Happy Holidays and a Great New Year to All!

JE Labs Loctal Preamp

Motivated by Ding's octal version of the 834P, I quickly got my hands dirty punching out and painting a chassis. 

Loctal tubes

The concept of this project was to build a full function stereo preamp utilizing loctal tubes based on the schematics below.

Preamp circuit

!!!WARNING!!! 

The voltages found in this circuit can be lethal! 
Build at your own risk!!!

Power Supply

5AZ4 rectifier = 5Y3 on a loctal base

Line Stage

Zero feedback single gain stage direct coupled to a cathode follower line stage topology featuring the two medium-mu triodes below

The 7AF7 is very similar to the 7N7 and 6SN7
but has slightly less
transconductance and inter-electrode capacitance

7N7 = loctal based 6SN7

Phono

The stock EAR 834P circuit (above) used all high-mu 12AX7s with the second stage capacitor coupled to the cathode follower stage. While preparing this blog entry, I remembered that my dearly departed friend, mono aficionado Brian monofantastico Clark, grafted his own interpretation of an EAR 834P phono stage to his SE 801 mono integrated amplifier. He was an active participant in this discussion of 834P modifications initiated by Thorsten Loesch.

Ding's octal version of the 834P uses all 6SL7s with the second stage direct coupled to the cathode follower stage. Without ever sounding harsh, Ding's octal 834P sounded brighter and had a refreshing airiness in the high frequencies compared to my darker and more midrange oriented RCA derived phono preamp. Even if I never heard an original EAR 834P, I now have a good idea why it was received with great enthusiasm.  

7F7  = 6SL7 on a loctal base

Although the 7B4 and 7B6 are high-mu loctals, they are single triodes. AFAIK, the 7F7 is the only high-mu twin triode available in loctal and was the obvious choice for the 1st and 2nd stages of the 834P circuit given my chassis configuration.

Tube rolling loctal style

I've been tweaking and listening to this preamp for the past 6 months.

During my Dyna PAS hacking days, the 12AU7 always sounded gutsier in line stage and cathode follower applications than the 12AX7 because it had lower Rp and pulled more current. Thus, there was some room to voice the 834P circuit through the cathode follower section.

Warning: 7F8 is NOT plug-in compatible
with the 7N7 and 7AF7

I initially set up the phono section to use the unique 7F8 loctal in the cathode follower position, hoping that the 7F8's greater transconductance will produce a darker and more robust sound. But ultimately, it was the ubiquitous 7N7 (loctal 6SN7) that gave me the tonal balance I wanted, with the 7AF7 as alternate.

With an amplification factor of 48, the 7F8 may not have enough gain as a phono preamp with the RIAA EQ in the negative feedback loop. However, it was too much for a zero feedback single stage line amp.

Typically, I don't split halves of twin triodes for left and right channels. I made an exception in wiring this line stage so that I could exploit the 7AF7 vs. 7N7 comparisons and usage options.

My ears finally chose the 7AF7 as the voltage amplifier for the line stage. The slightly lower transconductance and amplification factor mimics the exotic tonal qualities of its grandad, the 76. Each half of the 7AF7 is direct coupled to half of a 7N7 configured as the cathode follower. This combination is as close as I could get to my 76/6SN7 line stage.

But don't limit yourself to this report, use it as a starting point for your loctal tube rolling adventure. 😉

Which is better?

or

Both are here to stay. 😎

🎅🎅🎅 Happy holidays and merry listening! 🎄🎄🎄

Line Transformers Redux + Art Dudley + AQ Dragonfly Black

My boring digital life

Tascam DA-P1
courtesy of pgr.tv

Probably the most significant digital audio gear I ever owned was the Tascam DA-P1 DAT recorder. This machine recorded my recitals, chamber music performances and served as a back-up and playback deck for my CD projects from the mid 90s until the early 2000s. It was rendered obsolete when HD based recording became the industry standard.

DAC in the Box
courtesy of Wiki Commons

I never invested in a high-end CD player. The most I ever did for CD playback was get an Audio Alchemy DAC in the Box fed by the digital output of a consumer grade Philips CD player. When the Philips CD player conked out in the early 2000s, it was replaced by a Sony DVD/SACD player.

Line transformers as Digital Sound Processors

Tamura line transformers

Ever since I inserted a pair of Tamura 600:600 line transformers as a digital sound processor (DSP) between the CD player/DAC and my preamp line inputs, I didn't see the necessity of upgrading the Audio Alchemy DitB. I don't know if this holds water but my empirical rational for this is, magnetic coupling filters digital artifacts and RFI noise from the DAC output, which is manifested as harshness to my ears.

Art Dudley Listening

If I don't consider the few issues of Stereo Sound Tube Kingdom and MJ I picked up in Tokyo in 2015, it's been a long while since I subscribed to, let alone bought, a single issue of Stereophile, The Absolute Sound or any audio magazine. After the demise of Sound Practices in the late 90s, the only audio magazine I read was Art Dudley's Listener.

Although I've never had a chance to meet Art personally, I know he is a fine gentleman. I've been following his Stereophile column online and he has given credit to my musings on the open baffle as well as the Altec 755A. He even sent me a private message when my father passed away earlier this year. I was looking forward to meeting him at the Capital Audio Fest 2017 but missed the event because it coincided with the Harrisburg Symphony's November Masterworks.

iPad mini + UTC A20 line transformers

Due to my current location, access to quality FM programming is practically nil. I've relied mainly on digital streaming via iPad mini + DSP to widen my choice of free music. 😜

USB DAC

Audioquest Dragonfly Black V1.5

When I realized that the iPad mini's internal DAC can be by-passed through an Audioquest Dragonfly USB DAC, I searched the archives of Art Dudley's Listening to see if he had anything to say about the AQ Dragonfly USB DACs. After getting Art's stamp of approval, I placed an order for the cheaper Black.

Stereo > Mono

Whether I was listening in mono or stereo, this was the best $100 (ok, + $38 for the Lightning to USB 3 Camera cable adapter) investment I ever made in digital audio. The degree of improvement was at least as significant, if not greater than, when I started playing with transformer DSP(s) between the digital source and my line preamp input(s).

Stereo set up =
AQ Dragonfly Black > a pair of UTC A20 wired 1:1
> preamp line stage

The combination of the iPad mini + AQ Dragonfly Black + DSP = smooth analog-like detail across the audio bandwidth. So I take back my word, I need this USB DAC. 😎

Thank you Art and here's to us meeting some time soon. Cheers! 🍻

November 2017 Hifi Show

I actively participated in this annual event for nine consecutive years with my Harana/Tono/Setup buddies but will break the tradition this year. 😞 This is a must see for every audio/video enthusiast based in Manila. 👍👍👍 

more info

Grace G707 + Denon DP1250 = road less travelled

The 70s through the early 80s was the era of great development in direct drive turntable technology. It was only stifled by the introduction of the CD player in 1982 and to a minor degree by the revived interest in the classic suspended sub-chassis belt-drive system within the audiophile community.

Luxman PD444
[image from Pinterest]

Although I was exposed to some of the great direct drive turntables from the 70s, like the Luxman PD444 and the Technics SP10 MkII in a Mitch Cotter base in the home system of my late DIY audio mentor Tom Cadawas, I never had a direct drive turntable in my audio system till now.

Technics SP10 + Mitch Cotter base + FR66s
[image from dallas.freeclassifieds.com]

This was probably due to the almost cult-like indoctrination inculcated by early 1980s Haymarket publications like Popular Hi-Fi and Hi-Fi Answers exalting the virtues of the 3-point suspended belt-drive from the land of kilts vs. the evils of cogging and servo hunting direct drive turntables from the land of the rising sun.

Goldmund Studio
[image from Pinterest]

Even though the late Harry Pearson of TAS used a direct drive Goldmund Studio in his reference system, just about every reviewer for TAS and Stereophile had either a Linn, SOTA or VPI belt-drive turntable. These were merely an 80s techno-rehashing of Edgar Villchur's AR turntable design from the early 60s, which effectively killed the idler drive system except for professional and broadcast applications.

Kenwood KD500 + Grace G707
[image from kintavalleyaudio.blogspot.com]

Despite camping happily with my idler-driven turntables since the 90s, the specter of synthetic marble-based Kenwood KD500s and Denon motor units in heavy laminated plywood plinths sitting on the shelves of Audio and Stereo Exchange as well as the trade-in section of Harvey and Leonard Radio stores in early 80s NYC, haunted my dreams. 😱

Pioneer PLC590
[image from vinylengine.com]

Since my Thorens TD124s are currently in storage and the Garrard 301 plinth does not have provision for mounting a shorter tonearm like the Grace G707, acquiring a direct drive motor unit became a good excuse. 😉

Denon DP1250

The first direct drive I spotted was a reasonably priced Denon DP1250 motor unit on an original plywood plinth from the late 70s. While waiting for the package to arrive, I did research on direct drive turntables + DIY refurbishing tips.

Details on how the painted magnetic stripe (above)
is monitored by the tape head (below right)
to regulate speed 

Luckily, the DP1250 just needed a tiny bit of cleaning + a mist of Deoxit on the pitch control rheostat. The motor was extremely quiet. I couldn't detect any rumbling noises through the plinth using a stethoscope.

 I left the motor unit on while cutting a new arm board out of 3/4" plywood to mount the Grace G707. When I returned to install the tonearm, the strobe had not drifted the tiniest bit.

Grace G707 on a stable platform

Denon DP1250 + Grace G707 - reminiscent of 
turntable/tonearm combos I used to see in the trade-in section 
of audio stores in NYC in the early 80s

Whether it was the GAS Sleeping Beauty or the DL103S fitted on the G707 + DP1250, I was always rewarded by musically authoritative presentation - very dynamic and involving just like my idler-driven motor units. In hindsight, the many hours and $$$s I spent in the 80s adjusting and tweaking my AR/Merrill were futile. 😞 I could have just gotten a used KD500 or DP1250, sat back and enjoyed.😊

Denon DL103S

This reinforced what I had already discovered (but was in denial) in the late 80s. Aside from the superior speed stability of the Thorens TD124 drive system, the spring suspension + lower torque motor of a classic belt-drive turntable like the AR or TD150 slowed down transients and compressed dynamics.

Grace G707

I don't think I heard the fullest potential of the Grace G707 till now. This is a simple yet well designed precision-built instrument that just lets the virtues of any cartridge shine through.  Even if it is considered a low mass design, I do remember people using the Supex SD900 and Koetsu Black with this tonearm because of its fine tolerance bearings. At some point I will revisit the G707 mounted on my idler driven motor units.

Grace G540

Denon DP1250 + Grace G540L

My only beef with the G707 is its fixed head shell. Inconvenient when swapping cartridges, I replaced the Grace G707 with its pro-oriented sibling, the G540. As pictured, the G540 uses similar double gimbal bearings but has a higher mass "J" shaped tube, which can accept the Ortofon SPU derived SME standard head shell.

Rega R200

DP1250 + Rega R200

As I sank deeper into my direct drive initiation, I kept going through my LP collection and mounted another tonearm. This time, the Acos OEM'ed Rega R200 performed pretty much at par with its contemporaries, the Grace G707 and G540.

The inevitable

Although this Denon is not a top of the line model, a casual comparison to the Garrard 301 was inevitable.

Garrard 301 + Ortofon RMG309/SPU1s

 Unfortunately, the Denon plinth would not accommodate a spare SME 3012 I had on stand-by. The next best thing I could do to somewhat even out the playing field was cut another tonearm board for my Fidelity Research FR64fx.

Fidelity Research FR64fx

While the DP1250 and the Garrard 301 share a similar character of sure-footedness inherent in a stable drive system, the 301 does its job with less effort. There is a slight tendency to strain with the DP1250 on complex musical passages. If forced to split hairs, I also hear a trace of hardness and/or dryness on certain recordings which sounded more pleasing on the 301.

Denon DP1250 + FR64fx

In the past I found the FR64fx to sound more analytical compared to the SME 3009/3012 and Ortofon RMG309. Could the 301/SME 3012 combo be more euphonic while the DP1250/FR64fx more accurate?

Better late than never

Regardless of what I am hearing, this Denon DP1250 experience garnered my admiration and respect for the direct drive system such that I am inspired to probe direct drive motor units further.🍻

Grace G707 + TD150 = road most travelled

Grace G707

 By the time I acquired a used Grace G707 tonearm ca. '83, it was already an up and coming classic. Classic being a euphemism for affordable since TAS and Stereophile were already waxing poetic about heavier MC cartridges from Kiseki, Koetsu, Accuphase AC-2, etc, which required more massive tonearms. 

Original AR XA  > AR + Grace G707 

I had to do irreversible hacking to my thrift store-found ARXA turntable to mount the G707. All that effort paid off since the improvement this tonearm brought to my audio system was staggering - more transparency and definition throughout the audio bandwidth. The listening experience became a lot more enjoyable! Sadly, that G707 got lost in a maze of senseless upgrades I went through for the next ten years. I held a torch for this tonearm until I found another nice sample for this time travel episode.

70s MC cartridges

 Back in the day, I could only afford the Audio Technica low output moving coil AT31E + Sony HA-T10 MC transformers. Those two items are gone, so
 accompanying us on this journey are two classic MC cartridges from the 70s that are technically matched to the Grace G707.

GAS "Sleeping Beauty" aka
Coral 777

 The sweet sounding, almost SPU-like GreatAmericanSound "Sleeping Beauty"

Denon DL103S

And the higher compliance version of the NHK broadcast standard, Denon DL103S

Thorens TD 150 

belt-drive + 3 point suspension

From my pre-college days in the late 70s until I completed my undergrad degree in '84, the listening room at the Lila Acheson Wallace Library of The Juilliard School was equipped with several rows of Thorens TD150AB/Shure M7D/Shure headphone amp + humongous Koss ear cans, while the classrooms were fitted with Thorens TD124/Dyna SCA35/AR2Ax audio systems. Nope, I don't recall seeing AR1s in the building. 😞

In the early 80s, the original AR turntable could be found for $10-25 at thrift stores, but no Thorens. One had to go to Audio or Stereo Exchange and/or the trade-in section of Leonard or Harvey Radio stores where the Thorens badge started at around 100 bills.

When I purged my belt-drive collection in the early 90s, this TD150 was the only one that I retained because it was so unattainable in the early 80s. The tonearm board already had a hole from a long gone Rega RB250 which, fortunately, shared the same spindle to pivot geometry as the G707.

Since I owned half a dozen AR turntables from stock to various stages of modification, setting up the TD150's 3 point suspension was like riding a bicycle. 😉

Thorens TD150 + Grace G707

My reunion with the TD150 + G707 was bittersweet. I caught a glimpse of the "black background" atmospheric setting for the Reagan-era audiophile ideal - the 3D sound-stage phenomenon that is supposed to transport the listener on a magic carpet ride to Carnegie Hall. Ironically, this was achieved at the expense of dynamics, articulation and definition, which are vital elements also expected from a live musical performance. Things could have been much worse if I were still using negative feedback infected tube electronics driving inefficient speakers. But let's not go there... 😧

In search of a more stable platform...

Thorens TD 124 + Rega RB300

By the time I finished grad school in the late 80s, the audio systems at The Juilliard School had been upgraded to include CD players. The Thorens turntables were retired and replaced by Denon direct drive turntables with servo tracing tonearms. Meanwhile, I had acquired a Thorens TD124 and knew its speed/pitch stability was superior to my heavily modified AR/Merrill turntable but I would never admit that to my audiophile friends. 😃

Given the wisdom I've gained (or not) through the years, the Grace G707 deserves a more stable platform....stay tuned.

JE Labs Simple 46

I've been hoarding type 46 power tubes gathered from radio shows I attended with my buddy Chong in the late 90s. Building an SE 46 amp was in my to do list when I packed up for Manila in '08. But things got in the way. Finally, after a round trip across the Pacific, the amp has come into fruition.

Given its designation, one would think that it is just a 45 with dual grids. However, aside from the UX-5 tube socket requirement, the 46 is not quite a 45. It only puts out 1250 mWatts, 750 mWs less than the 45's 2000 mWs. Maximum plate dissipation with grid 2 tied to the plate is 5.5W compared to 10W for the 45. Although it will perform very well loaded with a 5k primary Z output transformer, the textbook recommended load is closer to 7k, due to its higher plate resistance of 2380 ohms vs. 1700 ohms for the 45.

46 tube base
diagram

chassis is punched out and ready for painting

It's been over 20 years since the Simple 45/2A3 was uploaded to the now defunct DIY section of the old Angela Instruments website. So I wanted to reprise that old-school topology with a twist. I considered retaining the octal base and using a grid capped 6F5 or a UX6 based + grid capped type 75, as a tribute to Asano-san. 🙏

However, since I am in loctal mode, I settled on the 7B4 hi-mu triode which is more in unison with the simple theme. The 7B4 is readily available NOS and can be had for less than $5 each from tube dealers. Tube rollers take note, even if loctal tubes are boxed/labelled RCA, Tung Sol, Raytheon, etc. most of them came from the Sylvannia factory in Emporium PA. 😞 

under the hood

!!!WARNING!!!

The voltages found in this circuit can be lethal! Build at your own risk!!!

JEL Simple 46 schematic

Adjust the dropping resistor* (use at least a 10W) so that the operating point for the 46 tube is as close as possible to the tube manual specified 250V max. plate voltage x 22 ma. current draw = 5.5W.  Ideally, the 46 should see 285 volts at the plate - 35V in the cathode = 250V. As shown in the schematic, I am still running my output tubes about 8% over because I was anxious to listen and got lazy to lower the B+ further. 😎

The big surprise was, subjectively, the triode-wired 46 sounds more powerful and authoritative especially in the lower register than the 45. It sounds like the union of virtues between the dark and mythical 10/VT25  + the refreshing airiness of a 45. I've been listening to this amp for over three months and haven't had the itch to switch on my other amps. 😄

CODA

Left to Right - Globe 46, ST 46, ST 45 and 2A3

Globe tubes look really cool and usually sound more lush than their ST counterparts. I personally prefer a Globe 45 over the later ST glass bottled samples. However in the case of the 46, the difference is not as apparent and close to negligible to my ears, So save your $$s and do something less nerdy, like going out on a date. 😉

Addendum

I received this email recently from a seasoned DIYer/audio enthusiast known in various audio forums as Salectric.

"I just saw your blog post about your Simple 46 amp and I read the question someone posed in the Comment section about a suitable power transformer. I actually had Edcor build a custom PT for my 46 amps and the voltages worked out perfectly so I recommend it to anyone wanting to build a 46. I don't know if the particular unit is listed on their website but it should be available through the part number which is the Edcor XPWR 258-120.

The B+ windings have two secondary voltages. It is 345-235-0-235-345 @ 300ma. The purpose of the two voltage taps is to let the transformer function for either choke input or cap input. The lower voltage windings with a 5U4GB and cap input filter give a roughly 290v B+, and so do the higher voltage windings with a 5R4GY and choke input. With a little loss in the OPT and a 32v bias, the 46 has almost exactly 250v across it. There is also a 5V@3A and 6.3VCT.

I ordered it this way because I wanted to compare choke input and cap input with as close to exactly the same conditions as possible. (I tried a 5U4GB with the choke input as well as cap input just to be as consistent as possible.) The best sounding setup was the choke input with 5R4GY so that's how mine is set up. The Edcor is super-quiet. No mechanical buzzing at all."