Showing posts with label JE Labs in the 90s. Show all posts
Showing posts with label JE Labs in the 90s. Show all posts

Saturday, February 15, 2014

JE Labs in the early to mid 90s


ca. '92 

I built my first triode amp - a PP2A3 with a Mullard type driver circuit using octal tubes driving AR M1 speakers. Initially, the amps used Fisher 500B output transformers which were later upgraded.
The modified PAS preamp already had an RCA phono section using Telefunken 12AX7s and a 6SN7 line stage.  B+ and filament supply was provided by a Heathkit tube regulated power supply.

The front end consisted of two belt drive suspension turntables - a Thorens TD150 with a Rega RB250 arm and a Merrill modified AR with a Sumiko Premiere MMT arm. Cartridges were a Grado ZTE + 1 and a Signature 8MZ. FM was provided by a Scott LT110B tuner and a cheap CD player rounded up the source components.

ca. '93 

I finally got my Spendor LS3/5A shipped from Manila and the PP2A3 monoblock amps were now fitted with Peerless 16309 output transformers. I also tweaked the operating points of the amplifier based on lessons I learned along the way. The LS3/5A sounded pretty good driven by an 8 watt class A amp. I was not very happy with the sound using the Heathkit tube regulated PS so I reverted back to a tube rectified CLC PS for the preamp.

ca. '94

I retired both belt drive turntables and never looked back. Idler drive is simply superior.

This is my TD124 which I bought at an antique auction in the late 80s for $1. It originally came fitted with an Ortofon SMG212 which I foolishly sold ;( I still had a lot of learning to do...

I started working on an octal preamp in '93 but could not iron out some bugs. Performing and teaching activities kept me away from the test bench. But by early '96 I succeeded in completely debugging the preamp. Using a Denon AU320 step-up, I also started listening through a Denon DL103 cartridge. More preamp and MC step-up info

As soon as my preamp was sorted I started prototyping an SE300B amp which became the JEL Classic SE300B amp. This amp also did a good job of driving the LS3/5As in a small environment.

In mid '96 I moved into an apartment where I would reside for the next 12 years. I was in search of a high efficiency speaker system. Behind the 2 ft. square baffles with Altec 755C is a pair of AES 5.2 TQWT and somewhere in the back was a pair of Diatone PM610Cs in original bass reflex cabinets. In the picture above, I had just decided that it was worth pursuing the Open Baffle route.

The Simple 45 prototype


Altec 755Cs in Open Baffles

 With these speakers I felt confident I had a pair of monitors for evaluating the sonic merit of my circuits. Besides, I had access to Ding's Altec 604-8G/OBs or Petite Onken when I was in NYC for gigs.


Various prototypes top left, clockwise: SE10 with Tango 7K OPTs, SE2A3 with Audio Note UK 3K OPTs, SE2A3 "monoplate" with Tango U808 and a breadboard where I tested several driver circuits using various 9-pin, 5-pin, 6 pin and octal, low>high gm tubes. 

Altec 755A

Within a couple of months I was able to put together a pair of Altec 755As. Both units came out of an AR1 speaker. I also acquired a grey Garrard 301 which I initially fitted with a Fidelity Research FR64x tonearm.

I sent pictures of my system to Joe Roberts and a few days later he called about featuring me as Homebrewer for Sound Practices Issue 17.

Meanwhile I had my sights on a speaker project of even greater efficiency. But the hideous looking carpet had to go and I had to rearrange things ;)