BIG, LOUD, CLEAN

[musicmaddness2011]

hey all!

ive got a studio recording in about a month and really need that pure clean sound.

now ive tried like hell to get some sss, or two rock custom clean/two john mayer sig schematics - but they just dont seem to be coming around.

So since im running out of time, from what i understand, do you reckon this would get me close to that great dumble clean?

a 100w blackface twin reverb with

- A low plate skyline clean section:
1 uF bass cap
.01uF Mid cap
330pf treble cap
mid switch
250KA treble pot
500KA bass pot with .001uF cap
250KA middle pot
- into AB763 reverb,
- ditch the trem and use that socket for the 7025 PI and, use the PI socket for an 7025 Driver ampeg style driver section.

i think thats what brandon said at some point many years ago - but i've never heard any clips of one thats been build.

so any suggestions/ thoughts?

peace

[David Root]

As someone else mentioned in another thread, maybe about 30% of an SSS.

Given that you only have one month, in that situation I would be inclined to tweak an early '70s SF Twin and upgrade to NOS tubes and a pair of old original cone P12Ns.

[musicmaddness2011]

Hey david,

SF? i was always lead to believe that the BF were much closer. Though i have heard a pretty nice SF Pro reverb...

hmmm...

[Cliff Schecht]

David, you've been pimping those P12N's pretty hard lately and my curiosity has been peaked. Do you have any sound clips? I'd love to find one for a 1x12" cab but they are bloody expensive.. I'd also like to find another alnico SRO but those are even more bloody expensive!

[thejaf]

I experienced a great clean sound in my recent modded 50-watt AB763 project.

For mine, stick to the stock AB763 except the following:
1. Tone circuit caps 250pf, .1uf, .015uf
2. Reduce value of cathode bypass cap on the tone recovery triode (I used .68uf)
3. Use a 12AU7 as reverb driver tube
4. Use a 12AT7 as PI tube

It was a huge, 3D spanking clean sound. Unfortunately, I wanted some more softer breakup and modded the circuit some more to suit my end goal.

[David Root]

musicmad, to my ears a '71 SF Twin cranked is cleaner than a late BF Twin ditto, maybe just me, but the AB763 is of course early BF and the model HAD cut his teeth on.

Cliff, is it that obvious?! The '61 P12N I got does sound good. It is definitely an original cone, but it is not a Fender unit as far as I can tell. It has no Jensen or Fender label, no label at all. No bell either, black painted. Has all the usual Jensen marked numbers including P12N and EIA #220147. I think it is an OEM unit out of an old organ most likely.

It cost me $170 plus $30 in freight, which is a lot less than you'd pay for one with a bell and a Fender label.

I will see if I can get a clip or two of it. It is in my EH-150. I'm hoping to get a friend over this Sunday to make some video recordings as I know nothing about doing that and have no equipment. He says the sound quality is much better than MP3.

[musicmaddness2011]

ah ok kewl.

so a SF will be much cleaner... hmm has anyone played one? what level do they break? is it a smooth thick break?

i plan on using my ts808 for some light crunch (more of a boost really) and my current amp sounds shocking when i kick it (its really a piece of sh*t haha)

[David Root]

If you put the right tubes in it eg 7581A it probably would not break up at all until the speakers started to give it up. I have heard SF Twin with a pedal steel pickup, she no break-a up. A pair of 200W each Fane Studio 12L would take care of that.

[vibratoking]

I have a 73 SF Twin with JBL D130s. It has Sylvania 6L6s from the early 80s in it. It is loud and very clean. It will break up, but only at 7 or 8 and above on the volume knob. The break up comes on relatively slowly and is smooth. It does not take OD pedals well. It plays soft, but sounds 'hard' if that makes any sense. That is probably the D130s. It is not one of my favorite amps, but I got it for free in the early 80s.

[Cliff Schecht]

I hate JBL's in guitar amps. They are fantastic speakers quality-wise and sound great in hi-fi situations but they tend to be very bright and brittle for guitar amp applications, especially in Twin's where you seem to find them the most. Those metal dust caps were added to extend high frequency response and it's painfully obvious that this technique works, too well IMO.

With that said I've never heard a Dumble loaded with JBL's up close but since they tend to be more smooth in the high end anyways I could see them working well in this application.. What do you Dumble guys think of JBL's?

[David Root]

I don't know about D130s but I have a pair of E130s, which are 15" speakers with massive ceramic magnets. Each speaker weighs 22 lbs. They have the aluminum dustcap but they don't beam like most JBLs do. They also don't blow their voice coils like D120s do. 4" VC, can't beat it!

I use the E130s to check out my amps because they are ruler flat like a Telefunken 12AX7. They are MI speakers designed for guitar applications but IMHO they would make OK hi-fi speakers too. Not as interesting as Altec 417s, but then those are Alnico magnets.

[Tone Lover]

Once you have it figured out then try a 12ay7 in the v1 tends to clean things up and has a good sound to it . Ive had amps that didnt take pedals well and the 12ay7 helped in that situation too.
Bill

[jelle]

I have played several Dumble amps built in the 70's that had a JBL speaker. Killer sound. Not harsh at all. Clear, open and full.


Please keep in mind that there are huge differences between the different JBL variants. The gray and orange ones are the D-series which break up fairly easily. To me, they sound great until they break up.

You might like EVM-12L or an Altec 417 as well.

Have fun!

Jelle