On the left is the passive preamp, sitting on top of Mr Ew’s excellent Rapsberry Pi – AD1865 DAC. On the right is Anna! An All Russian Push Pull amplifier.

The passive preamp is a restacked Intact Audio autoformer. By itself, Dave Slagle’s autoformer is already excellent, but restacked for more inductance to fit your system, that’s what a proper DIYer should do!

Note below, wired with Elma switches. I bought these years ago, back then could only afford the 12 steps… These switches are fantastic! The touch, the feel… it’s like Leica camera, you’ll understand if you are of particular vintage…

Here’s internals of Anna. It’s a heavy 2 chassis affair, done mainly because I want to hide the ugly power transformer and chokes inside. And also I don’t want anyone to accuse me of building a “lightweight” amp. Count the number of irons please…

Here’s a close-up of signal wiring. The iron arrangement… went through so many iterations before arriving at this arrangement. Mainly to minimize induced hum… Once it hums, it’s no fun… Resolving hum is just as fun as a root canal…

What is Anna? At first glance, looks like the Simple EL84 concept but instead of using differential long tailed pair as phase splitter, using iron here.

Driver stage is a plate choke loaded 6E5P. My previous experience with 6E5P wasn’t that good. Must have done something right this time… Circuitry wise, nothing special here, other than the 5 Schottkies at the cathode.

Next, it drives a center tapped choke. Yes, it’s an audio choke with its mid point tapped out. As this center tap is grounded, driving one end of the choke will induce an inverted signal at the other end. In other words… a phase splitter! It works very well here and I have no idea why we rarely see such design. So simple and elegant!

After that is our favorite SV83 in triode mode in Push pull fashion. All for a grand 4000 miliwats… Again, nothing special here…

So the magic is in the phase splitter. Push pull can be done right if you get the phase splitter right. None of that “push pull” veil here.

I would add that if you look at the music signal, every stage it sees lots of inductance.

From DAC output, it goes to an autoformer (an inductor with very high inductance ~200H)… Then to the 6E5P (high inductance on its plate 100H)… then driving another high inductance phase splitter choke (easily >100H)… then SV83… Output transformer (PP output transformers easily have >100H)…

Hmm… every stage it sees >100 Henries… Any idea what does it do?

Sorry, I’m not smart enough to tel you what it does. So I’ll just tell you what I hear here.

This is the most dynamic amplifier I have ever built. It’s only 4W but the dynamics, transients is striking. This raises a new bar to the word – realism.

Enuff said.

The post Anna – Push Pull done Right appeared first on diyparadise.

Now imagine 3!

Anyway, this article is supposedly a continuation of A Purist’ Wet Dream and The Purist’ Wet Dream Gets Wetter but I got to change to a more pedestrian title as if I were to continue along the same theme, it is actually bordering on obscenity…

From left to right, 6E5P, Sovtek 6C45Pi and Western Electric 417A.

In case you are wondering, I have been enjoying my Purist’ Wet Dream with below schematic.

Just a change of wiring to accommodate different tubes, and it’s all system go!

All 3 tubes run at 150V with 6E5P’s cathode at 3 Schottkies level while 6C45Pi and 417A sat at 2 Schottkies. Of course, as the latter 2 tubes are triodes, there is no 120 ohm resistor between plate and g2.

Here is my unscientific, humble opinion on its virtues.

So what does this tell you?

My choice of women sucks?

Who would have thought you could get 2 totally different type of sonics from one tube?

WE tubes are gifts from the gods?

At the end of the day, I don’t care. All I know is whom I want to hang out with. Sorry, girls.

The post Love Affair with Spuds – 6E5P, 6C45Pi and 417A appeared first on diyparadise.

I’m in sonic heaven with my new amp now!

Wait!

I don’t know about you but I’m certainly not like this. I know most folks would be satisfied with their tube amp after the first build but not me. I’m not like the 95% here. I’m an Alpha Diyer, I’m the top dog 5%.

But first of all, forgive me for I’m an uncouth fella. No, I don’t spout Byron, I don’t drink red wine or whatever the fancies that elitism hobbyists like audiophiles like to engage in. Instead, let me confess. I’m a pot bellied, hair receding, foul mouthed dude. Led Zep is my type of music and I love my brew of common man stout. In this regard, I’m the 95% Sir. Why heck, I even pick my nose in public. [*facepalm*]

An Alpha Diyer is always exploring ways to improve on his system. So much so that in the back of his mind, a trip to a hardware store, departmental store, IKEA etc is always an audio excursion.

And so, I’ll illustrate what an Alpha Diyer will do once he built his amp. And it’s certainly no lounging around.

But first of all, let me introduce you to the Expletive Factor. You know the reaction when the sound improved by so much that you JUMP (standing up doesn’t count) up from your seat and start spouting swear words, expletives… so bad that I can’t even write them here? (I still want this site to be family friendly, okay?)

What we are looking for is BIG XXXXing improvement in sonics. Not subtle changes that you have to A-B like hell, until your face looks like you are constipating to hear the difference. Imagine an improvement so great that you leap out off your listening chair and spew the most colourful language known to mankind!

Better still, if you swear words that aren’t in your daily vocabulary. That can only mean the sonic improvement is HUGE!

Okay, here’s what an Alpha Diyer will start off with.

Build the best power supply you have heard — Very High Expletive Factor
I mean it. The best power supply you have built, heard and optimized. Not because some dude (like me) said so. We all value different things in audio so it’s best to go back to your experience.

For me, I like choke input, lots of chokes, not too high capacitance and 100 Hz hum reduction via tuned choke.

I arrived at this supply after years of building tube amps. The 47uF caps are Solen metalized polypropylenes but the 20uFs are oil capacitors. Oh yes, the supply is HUGE, HEAVY and screams ALPHA all around. Notice there’s no electrolytics anywhere.

Move beyond simple self bias stage — Very High Expletive Factor
Initially I had a simple self bias stage at the cathode. However, you can’t move earth if you stop here. You got to experiment.

On another amp I built years ago, I used LED at the cathode and didn’t quite like the sound. The bass got too boomy. Looking back, it could be the speakers’ issue rather than the amp.

Anyway, for this mod, I’m using Cree Schottky diodes here, as illustrated by Maxamillion on Audio Asylum. 3 diodes gave me the cathode bias I need.

Optimize parafeed — High Expletive Factor
In my first build, I was using a 5k:8 parallel feed output transformer from Magnequest. The 4.7uF parafeed cap was optimized for bass response. A huge improvement over the initial 3.3uF.

As I was using 16 ohm speakers and I need a bit more gain from the tube, so I went for 3k:16 ohm trans also from Magnequest. Now the 4.7uF cap just doesn’t give me enough impact.

I don’t have any 6.8uF or larger caps. The next larger I have is a GE 17.5uF oiler so this went in and the bass impact came back after some running in.

Less Gain Stages — High Expletive Factor
Every gain stage somehow changes the signal. So if you could get by with less, do it! The 6E5P could actually put out 1-2W of power but as my DAC only outputs ~2V, the output power delivered to the speakers is now only ~0.3W.

By right, I should put in another gain stage to squeeze out more power from the 6E5P but since my speakers don’t need much power, I could get away with this. So what’s wrong with 0.3W?

Optimize signal/return path — High Expletive Factor
This makes hell lotta difference! If you ever worked on PCB layouts on high speed digital designs, the phrases “short signal path”, “return path”, “ground plane” etc all carry significant meaning to you. I’m not smart so I suffered and learned the hard way before I learned all this and I’m still learning.

Okay, that’s all I have done so far. In the spirit of this article, I’m not done yet! To be tried in the near future…

WE coupling

Try other spud tubes
Top of my head, 417, 5842, 6C45pi, 7788… Actually I have all these tubes in hand…

The post The Purist’ Wet Dream Gets Wetter appeared first on diyparadise.

What happened? Well, you could see I’m still alive, kicking and soldering but more than that, I have spent more than a year improving on Discreet Monica.

I know, I know, I’m a pain in the arse but with each improvement, you learn a lot more. I improved on her layout, grounding and even incorporated a FPGA for signal processing capability.

Err, in layman’s term, I had to redo the PCB layout through a few revisions (very expensive process I tell you), learn a new (to me) programming language called VHDL (VHSIC Hardware Description Language but to me it means Very Hard Darned Language), program the FPGA to replicate what I had with 14 integrated chips previously, measure and hand match the high precision resistors (a royal pain I have to tell you) etc etc…

All this effort, so that she sounds better and she’s much easier to build. She definitely sounds so much better now but unfortunately, still tedious to build. Is there more to come? Sure there is! But save that for another day.

I then wanted to build a proper All-In-One system. You see, back when we participated in the KLIAV show way back in 2008, I built an All-In-One.

Back then we have the Monica3, Maggie, output transformer coupled 6GM8 and Charlize2 built in separate chassis and linked via interconnect cables, like a typical separate system.

Once built into a single chassis, the sonics gained a quantum leap!

Why so you ask? It could be lack of RCA interconnections, much shorter signal path and more crucially, the much much shorter return path (also known as GROUND) path between components. Simply put, the electrons travel in a much much shorter loop and they are happier :). And my electronics background tell me that the happier the electrons, the better the sound! And so it proved.

That was then, so I had to build something better today. Since we are going on a purist’ path here, might as well go all the way with just a single gain stage throughout the signal chain. And nothing is simpler than a one-tuber aka spud amp.

Over the years, have always wanted to build a spud and back then the popular tubes were 417, 5842 as well as 6C45. There are others but those are usually 2 stages in an envelope. I’m being purist here. I want ONE and ONE only.

The last few years, another tube gained popularity and it’s a Ruskie 6E5P tetrode. I learned a lot about this tube thanks to the fine work done by Bartola Valves as well as Romy the Cat.

Now this little fella is a like a super tube. Specs wise, everything rocks! So much so that I just have to build it!

Also, over the years, I have heard a lot about the parallel feed scheme. I’m not sure how many commercial amps out there have such a scheme. Just shows us hard core DIYers are more cutting edge than mainstream. Ha! So this is a fantastic vehicle to put in everything together.

And so, we have… A Purist’ Wet Dream.

The initial idea was to build this to be mounted on to a wall but since I’m a such a pain the arse, I just can not build a simple amplifier. So 2 power transformers, 2 power supply chokes, 2 plate chokes, 2 parallel feed output transformers and 4 beer cans oil capacitors later… this whole contraption is just too heavy to be mounted on the wall. So now it has legs and it’s going somewhere!

Input takes USB from your Music Machine be it Windoze or Mac and
Output goes to your speakers via the binding post

USB Input – Discreet Monica – modified Intact Audio Autoformer Volume Control – triode-wired 6E5P Magnequest Iron Parallel Feed Output – Speakers!

All in all, there is only ONE gain stage throughout.

Want to know more about this Purist’ Wet Dream? Stay tuned for the next article.

The post A Purist’ Wet Dream appeared first on diyparadise.