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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 21st November 2011, 10:46 PM   #481
rknize is offline rknize  United States
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The choke helps to reduce hum and makes things a little easier on the rectifier then just increasing the size of the 2nd cap in the stock CRC filter. Folks with less sensitive speakers aren't going to notice it as much in the SPP because ripple on the B+ rail is common-mode at the output tubes. The previous stages have a bit more filtering behind them.

The cap is more about improving the dynamic response of the power supply by reducing it's impedance. This should result in better "detail" and "imaging", but again that benefit is in the ear of the beholder.
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Old 21st November 2011, 11:55 PM   #482
pso is offline pso  Spain
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Thanks , seems to be interesting to add.
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Old 5th December 2011, 04:43 PM   #483
brucetassin is offline brucetassin  United States
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I'm just about finished building my simple push-pull amp. I will be using an Edcor CXPP25-8-7.6k OPT and russian drivers (6N14N). George says that the feedback cap ( parallel with R104/204) is dependent upon the OPT and drivers. I'm not a designer so dont know how to choose a value, anyone care to offer a value?
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Old 5th December 2011, 06:23 PM   #484
Tubelab_com is offline Tubelab_com  United States
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See this thread:

feedback compensation capacitor on the Tubelab SPP
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
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Old 24th December 2011, 08:20 PM   #485
rmyauck is offline rmyauck  Canada
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Hi George!

I've read of a few people saying it's good to get the DCR of a PS as low as possible so they advocated low DCR chokes taking out resistors before the main B+. A few ohms may act as a shock absorber before the caps I've read. What do you think?
If it's okay to try say on the Simple EL84 PP one took out the 150 ohm 5W cap and put in a few ohm one or similar value with a choke. What would you need for a PS trans? 275-0-275 maybe?

No rush on this!


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Old 22nd January 2012, 08:03 AM   #486
zman01 is offline zman01  Bangladesh
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Tubelab Simple P-P
Question Got the Tubelab PP Kit, now the parts

Got my Tubelab kit from George. Shipping was really prompt, thank you George.

Been waiting for the other parts to come together.

Would really appreciate some suggestions on a good volume potentiometer or attenuator.

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Old 22nd January 2012, 01:09 PM   #487
nightanole is offline nightanole  United States
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DACT Type 21 Stepped Attenuator Potentiometer 50K 300B | eBay
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Old 28th January 2012, 04:31 AM   #488
John L is offline John L  United States
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You know, what's 'funny', as in strange, or sad depending on the thought, is that I am playing catch-up on this rather extensive thread, and I am going through all the trials and tribulations of bringing this amplifier to fruition.

But at the same time is the depressing knowledge that George is going through a trial in real life, in which loved ones are passing away, but doing so in one of the worst possible ways. Cancer is hell, and it is every bit as taxing on the family members as it is on the person who has the cancer. I can actually feel the exhaustion and fatalism of having to place one foot in front of the other, and not allow depression to get the best of one's self.

I read members offering prayers and condolences, and knowing they are actually over two years old, I still am experiencing the same emotions in real time, knowing that I am a day late and a dollar short here.

I am trying to eventually catch up with things, but in the meanwhile, I'll continue to empathize with everyone, and especially George and his wife, as they have no choice but take these handicaps in stride.

At the age of 67, I am always acutely aware of my own mortality. My 91 year old father passed away from alzheimers two years ago, and my 89 year old mother will soon be unable to care for herself. Its so depressing, knowing that as one's parents leave us, we will be the next ones in line, unless we check out ahead of time.

George, all I can say is that I hope that your inner being will be forever sunny, as with the state where you live, and all you have had to endure of late will pay dividends later on down the journey called life.

Sorry to interrupt everyone's train of thought, but I just had to say how much I am empathizing with events here.

Now, If I can just find a project I can get to work, so I can pass it on to my eleven year old grandson, and give him the opportunity to one day learn to enjoy this very hobby we all enjoy so much.
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Old 28th January 2012, 08:13 PM   #489
John L is offline John L  United States
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Ok, I have finished plowing through this thread a bit more quickly than I had anticipated. I remained up until 3AM, and got up early, and finished it. So far I have managed to take in a lot of information.

However, there is so much variation to things that any beginner(of which I am one) would be totally confused with all the things bouncing around. I've figured out that there are some things that are bounced around, but not written in stone for everyone else. Things such as:

1. Cost of the kit comes up first.

Cost of Kit, including PCB, and shipping - $108.00. Mail it to George at his home address.

That's a great price. Unfortunately, its not mentioned enough to get everyone's juices flowing IMO. This is indeed cheap compared to what else is out there. If this was in large lettering and in front of people's faces all the time, a serious builder would jump on it immediately, assuming the process is clear and concise. Just a suggestion, but perhaps I am looking for love in all the wrong places?

2. Also, there are different makes and brands of transformers being thrown around. So far, I'm settled in on Edcor, and don't mind waiting for them to be custom wound for me. Somehow I like the idea of having something done for me on an individual basis.

Zman has gone with the following. But I have read other different ones batted around. Which power and OutPut trans are really the best over all?

But Ian, in Canberra, used the Antek 2T-300, for his power trans. At $36 its cheaper than the Edcors, but for continuity I believe I'll stick with an Edcor.

3. And schematics, there are several floating around. One has little parts and huge distances between them, causing the viewer to have to scroll back and forth, without being able to view the entire schematic easily.

Ian has his own, which is more traditional, and much easier to interpret. But is it current? I'm just asking.

In other words, which one is the most accurate, easiest to read, and officially sanctioned?

4. Which 6BQ5/El84 is best and easiest to obtain? I think there is a consensus that the JJ brand(formerly Tesla) is the one to use. Is that correct?

Hey, I have a Czech SKS sitting down in my basement shop, and it beats the hell out of anything other communist block makers came out with. If they make some of the best firearms in the world, then that tradition must also have rubbed off on their electronics making.

If there is another 6BQ5 that is also part of the 'must have' variety, I'd like to know that too.

For most of you, this point I'm at is beyond you already. But for beginners, such as myself, we probably need some rock solid base point from which to begin. Things like total cost of the kit, bullet proof schematic, transformers that are a unanimous choice(well, almost anyway), tubes that are reasonable, easy to obtain, and perform when stressed with higher voltage.

There are other things that are not at the top of my 'gotta know immediately' list, but the things above are absolutely required if someone new to the genre is going to jump in and create a work of audio art.

I know it looks like I am complaining, but I am way down here at the beginner stage, and really want to move up into the "been there, done that" phase. I just need some positive direction, and the old military abbreviation of KISS works best for me.

Soo, I'm hip with the price. If there are kits left, count me in.

What Edcor transformers will best suit the project?

Which schematic is the best one to use?

Which tubes should I go with, and where can I get them without having to look under all the miscellaneous things lying on top them?

Again, thanks up front for everything. I haven't had a lot of sleep, and I will be fine tomorrow. I just need to keep things simple because my brain is filled with all sorts of unrelated things, such as space elevators. I know, what do space elevators have to do with tube audio? Its just one of the tunes that is constantly playing in my mind, and won't go away. And that is only one of many more.
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Old 28th January 2012, 09:41 PM   #490
brucetassin is offline brucetassin  United States
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Hello John L

Welcome. I will try to add some clarity.
1. you got that down OK
2. ZMAN is not in the USA so he has to use 220VAC on the primary of the
Power transformer. You could use the XPWR008-120 for power...the CXPP25-8-7.6k if you only have 8 ohm speakes or CXPP-25-MS-7.8K if you want multi output taps

3. All the schematics are the same, just drawn different.
4. read the SIMPLE PP online manual for info on tubes, transformers, caps and resistors.
Simple P-P Manual
Hope this helps
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