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PostPosted: 11 May 2011, 12:56 
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mwhouston wrote:
mA or uA?


:blush: ooops. It's uA, Mark. I was thinking micro and typed mili. Thanks for the sharp eye Mark!
Now, onward and forward....
I managed to find 4 JAN6418 tubes with nice, close, current draw @ ~75uA. Of the 15 tubes, I had uA ranges from 35uA all the way up to 125uA and one dud (started @ 45uA and dropped off rather sharply to less than 30uA, which is where I pulled it out - it hadn't stopped dropping).

I know, I know.. PICTURES! Well, here ya go......
Attachment:
Powered via lab supply.jpg

Paul designed the power supply to be a slow turn on. Very cool! Since the LEDs are to provide the illusion of heater filament glow, this slow turn on completes that illusion..

Attachment:
200mv in 15v out 1khz.jpg

Attachment:
10k bot is in top is out 3v.jpg

Attachment:
100 hz out 20v.jpg

Attachment:
Sqr wv 1k.jpg


Notes:
1.) The PCB has an error. This is noted in the assembly notes of the kit. Apparently, the GND pads for the signal input did not get connected, as in, no traces to the rest of the circuit. You will need to make an alternate GND connection for the input, say, one of the GND pads for the output. Paul's suggestion is to connect a short jumper to a close by component on the ground side. He provides an illustration.
2.) Paul provides the rubber rings, a total of 8. USE THEM! As usual, these tubes ring like a bell. The rubber rings help immensely, but not 100%.

Next steps:
1.) Connect 120VAC to power supply and test. I will be looking at ripple closely.
2.) With no signal input (input grounded), determine amount, if any, of injected / induced AC noise from the power supply.
(If both of these tests pass, then there will be no changes. If the first fails I'll try inserting snubbers. Failing that, transformer goes bye-bye and a PS external to the amplifier will be constructed. If the 2nd fails, the transformer goes bye-bye and a PS external to the amplifier will be constructed. I do want to keep the slow turn-on feature.)
3.) Case it!


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The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
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LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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PostPosted: 11 May 2011, 18:36 
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Leds are noise so drop a .01uf cheap cap across them. This works well.

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PostPosted: 12 May 2011, 09:19 
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update...
I didn't work with the pre-amp much last night. I spent my time disemboweling an old blown tuner/amp. Got some nice RCA jack pads, a center detent VR (balance), motor driven volume module, transformers, capacitors, etc. I did fiddle with the pre-amp enough to give it some AC power and do a quick check for noise. :( Can you say hummmmmm. I didn't check if it was ripple noise from the PS or induced hum from the tranny. It was plainly evident with the inputs shorted. This same amp that was giving me crystal clean audio on the lab supply was now buzzzzzzzy. It even made the "ringing" of the tubes sound a little growly. This is an automatic failure of condition "2" of the test checks of the previous posting. This means removing the tranny and associated rectifiers & zeners from the circuit and building up an external** sheilded PS. I am inclinded to believe it is induced hum. I say this simply because when I powered the pre-amp, my signal tracer instantly picked up a large hum with the signal probe just sitting on the bench. No biggy. Clean low voltage power supplies are easy for me. The parts from the K301's power supply will do fine. I just need to use good regulation and shielding - LM317, filter / snubber caps, and some tin shielding. :up:

**By external, I don't mean in a separate box. I mean not part of the amp PCB.

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The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
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LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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PostPosted: 12 May 2011, 17:08 
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If the PCB is set up like the one for the line driver the tranni and PS cct. is a snap away. With the line drive I made, when in the box, the tranni is too close to one of the inputs. therefore hum. So I must do the same thing.

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PostPosted: 13 May 2011, 09:21 
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Location: Lilburn, Georgia USA
So..... Is everything Oatley sells junk that has to be redesigned? Why bother with it? Robert P


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PostPosted: 13 May 2011, 09:32 
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mwhouston wrote:
If the PCB is set up like the one for the line driver the tranni and PS cct. is a snap away


Sorry, Mark, the K301 is not set up that way. You could cut the board if you were real careful as the is a little gap between the PS and the amp circuitry, BUT you would be cutting through the power feed to the amp and you would have no room to add holes to the remaining pieces for mounting.

Now, in the process of attempting to remove the tranny, I destroyed it - pulled the pins right out of it :mad: . Now I remember why I hate double-sided PCBs. Not a problem, however, as one of the items I scavenged from that old tuner/amp was a transformer of same design and voltage. So, I'm good. :up:

_________________
The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
_________________________________
LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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PostPosted: 13 May 2011, 09:37 
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rparsh wrote:
So..... Is everything Oatley sells junk that has to be redesigned? Why bother with it?


My K292 headphone amp (original version) is just fine. I haven't made any changes to it.

_________________
The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
_________________________________
LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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PostPosted: 13 May 2011, 18:00 
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rparsh wrote:
So..... Is everything Oatley sells junk that has to be redesigned? Why bother with it? Robert P

I have made a number of Oatley kits and I have found them very good. They ARE made to a price and that allows the young beginer to try the waters with little expense. I've found their cct. brds. good in the past: doubled sided. plated through, silk screened and solder masked. I do change most of the caps and all the carbon resistors but apart from that a kit for $30??

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 14 May 2011, 16:47 
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What is "good" and what is "bad"??
Azazello and me attended the yearly DIY metting in Gothenburg today. I had brought some amps (trimmed by Azazello) and my supersimple horns based on Hungarian Sonido SFR144 fullrange speakers and Azazello had brought from Bulgaria a supersimple SE-amp based on Russian tubes 4P1L. Many people claimed that our combination was the best sounding, though it must have been the most simple (and cheapest).
I think that there's no point nake any comparison between price and quality, but I also feel that the Oatley kits may be cheap but it's very oimportant to have a look at the quality of the parts used, especially the inferior (but dirt-cheap) tubes. I bouth a kit and honestly I cannot gather any enthusiasm as no actions taken can compensate for the microphony these tubes show.
I am very interested in submin tubes, but I prefer sturdy tubes that can withstand some "rough handling" and be driven by some substantial voltage, without singing like birds.

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PostPosted: 14 May 2011, 19:37 
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The only Oatley device I just could not use due to ringing in my system was my DC version of the phono preamp. No matter where I placed it near, in or around my system it ringed (or rung). I even had it sitting on books or pillows or placed things on it. Nothing stopped it. I have proven that these tiny tube devices behave better in plastic cases. Metal enclosues appear to ring more easily.

I took it to an audio club members house it is was dead silent and played beautifully. He aagreed. I just sold it to a guy in Syndey (600 miles north of me) and it works perfectly in his system. Go figure?

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
Website: retro-thermionic


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