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Old 9th November 2012, 09:12 AM   #2211
mogliaa is offline mogliaa  United Kingdom
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Glad to hear that more people like the CCS+VR supply :-)
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Old 9th November 2012, 09:46 AM   #2212
disco is offline disco  Netherlands
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I've no experience with Hammond 156C but on another circuit I experimented with series connecting two identical chokes. What I recall is high tones lost detail. Theoretically two caps in series represent a smaller cap, but we're forgetting the choke copper resistance here, presenting a LPF.

I try to get the exact workings of that CCS+VR supply in post 2200 but perhaps it's time to check theory for me again?

Here the 26 is represented by the R1, R2 combination and the gastube by R3. As I see it, they influence each other in a way that if the 26 starts pulling more current and the current source keeps current stable, the gas tube has to supply current. Is that 150 volt stable over operation?

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Old 9th November 2012, 01:34 PM   #2213
dhtrob is offline dhtrob  Netherlands
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Imho totally true Jaap!
When the 26 demands more current, it will come from the VR-tube, probably resulting in less stable regulation (and vice-versa).
I experimented with VR-tubes and found out that regulation gets better when more current flows through them.. So maybe increasing the current throught te CCS to 30mA will give "better" results? (at least, more stable regarding the VR-tube?)
Any ideas someone?

Rob
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Old 9th November 2012, 03:38 PM   #2214
disco is offline disco  Netherlands
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Consider that V-sign the 26 tube and R1 the choke. So, the 26 is loaded by the compound of three devices: A) the choke B) the FET CCS and C) the VR-tube which is bypassed for HF.

Rob, did you ever test those baco 'barrel' chokes for linearity?
Andy, if you leave out one 156C you'd probably not mis low. How's high turning out?
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Old 9th November 2012, 03:43 PM   #2215
mogliaa is offline mogliaa  United Kingdom
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VR is a shunt, so like a supply with low impedance. CCS is high impedance. The 26 sees the choke load in parallel with the output load...
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Old 9th November 2012, 03:46 PM   #2216
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I'll have to make another 26 preamp with a transformer out so I can compare that with the plate chokes. I have a LL1660/5mA, LL1692/10mA and LL1635/5mA. That would cure the hum and might have better treble. The treble isn't bad with the 156Cs, just a bit soft.
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Old 9th November 2012, 03:52 PM   #2217
disco is offline disco  Netherlands
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Alrighty, with the output four to count
For a VR to change current it has to change its impedance.
It's a complex load.

Ale, did you compare 26 reproduction against the SSHVSR and a sole resistive load ?
( added to the load presented by the output ).

Andy, mind the distortion product of that penthode which has a different spectrum than the 26.
Ale has probably data on that. It might turn out you're listening for a small amount of uneven harmonics, beafing up highs. Just guessing here.
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Last edited by disco; 9th November 2012 at 03:58 PM.
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Old 9th November 2012, 05:27 PM   #2218
dhtrob is offline dhtrob  Netherlands
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Quote:
Originally Posted by disco View Post
Rob, did you ever test those baco 'barrel' chokes for linearity?
No, I did not...
I "only" had Tribute and AE chokes..

Rob
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Old 10th November 2012, 11:20 AM   #2219
disco is offline disco  Netherlands
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Pity, I stock a load Compared to a resistive load I'm under the impression reproduction is in balance BUT hearing can be deceptive :d

I've plotted some points in a graphic once but it was a challenge turning knobs while reading meters. Besides, my bridge was capable for 50mA DC at the most. I once witnessed Remco 'analogaudio' examine random chokes with his $10K spectrum analyzer within seconds. The results were very diverse above 1KHz, most PS chokes presented a hefty bulge. Reason for me to buy established brands audio chokes indeed as there's something more to it than just winding copper.
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Old 10th November 2012, 11:47 AM   #2220
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As far as hum pickup is concerned I assume you have tried swapping the choke wires over?

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Susan
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