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Old 8th February 2012, 06:29 PM   #1571
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Goodness this is a large thread.

I am currently starting work on a 26 pre, with help from andyjevans and Rod. I find it a really interesting design - I just wondered if anyone had thought of using it in studio gear, an output stage for a summing mixer for example?

Cheers

Charlie
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Old 9th February 2012, 02:02 AM   #1572
regal is offline regal  United States
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Originally Posted by CSlee View Post
Goodness this is a large thread.

I am currently starting work on a 26 pre, with help from andyjevans and Rod. I find it a really interesting design - I just wondered if anyone had thought of using it in studio gear, an output stage for a summing mixer for example?

Cheers

Charlie
Your concerns in that application I think would be dynamic range and SNR. IF the mix was fairly uncompressed to begin with, it will add the sort of compression studio's should be using. Will take some tricks for studio quality noise levels, but I wish more studios would look into this sort of mastering.
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Old 9th February 2012, 06:08 AM   #1573
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Does the 26 not have enoguh headroom to compete in this application? After everyone's comments on the quality of this design, it would be interesting to see it used in the studio.
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Old 9th February 2012, 07:06 AM   #1574
regal is offline regal  United States
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Not that, if you are familiar with using tubes in the studio I am sure this would be a fantastic application.
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Old 9th February 2012, 04:23 PM   #1575
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Not that, if you are familiar with using tubes in the studio I am sure this would be a fantastic application.
Got to be worth a try
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Old 9th February 2012, 06:19 PM   #1576
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Using directly heated tubes in a studio application is a really interesting challenge. For a start the noise levels need to be low, but noise itself isn't really an issue - filaments can be kept pretty quiet. Microphonics probably is an issue, though. Reports of microphonics with the 26 vary - I've never had a problem with my 4mm thick aluminium top plates, but in critical applications others have had issues and have used things like grounded metal shields around the bottle.

The chassis needs some thought - needs to be fairly massive for a start. The other thing for studio use is height. All directly heated tubes need to be vertical - no exceptions I know about. So you're talking an absolute minimum of 3U rack size - 132mm.

And then items like chokes and transformers need to be kept away from the tubes. All needs some thought, but the sound quality should make a real difference.

Andy
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Old 9th February 2012, 06:26 PM   #1577
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Originally Posted by andyjevans View Post
All directly heated tubes need to be vertical - no exceptions I know about.
According to datasheet 4P1L works in any position:

Click the image to open in full size.
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Old 9th February 2012, 06:38 PM   #1578
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Originally Posted by andyjevans View Post
Using directly heated tubes in a studio application is a really interesting challenge. For a start the noise levels need to be low, but noise itself isn't really an issue - filaments can be kept pretty quiet. Microphonics probably is an issue, though. Reports of microphonics with the 26 vary - I've never had a problem with my 4mm thick aluminium top plates, but in critical applications others have had issues and have used things like grounded metal shields around the bottle.

The chassis needs some thought - needs to be fairly massive for a start. The other thing for studio use is height. All directly heated tubes need to be vertical - no exceptions I know about. So you're talking an absolute minimum of 3U rack size - 132mm.

And then items like chokes and transformers need to be kept away from the tubes. All needs some thought, but the sound quality should make a real difference.

Andy
Hi Andy,

It seems like a really interesting concept to try out, given the praise it has got on this thread alone. I was looking at some of our designs at work today, which are 3U and 4U (so already quite big) and was thinking of the practicle side to implementing the 26 - I really think that the issues you mentioned could be solved with careful planning, and maybe some thinking outside the box.

I'm looking forward to getting this line amp up and running - should be an interesting challenge!

Charlie
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Old 9th February 2012, 06:52 PM   #1579
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"I used separate power rail using a SMPS for filament and both filaments were connected serially with 3V supply."

Doing this you connect both cathode together , use separate floating power supply's of 1,5 V ( a battery is absolute humfree )
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Old 10th February 2012, 11:02 AM   #1580
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Just on a maintenance standpoint alone it would not be practical to use a 26 in a recording studio and or radio station. The 26 takes a lot of circuitry to obtain it clean clear output. Studios would not have the time to keep it running correctly because of being booked non-stop all day long. Another thing to consider is the tube availability and cost. They haven't made the 26 for probably 80yrs or so. Never worked in a studio yet that uses tube gear for mix purpose or recording purpose. You might hear a tube amplifier on a pair of monitors but that would be about it.

Leave the 26 where it belongs...in your home system.


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use separate floating power supply's of 1,5 V ( a battery is absolute humfree

Tried batteries and still had hum.
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