johnsonwu
Responses from johnsonwu
| Driver/Input tubes Download a copy of the schematic available at many websites. The 12AU7 is an SRPP totem pole configuration voltage gain stage where the output is the midpoint between the first half triode's plate and the 2nd half triodes cathode.The 12AT7 is 2 tr... | |
| Quad 989 repair - California FIzzing and ticking upon power on may not be the dreaded panel arcing problem.It may be as simple as that 220uF Lytic right @ the input that needs a replacement. Lytics do fail over time. Mine did.Re-doing the panels of course involve expert workm... | |
| Review: JM Labs Diva Utopia Be Speaker The Diva Utopia had home theater "lifestyle" speaker in mind according to the brochures.Bad compromise. Just the cost of the inductors I put in was over $450 so figure the usual 5-7x multiple it would have increased the price of this already expen... | |
| Retubing an ARC VT100 mkll Just waiting for the first report of someone popping the filament winding. | |
| Jolida jd-502p Gentlemen,I strongly urge you to do some reading on 12AX7 tube spec regarding Max heater to Cathode Voltage.The spec says 100V. SRPP based configuration calls for a raised filment to avoid this stress.Jolida does not have raised filament, just an ... | |
| AUDIO RESEARCH-WHERE ARE THEY GOING Leonard has retired. Call and ask for Kalvin. | |
| Linn Sondek is Dead - Looking for Service Greenstreet audio. David Genther | |
| Does this amp have a problem or is it OK to buy? There is a fair price for anything less than perfect, either due to an original design flaw, or a problem with the specimen itself. Some 302s sell for up to 700+ some for the high 500s.At around $600 (going ending price on 'bay) you cant even get ... | |
| Does this amp have a problem or is it OK to buy? If " barely audible" is something acceptable when the input is shorted with nothing, no CD connected, then go for it and fix the CD player, likely a ground loop or a bad RCA cable.If "barely audible" is a buzz reagrdless of volume and it annoys yo... | |
| Does this amp have a problem or is it OK to buy? Of course, cos the hum is not from the input jack or internal wire, its from the filament supply.Most modern power amps or integrated amps with reasonably high gain have DC filaments (read: no hum)Regardless of AC or DC filament, the textbook trea... | |
| Does this amp have a problem or is it OK to buy? Humming to the speakers is because the AC filament supply to the 12AU7 is making it into a buzzy microphone.Spent MONTHS on my previously modded 302B to fix the problem by taking out the center tap for the filament which had become intermittent, a... | |
| Could use your advice re: tube gear The Jolida 302 and 502s have wonderfully overbuilt power trannies (output is a different story but still very competent. Lots of space for mods. And a simple enough circuit topology to allow the modder to be flexible with tube choices and current ... | |
| KT120 transformer failures What's with all the posts about TCtubes all of a sudden everywhere on every thread that has to do with tubes? | |
| ARC SP-6 Warmup time Capacitor next to u555 timer ic is shot. Happened to my sp10ii a few years back. | |
| KT120 transformer failures Run the CL120 half power with 4 kt120 each mono block and you can have your kt120s. |