Tuesday, November 17, 2020

John Linsley-Hood Class A Headphone Amp

Having been a happy user of a John Linsley-Hood (JLH) 1969 Class A amp cloned by Nobsound, I was intrigued by the JLH Class A headphone amp boards featuring discrete circuitry (no ICs or op-amps) advertised on eBay. In the midst of the 2020 lockdown, I ordered this $25 pre-assembled board, which arrived in a padded pouch within 10 days. I also got a surplus 24 VCT @ 2A power transformer for another $15.

!!!WARNING!!! 
The voltages in this project are potentially lethal! Proceed at your own risk!


Typical of Chinese kits, this board didn't come with instructions or any type of documentation. But the board is marked for an experienced DIYer to decipher and set up in no time. Unlike the original JLH 1969 design, which needed DC blocking capacitors at the output due to the single rail supply, this headphone amp module was updated to work with a dual rail (+/-) supply so the output capacitors can be omitted.
 

Unfortunately, I couldn't get stable zero DC offset at the output terminals. Trimming for zero volts after 30-45 minutes of warm up was not a guarantee that in another 30 minutes it'll still be zero - I've measured as much as 0.3V.๐Ÿ˜ž


Since I didn't want to risk frying my headphones and classic speakers, I installed 2500uf @ 16V electrolytic blocking capacitors at each channel’s output. Then, I bypassed the electrolytic caps with hermetically sealed 4uf paper caps just like I did to the Nobsound NS02g.  

Top trace = audio generator
Bottom trace = amp output

In spite of the DC blocking caps at the output, the square waves still show excellent bandwidth, transient response with no trace of ringing. 

Before clipping, I measured 250mW/channel @ 4 ohms, 500mW/channel @ 8 ohms and 950mW/channel @ 16 ohms, 1.2W/channel @ 32 ohms,  395mW/channel @ 150 ohms, 190mW/channel @ 330 ohms and 115mW/channel @ 560ohms. I pretty much exhausted the resistor values from my parts bin to emulate the nominal impedance of typical headphones. 

The 115mW output into a 560 ohm load shouldn't worry headphone enthusiasts since this amp drove my Austrian AKG K240/600 ohm Monitor cleanly beyond SPLs my ears could tolerate. It also had no issues driving less efficient ortho-dynamic headphones like the Fostex T50RP below, courtesy of my friend Nate. Thanks, buddy!


This amp definitely outclassed the Rat Shack mini amps I'm fond of. Its class A design's purity and transparency puts it on another league. Unfortunately, Class A amp designs require a more substantial power supply, which is incompatible with portability. 

The character of this amp is exactly like that of its bigger brother, a fatigue-free solid state amp that almost (but not quite) succeeds in sounding like a good tube amp!


BTW, did I mention that it can also drive my Altec 755As in Silbatone cabinets?


Wednesday, November 4, 2020

Moving Iron Cartridges: Grado, Nagaoka, Pickering/Stanton and Piezo/Sparta


This is the last installment of my series on phono cartridges, which commenced with early stereo cartridges followed by moving magnet cartridges. These cartridges were evaluated in the near-field and main system in the man cave. Tonearms used include the Syntec S220, Denon DA305, Fidelity Research FR54 and Grace G565, mounted on the Garrard 401, Realistic MKVIII, Rek O Kut B12GH + L34 and Thorens TD124 or MKII.

Grado



This collection of Grado cartridges dating back to the 80s and 90s is a testament to my being a dyed-in-the-wool Grado fan. They served me well when I spun LPs via a suspended sub-chassisbelt-drive turntable, feeding hacked Dynakit preamps and classic push-pull EL84 and EL34 amps to drive BBC LS3/5As or Quad ESLs.

But as soon as I started dabbling with idler driven turntables + higher mass tonearms, no negative feedback preamps, single-ended triode amps and high efficiency speakersthe voicing of Grado cartridges started sounding contrived and unnatural. I switched to using the Denon DL103 and Ortofon SPU low output moving coil cartridges via mic transformers.

Grado GTE+1 + ZTE+1 stylus

Although the Pickering/Stanton 371 was more fatiguing to my ears, the GTE+1 has a similar tonal curve. The GTE+1's mid-bass sounds boosted, the midrange is slightly recessed, followed by a sudden rise in the upper female vocal range that gives a nasal quality, which is borderline shouty. The rising response goes all the way to the mid-treble range then it sharply rolls off in the extreme high frequencies. 

This kind of voicing presents an exciting sound that has created a fan base as well as harsh critics for Grado. Tonally, the early Grado SR80 headphones I own were voiced in a similar fashion.

Grado Signature 8MZ

The tonal curve I described above is still apparent in the Signature 8MZ but milder. The upper midrange/lower treble peak was refined and the frequency extremes more extended. In the process, however, micro and macro dynamics suffered. Refinement, detail and resolution improved at the expense of musical excitement.

I also noted a lack of air and spaciousness between instruments and vocals as presented by both 8MZ and GTE+1, which resulted in a drier and narrower sound field compared to the Nagaoka, Pickering/Stanton and Sparta S220.

Nagaoka


Nagaoka MP11

In the Fall of 1983, my dearly departed dad, a violinist, conductor and music professor, went on an observational tour of orchestras and music schools in the UK under the auspices of the British Council. Before heading back to Manila, he took a side trip to NYC to visit me and see his old haunts. The Nagaoka MP11 pictured above was his gift + a couple of Popular Hi-Fi and Hi-Fi Answers issues he picked up along Tottenham Court Road.

Nagaoka MP11

Mounted on my stock AR XA turntable in '83, I didn't think too highly of the MP11 and preferred the GTE+1. So it rested for more than three decades. When I revisited it, the tables were turned. Listening to the MP11 exposed the Grados' flaws.

To my ears, the MP11 is the moving iron equivalent of the Denon DL103R. It has a sweet midrange, detailed and extended in the frequency extremes with a middle row concert hall perspective. Even if the presentation is more relaxed than the Pickering/Stanton models below, it still presents musically satisfying dynamic nuances. 

Nagaoka MP110 body + MP10 conical stylus

Encouraged by my rediscovery of the MP11, I kept my eyes peeled for another Nagaoka MP cartridge at close to '80s pricing. Fortunately, I lucked out with a couple of NOS MP10 styli + a cheap MP110 body. 

I couldn't detect any sonic difference swapping the MP11 or MP10 stylus between the MP11 and MP110 bodies. The DCR of the MP11 coils averaged at ~ 550 ohms while the MP110 ~ 600 ohms. Thus, I assumed that the MP11 and MP110 bodies are identical.


Sonically, the MP110 body (or MP11 body) + MP10 stylus = the moving iron equivalent of the Denon DL103.

Pickering/Stanton


Pickering XV15 + D400 conical stylus

The positive attributes I noted about the Pickering 380 + Stanton 371Pickering XV15. Compared to the MP10/11, the concert hall perspective is more front row. The midrange is the most three-dimensional in this survey and comparable to the Shure M3/7D. Dynamically, this cartridge is the most exciting in this group. 

The MP11/10 beats the XV15 + original conical stylus in terms of detail resolution. Perhaps with an original elliptical stylus, the detail and resolution in the frequency extremes will most likely equal or even surpass the MP11.

Note that the Stanton 680 is the same exact cartridge and the stylus are interchangeable between the two bodies.

There's a lot of SPU juiciness from this cartridge!


Pickering V-15 Phase IV + IV AM stylus

The Pickering V-15 Phase IV was designed as the entry-level model in the Flux-Valve (moving iron) line up. I measured an average of 780 ohms DCR from its coils vs. 1200 ohms for its higher-end brother, the XV15. 

Its overall performance is formidable and the superiority of the XV15 might only shine through in a direct A/B comparison. The Stanton 600 is the equivalent model.

Sparta 220S



This Sparta 220S cartridge came with one of my Syntec S220 tonearms. The Japanese OEM was identified as a Piezo YM-114 aka Hitachi DS-ST101 by wualta in AudiokarmaIt's a very smooth-sounding cartridge with good detail and extension in the frequency extremes. Not as dry as the Grados, but like the 8MZ, it doesn't have the micro/macro dynamic prowess of the Nagaoka MP10/11 and Pickering XV15/Phase IV.

Coda

My Grado cartridge collection survived the '90s purge when I unloaded my two Merrill modified AR turntables, two pairs of Quad ESL57s, a 15 ohm pair of Rogers and a 12 ohm pair of Spendor LS3/5As, a pair of Acrosound TO330 push-pull output transformers, Lafayette KT600, Acrosound 20/20, Dyna ST35, Eico HF87, Leak 20Pilot SA232, SA260 and many other classic equipment. 

 
Pickering XV15 and V-15 Phase IV + Nagaoka MP11 and MP10

Since these four cartridges emerged as my favorites in this shootout, it might be the right time to let go of my collection of Grado cartridges...

The Wrap 

Moving Iron + Moving Magnet

Nagaoka MP10, MP11, Pickering XV15, Shure M3D
Pickering V-15, Pickering Phase IV, Shure M44

 A couple of moving magnet cartridges deserve pride of place along with my chosen moving irons - the Pickering V-15 + DAT2 for its sweetness, the Shure M44 + EMJ N44G for its dynamic qualities and the Shure M3D for its timelessness! 

Nagaoka MP10, MP11, Pickering XV15 and Shure M3D

Finally, if I could only have four, these are the cartridges I'm keeping!




Friday, October 16, 2020

Kutztown Radio Show Fall 2020


Pavilion 1

This was the first audio related event I've attended since the March 2020 lockdown.

Thorens TD124 MkII

Dyna PAS 3 + ST70, ARXA turntable, Heath W4 amp

H. H. Scott 710 + Gray 216

Garrard record changer, Harman Kardon tube receiver

Weathers Turntable

Time travel to 1948

NOS pair of WE755A + full documentation

If you need to ask how much for the pair, you can't afford it. ๐Ÿ˜†

Western Electric 597A, probably worth a kidney?


Vacuum Tubes

Pavilion 2

I thought it was a pretty good turn out.

More pictures from past events