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Planning on changing amps from PP KT120 to SET 2A3


DjOverdose

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That's a lot of iron...going to be a beast to pick up.  My 2A3 amps only take a few minutes to warm up. I know you are certainly going to enjoy your new amp, no matter what anyone else says. 😉 

 

So, the smaller 9 pin is the driver on each side? I would like to know what your builder used, mostly out of curiosity. SETs can be so simple. I like it!

 

Bruce

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11 hours ago, dwilawyer said:

That's some Mang, good for you.  So does that amp give you the option to go 300b, 45 like the one you described at the beginning of your thread?

 

If so you are going to be able to try a lot 9f every cool things!

Hello. 

 

Yes he placed a switch at the back of the amp. If i remember it xorrectly it has 4 modes. thats for the voltage selector. 1st is 5V for the 300b and JJ2a3 40w

2nd is 4.5 and 3rd is 4V these are for the normal 2a3. then 4th was like 3.5v? cant remember actually the volatge. he just explained to me that the latter one is for the 45 since its the lowest voltage. so i can use option 1 to 3 for the 2a3. just obeserve which amongst it will sound sweet to my ears. 

 

Also if youll check the first picture, youll notice at the back of the 2a3 tubes theres a label that says 2a3. thats actually the filament switch? for 2a3 and 300b. as for the 45, ill just use the 2a3 and then set the correct bias. theres alot of things to fiddle with this amp. requesting the builder to give me a manual because i might forget about it after awhile. it also has a hum balancer on top and a gain controller at the back. 

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38 minutes ago, Marvel said:

That's a lot of iron...going to be a beast to pick up.  My 2A3 amps only take a few minutes to warm up. I know you are certainly going to enjoy your new amp, no matter what anyone else says. 😉 

 

So, the smaller 9 pin is the driver on each side? I would like to know what your builder used, mostly out of curiosity. SETs can be so simple. I like it!

 

Bruce

Yup it does have alot of iron. He builds the whole OPT and chokes from scratch so that he can customize the amp depending on the clients specification or request. 

 

the 9 pin is a 12at7. it drives the 5u4gb for the 2a3 power tubes.. the the middle one is a rectifier tube. forgot the tyoe though. 

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On 7/7/2019 at 9:24 PM, Jeffrey D. Medwin said:

The rectifier tube should located be as FAR away as possible, from the input tubes. 

 

Here, we see just the opposite, close-to and smack dab between both of the input tubes.

 

 

the rectifier tube is in the middle. the tubes infront of the 2a3 are driver tubes same with the 9pin.

 

 

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On 7/7/2019 at 11:49 PM, Schu said:

I bet you can't wait to hear it fire up for the first time... you're going to be impressed and happy.

 

I had the opportunity to take her home when i took this pictures. however the cage was not yet finished. so i decided not to bring her home not until the tube cage is finished. I have kids in the house, though im not concern about them having burns since i always listen at night. but im afraid that they might hit the tubes with a rubber ball when they are playing. hahaja that would be a bummer. 

On 7/8/2019 at 2:34 AM, Backfire said:

That looks really nice!  Very nicely built.

 

thank you... itll take quite awhile. need to brake in the power tubes and the opt... 

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11 minutes ago, Jeffrey D. Medwin said:

 The JJ 2A3-40 tube has a 2.5 VAC rated filament.   So does a Type 45 have a 2.5 VAC rated filament.  A 300B has a 5 VAC rated filament.   Current draws may vary between these different size and type tubes,  ( eg : the 2A3 and the 45 ) and that will effect the actual  operating voltage at the tube socket .

 

Jeffrey

err... to be honest when he was explaining the switches and selector to me, I just nodded. hahaha o really cant remember which is which. all i can remeber is that the one at the back is the voltage selector for a certain tupe of power tube. the other switcj is for the filament. the 3rd i need to change the bias every time i change to a different power tube... 

 

at this point i dont know if i can still use my kt120 power amp or if i will still be switching to it. 

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20 minutes ago, Jeffrey D. Medwin said:

The smallest 12AT7 is the input tube.  A 5U4GB is a rectifier tube, part of the power supply.  He used a Electro Harmonix, my personal favorite 5U4GB tube choice in 2019.  The EH  5U4GB takes 75 to 200 hours to fully break in BTW. 

 

The middle sized tube between the Input tube and the Finals/2A3 tube is a " Driver" tube, which drives the Finals tube. 

 

This is a three stage amp, Input ( 12AT7), next a  Driver ( not specified yet ) and Finals ( JJ 2A3-40).  The JJ 2A3 is among the best cost VS performance choice today in 2A3s when properly operated.

the tube in the middle was a 6n3c. i think he used that as a rectifier tube? 

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just want to share the whole amp set up... 

 

in the middle is my kt120 PP then on the left is the PSU of my Phono/line pre amp. (right) 

 

i had requested to have my pre amp to have to outputs so that when the time comes that I will have 2 power amps either a SET or an SS, it will be easier for me to switch. 

 

tubes used in the power amps are kt120s, 12at7, and ecc99. while for the pre amp PSU, regulator(?) was a 274b or 5u4g the n rectifier was el34. can also use either 6v6, 6ca7. for the phono/line all tubes are 12ax7.

PicsArt_07-09-10.47.09.jpg

PicsArt_07-09-10.56.30.jpg

PicsArt_07-09-10.54.52.jpg

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14 minutes ago, Jeffrey D. Medwin said:

 

 

Hi, it can NOT ever be  a rectifier tube, as part of the middle audio-amplification stage  !!    A 6N3C is like a 6L6 power tube, Russian.   Look it up on line. 

 

The EH 5U4GB absolutely  IS the amp's rectifier tube., it is positioned on the amp chassis in the front, middle.    

noted on this... will ask the builder what those tubes are for. really have no idea.... 😁 

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16 hours ago, dwilawyer said:

It is sensitivity, not efficiency.  It would depend how he has them placed in his room, and his room, on whether they will be right at spec, below,  or even above, right?

room placement will impact the available room gain but the speaker will not change sensitivity no matter where you place it. Sorry if I used the wrong term I always get confused between the two. When you have a speaker it has an efficiency level and you can install that in  any boc you like or horn but that number does not change. A bass reflex may help boot the bass output or a horn can add up to 6db of additional output over a specific range but the efficiency of the driver does not change that is set by the driver design/build. So I guess sensitivity is a function of the overall loudspeaker system then? I have found factory numbers do not accurately reflect what you get most of the time they always seem to b e high to me generally in the 2 - 4 db range. YMMV as always.

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A Klipsch engineer once wrote on the forum:

  • The sensitivity figures given on the spec sheet refer to the equivalent sensitivity of the speaker in an average listening roomAn asterisk now informs consumers of this on most spec sheets.  I think this must be some kind of crunched average, because the location in the room makes a difference, and moving the speaker from out in the room to snug in a corner increases the output by 6 dB.
  • The engineer went on to say to get anechoic sensitivity, subtract 4 dB from the spec sheet figure. 
  • IMO, measuring sensitivity at 1K Hz only would be misleading and useless.
  • I believe Klipsch measures across the full advertised bandwidth of the speaker.
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37 minutes ago, garyrc said:

A Klipsch engineer once wrote on the forum:

  • The sensitivity figures given on the spec sheet refer to the equivalent sensitivity of the speaker in an average listening roomAn asterisk now informs consumers of this on most spec sheets.  I think this must be some kind of crunched average, because the location in the room makes a difference, and moving the speaker from out in the room to snug in a corner increases the output by 6 dB.
  • The engineer went on to say to get anechoic sensitivity, subtract 4 dB from the spec sheet figure. 
  • IMO, measuring sensitivity at 1K Hz only would be misleading and useless.
  • I believe Klipsch measures across the full advertised bandwidth of the speaker.

Another Klipsch engineer posted in that same discussion you are referring to that they measure using pink noise per AES standards.  So whatever the standard AES prescribes is what they measure to.

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3 hours ago, moray james said:

room placement will impact the available room gain but the speaker will not change sensitivity no matter where you place it. Sorry if I used the wrong term I always get confused between the two. When you have a speaker it has an efficiency level and you can install that in  any boc you like or horn but that number does not change. A bass reflex may help boot the bass output or a horn can add up to 6db of additional output over a specific range but the efficiency of the driver does not change that is set by the driver design/build. So I guess sensitivity is a function of the overall loudspeaker system then? I have found factory numbers do not accurately reflect what you get most of the time they always seem to b e high to me generally in the 2 - 4 db range. YMMV as always.

It should be -4 anechoic (or free from any room gain). As @garyrc mentions above, the spec sheets say "* Sensitivity in average listening room." (Direct quote from consumer speaker spec sheet I picked at random). So if your measurements are with room gain you have an "average listening room" or slightly better one at only 2db difference. 

 

Efficiency is directly related to sensitivity so it is easily confused, I still do it all the time, but I think efficiency accounts for work in the physics sense.

 

Travis

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2 hours ago, Schu said:

Manufacturers test speakers in pairs?

No, not typically, and not determining specifications.  They will listen to a pair speakers for voicing, soundstage,  etc. but that doesn't produce specs. 

 

However, on the pro side they will test groupings of speakers, like in a theater, to determine if they are meeting design criteria for reference levels or certification specs like for Dolby and THX, and actual real coverage patterns (seats to the far side of a theater, seats in the rear, etc.).  

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