Recent Posts

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81
Other DACs / Re: Marantz 94 mark 2
« Last post by stevenvalve on February 02, 2018, 03:20:29 PM »
82
Amplification (Pre/Power) / Re: New Amp: Tektron 2a3/50
« Last post by Tasdevil on January 16, 2018, 02:32:00 AM »
Hi Rab,
           Yes it is, I use it to drive some Quad 57's. Sounds great.
83
Amplification (Pre/Power) / Re: New Amp: Tektron 2a3/50
« Last post by rab on January 15, 2018, 08:39:06 PM »
Looks nice. Is that a Leak stereo 20 on the floor?
84
Amplification (Pre/Power) / Re: How to Build a killer Amp
« Last post by fallsaudio on January 14, 2018, 03:22:36 PM »
 ;D
Here are two fixes for the grid resistance on the 50 tube. I will post two circuits later today .
I have been playing around with some grid chokes in place of the standard grid leak resistor . I experimented with a few different brands and different inductions. All worked very well and gave there own signature to the sound . The one that I only had one of seem to work best . That was a Lundah LL1670 choke. It may not be to every ones taste as I find Lundah transformers can be too clean sounding for my liking. But this one work very well.

The other way to fix this problem is to increase the current coupling cap from .47mfd to 1mfd by adding another .47 in parallel . You also need to decrease the grid leak resistor to 100K .
2w resistor sound better than the small wattage. I used a Allen Bradly
I hope this will help you all :D
85
Amplification (Pre/Power) / Re: New Amp: Tektron 2a3/50
« Last post by kajak12 on January 10, 2018, 08:19:58 PM »
Hi, I'm a new member here although I did post occasionally on the old forum. Anyway I'm a good friend of Steve ( I think! ) and he wanted to see some photos of my new amp ( probably to bag it ) so here it is. It's a Tektron 2a3/50s power amp made in Italy. It has a switchable filament power supply so you can use various triodes like 45's, 2a3's, 300b's and 50's etc. Cheers.
Good friend with steve? I guess anybody with valves is a good friend now days  :D
86
Amplification (Pre/Power) / Re: New Amp: Tektron 2a3/50
« Last post by Tasdevil on January 07, 2018, 01:55:44 AM »
Hi Steve, here is makers take on using various triodes : yes you can use with 45. Of course. Must only use low current.

WIth 275 V or 300 V must set current at 30 mA like indicated in the manual..

why? because the limit of tube are 9W dissipation and 250 x 36 = around 9W.

if use 300 V x 30mA = 9W.

So if you want can use 45 max current 30mA.
87
Amplification (Pre/Power) / Re: New Amp: Tektron 2a3/50
« Last post by stevenvalve on January 07, 2018, 01:39:17 AM »
Nice Peter you devil, Interesting amp people because its can use 45s 2A3s and 50s but how does the maker do that. Obliviously there is a filament switch for 7.5v and 2.5v but running 350 volt measured at the tube when the 45 can only handle 250v in globe or ST form is interesting.
88
Amplification (Pre/Power) / New Amp: Tektron 2a3/50
« Last post by Tasdevil on January 07, 2018, 01:22:13 AM »
Hi, I'm a new member here although I did post occasionally on the old forum. Anyway I'm a good friend of Steve ( I think! ) and he wanted to see some photos of my new amp ( probably to bag it ) so here it is. It's a Tektron 2a3/50s power amp made in Italy. It has a switchable filament power supply so you can use various triodes like 45's, 2a3's, 300b's and 50's etc. Cheers.
89
Amplification (Pre/Power) / Re: How to Build a killer Amp
« Last post by zenelectro on January 05, 2018, 10:45:30 PM »
Hello to all!
              This amplifier is a rock solid circuit to be use with 2A3, 6A3 , 245, 246 ,PX25 etc. It will provide you with a amazing sound stage and a hi quality sound that a lot of others SE amps fail to do .  But the ux250 a tube that require 10000 ohms or less resistance on the control grid . Yes it will work in there but it will stress the tube and shorten the life of the tube . You can be overcome the problem by remove the coupling capacitor and the plate load resistor to the driver tube and placing a Hi Quality inter stage transformer 1:1 ratio 10K to 10K works great . The primary winding is connect were the plate resistor was and the secondary goes across the grid leak resistor from the grid to the signal earth .I will over the day post a circuit for those who are not sure what to do . :D
Paul
Fallsaudio

If anyone has a problem and need help, I am more than willing to help . Just email me at fallsaudio@yahoo.com

Another way to do it is use a high value choke to ground to bias the OP tube. This one would be perfect
https://www.hificollective.co.uk/components/audio-note-chokes/choke-200.html
450 Henries..... that's a beast   :o ;D

Even at 20Hz the load only will be >50k but DC resistance = 2k, should keep the OP tube grid current happy.  :)

T
90
Resistors / Re: Resistor games
« Last post by stevenvalve on January 03, 2018, 05:55:54 PM »
Received an message from one of our members in Italy and i thought it will be of interest here.

I have read with interest your post on resistor sound.
As you can read here:
http://www.diyaudio.com/forums/parts/182611-tantalum-resistors-whats-3.html
I have found results very similar to yours, i.e. Shinkoh are the best,
followed by Allen Bradley 2W and AN tantalum non-magnetic.
I have tried also the relatively new Takman (metal and Carbon) but
none was in same league with the previous 3, and with Shinkoh in
particular. My simple question to you is if you have any update (what
comes close to Shinkoh in your opinion?) or if you had the opportunity
to test also others like Vishay bulk/Z foil or Tepro RA or others.
Best regards!
Tino
http://digilander.libero.it/agostino.manzato/audio/audio.html

Tino, The Shinkoh 2 Watt are on a planet of there own, even compared to the Shinkoh 1 watt version, its just a little better, no its a lot better. The Allen Bradley 2W is very good, but only after a good run in, Its natural with excellent timbre. But its not the cleanest of resistors. The AudioNote tantalum magnetic 2 Watt is very musical but i find you need to be careful where you put them and must not be over used and rarely use them, the Takman resistors are OK. The New AN tantalum non-magnetic resistors i found disappointing, but only compared to the  Shinkoh 2 Watt or 1 Watt, they are not for me. Vishay bulk/Z foil are incredibly clean and clear but as with most of the newer made resistors just have this clinical and uninvolving sound that leaves me uninterested in listening. In the right spot most resistors can have a place, but the bottom line is the Shinkoh 2 Watt are so good, if you have them already there is nowhere to go. Nothing satisfies ultimately, like a Shinkoh 2 Watt or second best a 1 watt Shinkoh. In a brilliant system they rule. I often use a combination of resistors usually, rarely just one type. Every time i try a new resistor that has just hit the market i am always disappointed so i have given up unless there is a rave review.
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