As said, for the FET sub, from the junction of v1 cathode resistors that would feed the FET>150K 5w> ground. \m/
cheers Rog, yes I can see now what's what, I was knackered yesterday after getting home very late after Tuesdays gig...and we're 7 weeks in to a tour!!!!!
so to me the most elegant solution will be to put another eyelet on the power board after the 2k2 dropping string resistor and ground the other end with the B+ 3,4,5 grounds. Should have thought about that before I populated the board!!!!!
onwards and sideways......the Hawth theatre Crawley tonight!!
OK, while I'm thinking out loud; anyone got any good ideas with what to replace the FET input with. My first, and simplest though was to have two different value grid stoppers , 22k and a 47k? or 33k?
other option -high/ low? don't see much use in that for me as all my guitars are passive.
martin manning wrote:Oh just build the FET booster! ;^)
LOL...
I've actually got two FET boards laying around from my two previous sets!
just don't see the use myself of a pre amp with an electric guitar, and I'd never plug my acoustic into it in this day and age with all the other better options.
so to me the most elegant solution will be to put another eyelet on the power board after the 2k2 dropping string resistor and ground the other end with the B+ 3,4,5 grounds. Should have thought about that before I populated the board!!!!!
OK, while I'm thinking out loud; anyone got any good ideas with what to replace the FET input with. My first, and simplest though was to have two different value grid stoppers , 22k and a 47k? or 33k?
other option -high/ low? don't see much use in that for me as all my guitars are passive.
any other thoughts? Marcus
You don't have to drill another eyelet for the 150k bleeder resistor. You can hang that bleeder off of the B+5 node on the preamp board. You can use a 3 lug terminal board at the v1 socket and hang a 150k to ground there, a 2 lug terminal on that side of the chassis somewhere, mount a narrow eyelet board at the FET location or as my very, very last resort, heat shrink a 150k and hide it under the preamp board.
I don't see tangible value of having different value grid stoppers,the effect is way up in the tens of KHz range. Besides, it kind of defeats the advantage of mounting the resistor as close as possible to the socket. For aesthetics, just mount a dummy jack to nowhere.
thanks, just done it actually since I posted. It was no problem as it's on the corner of the board and I'd used a staking tool to hammer the eyelets in anyway yesterday so one extra in that position was easy.
thanks for the advice on the grid stopper, I might try it just to see if I can hear any difference, it's only one resistor and a length of shielded cable.
So, progress! all bloody day to get everything in the chassis. Nothing I'd bought fitted properly due to;
1: ordering some bourns pots, which I like due to their build quality , but are a different size to the Alpha's for which the chassis is drilled.
2: the slide switches I'd bought(switchcraft) were about 2 mm too long in their mounting holes.
3: Output valve sockets were slightly bigger than the holes.
I've got some interesting Pot size discrepancies going on with this build!! I presume it won't actually make any difference to the sound!!
I decided not to use the 4-8-16 Ohm switch as it was just too tight a fit in the external speaker socket. I'm going to use jusy the 8 and 16 Ohm taps on the two speaker outs. I never use 4 ohms so for aesthetics and probably safety this seems the best compromise unless someone chimes in and says it's fine to have very small gaps between speaker jack/output taps/send jacks.
so all in all it took me all day to re drill everything that needed doing, used the step drill to open out the valve holes. Drilled all the earth points and relay board standoffs.
All done now I think.
I've used JB weld to hold the weld nuts on the chassis mounting points , do you think it will hold? I'm going to put softwood rails on the inside of the cab to support the chassis so they'll only be stopping git moving back and forth.
Obviously if they came off inside the chassis it wouldn't be good!!!
now; the 'question du jour'
mid or deep?
the original has deep, the update has mid.......how's the sound of the deep?
Marcus
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the original has deep, the update has mid.......how's the sound of the deep?
Too many switches too little time!!
The classic stack uses a 100k mid pot and .047 mid cap vs the Skyliner which uses 250k/,01 setup.. So the net result is the classic stack does not lift the mids as much as the skyliner and is more Fender-esqe in it's function..Because of this I like the mid boost on the Classic (Especially in OD) However the PAB is also a kind of mid boost..So I find the mid switch w/mid boost on to me adds too much bass and flabbs out in OD (Especially with humbuckers!) Your milage may very!
To confuse this further the Jazz switch is also a kind of deep switch (Cuts the mids also)
Honestly for me I never really found the deep switch to be as versatile as the mid switch! (especially in the classic) But then again it might depend on the guitar/situation/type of music..etc etc!!
Tony
Last edited by talbany on Sun Dec 04, 2016 10:56 pm, edited 1 time in total.
" The psychics on my bench is the same as Dumble'"
thanks Tony.I'll build it all as original spec then see how I like it. I think with all the Dumble amps it's best to build them as close as possible first and then live with them a while before changing anything.
I've a day off tomorrow so will crack on. My studio is a complete mess at the moment with this build...I've a new project starting next week so need to get as much done as possible this week before I have to tidy up!!
I hope my transformers arrive soon...however working on the chassis without the transformers is a lovely experience so I'll wire up as much as I can without them
I wouldn't bet my life on JBWeld holding the weld nuts in place, but if they are too wide to rotate then at least you will be able to remove the screws and get the chassis out if it fails.
The classic stack is definitely more Fender-like. The mid scoop is deeper, and it's shifted down 200-300 Hz. Nearly all of that is the 100k slope and 50n mid cap.
martin manning wrote:I wouldn't bet my life on JBWeld holding the weld nuts in place, but if they are too wide to rotate then at least you will be able to remove the screws and get the chassis out if it fails.
I'd hoped to be able to use captive nuts I could bolt in but the chasse lip is too narrow for any I could find, it's just under 10mm. The smallest M 3 T-nuts were about 12mm wide which put the hole over the edge.
I've used jb weld before and it's very strong if applied correctly, I can't think of another way unless I could spot weld the nuts on but don't have the equipment.
Here's hoping...
On a different note, as I'm doing a 50w version would I be better using two 100uf caps instead of the two 220uf I have in there now? I was looking at the 3rd gen 50w amp and that's what it uses. My #102 50w has 220' s but another thread made me think about this.
On a different note, as I'm doing a 50w version would I be better using two 100uf caps instead of the two 220uf I have in there now? I was looking at the 3rd gen 50w amp and that's what it uses. My #102 50w has 220' s but another thread made me think about this.
I would take your own advice on this one!..
I think with all the Dumble amps it's best to build them as close as possible first and then live with them a while before changing anything.
50W =50Uf 100w= 100uf (although Dumble has occasionally used 50uf in 100w)
Tony
Last edited by talbany on Mon Dec 05, 2016 12:18 am, edited 1 time in total.
" The psychics on my bench is the same as Dumble'"
Your milage may very!