... I can get some bloom clean or OD with the rig as it is, so it is pretty close to where it needs to be. I just read up on the JJ 12AX7 Gold Pin that's my current PI tube, and it wasn't particularly glowing (sorry for the pun :roll:). I'm going to spend the money to get a good $50-$100 PI tube.

Thanks again!

Kevster
I have amps with NOS tubes but I typically use a $15-16 balanced Sovtek LPS and migrated to using Gil's PI technique. Why do you feel the need to spend up to $100 on a PI tube?

TM
I'm not just looking to spend money, but I am running a marginally reviewed PI tube. I'm also a believer in the adage, "you get what you pay for," and I didn't spend much on it when I put the rig together...

I've also seen lots of recommendations for tubes that are now going for well over $100. THAT isn't happening!!!

BTW, thanks for the Sovtek recommendation. That's what I'm running in V1 and V2.

Kevster
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