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Old 15th February 2013, 12:34 PM   #521
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I used the ECC40 quite a bit for a while, a few years ago. That was before I went over entirely to DHTs. I can't remember the operating point, but that didn't matter to me. Although the ECC40 saw off any of its close competition, I just found the sound so inferior in absolute terms to the best DHTs that there was no point in using it.

I realise that many people plan their amps on a rational basis - they need a stage with this amount of gain, that plate resistance etc. I don't. I listen to everything. Small signal DHTs were literally a jaw dropping experience for me. When I first fired up a 26 I almost jumped in the air for joy, and I may have even shouted out loud "this is what I've spent the last 30 years looking for!!!". I just hear enough of a difference for me not to want to use indirectly heated tubes, and that has determined how I've designed everything ever since - filament bias and transformer coupling.

So I'm not the person to ask about indirectly heated tubes - it's almost years now since I've used any.
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Old 15th February 2013, 01:13 PM   #522
RajkoM is offline RajkoM  Bosnia and Herzegovina
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Honest answer.
Thanks Andy
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Old 15th February 2013, 01:13 PM   #523
45 is offline 45  Italy
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Quote:
Originally Posted by RajkoM View Post
ECC40 direct coupled to 4P1L looks promising.

Question for 45 and Andy.

Do you have practical experience with smaller B+ on ECC40, say 130V/6mA op.point.
No, I am sorry I have not tried this. You can use this if you don't have high input signal. However I have noticed that grid current starts at about -0.5 V (average). For some tubes it might even be -0.7V. For such application I would select the valves for grid current occuring as close as possible to 0V.

Quote:
Originally Posted by RajkoM View Post
Also, if there is any difference in sound quality between Long glass Miniwatt ECC40 and Short glass Tungsram ECC40?

Tnx.
I actually have some ECC40's with short glass that are branded AEG Telefunken (who never made this valve) and others branded Siemens from 1978 and 1972, respectively. They are in original military boxes. However I never used short glass ECC40.
Those I used are all long glass and branded Philips Miniwatt (but actually they all have the same factory code which should mean made in France at the Radiotechnique factory) or Siemens & Halske. I should try....
In principle there can be a difference but this doesn't mean one is bad and the other is good. You might need to adjust the op. conditions to get the desired result.
I have seen this especially with PCL82's. Tungsram valves (made in Eastern Europe) are quite different from West European types.
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Old 15th February 2013, 01:21 PM   #524
RajkoM is offline RajkoM  Bosnia and Herzegovina
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Quote:
Originally Posted by 45 View Post
No, I am sorry I have not tried this. You can use this if you don't have high input signal. However I have noticed that grid current starts at about -0.5 V (average). For some tubes it might even be -0.7V. For such application I would select the valves for grid current occuring as close as possible to 0V.



I actually have some ECC40's with short glass that are branded AEG Telefunken (who never made this valve) and others branded Siemens from 1978 and 1972, respectively. They are in original military boxes. However I never used short glass ECC40.
Those I used are all long glass and branded Philips Miniwatt (but actually they all have the same factory code which should mean made in France at the Radiotechnique factory) or Siemens & Halske. I should try....
In principle there can be a difference but this doesn't mean one is bad and the other is good. You might need to adjust the op. conditions to get the desired result.
I have seen this especially with PCL82's. Tungsram valves (made in Eastern Europe) are quite different from West European types.

Good info, thanks.
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Old 15th February 2013, 01:22 PM   #525
Pano is offline Pano  United States
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Quote:
Originally Posted by andyjevans View Post
I'm only inputting 0.5v to my preamp, and it can't be hard to improve on that!
Andy and I are working (offline) to fix that.
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Old 15th February 2013, 01:49 PM   #526
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Pano is being very helpful - so nice!!
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Old 16th February 2013, 04:50 PM   #527
Pano is offline Pano  United States
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FYI & FWIW a few of data points from the real world.
My 4P1L is now running thus:
  • 6SN7GT on the input, LED bias. One section for each channel. AC heaters
  • 4P1L triode mode, battery bias @ -21V, cap coupled. DC heaters 4.1V
  • Plate at 252V, 38mA draw.
  • Small vintage 5K:8 OPT
  • Clipping at 1.3W output
  • Clipping at -1dB of max soundcard output at 6SN7 grid.
  • 14.2V RMS at 4P1L grid for onset of clipping.
  • Distortion @ 1V RMS out 1Khz
  • H2, -53dB, H3, -71db, H4 -85dB

I don't know if that helps anyone, but there you go.
For the most part and most music, I run with 6dB or more attenuation at the inputs.
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Old 16th February 2013, 05:19 PM   #528
iko is offline iko  Canada
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Pano, data from the real world is always helpful, thanks for reporting your experience.
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Old 16th February 2013, 06:08 PM   #529
Pano is offline Pano  United States
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You're welcome. What I'm getting doesn't look too far off Ale's numbers.
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Old 16th February 2013, 07:04 PM   #530
iko is offline iko  Canada
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Are you using this with speakers or headphones? Are you planning to two 4P1L in parallel for the output stage?
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