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Old 1st April 2013, 05:14 PM   #571
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by iko View Post
Thanks Ale. As I mentioned before, if you ever find the time to trace the 26 would be great. Dmitry's model of the 26 I think is based on the datasheet, not a working sample.
Hey Relu, I will put it on my "To Do" list which is getting bigger and bigger! Hopefully I can get a new model soon...
Cheers,
Ale
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Old 1st April 2013, 05:29 PM   #572
iko is online now iko  Canada
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No pressure, just saying, maybe one day. You've already helped a great number of us with your experiments.
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Old 27th April 2013, 11:18 AM   #573
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Could I use 3 resistor of 47R like these https://es.rs-online.com/web/p/resis...sante/1995937/ in parallel as cathode resistor?

How many mA have I to set the CCS?
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Old 27th April 2013, 01:30 PM   #574
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Those resistors should give you around 15R at 36W. Close enough for jazz.

If you are using glow tubes, it's useful to read the instructions for using them.
http://www.mif.pg.gda.pl/homepages/f...41/g/GL874.pdf

You will see that for the octal glow tubes they need 22.5mA and the 7 pin ones need 17.5v. Subtract the minimum current from the maximum current and divide by two. Then add that to the minimum current. So for 0D3 max is 40mA, min is 5mA. Difference = 35mA. Half of that is 17.5V. Add that to the minimum 5v and you have 22.5v. For the 7 pins the max voltage is 30v, so current you need is 17.5mA. That is true of all glow tubes of these types.

So what you then do is add the current through the glow tube to the current through the tube(s) you are using. For 2 x 4P1L at 36mA, add 22.5v and you set the DN2540 for 58.5mA.
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Old 27th April 2013, 02:03 PM   #575
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Thank you Andy, what prea do you like more: 26 or 4P1L?
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Old 27th April 2013, 04:17 PM   #576
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It's difficult to say if I prefer 4P1L or 26, because my amp is 4P1L into PSE 4P1L. Three stages of 4P1L are too much, so I'm using a 26 preamp. I'm going to try the 10Y next - I made a 10Y preamp before and preferred 26, but the 10Y wasn't optimised.

For a 4P1L preamp you need to do something about microphonics. Here's my latest idea using 1.5" plumbing parts. The brass parts don't touch the top plate - the rubber washers come in between, top and bottom. The tube socket is held between the two screwed pipes. I haven't tried it yet - should work! It's pretty heavy.....

Andy
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Old 27th April 2013, 07:12 PM   #577
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Clever idea! I gave up on the 4P1L in preamp or input mode, just couldn't beat the microphonics. Let us know how this works out.
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Old 4th May 2013, 02:36 PM   #578
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Even though I don't believe much in huge differences in sound between tubes of the same model, I am curious if anyone compared the Russian 4P1L with the similar Chinese 4P1S. How do they compare? Are they indeed similar and therefore interchageable?

Many thanks, Erik
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Old 5th May 2013, 02:00 PM   #579
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Quote:
Originally Posted by Wavebourn View Post
Yes, there will be transformers for parafeed drive. Let me test them first. I started a headphone 6W amp project about an year ago, then when potential partner became inpatient the project had been canceled, then the plant I contacted before come with some solution, so may be I will re-open the project if transformers are really as nice as they claim.
Do you have news?
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Old 27th June 2013, 05:42 PM   #580
PGDO is offline PGDO  Netherlands
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Originally Posted by andyjevans View Post
It's difficult to say if I prefer 4P1L or 26, because my amp is 4P1L into PSE 4P1L. Three stages of 4P1L are too much, so I'm using a 26 preamp. I'm going to try the 10Y next - I made a 10Y preamp before and preferred 26, but the 10Y wasn't optimised.

For a 4P1L preamp you need to do something about microphonics. Here's my latest idea using 1.5" plumbing parts. The brass parts don't touch the top plate - the rubber washers come in between, top and bottom. The tube socket is held between the two screwed pipes. I haven't tried it yet - should work! It's pretty heavy.....

Andy
Hi Andy,

I am leaning towards the 4P1L-IS-4P1L-IS concept myself to drive a 300B.

I guess the first tube is the most problematic considering microphonics. Is it the vibrations passed on via the case or air vibrations which are the most problematic?

What is your latest anti microphonics solution?

Thanks,
Peter
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