Parts shopping started. As usual, need lot of helps as a newbie.
PSU
Cheers
PSU
- My home voltage is about 215-225V. Talema 7xx series primary will be 230v. Is it still ok?
- Its stated that the PSU board will be ok for Talema 70054K or even 70064K. When I read catalog, they have different dimensions. Is it still ok for 70064K? I think using bit bigger VA will be better to offset lower primary voltage and also price difference is small.
- Snubbing resistor (R3 R4) should be determined by specific tools and a way which I can't. How much impact with improper values? Noticed that ut should be 39R for 70064K (though saying for Amvgis instead of Talema) and then Bloqhed mentioned to be 91R for 70054K.
- L1 (10mh), is 20mh or even 40mh will be better? They're almost same price
- R1, R2 as 22R. Assumed it was for 115V primary? Hence I need to adjust for 220v?
- If using IEC power inlet with integrated filtering (and fuse), should I remove or adjust L1, R1 and R2?
Cheers
1. You probably won't have an issue, most households don't have exact voltage output from outlet.
2. You can always go larger VA, but not lower. Do note that primary voltage also affects secondary, and there will be some drop. With LDO there shouldn't be an issue if there is a safe margin.
3. Yes it's called quasimodo, and you need osciloscope. If someone published values as you stated, for those transformers, use them, theoly don't deviate too much from transformer batches.
Rest circuit designer can answer
2. You can always go larger VA, but not lower. Do note that primary voltage also affects secondary, and there will be some drop. With LDO there shouldn't be an issue if there is a safe margin.
3. Yes it's called quasimodo, and you need osciloscope. If someone published values as you stated, for those transformers, use them, theoly don't deviate too much from transformer batches.
Rest circuit designer can answer
The regulators need sufficient headroom - at least 3 volts input-to-output - under maximum load to function properly. Clipping into 32 ohm, Omicron will draw about 300mA from each rail. With that load current and +/-17V rails, you'd need at least 20V at the input of each of the two regulators - that is, at the output of each of the two rectifiers. If you have less, you can reduce R1 and R2. If you have more, you can increase the two resistors, as this improves their filtering action.
Talema 7005xK and Talema 7006xK have different height but the same footprint. Either would fit the PCB, but the latter is taller.
For the snubbers, @Brijac is correct - Quasimodo and an oscilloscope (even a simple one) is the best way to find out. Alternatively, you can use values that someone found out for a similar trafo.
L1 value is not super critical. Use what's available.
A filtered power inlet does not replace the onboard LRC filter. I suppose a filtered inlet won't hurt, but it wouldn't add much, either. Such inlets typically add a meaningful insertion loss starting from high hundreds of kHz:
while the onboard filter suppresses noise starting from high 10s of kHz, where the regulator's ripple rejection starts falling with frequency:
Post #35 has some measurements of the actual hardware.
Talema 7005xK and Talema 7006xK have different height but the same footprint. Either would fit the PCB, but the latter is taller.
For the snubbers, @Brijac is correct - Quasimodo and an oscilloscope (even a simple one) is the best way to find out. Alternatively, you can use values that someone found out for a similar trafo.
L1 value is not super critical. Use what's available.
A filtered power inlet does not replace the onboard LRC filter. I suppose a filtered inlet won't hurt, but it wouldn't add much, either. Such inlets typically add a meaningful insertion loss starting from high hundreds of kHz:
while the onboard filter suppresses noise starting from high 10s of kHz, where the regulator's ripple rejection starts falling with frequency:
Post #35 has some measurements of the actual hardware.
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Re. the snubber resistance, when the PSU is wired you can connect a trimmer instead of the resistor in series with the snubber capacitor and use oscilloscope to adjust the waveform at the rectifier. Then measure the trimmer rsistance and replace the trimmer with a fixed resistor.
I've noticed that the snubber resistance thus obtained tends to be somewhat higher than the one determined with Quasimodo.
I've noticed that the snubber resistance thus obtained tends to be somewhat higher than the one determined with Quasimodo.
Sometime ago Alex was suggesting as above. Just realize about the voltage - which is very low. Is that because of ripple current?
Is Panasonic EEU-FC0J101B with Ripple Current @ Low Frequency 113.8 mA @ 120 Hz and Ripple Current @ High Frequency 175 mA @ 100 kHz sufficient?
Thanks
Tube gear, such as the Bottlehead Moreplay, tends to have a relatively high output impedance; Moreplay has up to 3.2kOhm, according to Bottlehead. They don't publish schematics, but from what I understand, each channel has a triode connected 6П6С (~6V6GT, plate resistance 2.4kOhm) with bypassed cathoide bias resistor and a 5kOhm anode load, followed by a 10k pot and the output. My calculations give 2.9kOhm, rather than 3.2, in the worst case, but I don't know all the details.
Omicron, on the other hand, has a lowish input impedance of 6 kOhm and, if you use crossfeed, the input impedance gets a tad lower above 1kHz. While this has not been a problem with solid state sources, with a tubed source like Moreplay it might be. Specifically, you may obeserve (1) a lower output level when Omicron is connected; (2) "bass boost" when using crossfeed; and (3) higher distortion if the 6V6s get overloaded ny Omicron's input impedance (the datasheet says 3.5kOhm load, which is about 5kOhm || 10kOhm, that is, the load impedance is expected to be high). All these effects would be dependent on the position of the output pot (the one closest to the power switch, if my understnding is correct).
So try it by all means, but don't be surprised is this particular match is not made in heaven.
Omicron, on the other hand, has a lowish input impedance of 6 kOhm and, if you use crossfeed, the input impedance gets a tad lower above 1kHz. While this has not been a problem with solid state sources, with a tubed source like Moreplay it might be. Specifically, you may obeserve (1) a lower output level when Omicron is connected; (2) "bass boost" when using crossfeed; and (3) higher distortion if the 6V6s get overloaded ny Omicron's input impedance (the datasheet says 3.5kOhm load, which is about 5kOhm || 10kOhm, that is, the load impedance is expected to be high). All these effects would be dependent on the position of the output pot (the one closest to the power switch, if my understnding is correct).
So try it by all means, but don't be surprised is this particular match is not made in heaven.
You may need a buffer in the middle (high likelyhood). Highest i would go is 600R output impedance from your source. But adding a buffer in the middle has it's fair share of influence on sound. Easiest way is to buffer trough an opamp. That way output impedance would be much much lower.