pedefede

Hi All My experience: I had a LOT of trouble with noise, and replace a lot of parts. Changing my Shinkohs to Xicons helped a bit, but the trouble/noise came back. This made me think, that Xicons were better because of the 50ppm, but that 50ppm is still way too high. So i re-replaced some of the resistors with only small benifit. Finally the one thing that did the job was replacing the 10K pots in the four battery-sections, with a super-low ppm resistor: 5ppm (!!) in the series ptf56 from vishay, that had the same value as what i adjusted the 10K-pot to (6K in my case). Then i could do all the final tuning with the 2K pot. http://dk.mouser.com/ProductDetail/Vishay-Dale/PTF566K0400BZEK/?qs=V4kc8PiwqSBAoWKdj%2fYdnMPewyQYMP1WCgstHSwEDSg%3d THIS thing made the amp TOTALLY stable, and dead silent. So for 6 month i have enjoy'd the fantastic sound from this beast of an amp Happy new year to you all!! Peter

jep ok, i'll wait till my balanced DAC is finished ....

Just measured my output voltage, and it was slightly out of balance: (which corresponds to R-channel having a very small weight) L+ 100% L- 110% R+105% R- 110% (Switching input channels produces same result, so it wasnt the signal source) What primarily controls the gain? EL34? K216?, ecc88?

I am starting to build an ackodac, and will use twistedpears IVY-iii as an IV (as well as a "new take D1" later on). http://www.twistedpearaudio.com/docs/linestages/ivy3_schematic_1_0.pdf IVY-iii has 22R resistors on the balanced output from opa1632, to "help drive capacitive loads". Does T2 count as a capacitive loads?? (due to C10/11) peter

hmm ... since the mere sound of the 009 bass is nice, you might get away with using some software equalizer. But maybe the PC processing will mess up the sound quality Another route could be choosing an IV-stage for DAC, or a preamp, that has slightly more bass - but this seems even more dangerous - because you arent shure, weather the 2 frequency-characteristics match ... To buy - or not to buy - that is the question ......

This week i have been listening to some 009s (and 007) on my T2, that i might spend $$$ on. As you all know, the transparency of the 009 is insane ... However, i dont feel that they are linear at the bottum/bass ... the volume of the bass is too low. (The mere sound of the bass though, is very nice - articulate, good impact etc). So drums etc. sounds nice, but fade a bit behind in the soundstage. As i am only started with a new DAC-project, - i am playing on a "lousy" emu0404. But doing quick A/B-switch ... the 007 do play bass! - and seems a bit more compressed (not nessecarily bad!) and controlled - and sounds a lot more overall linear. It's like: - if i want classic or Jazz - go 009. If i want rock - go 007. (i will be satisfied with either i think) So: Am i the only one having this experience on T2 Peter (To buy - or not buy - that is the question...)

You are evil Voltron ... as if the T2 wasn't expensive on its own ... (Otherwise i need to 1. get broke 2. send my sister in law to fetch me a "cheap" pair from HongKong, )

Black sheep has been finished (almost): http://dl.dropbox.co...phone%20326.jpg (quick iphone pic in the dark) Noise issue solved - Replaced shinkohs 390K, 820K, 100R in one of the batteries for xicons. There is NO noise now, even at full volumen. Feels a bit wierd actually, to put the beast to full volumen, and to be unsure wether it has been turned on ... (I allmost blew my ears, when i accidently left the volumen at 100%, and put on a 1 KHz sinus signal ... ) You can measure the 50Hz noise from the unregulated heaters on the batteries ... but during to the balanced nature of the beast - it is canceled at output It plays fantastic ... I still have some to-do stuff (balanced volumen attenuater with fixed resistors, optimizing balance by switching tubes, trying with current-stock.tubes, eventually replacing more resistors for Xicons) (During measuring - i discoverd a small volumen-dependent oscillation (200KHz, 30mV pp at 100% volumen) . Too small to cure for now. - but that can wait ... now i really just wanna listen to the sweet, sweet music - and improve my signal sources, to match this thing ....! peter

Lifted all resistors (shinkoh) in the batteries on left channel 2+ mm. HUGE difference - noise is almost gone, and voltage is now stable. So no replacement seems to be needed. There is still some small scratching noises, and very small white noise. I'll poke around with a scope - and probably do INU-fix on pots. Right channel was born dead quiet, without any mods.

Both Channels are working, and playing music. There is still no more sign of oscillation. I do have noise in left channel (very same sympoms as Kerry, Bubliss), and 1 battery there is adjustable, but voltage is drifting a lot - so keeps having to being re-adjusted. - So i will try lift my resistors - and if that doesnt change, ill replace. What resistors are reported as "noise-curing" as of now? - Gilmore: Xicon - Inu: Takman - chinsettawong = 1% Royal resistors (Thai brand)

Does anyone have a working link to Craigs excelsheet from post 1830, about RV1 and RV2 ?

Well, oscillations killed pretty easily. I only had one C12/13 = 2,2pF (per channel), like Gilmore. So i added 1 more for the other side, and the oscillation died. (It MIGHT have been caused by pickup noise etc, from all the test leads for the 8 multimeters (i borrowed from work). These were remove in the second test. ) I will go to sleep with such a happy smile on my face, that my wife will think I had sex elsewhere ....

YESSS!!! first channel has a LIFT OFF!! All leds light up nicely (Replaced the other J79, that was only "slightly" dead, so it took my quite a long time to find the bugged part) anyway - battery adjustable and fine at 740 - and all voltages measures fine. However, i have oscillation problem: There is a 860KHz (i think) oscillation around 14V peak-peak at each output (though in phase - so V-out-difference is only at 1,5 V peak-peak). The V across R42 in battery - minus-side: is adjustable through 2K pot, to 6,55V (like kerry). (A humming can be heard somewhere, while measureing) - plus-side: is not adjustable through 2K pot (?!?), sits steady at 5,3V (No humming). Oscillations sounds somehow like Craigs problem. (I do have 5pF caps across each 100K feedbackresistor ... gotta read/check, weather the resistor it has to be moved) - Its the non-adjustability of the one side R42 that puzzles me ...

Gratz Kerry!! I finally have another day off, so I hope to soon be finished debugging mine.

I used the LEDs from the Mouser-BOM: 859-LTL-4213 In the datasheet: http://datasheet.octopart.com/LTL-4213-Lite-On-datasheet-125834.pdf they are indeed specified at 2,1V at 20mA, but the operating voltage in T2, they work at 0,5mA - where Vf is down to around 1,82V (see page 4 on datasheet)