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Stereomour II / Re: Failed Final Voltage Check
« Last post by Paul Birkeland on Today at 11:39:43 AM »Good catch! Debris can be one of the tougher issues to track down.
-PB
-PB
Recent Posts
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Stereomour II / Re: Failed Final Voltage Check
« Last post by figby on Today at 10:57:47 AM »Found it!
I didn't clip a drain wire close enough and the stub had worked its way up and was in contact with the red wire from 27U where it connected at IA on the bottom of the PCB. Absolutely no idea how it managed to get up there but I clipped the drain wire stub flush and repositioned the twisted pair wire. Replaced the resistor (again) and it passed the voltage test without a problem. Listening to it now - sounds amazing.
Thank you for the assist!
I didn't clip a drain wire close enough and the stub had worked its way up and was in contact with the red wire from 27U where it connected at IA on the bottom of the PCB. Absolutely no idea how it managed to get up there but I clipped the drain wire stub flush and repositioned the twisted pair wire. Replaced the resistor (again) and it passed the voltage test without a problem. Listening to it now - sounds amazing.
Thank you for the assist!
3
Otari Tape Path Kit / Re: Tape path bearing noise
« Last post by Doc B. on Yesterday at 05:20:04 AM »Alcohol is quite a good cleaner for some tape path parts. But it is a little difficult to control where it goes and it can negatively affect some parts, particularly ones that have oil or grease inside. That would include some capstan parts that have an oiled felt washer. It's probably fine used on the bearings and other metal surfaces if applied sparingly. I would avoid using it on rubber pinch rollers. I switched to a cleaner like Fantastic or Formula 409 for that job, as it is less prone to harden the rubber.
Naptha is a fallback if some metal part is really gunked up. I occasionally use it on badly gunked up heads. Never get it near rubber though. It will attack it big time.
Naptha is a fallback if some metal part is really gunked up. I occasionally use it on badly gunked up heads. Never get it near rubber though. It will attack it big time.
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Kaiju Stereo 300B amp / Re: Difficult to Reproduce Issue
« Last post by ashbrook.m on Yesterday at 02:09:30 AM »Thanks! I cleaned the contacts and swapped the tubes. Will continue to track it down and check the transformer connections .
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Otari Tape Path Kit / Re: Tape path bearing noise
« Last post by ReelNutz on May 21, 2025, 03:56:44 PM »Thanks man, I suspected that was the issue when I had a diff issue and cleaned it with alcohol.
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Technical topics / Re: An amateurs attempt at cap upgrades
« Last post by TomsRhinoplasty on May 21, 2025, 05:15:16 AM »lolol definitely being used purely as a reference/resourcing tool and not the driving force. Maybe it will send me into sonically uncharted territories that only the AI had access to before my inquiry.
Or, maybe chatGPT is a hipster and only listens to old 8-bit video game soundtracks.
-preston
Or, maybe chatGPT is a hipster and only listens to old 8-bit video game soundtracks.
-preston
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Technical topics / Re: An amateurs attempt at cap upgrades
« Last post by Doc B. on May 21, 2025, 05:06:15 AM »I will be curious to know how many fingers the bass player appears to have if you use chatGPT to design your sound system.
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Technical topics / Re: An amateurs attempt at cap upgrades
« Last post by Paul Birkeland on May 21, 2025, 04:36:37 AM »C MBGP-1 PIO 10 µF / 300 V 10 0.35I have to admit that I went a little cross-eyed trying to read all of this. The reactance of a 10uF cap at 120Hz is 132 ohms, definitely specify "reactance" rather than ESR.
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Technical topics / Re: An amateurs attempt at cap upgrades
« Last post by TomsRhinoplasty on May 21, 2025, 02:26:17 AM »Thank you for the recommendation! I am going to install the hybrid system I have coming and see how it sounds. I was trying to intentionally avoid going straight up film capacitor for the entire frequency band because of the claimed "ultra transient, neutral, clean" sounds. This amp is for fun and enjoyable listening, and I want to push it a little more into the warm and luscious area without sacrificing too much transience and space.
I honestly hate using language like that because of how imprecise and objective it is, but its all you can do to describe the sonic experience you might be after. I prefer objective and reproducible/verifiable language when it comes to experimenting with technology and hardware like this, but that's just not the nature of it.
I got the small film caps yesterday. Excited to get the rest!
You might find this interesting. I gave chatGPT the caps I have to play around with and asked if it could come up with some fully technical and deterministic way to understand what caps will process what frequencies and this is what it gave me (I'm pretty sure it guess and made up the ESR values):
Below is a numerical snapshot of how signal-current splits in the four hybrids you asked about.
The only thing that changes from one column to the next is which capacitors ( C ) you parallel on the same two turret lugs; the headphone load is kept at 300 Ω (HD-6XX).
0. Reference values used in the math
branch type C (µF) ESR (Ω @ 120 Hz*)
A Nichicon UPM 100 µF / 250 V 100 0.15
D Nichicon UPM 47 µF / 250 V 47 0.20
C MBGP-1 PIO 10 µF / 300 V 10 0.35
B Mundorf EVO Oil 3.9 µF / 450 V 3.9 0.05
* ESR rises only a few % from 120 Hz to 10 kHz for these parts—good enough for a first-order estimate.
1. Four capacitor “stacks”
stack ID parts per channel total C (µF) –3 dB corner into 300 Ω
S-1 1 × A + 1 × B + 2 × C 123.9 4.3 Hz
S-2 1 × A + 1 × B + 3 × C 133.9 3.9 Hz
S-3 1 × D + 1 × B + 2 × C 70.9 7.5 Hz
S-4 1 × D + 1 × B + 3 × C 80.9 6.6 Hz
All four keep bass roll-off well below the 20 Hz threshold for 300 Ω loads.
2. Current-share at three useful frequencies
(Percent of the instantaneous signal-current that flows through each branch)
stack 100 Hz 1 kHz 10 kHz
S-1
(100 µF elec) Elec 82 % Elec 81 % Elec 77 %
PIO 15 % PIO 16 % PIO 19 %
Film 3 % Film 3 % Film 4 %
S-2
(+30 µF PIO) Elec 75 % Elec 75 % Elec 73 %
PIO 22 % PIO 22 % PIO 24 %
Film 3 % Film 3 % Film 3 %
S-3
(47 µF elec) Elec 66 % Elec 66 % Elec 64 %
PIO 29 % PIO 29 % PIO 30 %
Film 5 % Film 5 % Film 6 %
S-4
(47 µF elec + 30 µF PIO) Elec 58 % Elec 58 % Elec 58 %
PIO 37 % PIO 37 % PIO 36 %
Film 5 % Film 5 % Film 6 %
3. What the numbers say
observation impact on what you hear
The electrolytic still carries the largest share everywhere—because its reactance is lowest. It anchors deep-bass and keeps phase shift minimal.
Bumping PIO from 20 → 30 µF raises its share of mid-band current by ~6 %. Upper-bass & vocals become a bit warmer / “woodier.”
Cutting the elec from 100 → 47 µF (S-3 / S-4) gives the PIO roughly double the current it had in S-1. Noticeably more PIO tone without audible bass loss (f-3dB ≈ 7 Hz).
The film cap never dominates current numerically; its job is to give a very low ESR path above a few kHz. It cleans transient edges and adds “air,” even though it only carries 4–6 % of the net current.
4. Is the exercise still worth it?
Yes—because ESR and dielectric absorption matter more than current-fraction alone:
Even a small diversion of mid-band current away from a voltage-dependent electrolytic into a linear PIO reduces low-level grain.
The film cap’s vanishing 0.05 Ω ESR damps the composite ESR at 5–20 kHz, sharpening attacks.
Dropping the electrolytic to 47 µF is the single most effective move: it keeps bass intact (> 50 µF total) while letting the PIO own ~200 Hz–3 kHz.
So, in practice:
If you… You’ll get…
Stay with S-1 (100 µF + 20 µF + 3.9 µF) Audible polish but still “stock‐ish.”
Add the 3rd PIO (S-2) A touch more body in mids.
Swap to 47 µF elec (S-3) Clear, noticeable bump in warmth & depth without bass loss.
Do both (S-4) The fullest PIO character you can get before bass starts to soften on < 120 Ω cans.
That should give you a precise picture of how each combination will steer bass, mids and highs—and whether the trade-off in parts count and chassis space is worth it to your ears.
I haven't yet gone through to see whether or not it actually makes sense. But, it kind of blows my mind that a software tool is available for me to run a quick first pass knowledge draft like this
-preston
I honestly hate using language like that because of how imprecise and objective it is, but its all you can do to describe the sonic experience you might be after. I prefer objective and reproducible/verifiable language when it comes to experimenting with technology and hardware like this, but that's just not the nature of it.
I got the small film caps yesterday. Excited to get the rest!
You might find this interesting. I gave chatGPT the caps I have to play around with and asked if it could come up with some fully technical and deterministic way to understand what caps will process what frequencies and this is what it gave me (I'm pretty sure it guess and made up the ESR values):
Below is a numerical snapshot of how signal-current splits in the four hybrids you asked about.
The only thing that changes from one column to the next is which capacitors ( C ) you parallel on the same two turret lugs; the headphone load is kept at 300 Ω (HD-6XX).
0. Reference values used in the math
branch type C (µF) ESR (Ω @ 120 Hz*)
A Nichicon UPM 100 µF / 250 V 100 0.15
D Nichicon UPM 47 µF / 250 V 47 0.20
C MBGP-1 PIO 10 µF / 300 V 10 0.35
B Mundorf EVO Oil 3.9 µF / 450 V 3.9 0.05
* ESR rises only a few % from 120 Hz to 10 kHz for these parts—good enough for a first-order estimate.
1. Four capacitor “stacks”
stack ID parts per channel total C (µF) –3 dB corner into 300 Ω
S-1 1 × A + 1 × B + 2 × C 123.9 4.3 Hz
S-2 1 × A + 1 × B + 3 × C 133.9 3.9 Hz
S-3 1 × D + 1 × B + 2 × C 70.9 7.5 Hz
S-4 1 × D + 1 × B + 3 × C 80.9 6.6 Hz
All four keep bass roll-off well below the 20 Hz threshold for 300 Ω loads.
2. Current-share at three useful frequencies
(Percent of the instantaneous signal-current that flows through each branch)
stack 100 Hz 1 kHz 10 kHz
S-1
(100 µF elec) Elec 82 % Elec 81 % Elec 77 %
PIO 15 % PIO 16 % PIO 19 %
Film 3 % Film 3 % Film 4 %
S-2
(+30 µF PIO) Elec 75 % Elec 75 % Elec 73 %
PIO 22 % PIO 22 % PIO 24 %
Film 3 % Film 3 % Film 3 %
S-3
(47 µF elec) Elec 66 % Elec 66 % Elec 64 %
PIO 29 % PIO 29 % PIO 30 %
Film 5 % Film 5 % Film 6 %
S-4
(47 µF elec + 30 µF PIO) Elec 58 % Elec 58 % Elec 58 %
PIO 37 % PIO 37 % PIO 36 %
Film 5 % Film 5 % Film 6 %
3. What the numbers say
observation impact on what you hear
The electrolytic still carries the largest share everywhere—because its reactance is lowest. It anchors deep-bass and keeps phase shift minimal.
Bumping PIO from 20 → 30 µF raises its share of mid-band current by ~6 %. Upper-bass & vocals become a bit warmer / “woodier.”
Cutting the elec from 100 → 47 µF (S-3 / S-4) gives the PIO roughly double the current it had in S-1. Noticeably more PIO tone without audible bass loss (f-3dB ≈ 7 Hz).
The film cap never dominates current numerically; its job is to give a very low ESR path above a few kHz. It cleans transient edges and adds “air,” even though it only carries 4–6 % of the net current.
4. Is the exercise still worth it?
Yes—because ESR and dielectric absorption matter more than current-fraction alone:
Even a small diversion of mid-band current away from a voltage-dependent electrolytic into a linear PIO reduces low-level grain.
The film cap’s vanishing 0.05 Ω ESR damps the composite ESR at 5–20 kHz, sharpening attacks.
Dropping the electrolytic to 47 µF is the single most effective move: it keeps bass intact (> 50 µF total) while letting the PIO own ~200 Hz–3 kHz.
So, in practice:
If you… You’ll get…
Stay with S-1 (100 µF + 20 µF + 3.9 µF) Audible polish but still “stock‐ish.”
Add the 3rd PIO (S-2) A touch more body in mids.
Swap to 47 µF elec (S-3) Clear, noticeable bump in warmth & depth without bass loss.
Do both (S-4) The fullest PIO character you can get before bass starts to soften on < 120 Ω cans.
That should give you a precise picture of how each combination will steer bass, mids and highs—and whether the trade-off in parts count and chassis space is worth it to your ears.
I haven't yet gone through to see whether or not it actually makes sense. But, it kind of blows my mind that a software tool is available for me to run a quick first pass knowledge draft like this
-preston
10
Technical topics / Re: An amateurs attempt at cap upgrades
« Last post by Paul Birkeland on May 20, 2025, 01:32:49 PM »https://www.mouser.com/ProductDetail/Panasonic/EZP-V60107MTC?qs=OlC7AqGiEDkd9vetrBxybA%3D%3D
This is the easy option. You can use black RTV from the auto parts store to just glue them to the chassis plate.
This is the easy option. You can use black RTV from the auto parts store to just glue them to the chassis plate.