#17-19
Here is an example for a coil replacement,
in this preamp the coil is replaced by a Gyrator Triode
fundamental schematic
Gyrator blog
Advantage: Less phase shift at low frequencies against the coil topology.
Kind regards,
Darius
Here is an example for a coil replacement,
in this preamp the coil is replaced by a Gyrator Triode
fundamental schematic
Gyrator blog
Advantage: Less phase shift at low frequencies against the coil topology.
Kind regards,
Darius
Re: #17-19
I use the "gyrator" topology Darius mentions in my phono stage as a load for a D3A and a 5842.. Works quite well. I called it a boot-strap follower until today, gyrator is a much more convenient term. I've been using this circuit off and on for about 20yrs now. And I thought I was original... Guess not...
One more advantage Darius did not mention and the reason why I use it in my phono stage is that it is not susceptible to magnetically picked up hum and buzz as an inductor would be.
I was having an objection to sand at the time I designed this phono stage which is why I used this instead of a sand based ccs. Silly I know...
I like real choke loading in higher level applications, particularly where large swings are required.
oldeurope said:Here is an example for a coil replacement,
in this preamp the coil is replaced by a Gyrator Triode
fundamental schematic
Gyrator blog
Advantage: Less phase shift at low frequencies against the coil topology.
Kind regards,
Darius
I use the "gyrator" topology Darius mentions in my phono stage as a load for a D3A and a 5842.. Works quite well. I called it a boot-strap follower until today, gyrator is a much more convenient term. I've been using this circuit off and on for about 20yrs now. And I thought I was original...
Guess not... One more advantage Darius did not mention and the reason why I use it in my phono stage is that it is not susceptible to magnetically picked up hum and buzz as an inductor would be.
I was having an objection to sand at the time I designed this phono stage which is why I used this instead of a sand based ccs. Silly I know...
I like real choke loading in higher level applications, particularly where large swings are required.
Re: #20
0.008% distortion, rising with frequency. I tried. Granted it holds that low distortion to DC. A choke was chosen on the theory it stores and returns energy on the 'turn off' cycle, addressing one of the main complaints against CFs. Seems to work. The distortion profile of this 3-element SE design at low frequencies is pure push-pull, all odd harmonics until around 300 Hz, then pure second to the limits of my measurements.
A CCS is cheaper and provides you better results.
It works from DC onwards...
0.008% distortion, rising with frequency. I tried.
Granted it holds that low distortion to DC. A choke was chosen on the theory it stores and returns energy on the 'turn off' cycle, addressing one of the main complaints against CFs. Seems to work. The distortion profile of this 3-element SE design at low frequencies is pure push-pull, all odd harmonics until around 300 Hz, then pure second to the limits of my measurements.
@kevinkr #24
Hello Kevin,
I don't think so, I am sure you use something that is similar on the first look.
The gyrator stage is noisy against a resistor or a coil solution.
I use this stage at line level and selected a low noise ECC82.
Therefore it is possible to use this Gyrator in my application.
The advantage of the Gyrator is very low phase shift at the (low)cut off frequency.
The Gyrator and the coil are not constant current sources [ccs] and are not replacements for a ccs.
Yes thanks,
I forgot this important aspect.
Yes, of course.
I prefer the resistor at higher supply voltage.
Kind regards,
Darius
Hello Kevin,
I don't think so, I am sure you use something that is similar on the first look.
The gyrator stage is noisy against a resistor or a coil solution.
I use this stage at line level and selected a low noise ECC82.
Therefore it is possible to use this Gyrator in my application.
The advantage of the Gyrator is very low phase shift at the (low)cut off frequency.
The Gyrator and the coil are not constant current sources [ccs] and are not replacements for a ccs. Yes thanks,
I forgot this important aspect.
Yes, of course.
I prefer the resistor at higher supply voltage.
Kind regards,
Darius
#25 #26
This is a funny coil advertising post, maybe some audiofools will believe it.
A constant current source provides the best results in a cathode follower stage.
Guess why ...
A Resistor at high (negative) supply voltages and a coil are not constant current sources.
Definitely not.
You need a low damping resistance in parallel to the coil to make it broadband.
This requires high anode current to keep the resistance of the triode low
or you have to put a resistor in parallel to the coil that downloads the triode .
The attachment shows an early set (1932/33) that takes the advantages of resistors against coils. Low anode current and high resistor values provides excellent linearity, it does not suffer with audio bandwidth problems compared to sets that uses coils.
Stassfurt G43
Kind regards,
Darius
Originally #25 posted by rdf
0.008% distortion, rising with frequency. I tried.
This is a funny coil advertising post, maybe some audiofools will believe it.
A constant current source provides the best results in a cathode follower stage. Guess why ...
A Resistor at high (negative) supply voltages and a coil are not constant current sources.
Definitely not.
You need a low damping resistance in parallel to the coil to make it broadband.
This requires high anode current to keep the resistance of the triode low
or you have to put a resistor in parallel to the coil that downloads the triode
.The attachment shows an early set (1932/33) that takes the advantages of resistors against coils. Low anode current and high resistor values provides excellent linearity, it does not suffer with audio bandwidth problems compared to sets that uses coils.
Stassfurt G43
Kind regards,
Darius
Re: #25 #26
Yes, you caught me out. None of these measurements were really taken, the CCS wasn't adjusted to the same plate current as the coil and the coil was chosen over the easier-to-package drawer of IXYS adjustable CCS PCBs for 'audiophool' purposes. I'm really here advertising coils for a company I've openly and repeatedly slammed on this forum for poor design, marginal ratings and shoddy construction. Nice work Sherlock.
You get to learn a new word today: Tautology.
oldeurope said:
This is a funny coil advertising post, maybe some audiofools will believe it.
Yes, you caught me out. None of these measurements were really taken, the CCS wasn't adjusted to the same plate current as the coil and the coil was chosen over the easier-to-package drawer of IXYS adjustable CCS PCBs for 'audiophool' purposes. I'm really here advertising coils for a company I've openly and repeatedly slammed on this forum for poor design, marginal ratings and shoddy construction. Nice work Sherlock.
Guess why ...
A Resistor at high (negative) supply voltages and a coil are not constant current sources.
You get to learn a new word today: Tautology.
Hi Mike. It's dead simple and, in its current state, unoptimized but works well. The power supply is a stacked pair of 0C3s, individually bypassed with a 5.6nF Teflon and the string with a 0.1uF Teflon, both Russian. The 0C3 string is fed by a solid state IXYS CCS set to 38ma. The transformer/rectifier side needs to deliver a minimum of 250 VDC to the CCS, otherwise non-critical save for remaining within the bounds of the CCS power dissipation.
The CF is triode wired 6W6GT, plate/screen to B+, cathode to Hammond 156C, other end of Hammond choke to ground. The choke's DCR biases the 6W6. The grid is fed by a 100K pot and tied to ground with a 750K 'safety' resistor. A .22uF Auricap (should be larger) ties cathode to RCA output, the latter tied to ground with another 750K to bleed DC.
This was a simple experiment to make use of spare parts and give my Sonic Frontiers tube phono a better load than the 10k passive pre I've used for a decade. It just worked out perfectly that the DCR of the Hammond biases a triode 6W6 at ~7.5ma with 200 VDC on the plate, just within the choke's 8ma rating. A higher B+ - maybe stacked 0D3s - and higher current/henry choke will no doubt provide better performance, I didn't have them laying around.
A 6V6 or 6K6 plug straight in but don't measure as well. The circuit works into 10K at roughly 0.015% THD but is much happier into >50K loads, easy for me since it drives a DIY amp. Wired well noise and hum are 100 dB below 1 volt.
One final thing to note; gain is negative, the circuit has about 1dB of loss. It's not an issue with my amp's sensitivity but might not work with yours. Wiring the 6W6 pentode (~670K resistor B+ to screen, ~10uF cap screen to cathode in quick and dirty benching) brought the gain back to near unity and halved the mid-band distortion but raised it at the bottom end. I preferred the simplicity of the triode version.
The CF is triode wired 6W6GT, plate/screen to B+, cathode to Hammond 156C, other end of Hammond choke to ground. The choke's DCR biases the 6W6. The grid is fed by a 100K pot and tied to ground with a 750K 'safety' resistor. A .22uF Auricap (should be larger) ties cathode to RCA output, the latter tied to ground with another 750K to bleed DC.
This was a simple experiment to make use of spare parts and give my Sonic Frontiers tube phono a better load than the 10k passive pre I've used for a decade. It just worked out perfectly that the DCR of the Hammond biases a triode 6W6 at ~7.5ma with 200 VDC on the plate, just within the choke's 8ma rating. A higher B+ - maybe stacked 0D3s - and higher current/henry choke will no doubt provide better performance, I didn't have them laying around.
A 6V6 or 6K6 plug straight in but don't measure as well. The circuit works into 10K at roughly 0.015% THD but is much happier into >50K loads, easy for me since it drives a DIY amp. Wired well noise and hum are 100 dB below 1 volt.
One final thing to note; gain is negative, the circuit has about 1dB of loss. It's not an issue with my amp's sensitivity but might not work with yours. Wiring the 6W6 pentode (~670K resistor B+ to screen, ~10uF cap screen to cathode in quick and dirty benching) brought the gain back to near unity and halved the mid-band distortion but raised it at the bottom end. I preferred the simplicity of the triode version.
Thanks, very interesting. Another advantage I see to this over normal CF is that one can bias the heaters above the DC potential of the CF cathodes without going way over the cathode potential of other tubes in the circuit when used in something like an integrated amp.
Would be fun to play with.
Would be fun to play with.
@ analog_sa
Sorry for the delayed answer ...
What do you think about this one?
Cathodefollower V10
Constant current source V9
http://coupling-triode.blogspot.com/
Kind regards,
Darius
Sorry for the delayed answer ...
What do you think about this one?
Cathodefollower V10
Constant current source V9
http://coupling-triode.blogspot.com/
Kind regards,
Darius
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