Caiman passive output mod revealed

[vid]

OK - thank´s
now I will start !!!!!!!

greets
vid

[LittleTone]

Hi Guys - Just a bit of final advice please.

Have been running a 7520 with a 4526 and ML5/6 removed into a pre-amp with a 33k input impedence.
Today I carried out Stans suggested initial passive mod
http://theartofsound.net/forum/showp...&postcount=207

Well that was definately a step closer to audio nirvana; but I guess I now need to fit the capacitors.
I've read all 101 posts on this thread and have come to the conclusion that I should be considering a cap' with a value of 2.2uf. In fact Martin has been so impressed with the 2.2uf 200v Auricap that I'm thinking I'll try these.
I just looking for confirmation from the experts out there that even with a standard 7520 this is the way to go
Great site guys - keep up the good work

Regards
Tony

[isj1202]

Tony I would go a little bigger than 2.2uf say 3uf.

I use 3.9uf Claritycap ESA into 24k for a Linn Kairn. I prefered these to the 4uf Auricaps I tried, 250V version of Clatiycap also allow the case to close.

[MartinT]

The Claritycaps are good but I preferred the Auricaps. The value is not too important as long as your preamp has a decent input impedance of, say, 50k ohm or greater.

[LittleTone]

Hi Guys - Just a bit of final advice please.

Have been running a 7520 with a 4526 and ML5/6 removed into a pre-amp with a 33k input impedence.
Today I carried out Stans suggested initial passive mod
http://theartofsound.net/forum/showp...&postcount=207

Well that was definately a step closer to audio nirvana; but I guess I now need to fit the capacitors.
I've read all 101 posts on this thread and have come to the conclusion that I should be considering a cap' with a value of 2.2uf. In fact Martin has been so impressed with the 2.2uf 200v Auricap that I'm thinking I'll try these.
I just looking for confirmation from the experts out there that even with a standard 7520 this is the way to go
Great site guys - keep up the good work

Regards
Tony

Thanks for you input guys (no pun intended)

Pre-amp has two switchable settings. i.e.input impedence is 33k on 150mV setting (currently using )
OR an input impedence of 50k on 775mV

Also have a switchable subsonic filter engaged 12db/octave Butterworth, -3db at 17Hz

Please advise if ok to go ahead...............

Tony

[MartinT]

You definitely want the 50k 775mV otherwise the input circuit will be saturated into distortion.

[LittleTone]

Hi Martin,
Thank you for your assistance; I'm getting there

Yes, OK I'll switch it over to the 50k impedence setting. I had wondered about this; considering the output from the DAC was probably quite high.Needs a bit more stick on the volume control control though.
The Cap' calculator would suggest a value of around 1.6 uf now. Do you think that would be OK.
Curious - As I have no caps' in place at the moment does that mean my optimal
low frequency response is infinity. The sound is better; vocals have really come alive; more detail and the difference between good and bad recordings seems more noticeble. but does sound less controlled, especially at the bottom end. Hence the caps I guess.
TIA
Tony

[MartinT]

As I have no caps' in place at the moment

Hi Tony, what do you mean by this? Are you still using the op-amp board output? If so, then the lo frequency cut-off will not be DC but it will be very low.

With coupling caps, as you have calculated 1.6uF upwards will be fine, making 2.2uF the obvious choice unless you have a size restriction with certain brands of cap.

P.S. there is no need for the subsonic filter unless your speakers have very limited power handling.

[Reid Malenfant]

I'd get some capacitors in the respective positions as soon as possible if i was you If i'm right the output of the DAC is sitting at about 2.5V for zero volts output as it's only powered by a single 5V rail. This means you are putting 2.5V DC down the audio cables to your amplifier & it'll probably be dropping this accross the input resistor which will result in an increase in Johnson noise.

I think you are lucky that it's not a DC coupled amplifier & must have capacitors on the input or you'd experience some serious problems

[MartinT]

Eek, I was hoping that Tony is not doing that!