#26 pre amp - Page 158

CSlee · 8th February 2012, 06:29 PM

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

regal · 9th February 2012, 02:02 AM

Quote:

Originally Posted by CSlee

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.

CSlee · 9th February 2012, 06:08 AM

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.

regal · 9th February 2012, 07:06 AM

Not that, if you are familiar with using tubes in the studio I am sure this would be a fantastic application.

CSlee · 9th February 2012, 04:23 PM

Quote:

Originally Posted by regal

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

andyjevans · 9th February 2012, 06:19 PM

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

Wavebourn · 9th February 2012, 06:26 PM

Quote:

Originally Posted by andyjevans

All directly heated tubes need to be vertical - no exceptions I know about.

According to datasheet 4P1L works in any position:

CSlee · 9th February 2012, 06:38 PM

Quote:

Originally Posted by andyjevans

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

Bouquet · 9th February 2012, 06:52 PM

"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 )

Original Burnedfingers · 10th February 2012, 11:02 AM

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.

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

Tried batteries and still had hum.

8th February 2012, 06:29 PM	#1571
CSlee Clueless diyAudio Member Join Date: Mar 2009 Location: London	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 __________________ Broke solderer with delusions of grandeur

9th February 2012, 06:08 AM	#1573
CSlee Clueless diyAudio Member Join Date: Mar 2009 Location: London	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. __________________ Broke solderer with delusions of grandeur

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9th February 2012, 07:06 AM	#1574
regal diyAudio Member Join Date: Jan 2004 Location: MD	Not that, if you are familiar with using tubes in the studio I am sure this would be a fantastic application.

9th February 2012, 06:19 PM	#1576
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	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

9th February 2012, 06:52 PM	#1579
Bouquet diyAudio Member Join Date: Jul 2007	"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 )

10th February 2012, 11:02 AM	#1580
Original Burnedfingers diyAudio Member Join Date: Nov 2002	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. Quote use separate floating power supply's of 1,5 V ( a battery is absolute humfree Tried batteries and still had hum.