nickcase
Enlightened Member
I am trying to understand why for me the results of replacing the LM317's powering the analog stages of my CD3.5 with SR's (as described on Martin Clarke's page on Acoustica) were so poor that I have since removed the SR's and gone back to the original LM317's.
With the SR's in place the sound completely lack life and vitality. All the 'noises' seemed to be there however something was not right. After going back to the 317's the sound was back, instruments were instruments again and music returned.
This was not what I was expecting and clearly differ from others experience of this modification. Something must be wrong with my implementation and I'm polling for suggestions.
My setup:
External Dual rail OSCAP with one SR per rail set for 27.3V.
Custom 'mains SNAIC' PSU interconnect.
Link plug removed (of course)
SR's inside the CDP set for 17.2V each.
Measured output of LM317's (now back in-situ) 18.3V
All analog stage op-amps are OPA627's
The rest of the changes are on the digital and mains power side.
Thoughts:
1. Are the SR's in the *CAP and those inside the CDP conflicting? Are there any amendments to the SR's I should make when 'daisy chaining' them like this?
2. Is the 1.1V difference between the SR Vout and LM317 Vout enough to cause this problem?
3. Not checked the data sheet but maybe the OPA627's require a greater Vout than 17.2V?
4. I've gone deaf.
Things I'll try:
1. Putting the CDP back on the link plug (i.e. disconnecting the *CAP) and refitting the internal SR's. Will rule out SR -- SR interaction.
2. Changing R8/R9 on the internal SR's to increase Vout - 19V? more?
3. Changing LM317's for LM1086T's. According to the data sheets I need to add approx 22u - 150u of low ESR capacitance across the output for stability. I like this option as I've parts to hand and it'll be quick to do. Any body tried this?
Help, comments, abuse, all welcome.
Nick
With the SR's in place the sound completely lack life and vitality. All the 'noises' seemed to be there however something was not right. After going back to the 317's the sound was back, instruments were instruments again and music returned.
This was not what I was expecting and clearly differ from others experience of this modification. Something must be wrong with my implementation and I'm polling for suggestions.
My setup:
External Dual rail OSCAP with one SR per rail set for 27.3V.
Custom 'mains SNAIC' PSU interconnect.
Link plug removed (of course)
SR's inside the CDP set for 17.2V each.
Measured output of LM317's (now back in-situ) 18.3V
All analog stage op-amps are OPA627's
The rest of the changes are on the digital and mains power side.
Thoughts:
1. Are the SR's in the *CAP and those inside the CDP conflicting? Are there any amendments to the SR's I should make when 'daisy chaining' them like this?
2. Is the 1.1V difference between the SR Vout and LM317 Vout enough to cause this problem?
3. Not checked the data sheet but maybe the OPA627's require a greater Vout than 17.2V?
4. I've gone deaf.
Things I'll try:
1. Putting the CDP back on the link plug (i.e. disconnecting the *CAP) and refitting the internal SR's. Will rule out SR -- SR interaction.
2. Changing R8/R9 on the internal SR's to increase Vout - 19V? more?
3. Changing LM317's for LM1086T's. According to the data sheets I need to add approx 22u - 150u of low ESR capacitance across the output for stability. I like this option as I've parts to hand and it'll be quick to do. Any body tried this?
Help, comments, abuse, all welcome.
Nick