I have tried parallel TDA1541A, big improvement on sound.
But this mod give more output level compare with using only one TDA1541A.
I am using the Lm4562 opamp output stage, how do I lower the output gain to the same level ?
But this mod give more output level compare with using only one TDA1541A.
I am using the Lm4562 opamp output stage, how do I lower the output gain to the same level ?
fastvideo said:
Use half the value of the feedback resistor (at I/V opamp feedback loop) as it is now, or just place the same value in parallel.
aparatusonitus said:
I measure the parallel TDA's output is double as to single, parallel the feedback resistor did solve my problem.
Thank you.
Only re-clock and power supply mod left to play with.🙂 🙂 🙂
Guys....juz did my 3rd tweak for my RCD855....its the best result i achived currently...then again, still need a few more touch of perfection.😀
What tweaks did you perform ?
I just got a rcd-855 from my dad today and ofcourse I want to mod it 🙂
It came with a rx-855 receiver, but there's no info on that amp here in diy...
The parallel tda makes a huge difference.
I like the sound with lm4562.
It is running with EC's new dem clock circuit for a few days now, still in a test stage. Separate +/-5V and -15V for the parallel tda using 78/79 regulator ics.
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Update:
Cap mod, separate regulator mod, mute transistors mod, dual TDA1541A mod, NOS mod, Opamp mod, Dem clock mod.
I am very happy with the sound. DEM re-clock at 352.8Khz with some minor modification from EC's latest dem clock circuit. Sound like listening to a different unit!!!
http://www.diyaudio.com/forums/digital-line-level/79452-building-ultimate-nos-dac-using-tda1541a-307.html#post1954366
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My 855
This is the 855 I've had for years and have done some mods to. It is still in a state of flux, but since doing the discrete I/V I haven't had as much motivation to do anything else to it. I will eventually do a commercially-fabbed PCB for the I/V stage, etc.
I may also do some PSU changes around the DAC chip, and possibly look at DEM reclocking more.
This is the 855 I've had for years and have done some mods to. It is still in a state of flux, but since doing the discrete I/V I haven't had as much motivation to do anything else to it. I will eventually do a commercially-fabbed PCB for the I/V stage, etc.
- Schottky PSU diodes (11DQ10)
- Tentlabs XO on a PFM Flea board (my own layout), modified to provide /2 direct DAC clocking and get the SAA7220 out of clock distribution since it is incredibly noisy! I wanted to keep the player 4xOS.
- Tread PSU taking ~25Vdc down to 18-20Vdc for the Flea
- home layout of an amb o22 PSU for the discrete I/V stage (I needed a smaller board than the commercial one)
- rbroer's less simple I/V for TDA1541a, using 2SA970/2SC2240 transistors and the addition of a muting relay.
- Replacement of most PSU caps with Panasonic FMs for the most part.
- Simply Physics IsoDrive
I may also do some PSU changes around the DAC chip, and possibly look at DEM reclocking more.
Attachments
I just finished the mods/upgrades on mine,and the strangest thing has happened,, when I power it up Nothing,, but when I power off the mechanism spins,,can anyone tell me what I have done?I guess that I have wired something backasswards,,but I cannot figure it out.
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