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PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=1232
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Author:  gofar99 [ 11 Feb 2019, 08:43 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

Ouch, check the value of that resistor. 40 volts across it would indicate about 40 amps going through that tube, not possible. So probably it is a a 1K not a 1R. Also verify that you have not attached it to the heater circuit which is the only place in the amp that might have that range of voltage. The voltage across the LM317 is in the correct range. Measure each cathode to ground separately and see if they are approximately equal.

Good listening
Bruce

Author:  gallileo1982 [ 19 Feb 2019, 07:04 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

Hi Bruce,
first of all I would like to thank you very much for all the help and advises here.
I'm not electronics nor ever electrician and Poddwatt is my first audio device I have ever built. Luckily I succeeded after some minor issues.
As to the last one, it turned out that 1R resistior wire was broken. I didn't noticed it before because it was in a heat-shrink sleeve.
Second issue was ground wire detached of speaker jacks.
So both have been fixed and additionally I added small computer cooling fan, because I have LM317 heatsinks inside chassis and it warmed up too much.

Finally I seat and listen the amp through old (1975) German Telefunken TL700 speakers and feel really touched by how my favorite music sounds! It's amazing, I have never heard so many details!
For all the Europeans interested it this project I would add, that EDCOR transformers are available in Europe by one of the German audio parts retailer. Please PM me for details.
I hope you don't mind if I post my built on one of polish audio DIY forums, obviously with reference to this thread and your project website?

Cheers:)

Author:  gofar99 [ 19 Feb 2019, 10:01 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

Hi, I'm glad you managed to solve the problem. Yes the Poddwatts are excellent sounding and one of my favorite designs. One of the goals of diy and indeed kits is to get quality electronics out to as many folks as possible. So I have no problem with you posting on another site. Most of my projects are spread out throughout a goodly part of the world on various sites already. One more posting may inspire someone else to jump into the diy field.

Good listening
Bruce

Author:  NiaDebesis [ 19 Feb 2019, 13:06 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

gofar99 wrote:
Hi, I'm glad you managed to solve the problem. Yes the Poddwatts are excellent sounding and one of my favorite designs. One of the goals of diy and indeed kits is to get quality electronics out to as many folks as possible. So I have no problem with you posting on another site. Most of my projects are spread out throughout a goodly part of the world on various sites already. One more posting may inspire someone else to jump into the diy field.

Good listening
Bruce



Hi, can you please answer to my questions in pg 63?

NiaDebesis

Author:  gallileo1982 [ 19 Feb 2019, 15:41 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

gofar99 wrote:
Hi, I'm glad you managed to solve the problem. Yes the Poddwatts are excellent sounding and one of my favorite designs. One of the goals of diy and indeed kits is to get quality electronics out to as many folks as possible. So I have no problem with you posting on another site. Most of my projects are spread out throughout a goodly part of the world on various sites already. One more posting may inspire someone else to jump into the diy field.

Good listening
Bruce


That's my goal, to share this project with other DIYrs as quite easy to built and great sounding.
Thank you :)

Author:  gofar99 [ 19 Feb 2019, 16:48 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

Hi, I didn't see them earlier.

"Hello I' am new in the forum, and I am very pleased to be here.
I am trying to build the Poddwatt series 2 and I have some question to ask for.

Q1 The 10uF cap is both to the two channels and is only one? And there are preferences about it? I have chosen a Mundorf oil cap
One capacitor is all that is used in this version I typically use Solon
In the dual mono block version that has two separate power supplies then two are needed

Q2 Does it matter if I use a output transformer fixed to 4 ohm? No, the amount of negative feedback will be slightly reduced, but since it is there for stability at frequencies way above the audio level it will not cause any problems. The amplifiers will operate fine without any NFB. Some folks like it better without the NFB.

Q3 The heater circuit, pins 9 of the 5751 valves are floating? (it's the center of the heater)
Yes they are left floating

Q4 The DC reference for the heater circuit can be taken from one of the two 200V regulator? Or I have to make a third regulator?
Either one as there is nearly no current draw

Q5 The SSL, what is purpose? I don't understand the purpose of 3 led in parallel, and is not recommended to add a backverse diode in parallel to each led? to reduce reverse current
The three LEDs are indicators of what input selection was made. They are optional. The voltage across the LEDs is DC so there should not be any reverse flow. Protection diodes are thus not needed.

Q6 For the power supply I am ordering a PCB, is recommended to do the same with the valve circuit?
I don't know of a source for such a PCB. All my designs can use perf boards, preferably with solder through holes

Q7 The ground buses, I ground all the components of the power supply and the I connect it to the anti ground loop, I ground all the signal components, and then I tie them both together at the input connection?
I use a single ground buss wire at the input jack grounds (not to the chassis) and run separate grounds from each section (power, signal etc)

Q8 As potentiometer a 100+100K by alps is good? (I don't know this brand)
Alps are common and pretty good. They use conductive plastic elements and I have found them to last long and perform well. Other brands are fine, but avoid really inexpensive ones as they don't track well between the channels and can be noisy

Q9 The only connection that have to be made with shielded wire are, from jack to potentiometer (I don't need more inputs), and then to the potentiometer to the board?"
That would be correct. I generally shield any low level signal carrying wire that is over about 2 inches. Remember to ground only one end of the shield unless it is used as a signal ground wire. This could happen if there is no ground buss at the inputs and each one was brought in separately directly to the volume control.

Let us know if you run into any problems.

Good listening
Bruce

Author:  gallileo1982 [ 23 Feb 2019, 10:15 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

Hi again,
As I said curently amp performs very well. However I used there very common parts.
So I would like to ask which parts (I mean reststors and capacitors) have the highest impact on the sound quality? I want to replace them by some good brands.

Author:  gofar99 [ 23 Feb 2019, 15:34 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

Hi, The components that have the largest effect are the coupling capacitors, then the output transformers. If I had to upgrade anything it would be the capacitors.

Good listening
Bruce

Author:  gallileo1982 [ 25 Feb 2019, 12:56 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

gofar99 wrote:
Hi, The components that have the largest effect are the coupling capacitors, then the output transformers. If I had to upgrade anything it would be the capacitors.

Good listening
Bruce


Hi,
Are these 0,33uf and 2,2uf connected to the ground, right? The one 0,33uf between 5157 and EL84 also?
What brands and series do you recommend?
At the moment I have all 0,33 Russian PIO K42y.

Author:  ILoveHiFi [ 26 Feb 2019, 00:13 ]
Post subject:  Re: PoddWatt EL84 Push-Pull Stereo Tube Amp - Support Thread

ERSE Pulse X is recomended for low cost and top sound quailty, at this price point you get most worth of your money while being close to absolute best caps.
Any geniune metalised polypropene capacitors also work well for hifi, in genrall I think this is best bargin most quality per dollar.

I tried ECWFE and is really good, it beats a polar nichicon fine gold in all areas when used as input capcitor.
RS components you can but like $1 of goods but still get free shipping also fair price.

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