I've been bypassing the inferior sounding pre-amp section of this integrated by utilizing the pre out jacks as a power amp input. The DAC I have connected has it's volume controlled line out capacitively coupled, so I removed the bipolar cap C55 from the pre and jumpered across C3 at the power amp input. The sound quality improved in all areas aside from a quite noticeable low frequency attenuation from about 80hz down.
Space limitations prevent polypropylene caps from being installed, and I've read that PET or MUSE bipolar caps would offer little sonic improvement over the stock electrolytics. Any insight as to what might be causing this? There is no DC potential on the input.
Space limitations prevent polypropylene caps from being installed, and I've read that PET or MUSE bipolar caps would offer little sonic improvement over the stock electrolytics. Any insight as to what might be causing this? There is no DC potential on the input.
If the answer is yes then the series combination of C55 , R59 and the low output impedance of IC2 would have been shunting the high frequencies . By removing C55 you stopped that as a result the high frequencies have been restored.
From what I am reading, is the input design around TR1 of this particular amplifier not friendly to direct coupling? Do the components preceding TR1 form a subtle filter network? This amp did seem to have a slight bass emphasis prior to the changes I made.
What DAC are you using and what is its output impedance , a schematic would help . Did you miss #6
Why do you think the coupling capacitors are there ? The designer would not have added them "for the hell of it".
C3 will ABSOLUTELY be neccesary to avoid upsetting the DC biasing of TR1. If you want to use a good capacitor, Wima MKS2 should fit.
C3 will ABSOLUTELY be neccesary to avoid upsetting the DC biasing of TR1. If you want to use a good capacitor, Wima MKS2 should fit.
I did read post 6, and the output impedance from IC2. The DAC is an ifi iDSD black label. It's RCA out impedance is on the high side at 200 ohms.
I have ordered the following capacitors to hopefully improve over what came stock (the Wima is one of them).
Attachments
The mks you probably want as decoupling (ie to ground) rather than coupling. No harm trying them but typically polypropolyne (PP) are favoured for the audio path instead of polystyrene caps (PS).
I’ve used MKP4 10uF to replace MF’s 10uF jamicon electrolytics but the size difference is massive. Nichicon Muse ES is a good call although i like bypassing them with the very large 0.22uF FKP1. Note both fkp and mkp won’t fit the existing electrolytic spacing.
I’ve used MKP4 10uF to replace MF’s 10uF jamicon electrolytics but the size difference is massive. Nichicon Muse ES is a good call although i like bypassing them with the very large 0.22uF FKP1. Note both fkp and mkp won’t fit the existing electrolytic spacing.
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Since size is an issue, would you choose the Nichicon Muse or that Illinois Capacitor over the Wima mks?
I would say try them and listen to the amp with each of the types of caps as a self education. I would also say put the caps on a bench power supply for an hour or two to let them form (self heal).
I have to admit I’ve not listened to mks in an audio coupling role but the general dogma is not to use them in the audio signal path.
I do understand the importance of maintaining C3 to properly bias TR1 however, epilytic indicated that IC2 with C55 and R59 might affect the frequency response. I would like to leave C55 out of the circuit to increase the SNR. Anybody see an issue by doing this?
MF (this is the same with the A220) ground the preout-power signal path to mute the circuit. So removing C55 means there is a DC path to ground when muted which in turn will cause the preamp of output op amp IC2 to burn lots of current attempting to correct as the opamp feedback will be the natural bypass and this the op amp will see a difference between it’s inputs.
So if the op amp is happy and within spec todo that (check all along the audio path if it’s happy with a long term short) then you could but a DC shorted preout for long periods may cause components to heat up, go out of spec (resistors) or simply fail.
So if the op amp is happy and within spec todo that (check all along the audio path if it’s happy with a long term short) then you could but a DC shorted preout for long periods may cause components to heat up, go out of spec (resistors) or simply fail.
If it’s a buffer .. then it’s power supply may have current limiting. However this is MF we’re talking about.. so i doubt that!
Those Wima MKS are better than the average electrolytic cap and you don't need to replace them in the future. They also fit exactly so no added antennas. Recommended as coupling caps. I do this since they came out and never found disappointment in doing so. They have even been improved compared to the old type somewhat. The 16V types were not excellent when driven with high AC voltages, the 50V types are as good as you can wish for. Try to find an electrolytic cap that that comes close with regards to specifications.
So regardless of opinions of those that haven't tried it 🙂 (makes you wonder) and what can be read on the web 😀 I can tell it works out fine and it is one of my more or less standard mods in various (pre)amplifiers. No need for flying and/or extended lead wires ands such "just doing something" practices either.
BTW the cause of the preamp not to perform as it should is the choice of opamps. MC33079 is mediocre at best. You could have tried out OPA4134....
Please make sure to always keep 1 coupling cap per channel in the signal path of source/pre to power amplifier as a DC fuse in case things do not go as planned.
So regardless of opinions of those that haven't tried it 🙂 (makes you wonder) and what can be read on the web 😀 I can tell it works out fine and it is one of my more or less standard mods in various (pre)amplifiers. No need for flying and/or extended lead wires ands such "just doing something" practices either.
BTW the cause of the preamp not to perform as it should is the choice of opamps. MC33079 is mediocre at best. You could have tried out OPA4134....
Please make sure to always keep 1 coupling cap per channel in the signal path of source/pre to power amplifier as a DC fuse in case things do not go as planned.
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