Search found 1630 matches
- Wed Aug 31, 2011 9:31 pm
- Forum: Dumble Discussion
- Topic: Hum troubleshooting Dumbelator clone
- Replies: 15
- Views: 1922
Re: Hum troubleshooting Dumbelator clone
i think that ground loop occurs from grounding heaters supply 7806, and High voltage DC, which coming from the same AC source (if i understand correctly). one power transformer will resolve problem if so..
- Wed Aug 31, 2011 3:03 pm
- Forum: Dumble Discussion
- Topic: GE 6L6GC for ODS build
- Replies: 10
- Views: 1466
Re: GE 6L6GC for ODS build
also to be noted that GM from old tubes don't decrease linear with use, many tubes hold GM at maximum values until the end of life...i measured (visible, very used) EL34, which were used maybe 30 years in guitar amp, GM was on max.. new ones (modern production ) dont have this behaviour (JJ EL34 aft...
- Wed Aug 31, 2011 1:59 pm
- Forum: Dumble Discussion
- Topic: #183 w/Switchable HRM, Almost Finished
- Replies: 28
- Views: 4076
Re: #183 w/Switchable HRM, Almost Finished
I have three NOS GE 12AX7WA and a quad of NOS Mullard Xf4 just bursting to sing their little hearts out in it and I don't want to disappoint them! :idea: xf4 tubes are so god, that you can put them in cheap and anemic amp to make alive quickly. when you put them in excellent amp, they have 3D effec...
- Wed Aug 31, 2011 1:57 pm
- Forum: Dumble Discussion
- Topic: #183 w/Switchable HRM, Almost Finished
- Replies: 28
- Views: 4076
Re: #183 w/Switchable HRM, Almost Finished
Thank you bepone, that is very interesting! I'll definitely compare 12AX7 and 12AT7 in the loop and post what I find here. Once I get the footswitch done! Is that a function of plate resistance limiting bandwidth? yes please, let us know diferences :wink: i dont know for sure, but ECC83-12AX7 has b...
- Wed Aug 31, 2011 5:09 am
- Forum: Dumble Discussion
- Topic: GE 6L6GC for ODS build
- Replies: 10
- Views: 1466
Re: GE 6L6GC for ODS build
fantastic and rich tubes/ experience from soldano hot rod 50
- Mon Aug 29, 2011 9:44 pm
- Forum: Dumble Discussion
- Topic: #183 w/Switchable HRM, Almost Finished
- Replies: 28
- Views: 4076
Re: #183 w/Switchable HRM, Almost Finished
no, it doesn't matter, while resistors value are the same, i put 470R when dont have 100R nearStructo wrote:Gottcha
Can anybody tell me the difference in using different value resistor for the artificial center tap for the heater winding??
- Mon Aug 29, 2011 9:41 pm
- Forum: Dumble Discussion
- Topic: #183 w/Switchable HRM, Almost Finished
- Replies: 28
- Views: 4076
Re: #183 w/Switchable HRM, Almost Finished
hello david, i build many fx loops in the past, mainly for soldano type of amps (all DIY) with 12AX7, 12AT7, 12AU7, 5693, mosfets, subminiature tubes, and for every tube i picked working point from the graph.. i have no experience with "dumble type " fx loops.. from my experience bigger current loop...
- Mon Aug 29, 2011 3:15 pm
- Forum: Dumble Discussion
- Topic: #183 w/Switchable HRM, Almost Finished
- Replies: 28
- Views: 4076
Re: #183 w/Switchable HRM, Almost Finished
bepone, not sure I follow you on "smoothing effects" with the buffered loop. Are you referring to possible capacitative high end losses from interaction with adjacent components? If so, I'll soon find out, but I have used the very same loop twice before in a 2nd gen build and a Bluesmaster w/HRM wi...
- Mon Aug 29, 2011 10:02 am
- Forum: Dumble Discussion
- Topic: #183 w/Switchable HRM, Almost Finished
- Replies: 28
- Views: 4076
Re: #183 w/Switchable HRM, Almost Finished
very nice.. one question, how FX loop interacts with other circuits inside (do you have "smoothing" effects also when fx loop is built inside?)
- Mon Aug 29, 2011 9:57 am
- Forum: Dumble Discussion
- Topic: Modding a non-HRM 124 to HRM... any info appreciated
- Replies: 22
- Views: 2700
Re: Modding a non-HRM 124 to HRM... any info appreciated
simple, when anode resistor goes up (cathode res. follow also), more "glassy" tone you can expect in (lead) overdrive. because ECC83 in OD section, is overdriven hardly and more higher harmonic develops in tone spectrum.. i had in one experimental version of #183 amp 68k resistors in V2 anodes, 5751...
- Sun Aug 28, 2011 2:17 pm
- Forum: Dumble Discussion
- Topic: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
- Replies: 29
- Views: 2673
Re: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
checked schematic and there is no grid resistor EL84 to the ground in design?? [IMG:160:112]http://i284.photobucket.com/albums/ll34/bepone/th_86SpecialVoltages_cr.png[/img] i don't think that this can damage EL84 tube soo much, but there was moments in action, like switching channels maybe or puttin...
- Sun Aug 28, 2011 2:09 pm
- Forum: Dumble Discussion
- Topic: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
- Replies: 29
- Views: 2673
Re: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
What you need to do now is some forensic examination of the circuit to find out what caused such massive overload on the PT. The diode failing open circuit wouldn't alone do it. Check the ripple filter caps. Check also loop jacks for intermittent opens. This could have caused EL84 grid to lose dc p...
- Sun Aug 28, 2011 11:40 am
- Forum: Dumble Discussion
- Topic: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
- Replies: 29
- Views: 2673
Re: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
also, schematic will be helpful.. which amp, which pt, etc etc
how i follow this board, this is some 5 Watter with EF86?
how i follow this board, this is some 5 Watter with EF86?
- Sun Aug 28, 2011 11:34 am
- Forum: Dumble Discussion
- Topic: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
- Replies: 29
- Views: 2673
Re: Burning varnish smell!!!!! Oh No :-( PT suddenly got hot
Any further advice or checks would be really appreciated! Damn shame as I was going to take the amp to a jam tomorrow night, oh well... :oops: hello rogb, step by step, you will find and fix the fault. 1) disconnect PT from the circuit, (all leads, heaters too) and change the fuse. power on and mea...
- Sat Aug 20, 2011 3:29 am
- Forum: Dumble Discussion
- Topic: New build Complete: 45W, four 6V6, non-HRM
- Replies: 85
- Views: 12071
Re: New build Complete: 45W, four 6V6, non-HRM
when you simple disconnect two tubes in PP amp(or put 10K in cathode), primary impedance will be the same, BUT YOU MUST REARRANGE OUTPUT SELECTOR FOR HALF POWER option. this means if 4 tubes works with 4K impedance ratio and you disconnect two of them, remaining two of them will be connected also wi...