4p1l line stage
I happily have my line stage finished today and it is singing for me at the moment. Luckily I don't come across any problems with noises and or microphonic, dead quiet. It sounds very natural with detail, warm and lush sound, sounds better to my 26 for a big margin when start. I have to let it break in for 100 hours before detail comment.
First of all I have to thanks Andy for his advices, Rod's guildence in converting the filament board and of course have to thank Ale for his design.
I happily have my line stage finished today and it is singing for me at the moment. Luckily I don't come across any problems with noises and or microphonic, dead quiet. It sounds very natural with detail, warm and lush sound, sounds better to my 26 for a big margin when start. I have to let it break in for 100 hours before detail comment.
First of all I have to thanks Andy for his advices, Rod's guildence in converting the filament board and of course have to thank Ale for his design.
Thanks Andy,
I'm planing the PSE amp at the moment. Could it be possible to put everything together instead of separate psu chassis. I run out of space.
Albert
I use separate chassis for everything - 6 in total! Just means I can change stuff about and mix and match. I experiment a lot.
A few days ago I did some inevitable browsing and came across Intact Audios filament modules intended for Rod Colemans filament boards. intact audio
Could someone comment on the effectiveness of this simple approach for use in a DHT preamp? Is this enough filtering for the filament boards? I feel it kind of defeats the purpose if one makes an extremely quiet DC supply and THEN uses the Colemans.
I like this common mode choke approach. It somehow feels right. But is it just for output stages?
Could someone comment on the effectiveness of this simple approach for use in a DHT preamp? Is this enough filtering for the filament boards? I feel it kind of defeats the purpose if one makes an extremely quiet DC supply and THEN uses the Colemans.
I like this common mode choke approach. It somehow feels right. But is it just for output stages?
For all my Coleman regs I use choke input, just a Hammond choke of the right current capacity. This is particularly important for filament bias which needs to be uber clean. So no - I don't think a choke is "too much" and I think you need both the choke and the reg for best results. I believe Thomas Mayer uses just the chokes so that's his preference if that's still his current setup.
I've recently changed my preamp from filament bias to using SIC diode bias and this is probably less critical than filament bias, but since I like overkill and a good Dunker Factor I'll be leaving the chokes in, certainly for my daily listen setup. I haven't looked at SIC diode bias for my PSE 4P1L stage. It's possible but the diodes give me only 0.9v of bias so less practical for an output stage. For my 26 preamp I'm using 10 diodes for 9v plus a 120R resistor to give me a touch of feedback. Sounds very detailed indeed, and this is now my daily listen with 7mA current through the 26 and an amorphous plate choke. I haven't used 4P1L in a line stage for a while - I was using 01A or 2P29L until the 26 just "clicked" and came right with SIC diode bias like it had never done totally in other setups.
I've recently changed my preamp from filament bias to using SIC diode bias and this is probably less critical than filament bias, but since I like overkill and a good Dunker Factor I'll be leaving the chokes in, certainly for my daily listen setup. I haven't looked at SIC diode bias for my PSE 4P1L stage. It's possible but the diodes give me only 0.9v of bias so less practical for an output stage. For my 26 preamp I'm using 10 diodes for 9v plus a 120R resistor to give me a touch of feedback. Sounds very detailed indeed, and this is now my daily listen with 7mA current through the 26 and an amorphous plate choke. I haven't used 4P1L in a line stage for a while - I was using 01A or 2P29L until the 26 just "clicked" and came right with SIC diode bias like it had never done totally in other setups.
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The Intact modules are a transformer with rectifier & caps directly attached and some filtering. They provide a raw unregulated DC suitable for the Filament regulators.
If the form-factor suits your build, they should work in preamps or output stages.
If you want ultra-low noise, the first step is to keep the transformer and raw DC (rectifiers & big caps) located well away from the signal chassis, to avoid direct-coupling of rectifier recharge & recovery pulses.
Purpose-designed current-drive regulators like mine do more than reduce noise - they isolate the filament from the rest of the outside World. In contrast, using a voltage regulator destroys the part of the music-signal that naturally appears across the filament (because feedback nulls it out). The effect on the sound is easy to discern in a listening test.
If the form-factor suits your build, they should work in preamps or output stages.
If you want ultra-low noise, the first step is to keep the transformer and raw DC (rectifiers & big caps) located well away from the signal chassis, to avoid direct-coupling of rectifier recharge & recovery pulses.
Purpose-designed current-drive regulators like mine do more than reduce noise - they isolate the filament from the rest of the outside World. In contrast, using a voltage regulator destroys the part of the music-signal that naturally appears across the filament (because feedback nulls it out). The effect on the sound is easy to discern in a listening test.
Why do you need expensive solutions? What's wrong with a Hammond choke for a choke input supply? In terms of henries, just start with the current you need (plus a bit extra) and choose whatever choke in the Hammond range gives you the maximum henries. Follow that with a good 10,000uF cap and you have an excellent supply for your Coleman regs. And like Rod says, make an outboard supply situated away from the circuit. A 4 pin XLR makes a good connector for a couple of tubes, R and L channel.
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Psud 2 for calculations. These for filamentvoltages ( Rod provided this link before)
JMS Transformers - Transformers, Fittings & Enclosures
I am sure other’s have choke suggestions...
JMS Transformers - Transformers, Fittings & Enclosures
I am sure other’s have choke suggestions...
First of all Andy you are misunderstanding me (or my English is't as good as I'd like to think it is). I like the principle of a common mode input choke, not Intact per se. And it don't have to be expensive. Rather the opposite in fact - if possible.
And second, Vegard. Thank you for the link for the JMS Transformers. Regarding the Psud2 - how do you emulate the behavior of a common mode input choke in this program?
And second, Vegard. Thank you for the link for the JMS Transformers. Regarding the Psud2 - how do you emulate the behavior of a common mode input choke in this program?
Your English is fine. A better way to describe it is that I don't understand the benefits of a common mode input choke over a regular one. I'm open to any explanation, preferably one which assesses the affect on eventual sound quality.
The Intact module's choke looks (at first blush) like a common-mode winding in the schematic - but it is not!
The position of the dots that mark the start of the windings is the first clue: common-mode chokes have the dots of both windings at the same end.
Also, the text makes clear that it is designed as a differential-mode choke-input filter.
If you want to model the module, ask Dave for the values to use in PSUD2. As Vegard says, it will model just like a normal choke-input filter.
BTW, common-mode chokes are sometimes appropriate for filament supply filtering. This is true because the filament supply floats above ground, only to be grounded via the cathode resistor/capacitor or whatever « tail » circuit is used in a PP circuit. If common-mode noise enters via the power transformer (example: toroid with high leakage-capacitance) the noise can run through the cathode circuit which may be a problem for some tail circuits, if broadband noise is present.
The position of the dots that mark the start of the windings is the first clue: common-mode chokes have the dots of both windings at the same end.
Also, the text makes clear that it is designed as a differential-mode choke-input filter.
If you want to model the module, ask Dave for the values to use in PSUD2. As Vegard says, it will model just like a normal choke-input filter.
BTW, common-mode chokes are sometimes appropriate for filament supply filtering. This is true because the filament supply floats above ground, only to be grounded via the cathode resistor/capacitor or whatever « tail » circuit is used in a PP circuit. If common-mode noise enters via the power transformer (example: toroid with high leakage-capacitance) the noise can run through the cathode circuit which may be a problem for some tail circuits, if broadband noise is present.