John's Build Pics

For the serious and not so serious in audio: DoItYourself and Tubes (SET, PP, Vintage).

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John's Build Pics

Postby johnravacio » Sun Jun 28, 2015 10:15 pm

After more than two years on my tube journey, I think it's about time to give back to the DIY community and share my experience. Hopefully this will inspire individuals who have zero knowledge about tubes to start their own tube journey as well.

What's up with Ravacio Amplification?
My son asked me about that last year (he was 9 years old then) and I joke at him saying "that's the seal of awesomeness" hahha Seriously, it would be a good idea for children to see Daddy's handmade equipments at home. Who knows it will inspire them to become Artisans when they grow up.

I'm not selling my amps or my services. I may have advertised the parts I have used one way or the other. Just ask pricing directly from my sources.

How did I start my DIY endeavors?
As early as 2nd year high school, I built my first amplifier using AN214. Although I didn't understand circuits fully at that age I was a persistent little dude who wants to build things from ground up. Somehow, this interest has faded and I then took Computer Science when I went to college. Thus, the last related subjects I took about circuits were General Physics and Logic Circuits and switching.

Fast forward 21 years later from my last build, I started building guitar effects pedal and finally bumped into a starved plate designed overdrive pedal "Matsumin's Valvecaster". From there, I hangout at Philmusic's DIY thread and Elab and started to ask questions. If you look at my posts, I never knew or remember what a voltage divider was way back 2013.

Thanks to the legendary Tony who has been very active and helpful to the DIY community.

What's expected on this thread?
Well previous, current and upcoming build pics and a small write up.Circuit Analysis, and Design Reviews will still be at Elab. The write up may contain what was good and what needs improvement for each build. That way, new DIYers may learn from it.
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Re: John's Build Pics

Postby johnravacio » Sun Jun 28, 2015 10:15 pm

Single Ended 808/811A Monoblocks

.... drum roll...... tada!!! This is my latest build. It uses a 1930's transmitting triode 808. A switch is also provided to toggle from 808 to 811A.

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Brief Overview

I wanted to gain knowledge and experience on Class A2 amplifiers as well as zero-bias type of tube. In the absence of an inter-stage transformer, I initially thought of using 6EM7 to achieve a positive grid for 808 or 811A tubes.

After going through discussions with Tony at elab(see link below) and readings from the internet, I finally came-up with using 717A as an Input tube, a triode connected 6V6 to provide a positive grid voltage and current to 808/811A tubes.

Full Discussion at: http://www.elab.ph/forum/index.php?topic=34991.1740

Output Transformers

Who doesn't know Edrel's Irons(AT&S) and the quality it has? This build uses an SE 15 Watt OPT which has an M6/Z11 core of 1 1/4 X 1 1/2(inches). Primary Impedance of 3,500 Ohms with Ultra-Linear(which I didn't use in this circuit) and a Secondary Tap of 4, 8 and 16.

Power Transformers and Choke

I tried to bring down the cost at a reasonable level because I have 5 other builds to fund but I'm not selling a single one of them. I'll wound my own power transformers and choke for the upcoming projects. ( :P committing something publicly will most of the time gets a job done). These Irons are M50 which runs hot if not properly compensated via specifications.

Power Transformer specifications:

Secondary:
320-CT-320V @ 200mA - I'm using it about 120mA only.
7.5V @ 6A - Just about what I need to supply the Heaters of 808 which is 7.5 @ 4A FW Bridge.
6.3 @ 2A - I'm using it at about 675mA for 6V6 and 717A heaters

Choke is 1H 200mA (Appproximate since this was measured at about 2H without a load)

These Transformers came bare so I had to put some flux band and paint the end bells. I used a 100W Soldering Iron so the solder was cold and messy. (It needs at least a 150Watt Soldering Gun to install a flux band).

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The Power and Choke is wound by Mang JV. His shop, is located at inner part of Main street of Paco Manila. He's been supplying transformers to guitar amp DIYers at Philmusic.

Layout and enclosure work

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Front and Rear View

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Gut Shots

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Below the sockets of of 717A Tube

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Below the sockets of 6V6

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717A Input Tube

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What's up with those transformer wires? Why not cut them short?
Re-usability. The tubes I'm using are very rare. Ones they go or you run out of tubes, you can easily re-use your transformers into another amp.

In action

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Testing and Final Configuration?

I only have 2pcs of 808 tubes(the rest are 811A) that's why I was aiming for longer tube life. At initial startup, 808 tubes have plate voltage of 375, plate current of 60mA, grid voltage at around +20. Both tubes are dissipating at only about 22.5 watts. From Tony's advice, I could still push it to about 100mA or around 40Watt dissipation and still get a reasonable tube life.

On the 2nd day of testing. I tried to increase the Amps overall B+ by adding a parallel resistor to the existing B+ dropping resistor. Now I'm getting a B+ of 400VDC. I've tested back both 808 tubes at 1ohm cathode resistance. One 808 can dissipate at a maximum of 35 Watts (plate voltage at 390 and plate current of around 90mA, while the other tube is only at about 29watts. Not. sure if it's gassy or just have low plate dissipation. I've swap them too and got the same results.

Now, I have them both dissipating at about 29Watts per tube and just have to live with it for the meantime. When they retire, I'll replace them with 811A.

How does it sound?

Wifey said: "I like that I'm hearing percussion in just the right amount. Cymbals are sprinkled across but doesn't dominate. There is so much clarity in the vocals section it feels like the singer is in front of you. Lastly, the bass feels so smooth that I would like to assume the recordings had fret-less bass on them."

I say, this amp is a very sweet sounding amp. The likes of 300B. This is very good when you're listening to bossa nova, smooth jazz and ballad music. Since I listen mostly to Rock music, I tend to like the dynamics that Tetrodes and the Pentodes have. I played Reggae music on this amp and the bass sounded like a fret-less bass with long sustain. It's supposed to be tight and for Rock a bit punchy. But the Mids and Highs are sparkling.

Well, at the end of the day, the Wifey is very happy with the sound. I wouldn't have to argue with that wouldn't I? :P

Thanks also to Paul Chin for this wonderful Anthony Audio Gold Titus BS. It really brings out the beauty of the amp :)

Schematic

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* All 22uf Capacitors were replaced with 47uF

* B+ dropping resistors have an effective resistance to 250ohm. In my build, I've installed 2 parallel 1K plus a 500ohm resistor. Installed the 500ohm resistor at the final tweaking.

* Bridge Rectifier right after the 7.5 secondary tap. Note that 4A is wrong and you need 6A.

Acknowledgements

This amp could not be made without all the advises from Tony Tecson. Thanks for always being there.

Edrel and his irons. The amps sound would not be as good as now without AT&S OPTs.

Gerry Sta. Maria. Our regular tube pimp in the DIY community.

To my best ever sound critic, my wifey :P

Reference Circuits
http://www.single-ended.com/direct811.htm
http://park21.wakwak.com/~eyp/jk1eyp/amp/811A/811AS.htm

What's next?
A lot of builds :) but we can't get to the bottom of this journey until we know how to wound our own transformers. So I'll stop building for a month or two and would my own transformer.
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Re: John's Build Pics

Postby babydoc » Mon Jun 29, 2015 7:58 pm

Thanks for sharing. Congrats. Ganda ng build
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Re: John's Build Pics

Postby johnravacio » Mon Jun 29, 2015 10:55 pm

babydoc wrote:Thanks for sharing. Congrats. Ganda ng build


Thanks for the complement babydoc :)
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Re: John's Build Pics

Postby detubo » Mon Jun 29, 2015 11:56 pm

8) bravo! maybe we can view and listen to it at the Nov Hifi Show 2015?
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Re: John's Build Pics

Postby Mamimili » Tue Jun 30, 2015 12:44 pm

Tubes must be in the genes over there!
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Re: John's Build Pics

Postby johnravacio » Wed Jul 01, 2015 9:51 am

detubo wrote:8) bravo! maybe we can view and listen to it at the Nov Hifi Show 2015?


Thanks detubo, heheh we'll see :)

Mamimili wrote:Tubes must be in the genes over there!


Thanks too! this is my 8th build. I've been through not so successful builds then. I'll post them sometime so that some people can learn from it :)
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Re: John's Build Pics

Postby Jon Agner » Thu Jul 02, 2015 7:31 pm

Hoping to read more updates from your tube amp builds :) Its always nice to read anything DIY :)
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Re: John's Build Pics

Postby johnravacio » Sun Jul 26, 2015 10:58 pm

Jon Agner wrote:Hoping to read more updates from your tube amp builds :) Its always nice to read anything DIY :)


Thanks Jon :)
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Re: John's Build Pics

Postby johnravacio » Sun Jul 26, 2015 11:00 pm

My first DIY Power Transformer

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I follow a personal rule, "Thou shall not haggle over a handmade product. Paying the asking price of an Artisan, is a form of respect.".

Now, let's see what we are paying for:

Direct Cost
* Cost of materials used to build the product.
* Direct Labor Cost
* ... and the list goes on


Yet, it is so very comforting to be fearful or lazy and just simply pay for someone else to do the job. But what am I missing? Well unfortunately, almost everything that's not the obvious. Like the following Indirect Cost:

* Time and effort to acquire knowledge and skills to build a product.
* Cost of failures, frustrations and successes along the way or the Artisans experience.
* Time and effort in planning and designing
* ... and the list goes on

More importantly, where's the Kaizen(Continuous Improvent) in there? I've been building tube amps for the last few years but never built a transformer.

Although I have expressed intents to wound my own transformers more than a year ago, I never had the courage to build one. From a DIYers perspective, the experience that we get from these activities are the things money can't buy. But going through all those activities is the ultimate way to go.

Actual Construction[/size]
For this build, I've only used M50 or also known as Deeco Cores. That is because my expectation is that it will have a 50% chance of failure. I'll just use a better core the next time around.

"You have to let it all go... fear, doubt and disbelief" :)

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Winding Setup

I don't have a pulley so I have to use Dumbells as pulley. At this point it's 100 turns Primary Winding at 100 Turns... 485 turns nalang for the primary :)

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Primary Winding at 300 Turns... Pwede naman mag-order kay Edrel, sa kanya mo nlng ipagawa >:D . Sarili mo lang kalaban dito.

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Primary Winding Done! Primary and Secondary Insulation

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In terms of safety, this is the highest priority. I had to stop at the primary winding because it's painful to the hands.

HV Tap

This was done few days after I wound the primary winding. Enough days interval for my hand to build muscles. When I wound the secondary, it's no longer painful to the hand.

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There where imperfections on the winding because the layers were not fully flat
[img]https://farm1.staticflickr.com/437/19836077988_64ebe5de6a_c.jpg][/img]

Here at 500 turns still struggling to make it perfect without spaces between the wires

HV Tap Done
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All windings done!

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Placing of Iron Sheets - After I dipped the coil into a varnish and dried it for few days

The coil was dipped into a varnish. I only have 500ml of varnish at the moment so alternatively I have to paint the EI Core with Oil-Based paint (Enamel) to prevent EI Core vibration or mechanical hum. The best practice is to dip the whole transformer not just the coil.

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Painted the EI Core with Enamel

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The transformer is complete, let's test it.
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[size=10pt]Measurements[/size]


HV Tap measured at 302VAC - Target is 290VAC @ 414mA

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Tube Rectifier Tap measured at 5.7VAC - Target is 5VAC @ 3A

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Heater Tap measured at 6.9 - Target is 6.3 @ 6A

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What's brewing?[/size]

The finished transformer will be used for an SRPP-LTP driven 829b Push-Pull Amplifier.

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Thanks to Tony for having this very informative thread at elab: http://www.elab.ph/forum/index.php?topic=17495.0
Last edited by johnravacio on Sun Jul 26, 2015 11:27 pm, edited 1 time in total.
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Re: John's Build Pics

Postby johnravacio » Sun Jul 26, 2015 11:11 pm

Design as Built

Safety Note: Transformers for Tube amplifiers contain lethal voltages, often several hundred volts, which will leave burnt entrance and exit wounds in skin. In addition to burnt skin, these voltages can also cause permanent physical damage and death.


Tube Amp Power Requirements

Primary: 230VAC @60 Hz

Hybrid Rectification on HV using Fullwave Bridge Rectifier then 5u4G Rectifiers

* B+ - 400VDC @ 230mA
* Heater tap - 6.3VAC @ 6A
* 5U4G Heater tap - 5VAC @ 3A

Power Transformer Requirements

Primary: 230VAC @60 Hz
Secondary:

290 VAC @ 414mA (non-center tapped)
6.3VAC @ 6A (We will use 6.8VAC @ 6A for computation)
5VAC @ 5V (We will use 5.4VAC @ 3A for computation)

1. Compute the Output Power

290 * 0.414 = 120.06
6.8 * 6 = 40.8
5.4 * 3 = 16.2
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Pout = 177.06 VA

2. Compute the required Input Power
Reference: http://www.elab.ph/forum/index.php?topic=17495

177.06/0.6 = 295.1
Where: 0.6 (Tony's recommendation when using M50 or Deeco Irons).

3. Compute the Core Area
Reference: http://www.elab.ph/forum/index.php?topic=17495

CA in SQ. INCH = SQRT(295.1) / 5.58
3.078 SQ. INCH

Commercially available bobbin: 1.5" X 2" = 3

4. Compute the Number of Turns in the Primary (Np)
Reference: http://www.elab.ph/forum/index.php?topic=17495

Np = 1750/3
= 583.33 or 583 Turns

Where: 1750 is Tony's Derived Constant

5. Compute Current in Primary (Ip)
Reference: http://www.elab.ph/forum/index.php?topic=17495

VA=(5.58 * Core Area)^2
=(5.58*3)^2
= 280.2276

Ip = 280.2276/ 230VAC
= 1.218 Amperes

Best wire gauge based on wire power handling: AWG #21 but in order to fit into the bobbin, I used AWG #22 instead.

6. Compute Turns per Volt
Reference: http://www.elab.ph/forum/index.php?topic=17495

Turns per Volt=(1750/3) / 230VAC
= 2.5391 or 2.54

7. Compute Turns per Volt in the Secondary

Ns1 = 290VAC x 2.54
= 736.6 or 737 turns

Best wire gauge based on wire power handling: AWG #25 but in order to fit into the bobbin, I used AWG #26 instead.

Ns2 = 6.8VAC x 2.54
= 17.272 or 17 turns
Best wire gauge based on wire power handling: AWG #14 but in order to fit into the bobbin, I used AWG #16 instead.


Ns3 = 5.4VAC x 2.54
= 13.7 or 14 turns

Best wire gauge based on wire power handling: AWG #17 but in order to fit into the bobbin, I used AWG #18 instead.



8. Determine Bobbin Width
Reference: http://www.elab.ph/forum/index.php?topic=17495 -> Page 77

= 2.25" (2 1/4")

9. Determine Bobbin Height
Reference: http://www.elab.ph/forum/index.php?topic=17495 -> Page 77

= 0.75" (3/4")

10. Determine Winding Width(Ww) and Winding Height(Wh)
Reference: Alexan Electronic Enthusiast - Volume 4 - Transformer Design

Ww = Bobbin Width - 2(margin) - 2(bobbin allowance)
= 2.25 - 0.25 - 0.064
= 1.936"

Wh = 0.75 * 0.80
= 0.6"


11. Compute Primary Turns per Layer
I've used Enamelled Inch diameter for AWG.

If AWG #22 then 1.936"/0.0266" = 72.55 turns per layer

No. of Layers (Primary) = 583/72 = 7 layers

12. Compute Secondary Turns per Layer
I've used Enamelled Inch diameter for AWG.

S1 Turns per layer

If AWG #26 then 1.936"/0.0169" = 114 turns per layer

No. of Layers (S1) = 737/114 = 7.28 or 7 layers

S2 Turns per layer

If AWG #16 then 1.936"/0.0524" = 36 turns per layer

No. of Layers (S2) = 17/36 = 1 layer

S3 Turns per layer

If AWG #18 then 1.936"/0.0418" = 46 turns per layer

No. of Layers (S2) = 14/46 = 1 layer

13. Compute Winding Buildup Total for primary and secondary windings

Inter winding insulation = 0.002"

WB Primary = 8 layers * (0.0266 + 0.002)
= 0.2288"

WB Secondary 1 = 7 layers * (0.0169 + 0.002)
= 0.1323"

WB Secondary 2 = 1 layer * (0.0524 + 0.002)
= 0.0544"

WB Secondary 3 = 1 layer * (0.0418 + 0.002)
= 0.0438"

WB Total = 1.1 * [0.095 + 2*(0.002) + 0.22288 + 0.1323 + 0.0544 + 0.0438]
=0.5623" still within Winding Height(Wh) which is about 80% of the Bobbin


You can compute the MLT for each wire to get how many Kilograms of copper wire you need. In my case, I bought 1/2 kgs for each wire gauge I need.
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Re: John's Build Pics

Postby Mamimili » Sun Jul 26, 2015 11:46 pm

I think Tony also posted a few years ago about the cost of DIY.
Anyway :clap: :clap: i agree about not haggling over the price, most times you are get more value and there is always the pleasure of ownership of a unique piece which is hard to match with mass produced goods.
Which is why i proudly use equipment made by Hypertriode and Trodt Audio.
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Re: John's Build Pics

Postby johnravacio » Mon Jul 27, 2015 1:27 pm

Mamimili wrote:I think Tony also posted a few years ago about the cost of DIY.
Anyway :clap: :clap: i agree about not haggling over the price, most times you are get more value and there is always the pleasure of ownership of a unique piece which is hard to match with mass produced goods.
Which is why i proudly use equipment made by Hypertriode and Trodt Audio.


Thanks Mamimili :) Oh yes those two great builders will give you the sound perfection you need, you should be proud. Those are the people including Tony and Edrel who has inspired us newbies with our DIY endeavors.
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Re: John's Build Pics

Postby johnravacio » Mon Aug 03, 2015 11:16 pm

A tour at AT&S factory

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I'm a fan of AT&S transformers(as seen on the picture above, :) I have a few pairs of OPTs). Over the weekend I had the privilege of visiting Edrel's manufacturing center at EPZA Cavite.

Let us see what and how AT&S transformers are made and why they're world class.

1) Transformers are conservatively designed, that means they're not squeezing in more watts per kilogram. Effectively for power transformer they run cooler and for OPTs have greater frequency response

2) High-end magnetic wires are carefully chosen and used based on current density, thermal ratings, and other quality factors.

3) These are SET OPTs for 845 in the making. Yes, that's 24 interleaved layers of perfectly wound wires of AWESOMENESS.

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4) Computer controlled winding machine for accurate number of turns. A wire tension tool is pulling the wires from the bobbin and the spool so that every turn has accurate tightness. Bifilar winding is done by hand instead of the tension tool.

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5) Japanese Z11 EI Core. Yes, simply Japanese greatness.

6) High-end Insulating materials. Nomex, Teflon. etc. The works! These materials are quite pricey.

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What's the other side of the tour?
Here are some M18 EI Core for some serious Power Transformer Winding.
All these quality parts came from Edrel, get yours now :P
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Re: John's Build Pics

Postby johnravacio » Sun Apr 10, 2016 10:20 pm

829b Push-Pull Amplifier

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Overview

The thing about DIY is that you can do it in your spare time. Yes, it took me about 7 months to finish this amplifier. But it was all worth it. I had doubts on my design, thinking it will not work the way I want it but it turned out to be awesome.

On top of the laws (Ohms, thermodynamics, etc.) that we have to follow, designing an amplifier has subjectivity as well. And the designer has to balance things or be biased on some aspects of it. I guess an analogy to this is a man looking for a woman. At some point he has to determine if he wants to have a high performance woman at a high cost or a woman with moderate performance at a moderate cost. Performance and cost are most likely to go together but in worst cases it could be a low performance at a high cost. John, what are you talking about? Amplifiers are our mistresses... Well that's what I was suspecting hahahha :)

But anyway, this amp was loosely based on Seiichiro Suzuki 829b Push-Pull amplifier. However, instead of using a cathodyne phase inverter, I took the route of using LTP. Many amps like Audioromy FU29 have already used Cathodyne Phase Inverter. The main advantage of LTP over Cathodyne is that LTP is very linear. The 829b needs to be driven by low impedance output and this LTP using 12AU7 is a good candidate.

Playing safe with the input driver design, I have used a 12AT7 SRPP like you usually see on HIFI amps. Amplifiers using SRPP were called "distortion less audio amplifier" way back in the 50's.

The Output Stage uses the exquisite 829b a double tetrode tubes used in VHF radios in its hay day. I have been collecting a few of these tubes since about two years ago. And prices including the Russian GU-29 soared up on ebay after Cayin and Finale Audio made their amps using these tubes.

...And here's how I did it.

Power Transformer Winding

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Enclosure layout, Drilling and Paint Job

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Point-to-Point - Look mom, no PCB

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Gut Shot
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Cathode Bypass Capacitors
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HV, Bias and Heater Supply
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Back Panel
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Side-by-side with my 6V6 Push-Pull amplifier
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In Action
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12AU7 Glowing
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829B Glowing
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Sound Review

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Wifey's Review
Listened to mostly Crossover Jazz
This design is one of those that allows one to listen to all instruments/frequencies in a song. In fact, it was the first time I noticed a husky voice from a song I've been hearing forever from radio stations (okay, it would be a little too unfair to compare far too distant sound qualities, but...) But even if you are hearing these instruments and voices all at the same time, they do not compete with each other for your attention. What each does is do their part, and complement each other, like how a good sound engineer should arrange a song.

My Review

This amplifier sounds like a MOSFET in a tube. Clear, Punchy and Lively. I have listened mostly to 90's music to test this amp and turned out awesome. I could say this is not a Luscious kind of amplifier.

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Acknowledgements

As always, this amp could not be made without all the advises from Tony Tecson. I am and the rest of the DIY community is thankful of having you around.

Edrel Sison for bringing the best goddies we could have for our builds.

Gerry Sta. Maria for the driver tubes.

Enrico Resurreccion for the wood works.

People at Elab and fb group "POWER AMPLIFIER & ELECTRONICS CIRCUIT TECHNICIAN FORUM" for continuous technical discussions :)
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Re: John's Build Pics

Postby johnravacio » Tue Nov 01, 2016 10:46 pm

1625 Push-Pull Amplifier driven by 6N9S-6N8S(Concertina phase inverter)

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Overview
After 3 years on my DIY Audio journey, I finally made my own Output Transformers. Looking back wasn't that easy. I'm not intrinsically a patient man to take-on the complexities of winding an Output Transformer. I have to grow my hair literally and extend my patience a little bit. Girls called the process "Tiis Ganda" hahahah ;)

The design was pretty much similar to the OddWatt but instead of using 6l6gc, I have used 1625 which is very similar to 6L6 but uses 12.6V on the heater.

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Winding the Output Transformers

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These OPTs were design to run at 40W @ 20Hz with an Impedance of 8K. But this amp is only running approximately at 25 watts per channel. This OPT uses an interleaved design of 5 primary winding sections and 3 secondary winding sections. Sounds complicated? Yes, for first timers like me it is but maybe I'll get used to it as time goes by and more practice.

Draft paper for inter-layer insulation. Without those, wires will fall in between the previous layer.

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At this point, 1st primary winding sections were done. Side-by-side comparison for each section to ensure consistency between both OPTS.

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Double NOMEX insulation plus Kapton tapes at the side.
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1st secondary winding section were done. This is the 16 ohm tap.
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2nd primary winding section continuous.

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Done.. One layer of Draft Paper and then Nomex tape
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Bifilar winding on the 4Ohm secondary winding section.
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Done with the 4Ohm secondary section
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Another primary winding section
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Done with the primary section
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After 12 days of OPT winding or 6 weekends windings are finally done

and time to put those eyelets.

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Impedance testing with a Variac
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Varnish Dipping and Sun baking
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Winding the Power Transformers
After winding those OPT, it makes Power Transformer a walk in the park :)
Starting off with the primary winding
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Secondary Windings
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HV tap done
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Meanwhile, Transformer covers are painted with Hammer tone paint
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Heater windings done
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Ready for Testing
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Enclosure works
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Enclosure done and painted.. Installed the faceplate
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Wirewound pots for balancing the cathode current
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70% done
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All done... I have to wait another weekend before doing the actual test.
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Actual Testing
After I turned ON this amp, I didn't have much problems and most voltage measurements are as Expected. After one hour of playing at full volume, my Power Transformer temperature rises from 30 degrees to 47 degrees Celsius. Although a temperature rise of 17 degrees Celsius is okay I have tried removing the CCS using TL783 and changed it to Cathode Resistor with a bypass capacitor (blue one on the picture above). After listening to it, I have decided to keep the Cathode Resistor.

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Sound Review

It's been a long write-up so I'll make this short. The sound sits between being punchy and luscious. Just exactly the right tightness but not punchy. It has the clarity and warmness of 6L6 tubes. Tested several records on this amp from Louis Armstrong, Earth Wind and Fire to the heavy metal ACDC, Megadeth and Pantera.

Acknowledgements

Big Thanks to Tony Tecson for our never ending design reviews and discussions at elab.

Many Thanks to Edrel Sison for bringing-in the best quality materials for our builds.

Gerry Sta. Maria for these lovely 1625 bottles.

And to my lovely Wife for her never ending support for my DIY endeavors.
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Re: John's Build Pics

Postby dimfer » Sun Nov 20, 2016 6:37 pm

thanks for sharing your builds. I hope to get to listen to them someday
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Re: John's Build Pics

Postby johnravacio » Mon Feb 06, 2017 7:36 pm

dimfer wrote:thanks for sharing your builds. I hope to get to listen to them someday


Thanks dimfer..yes hopefully sometime :)
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Re: John's Build Pics

Postby johnravacio » Mon Feb 06, 2017 7:36 pm

750Watt Isolation Transformer Project


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For DIYers like me Isolation Transformers are a MUST for safety reasons. Also, I was inspired to create my own after seeing Tony's isolation transformer during the HiFI show.

Isolation transformer generally has a winding ratio 1:1 with a Faraday Shield to block capacitive coupling between the primary and secondary windings. However, for this project it is not exactly a 1:1 ratio because the input voltage is computed at 240 and the output voltage is 220V. Mains at our home normally run 237V during daytime and 244v during night time. That drives the reason why I decided to make it 240->220. Another advantage of doing it is when the main voltage surges about 10 volts my output will only go up to 230 Max.

External design
My day job mostly deals with Operator Interface software applications for industrial plant. Interface designs are geared at displaying software representation of Analog panel meters which displays measurements (e.g. flow, pressure, etc) which is awesome. But this inspires me to use the real and tangible panel meters for this project.

In almost all of my builds I liked to use only 3 colors.. In this case Silver, blue and black. This keeps the appearance clean and neat. Color combination is also critical.

Transformer winding

Primary Winding
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Faraday's shield

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Secondary Winding

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Transformer work done

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Enclosure Work

Got this custom made from Unity Metalworks at Sta. Cruz Manila (2mm)
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Here's a snapshot of my newly acquired drill press.
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Drill bits and Personal Protective equipment
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52mm hole saw
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Drilling done
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Paint Job

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Final build

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Testing
This shows that when the line voltage is 242 the output is 222volts. There's always a 20volt difference between the input and output. At almost full load voltage drops around 6 volts.

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What can be improved?
I had a chat with Edrel and got his advice to make a multi-tap primary the next time around. It's always a good idea to change the ratio when more power is needed.


Acknowledgements

Well I'd like to thank the usual suspects when in comes to DIY. That is Tony Tecson and Edrel Sison. And mostly to my wife who checks the visuals in all my builds.


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