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Full music 274b and 2a3 mesh glowing20190205_001144.jpeg

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Look what arrived in the mail!

 

Very easy to see the 6550 on the left is faulty.  Plate current and transconductance is reading less than 1/10th of the one on the right. I'm curious under what conditions thetubestore does its matching since it rates the idle plate current as 59 (how they match their tubes) whilst I get 65 after it gets to steady state. I know they fluctuate but that's more than I would have expected. The other one that is "matched" by them also reads 65.

 

IMG_20190522_103106.thumb.jpg.c8266108d4185cc4f5fd8d34d0966c33.jpgIMG_20190522_103540.thumb.jpg.00f1e5a415004f8e8aa277bfb9299b19.jpg

 

 

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7 minutes ago, Ittaku said:

Look what arrived in the mail!

Looks great.

 

8 minutes ago, Ittaku said:

I'm curious under what conditions thetubestore does its matching since it rates the idle plate current as 59 (how they match their tubes) whilst I get 65 after it gets to steady state. I know they fluctuate but that's more than I would have expected. The other one that is "matched" by them also reads 65.

Depends on plate voltage and bias.  As long as the two valves measure the same under same conditions.

 

 

 

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1 hour ago, aussievintage said:

Depends on plate voltage and bias.  As long as the two valves measure the same under same conditions.

Yeah I'm pretty sure I'm using standard plate voltages and bias (400 and -48). Doubt anyone would use anything else on a 6550.

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10 minutes ago, Ittaku said:

Yeah I'm pretty sure I'm using standard plate voltages and bias (400 and -48). Doubt anyone would use anything else on a 6550.

I would think it's up to the designer.  Take a look at some old datasheets.  They give a range of typical operating points. https://frank.pocnet.net/sheets/049/6/6550.pdf   I used to use a spreadsheet I wrote to fiddle with different operating points to maximise power, minimise distortion, etc depending on the load line.

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39 minutes ago, aussievintage said:

I would think it's up to the designer.  Take a look at some old datasheets.  They give a range of typical operating points. https://frank.pocnet.net/sheets/049/6/6550.pdf   I used to use a spreadsheet I wrote to fiddle with different operating points to maximise power, minimise distortion, etc depending on the load line.

Thanks yeah for their usage in an actual application I can understand that. For testing though you'd use a standard setting of some sort, it just appears they use something different so I can't compare their results to my own. One thing I have confirmed though is they're definitely tightly matched which is reassuring about thetubestore (where I buy most of my new valves from). Idle current and transconductance to within 5% which is excellent matching I believe.

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2 hours ago, Ittaku said:

Look what arrived in the mail!

 

Very easy to see the 6550 on the left is faulty.  Plate current and transconductance is reading less than 1/10th of the one on the right. I'm curious under what conditions thetubestore does its matching since it rates the idle plate current as 59 (how they match their tubes) whilst I get 65 after it gets to steady state. I know they fluctuate but that's more than I would have expected. The other one that is "matched" by them also reads 65.

 

IMG_20190522_103106.thumb.jpg.c8266108d4185cc4f5fd8d34d0966c33.jpgIMG_20190522_103540.thumb.jpg.00f1e5a415004f8e8aa277bfb9299b19.jpg

 

 

Testing times. 

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Just now, mwhouston said:

Testing times. 

Meaning leaving them for different durations? I found after 2 minutes they stabilised and were ~the same after about 20 minutes.

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20190519_100301.thumb.jpg.79bf610bd8cf5925617f1e3e313f89e9.jpg

Ming Da MC- 2A3 Pre.

Edited by Braddles 63

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8 minutes ago, Ittaku said:

Meaning leaving them for different durations? I found after 2 minutes they stabilised and were ~the same after about 20 minutes.

I’ve found the same. Not much different after a while. 

 

Most testers don’t apply a very high voltage to the tube but the amp they are to go in may. Tubes can test OK then arc and hiss in the amp. Always watch a suspect tube as it comes up, If you see racing know tube is not suitable for the amp. Most times just dump them. Once suspect you don’t know what other damage they may cause. . 

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GEC CV6091 (A2900) NIB and for some VTL amps which will arrive soon. I hope they sound good!

 

IMG_0194.thumb.JPG.40f86549bb8fe2d2eeeb40fe2349d4bb.JPG

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Just now, Gryffles said:

GEC CV6091 (A2900) NIB and for some VTL amps which will arrive soon. I hope they sound good!

 

IMG_0194.thumb.JPG.40f86549bb8fe2d2eeeb40fe2349d4bb.JPG

Nice. Will like your post when I see them glowing :)

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Change of tubes in the new HP amp, LeManja. Sovteks with tiny little plates expose a lot more filament. 

7012799B-1624-4BA5-8A24-00DEBA17ACEB.jpeg

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On 22/05/2019 at 8:47 AM, Ittaku said:

 

 

Very easy to see the 6550 on the left is faulty.  Plate current and transconductance is reading less than 1/10th of the one on the right. I'm curious under what conditions thetubestore does its matching since it rates the idle plate current as 59 (how they match their tubes) whilst I get 65 after it gets to steady state. I know they fluctuate but that's more than I would have expected. The other one that is "matched" by them also reads 65.

 

 

 

 

 

Test the tubes in another tester and you might get a different result again.  Power supply might not be regulated for starters so you will get voltage variations. Older testers lose their tolerance and bias voltage might fluctuate and so on......

Your tester will test the tubes at one operating point only and it is not necessary the operating point the tube runs in your amp. If you truly want to mach tubes you will have to match their curves as well. And you will not find many sellers that will provide that service.

So just enjoy your new toy for what it is.

 

 

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3 minutes ago, Ihearmusic said:

Test the tubes in another tester and you might get a different result again.  Power supply might not be regulated for starters so you will get voltage variations. Older testers lose their tolerance and bias voltage might fluctuate and so on......

Your tester will test the tubes at one operating point only and it is not necessary the operating point the tube runs in your amp. If you truly want to mach tubes you will have to match their curves as well. And you will not find many sellers that will provide that service.

So just enjoy your new toy for what it is.

 

 

Sure thing. Just for reference I can vary the operating point and get wildly different results but I'm using the recommended settings for 6550. The maximatcher manufacturer (that's a mouthful) says the power supply in it is not regulated but I check the wall voltage when I do my testing now so I can compare them next time. The other tube types I tested matched the idle current values thetubestore measured so I'm guessing it's just the 6550 they test at a different operating point.

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I have a pair of 'matched' 300Bs.

One tested 104% of nominal plate current and the other 91%. So much for matching.

I do use them in a SET mono block with negative bias so it is not much of a problem to me.

 

20190528_154912.jpg

 

20190528_154912.jpg

Edited by Ihearmusic

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All this talk of tube testing!  I have an eTracer on its way to me so that I can test my own tubes. 

 

Some of my DHT's are coming up on 100yo and I really need to get them matched into groups based on their actual curve traces rather than just a single, seemingly random operating point...plus I would really like to know how well they are really matched, if at all.  Some of them are quite rare and being able to buy the less expensive singles and matching them into my stock is likely to be more useful as the years tick over.  Likewise the tubes for the phonostage could do with proper matching and then there are the Russian IDHT's with their large variations in mu and gm.  Sure they are cheap as chips but with six 6e5p/6e6p in each mono amplifier knowing which tube from the stash to put in next will be nice. 

 

Before testing, the big 6c33c's will need to be baked 30-50 hours until their current draw stabilises, but it will be very nice to have actual properly matched sextets of those guys.

 

 

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😃😃😃😃😃

i don’t even know how to change a light bulb

Here I am changing 8 of them

Later on I’ll be pretending I can here a different sound

Don’t mention the price

They look tiny compared to the 120’s

toylike even

BE56BFEF-8F24-41E7-99D0-A23C634BBBAE.jpeg

ECEEEFD7-3E1B-46A5-80BF-B81908C47F4C.jpeg

6245EDA5-0100-42B5-ACFB-78AAB5B07082.jpeg

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On 29/05/2019 at 9:30 AM, acg said:

All this talk of tube testing!  I have an eTracer on its way to me so that I can test my own tubes. 

 

Some of my DHT's are coming up on 100yo and I really need to get them matched into groups based on their actual curve traces rather than just a single, seemingly random operating point...plus I would really like to know how well they are really matched, if at all.  Some of them are quite rare and being able to buy the less expensive singles and matching them into my stock is likely to be more useful as the years tick over.  Likewise the tubes for the phonostage could do with proper matching and then there are the Russian IDHT's with their large variations in mu and gm.  Sure they are cheap as chips but with six 6e5p/6e6p in each mono amplifier knowing which tube from the stash to put in next will be nice. 

 

Before testing, the big 6c33c's will need to be baked 30-50 hours until their current draw stabilises, but it will be very nice to have actual properly matched sextets of those guys.

 

 

Please let me know how the etracer goes, I have been on the fence for a long time to purchase either the utracer or etracer. I have access to a crate of WE 300B’s from the 50-60’s I want to help a friend test.

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Guest Muon N'
21 hours ago, keyse1 said:

😃😃😃😃😃

i don’t even know how to change a light bulb

Here I am changing 8 of them

Later on I’ll be pretending I can here a different sound

Don’t mention the price

They look tiny compared to the 120’s

toylike even

BE56BFEF-8F24-41E7-99D0-A23C634BBBAE.jpeg

ECEEEFD7-3E1B-46A5-80BF-B81908C47F4C.jpeg

6245EDA5-0100-42B5-ACFB-78AAB5B07082.jpeg

EL34 is a great tube, I prefer some of them over KT120's, but then I have only heard the KT's in other peoples amps/systems.

 

Haven't heard the TAD's what are they originally?

 

DOH! just looked at the link, original production Svetlana Winged C's...cool! that's what I use and is my favourite :thumb: Very well balanced tube from top to bottom and everything where it should be in appropriate proportions....IMO :wub:

 

Edit: I thought they looked familiar, but could have been non winged C Svetlana's.

Edited by Muon N'

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1 hour ago, F18 said:

Please let me know how the etracer goes, I have been on the fence for a long time to purchase either the utracer or etracer. I have access to a crate of WE 300B’s from the 50-60’s I want to help a friend test.

Will do.   The etracer is much more capable.  Mine will be here next week... will have to find a bit of time to put it together and then I'll get to testing some tubes...

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10 hours ago, keyse1 said:

😃😃😃😃😃

i don’t even know how to change a light bulb

Here I am changing 8 of them

Later on I’ll be pretending I can here a different sound

Don’t mention the price

They look tiny compared to the 120’s

toylike even

BE56BFEF-8F24-41E7-99D0-A23C634BBBAE.jpeg

ECEEEFD7-3E1B-46A5-80BF-B81908C47F4C.jpeg

6245EDA5-0100-42B5-ACFB-78AAB5B07082.jpeg

If your amp uses the el34 tubes try some day the vintage  RCA 807 tubes. You will need adaptors. I use them and the music is amazing.

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Guest Muon N'

They warn about using the 807 triode connected at high voltage ( "Failure to observe this precaution will cause screen grid failure" ) I wonder what range they are talking about in referring to high voltage. My amp is hard wire triode connected. I have about 450 to 460v on the anode but forget what my screen voltage is. The 807 doesn't draw much heater current at least so safe there.

 

Meh....can't find much info on triode connected voltage limits, so I better pass.

 

If I felt like I was lacking something with the EL34 winged C's I and could confirm they could run in my amp without being stressed....maybe I would give them a try.

 

Interesting old school tube though, I think I looked them up another time when I saw you running them.

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