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hi, i have on hand opa2604/opa2134/ad826/lt1364/lm6172 chips and would like some opinions, from those who have had good success using any of these chips for upgrading the jrc2114 chips that come stock. i also, have some ad8620 mounted on BrownDog adapters but, i'm not sure what voltages i will be dealing with yet, as i'm waiting for unit to arrive today and i know the 8620s are only good up to +/-13v. also, anyone know of a link listing which resistors to remove, and which 2 to bypass in order to bypass the HDAMS? Thanks for any help!
Follow Ups:
hi folks, and thanks for all the great info! right now i'm running the AD826 chips for awhile. i'll try something else later once these burn in good.i bypassed the output caps, and removed the muting transistors. at present, i've only got 2mv. dc offset per channel so i guess that's pretty good. Thanks again, alley-kat
I've tried many op-amps in my CD-67SE.OPA2604, OPA2134, OP275 - rubbish
AD8610x2 on browndogs - good bass, punchy sound, HF a bit rough.
AD826 - very clear, very extended HF, solid bass, a bit too polite, lacks warmth.
AD8065x2 on browndogs with 100nF stacked film from +ve to -ve - very detailed HF yet still smooth, good staging, deep bass tight and extended, mid-bass AWOL vocals lack warmth ultimately. Not bad though and very refined.
AD825x2 on browndogs with 100nF - reticent mids of this chip balance the forward mids of the player, excellent mid-bass punch, brings warmth to vocals, punchy and detailed sound and a nice balance in this player. Very good.
LM6172 with 1uF stacked film across top of chip - bass very tight and detailed, HF clean and extended, mids gorgeous. Whole sound is very tight and this chip never gets confused. Very musical.
OPA627x2 on browndogs - very wide soundstage, big bass, HF edgy, very 'hi-fi'. Too slow I suspect for the raw PWM coming from this DAC.
If you fancy trying SMD devices on Brown Dogs, it's very easy. LM6171+OPA627 is good combination also. LM6171 on top (differential signal from SM5872 DAC) then OPA627 in second filter.
Still trying to decide between AD825 and LM6172 as the AD825 sounds more balance in this player but the LM6172 is better overall.
I have some LT1361 and LT1364 samples on order.
Trying the original NJM2114 back in the circuit gives an LF emphasis, so expect the unit to sound a bit thinner with most of these op-amps.
If the player sounds too bright to you change C605 and C606 from 1000pF to 470pF. This will change the filter slope from having a slight peak at HF and non-linear group delay to constant group delay Bessel slope with a slight roll-off at HF. -0.2dB at 10kHz, -0.5db at 14kHz, -1db at 20kHz.
Just to add - I tried LM4562 and didn't like it. Sounded quite mechanical and robbed the music of all emotion. HF sounded sterile.
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