I have silver mica, but I prefer teflon FT-2. I don't understand why some don't like teflon.
Agree about the natural fibres. The application for this particular gauge OCC wire was high voltage DC transfer from external power supplies to preamps and phono stages, typically a 6 wire, 2m run, some of the wires carrying about 300v. Teflon sounded great on paper.
I always preferred polypropylene to Teflon because it is cheaper. I have some with TIN foil... way better than copper or silver, etc.
But electrically it should make no difference.
I prefer chokes that for a given inductance, have a higher first resonance frequency and a lower DCR, but sadly none of those manufacturers want to publish all that data.
Also most of this thread is now off-topic about caps??
Also most of this thread is now off-topic about caps??
I've experienced with plate chokes for the last year and I had to get expensive shielded one to not pick up too much noises. but even with those I had to add mu metal sheet and use proper positioning. My speakers are horns and compression drivers so any mV of noise need to go.
I've switched all my amps to CCS eventually, this helped reduce noises and distortion. I find the perfect operating point adjusting the ccs in real time while analyzing the output for each tube. Nothing very complicated, just using cascoded 10m45 or dn2540. It was a big step forward but I need to readjust every 3-6 months and it's a little bit more work. Well worth it but not compatible with the tube rolling mindset. Doing that kind of defeat the tube rolling differences with tend to perceive too.
The Hammond plate chokes are very hard to isolate, I used two in serie for 200h but position them to get some noise cancelation one under the other in opposition. It worked relatively well and wasn't expensive to experiment with. Sounded better than a simple resistor but much noisier. The lundhal are better for noise rejection with the shielding, more expensive but introduce some level of distortion, like the Hammond, when compared to a plate resistor or a ccs.
The ccs is, for me, best of both world and don't plan on returning to plate choke for now.
When it's possible I prefer going gapped interstages (have great results with Hammond 126b right now) , when I can't use them I go ccs and good Solen teflon capacitors (green ones are really good and cheap for teflon) or large polystyrene capacitors but they are hard to find (multicap rtx are quite big and limited in value but sound fantastic too).
Things can change but this is the results of hours and hours of trials, listening and measurements on my builds. I'm not looking for overly warm tubby sound and prefer vividness and immediacy and those choices reflect that I think.
I've switched all my amps to CCS eventually, this helped reduce noises and distortion. I find the perfect operating point adjusting the ccs in real time while analyzing the output for each tube. Nothing very complicated, just using cascoded 10m45 or dn2540. It was a big step forward but I need to readjust every 3-6 months and it's a little bit more work. Well worth it but not compatible with the tube rolling mindset. Doing that kind of defeat the tube rolling differences with tend to perceive too.
The Hammond plate chokes are very hard to isolate, I used two in serie for 200h but position them to get some noise cancelation one under the other in opposition. It worked relatively well and wasn't expensive to experiment with. Sounded better than a simple resistor but much noisier. The lundhal are better for noise rejection with the shielding, more expensive but introduce some level of distortion, like the Hammond, when compared to a plate resistor or a ccs.
The ccs is, for me, best of both world and don't plan on returning to plate choke for now.
When it's possible I prefer going gapped interstages (have great results with Hammond 126b right now) , when I can't use them I go ccs and good Solen teflon capacitors (green ones are really good and cheap for teflon) or large polystyrene capacitors but they are hard to find (multicap rtx are quite big and limited in value but sound fantastic too).
Things can change but this is the results of hours and hours of trials, listening and measurements on my builds. I'm not looking for overly warm tubby sound and prefer vividness and immediacy and those choices reflect that I think.
Hammond 156C experiments
I set up a test, measure and listen rig rig for a potential choke loaded preamp. I tried evaluated various triodes (6W6GT as triode, 7233, DHTs like the type 30 and the 1E4G) each loaded with the Hammond 156C. I enjoyed that adventure and quite liked the 6W6GT, though I am yet to build that amp. My experiments were inspired by a post from Gary Pimm that I printed out and put in my files, reproduced below:
I set up a test, measure and listen rig rig for a potential choke loaded preamp. I tried evaluated various triodes (6W6GT as triode, 7233, DHTs like the type 30 and the 1E4G) each loaded with the Hammond 156C. I enjoyed that adventure and quite liked the 6W6GT, though I am yet to build that amp. My experiments were inspired by a post from Gary Pimm that I printed out and put in my files, reproduced below:
Yes, good call. I tried that as well but a little hum was an issue and I had to be careful where I put them.
They do, however, have a large DCR. The Hammond 157G used by Jim Hagerman has a much lower DCR.
All the reports are that the Lundahl LL1668 with lower DCR sounds better than the LL1667 with higher DCR.
I haven't listened to a simple resistor loaded stage with cathode resistor plus bypass for quite a while. I put one together and found the results interesting. The music sounded pure and mellow, which was nice. But also rather more distant - it seemed like you were hearing it from distance as in a large hall. I'm used to the more close-up sound of plate chokes with their sharper focus. This is even more pronounced with the SIC diode plus resistor (unbypassed) I've been using lately. Nevertheless, I'm enjoying the smooth and unfatiguing sound. Very easy on the ear.
It also struck me that the back-to-back trick of 2 156C could be used with the 157G. Two in series would give 60H at 1K DCR. Four would cost about £50. I actually do have four - I should try them out.
It also struck me that the back-to-back trick of 2 156C could be used with the 157G. Two in series would give 60H at 1K DCR. Four would cost about £50. I actually do have four - I should try them out.
They are a pretty good search coil to study magnetic fields.😱
Better housed in an iron box!
Nothing special in this post, just validating that the Hammonds work as expected as plate chokes, within their ratings.
Some years (decades?) ago I build a preamp test bed with several switchable chokes 30H to 72H if I recall correctly. The tube was a 6BL7, rp 2K2. There were four different inductances, and each increase was an audible improvement. (I was mostly listening for midrange clarity/resolution at the time, not frequency extension.)
I added a current source to the options, and that seemed clearly better than any choke, but it shifted the operating point too far to call it a valid comparison.
I've also used the 157G in a prototype 2-watt amp with 6DN7, rk 2K5, parafeed into an 8K:8 ohm output transformer driving an 8-ohm speaker. It worked without issues, but neither the choke nor the transformer I used was adequate for very deep bass - see first paragraph.
Some years (decades?) ago I build a preamp test bed with several switchable chokes 30H to 72H if I recall correctly. The tube was a 6BL7, rp 2K2. There were four different inductances, and each increase was an audible improvement. (I was mostly listening for midrange clarity/resolution at the time, not frequency extension.)
I added a current source to the options, and that seemed clearly better than any choke, but it shifted the operating point too far to call it a valid comparison.
I've also used the 157G in a prototype 2-watt amp with 6DN7, rk 2K5, parafeed into an 8K:8 ohm output transformer driving an 8-ohm speaker. It worked without issues, but neither the choke nor the transformer I used was adequate for very deep bass - see first paragraph.
Good to hear your very extensive experience, Paul. Thanks for coming in.
I also have found that each increase in inductance was an audible improvement, again in midrange clarity. I'll have to get my Bartola gyrators working - some glitch I haven't fixed.
Could you say something about comparing plate chokes and active loads to a plain resistor load?
I also have found that each increase in inductance was an audible improvement, again in midrange clarity. I'll have to get my Bartola gyrators working - some glitch I haven't fixed.
Could you say something about comparing plate chokes and active loads to a plain resistor load?
I came across this:
"Hammond 200H@40mA 193A i use on 6C4C to direct coupled drive 6C33C
psu stackeds https://www.hammfg.com/files/parts/pdf/193A.pdf"
Fairly new model. Anyone tried it?
"Hammond 200H@40mA 193A i use on 6C4C to direct coupled drive 6C33C
psu stackeds https://www.hammfg.com/files/parts/pdf/193A.pdf"
Fairly new model. Anyone tried it?
I have not done any formal listening comparisons of chokes to resistor loads, so I can't offer much comment on subjective sound. Anecdotally, changing a resistor to a current source has always increased clarity and reduced "tubiness" in amps and preamps. (My experience is mostly with the Bottlehead line, of course.)
I'll just offer the observation that both current sources and resistor loads reduce the plate voltage to about half of what you can get from chokes, thus giving choke loads a 6dB headroom advantage. That means (approximately) 6dB less 2nd harmonic distortion, 12dB less 3rd harmonic, 18dB less 4th harmonic, etc... That's especially relevant for driver stages in SETs with low-mu output tubes.
I hope to do some experiments with choke-loaded drivers in the future - that new 200-henry Hammond looks attractive!
So far when I measured a number of hammon chokes have found the rating is optimistic an example a 30h choke that measure such at 2k hz where it peaked . The standard is at 1k hz that was 16H . So they are good for lower priced chokes . 🙄
Anybody checked the other end of the audio spectrum? The 200H choke driving a following load of say 100 pF must be getting close. But would be heavily damped by the driving triode.🙂
Hi, i have the dude. is any difference in gain between choke plate load and interestage coupling transformer for a tube preamp?
