Thursday, August 9, 2012

SETUP





SETUP

These guys are pioneer users of idler driven turntables and flea power amps driving high efficiency speakers.



Joel


It is a small room and I forgot to bring a wide angle lens, so here's a cropped view from the listening position. Those monoblocks at the bottom of the shelf are SE2A3 [monoplate] amps with Tamura F7001 permalloy OPTs. Barely visible towards the top left is his Garrard 301 [oil bearing] with an Ikeda 12" arm. Depending on his mood, you may find him alternating between an Ortofon SPU-GME, Koetsu Black or Denon 103R through Tango MCT999 MC-step ups.


Altec 414Z on hardwood OB, Altec 511 horn mounted on top, 902 ceramic magnet compression drivers with original aluminum diaphragms and tangerine phase plugs. Alnico is nice but execution is more important and Altec did not skimp on this underrated model. This is really a nice sounding system. He built/tweaked his own crossover and L-pad to match the levels between the horn and woofer. 


He also has a pair of Altec 755Cs in OBs. EV T35Bs supplement the top end on both speaker systems.

Joel's got really good ears and gifted with a nice singing voice, aside from the fact that when he is "in the right mood" he can really build very nice projects like this PAS chassis based preamplifier. This is an RCA phono preamp circuit with battery bias using 12SL7 tubes and 12SN7 for the linestage driving Tango NP216 line output transformers mounted horizontally at the back.


Aside from being the JE Labs master builder/technician in Manila, Joel is known as the analog meister and sets up and restores anything from TD124s, 301s to suspended TD150s/160s and etc.


Nonong

These open baffle loaded Altec 755As are probably the only existing ones in Manila as far as we know. Someday he dreams of owning a pair of WE/Altec 756s [10"] with 3000A tweeters.


Prior to idler drive he had a VPI TNT Jr. with an Air Tangent 10B airbearing linear tracker. He sold the TNT Jr. and fitted the A-T10B on a TD 124 as an interim front end. Finally he settled on a Garrard 301 with an Ikeda 12" arm wherein an SPU Meister takes duty to the grooves. This is hooked to a pair of Tango MCT999 step-up devices which is routed into an RCA based phono preamp using 5691s and a linestage with 76s driving the NP216Ns built by Joel.


His amps include a pair of SE 300B amps with Tamura F7002 permalloy OPTs exclusively tuned for the OB755As that replaced a pair of SE2A3 amps with NY15S OPTs.


SE WE205D amp with F7004 OPTs and an SRPP 45 with Tamura F475.


equipment rack




William


When I visited William in the mid 90s, he had equipment that would turn a reviewer for any of the high-end rags green with envy - Wilson Grand SLAMM, VPI TNT, Air Tangent, CAT-SL1, Kondo's PSE300B Kegon, TAS/HPs cartridge of the month, connected with cables using "controlled substances" or "classified materials". 


However his taste and listening habits quickly evolved to a system centered on Tannoy Westminsters [now sitting sadly behind] and subsequently, RCA LC1s [early version without the cones] housed in walnut veneered "furnace style" cabinets [aged to perfection] that were originally intended as monitors made for executive suites at RCA... 



...driven by an all out stereo SE WE205D amp with Tamura F5004 OPTs, custom wound Tango power transformer, tantalum resistors, silver foil paper in oil coupling caps, Cerafine and Black Gates for decoupling built on a copper chassis by Joel. 


The preamp is either a Kondo M10 or JE Labs preamp [depending on his mood] fed by top of the line Audio Note, Japan MC step-ups.


High-end dealers may think it's a major step down to use a Garrard 301 with an Ikeda 12" arm from his previous front end or tracing grooves with an Ortofon SPU instead of a Lyra since William took his business elsewhere..... purchasing more records! The 301 has since been upgraded with Shindo platter and bearing, now he is hunting for an EMT turntable....

Aside from this system, he has another listening room at a remote location where he hibernates equipped with a TD124, Fidelity Research FR64s, Denon 103R front end into JE Labs preamp/amp electronics driving vintage Altec speakers.

William is a music lover and Art aficionado. His LP collection include not only LSC "shaded dogs" or Mecury SRs, but also mono LPs acquired purely on musical merits.




Nilo


Analog Sources

Thorens TD124/SME3012/SPU - lit by an uber cool glass art deco lamp

Empire 208/SME3009


Garrard 301/SME3012/Fidelity Research MC202 cartridge and headshell [restored at Joel's shop]
Cartridges- Ortofon SPU, Ortofon MC25fl, Denon DL103, various Fidelity Research MCs and Goldbug Clement
MC Step-up devices- Ortofon STM72, Supex SDT-77 [used with SPU/Goldbug], Altec 15095A [primarily with MC25fl], Denon AU320 [spare] and FRT-3 [on loan from Joel].


Digital - Marantz Tube CDP
Preamp- JE Labs [Telefunken 12AX7s on phono and 6SN7GTBs linestage] and Harman Kardon Citation I
Amplifiers- SE 300B silver which uses 6SN7/6V6 tubes/Tango XE20S and an SE 2A3/45 using 6H30pi/5687/Tango U-808. Both custom made by Khun Kittipol in Thailand.


Main Speakers- 12" Altec 419A on custom furniture grade cabinets internal volume made exactly according to Altec 614 plans, Fostex FT-600 Horn crossed around 1khz and vintage Telefunken alnico super tweets to add a bit of sparkle

Nilo's comments on his system:

Other speakers - Klipsch La Scala, Pioneer PIM8L [on vintage sony portable cabs], 15 ohm 10 inch Goodmans Triaxiom on vintage BR cabs

Future plan - convert the SE 2A3/45 to a JEL Simple 2A3/45.
I have this philosophy that any "upgrade" should be funded by disposing the least utilised inventory of equipment. First to go was my Project RPM-9- used half of the proceeds to buy the klipsch/ pioneer PIM8/various stepups and the other half on software, equipment shelves, and 2 paintings (!). Next to go were my vintage fisher amps [x-100, x-202, 400] which went to fund my turntable restorations, cartridges and as always, more software [LPs].



Rex


Altec 2 way horn - 414 woofers in 614 cabinets, 811B horns with 804 compression drivers and Fostex FT-17H working as super tweets.


DIY Simple 45 with Tango ISO U808s and locally wound power transformer

Garrard 301 grease bearing Neat 10" tonearm/DL103 and an SME 3012 at the back


Another Garrard 301 in a Shindo inspired plinth crafted by Joey with a Neat GA-04 transcription tonearm (Pickering 190 clone). Is that an Audiophile label 78 rpm microgroove record?

He is trying to decide which one of the three 301s he will keep and is contemplating on an octal based RIAA preamp to replace his present 6DJ8 phono preamp.




Rofiel


JEL deluxe preamp [6SL7, 76 & 6SN7] and JEL SE2A3dx amp 56/6SN7 [front end] James 6123HS opts


Garrard 301 and Grace 12" on solid Acacia wood plank taken from an ancient tree that fell in their backyard during a typhoon. Cartridges are vintage Pickering, Stanton and Shure shared between these 2 turntables.

Rek-O-Kut L34H [Papst motor] and Ortofon AS-212, plinth is from the same tree. He is contemplating whether to get a step-up transformer/DL103 combo or a monaural cartridge.


Tannoy 3828 pulled out of Berkeley II enclosures and mounted on an open baffle. Crossover modified to a simple capacitor filter and L-pad for the HF unit by Joel.




Let's fly back to the USA and down to earth, particularly the SETUP branch in NYC.

This is Ding's system, a pair of Altec 604-8Gs on OBs driven either by a pair of SE300B monoblocks with Tamura F2007 opts...

...depending on his mood he might change output transformers on anotherpair of SE300B chassis using alligator clips to either a Tango NY15s or Audio Note UK 3ks.

...or Simple 45 with OPTs scavenge from an old Fisher integrated

JE Labs Preamp with external PS

A long time Linn Sondek LP12 user he eventually discovered the potential of classic idler driven turntable in the form of a Thorens TD124/Rega RB300 +... 

...Dynvector DV505/Denon 103S fed through vintage Thordarson mic input transformers of excellent quality!


His other sources include a Fisher FM200B tuner and a Pioneer DVD/CD player.

One thing I love about this guy is that he is so level headed about audio. Enjoying music is first and foremost. It's not typical to meet people in this hobby who will never engage a conversation on, "what is the best circuit, capacitor, output transformer or anything like that......" Obviously, he has no inclination towards audio neurosis.
He keeps me on the level and many times, has been my worst critic when I come up with a new idea or design.

Here are some of his current projects.....mono system in the making?


Gray 108 to be fitted with a Fairchild mono MC and mounted on the Gates CB77 idler driven turntable sitting on a wooden EMT inspired skeletal base.


Where's the Fisher mono preamp picture bro'?




Now let's visit Abe's system in the west coast


Altec 604-8G in open baffles

Garrard 301 and Schick 12"


Thorens TD 124/SME3012
+
a few modified DL103 cartridges and Cinemag MC step-up 

JE Labs preamp

Simple 2A3/45

Everything was built by Abe!



Sunday, August 5, 2012

Radiotron SE2A3



Revisiting the classic pentode driver
Radiotron's answer to the WE91A
Right before the end of the 20th century, a friend brought over a Japanese built pair of WE91A clones sporting top of the line Tango X-3.5S output transformers, matching chokes and power transformers, input tubes were original WE310As and 50s date code WE 300Bs, WE274B rectifiers, Allen-Bradley carbon and NOS wire wound resistors, Vitamin Qs for coupling and can type paper in oil caps for the power supply. The amp was huge easily dwarfing my JEL SE300Bdx monoblocks and the quality of construction and wiring was impeccable. Although this WE91A clone had great qualities in the midrange my friend was convinced my amps sounded better overall. Does that mean my amp design is absolutely betterDefinitely not! Only in the context of my system - Denon DL103R/SME 3012/Garrard 301 feeding Tamura TKS83 MC transformers into a JEL deluxe preamp, JEL SE300Bdx mono blocks driving a pair of Altec 755As in open baffles - since I optimized the signal chain so that it sounds good according to my standards. I told my friend that his decision to purchase those amps should be based on how it sounds in his system not on what he heard in my listening room.

That amp made a lasting impression and reinvigorated my interest in the classic pentode driver topology which has a lot of esteemed followers and practitioners. After my friend left that night I pulled out Joe Roberts WE91A article in Sound Practices Issue No. 1, reviewed my notes on the 6SJ7-->300B I briefly prototyped - slight upper midrange glare through the 755As, the top end was a bit rolled off with a tubby bottom. I was thinking....could it be the pentode 6SJ7 being a later compact version that kills the magic? Remember that even in the 90s WE310As were already unobtaniumSo I thumb through the pages of the RC-12 tube manual in search for a close equivalent and found the 6SJ7's grandfather, the 6C6 which has similar electrical specifications and bears a physical resemblance (BIG plate and grid cap) to the WE310A. The 6V filament is a convenient bonus. By that time, I've maximized the potential of all my triode input/driver circuits for the 755A/OBs and Altec 2-way. I pursued other interests and kept the 6C6 project in the back burner...


!!!WARNING!!! 

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



At the beginning of the year (2007) I was looking for a winter project that will not entail chassis building. I reread Joe Roberts article "I never met a 2A3 amp that I didn't like" SP15 and noticed a familiar looking SE2A3 amp schematic using a 6C6 pentode driver from the Radiotron, 3rd edition. He had good things to say about this circuit and it looked easy to graft this topology on my long-time SE2A3 test mule with Tango U808s. I took inventory of my tube stash and was frustrated to find just a single RCA 6C6, a couple of 6-pin sockets but needed 1/4" medium sized grid caps.

One chilly morning I downloaded an email from an internet buddy Sergey Didkovsky from Ukraine. We have exchanged emails a few years back when he was building the JEL classic 300B circuit. He was telling me about a pentode driven SE amp that he thinks sounds better. This was a fortuitous moment because the clairvoyant Sergey was talking about a Radiotron derivative. In the course of our correspondence he pointed out a quick source for additional 6C6s and grid caps with several links and attachments of Japanese and European DIYers' single pentode driver stage schematics including tips on operating points and parts tweaks.

I started my listening evaluation with this circuit and sent my impressions to Sergey for comments:
"Try please, to a little increase the cathode resistor (up to 1,2-1,5Kohm) and reduce anode resistor (to 75k-82k). It will allow to increase Ua up to 150V and to receive ratio Ua:Ug2 = 2:1 ratio. The sound should become more "interesting and old". That is especially good for jazz. Still mine 5 cents....use good NOS Oil capacitors in G2 circuit. I use TCC VisconolI think, oil caps in the grid - adds a bass. Reduction of the anode resistor - improves the hi range a little."
His use of adjectives "interesting and old" prompted me to get as close to the suggested 2:1 plate to screen grid suppressor voltage ratio as it seems to be a key ingredient for his recipe. So far I have achieved a 1.8:1 ratio and was still hearing a slight upper midrange glare that I originally attributed to the 6SJ7 years ago. The BIG plate = FAT midrange I was expecting from the 6C6 was already there but the glare did not disappear until I replaced the plastic 2uf cap with can type 2.8uf paper in oil caps for the screen grid (suppressor) and as Sergey said it did improve the bass. Maybe the paper in oil decoupling cap will give the same results with the 6SJ7....
"Thanks for your patience, not looking at my very bad English language...."
There is a saying that music is a universal language, Sergey apologized about his English but I assured him that his communication skills were fine. Certainly driven by his passion for good sound, I had no problems understanding his tips and it was quite evident that he has done some serious research, listening and is blessed with good ears!

With these thoughts in mind I did not argue and simply looked up to him as a mentor. In this revised circuit I captured the 2:1 ratio, to be exact 1.98:1 with 152V on the plate drawing about 1.8ma. of current. I changed the grid resistor from a 270k to 330k because not only does this make an easier load for the driver stage but from experience the sound becomes warmer as the grid resistor value is increased but only to a certain extent. If you exceed the maximum 500k grid resistor value specified in the tube manual for a 2A3 you might find the plates running away cherry red! So check your tube manual before messing around with this tweak on other triodes. A 220k will give more focus and detail but lower than that value the driver stage will have limited headroom. It will clip prematurely from not having enough voltage swing to drive the 2A3 to a full 3.5W output since the grid resistor is effectively in parallel with the plate load resistor.
Radiotron SE2A3 Power Supply

I am grateful to Sergey for sharing his experience saving me time and effort to build a classic pentode driven SE2A3 amp!




100Hz - both channels

1kHz - both channels

10kHz - both channels

Radiotron derived SE2A3 - 6C6 pentode driver, Tango U808
Power output = 3.8W per channel before clipping
Frequency response = +/- 1dB from 30hz - 15khz @ 1W
( - 3dB @ 20hz & - 5dB @ 20khz)

100Hz - top trace  = signal generator

1kHz - top trace = signal generator

10kHz = top trace = signal generator

JEL SE2A3dx - 76/6SN7 input/driver, Tango U808
Power output = 4.5W per channel before clipping
Frequency response = +/- .5dB from 20hz-20khz @ 1W
( - 3dB @ 50khz)

100Hz - both channels

1kHz - both channels

10kHz - both channels

JEL Simple 45 - 1/2 6SL7 [or 6SF5], Tamura F475
Power output = 2W per channel before clipping
Frequency response = +/- 1dB 20hz-20khz @ 1W
(- 5dB @ 30khz)
Compared to my favorite topologies in driving power triodes, this R-C coupled 6C6 pentode has slightly narrower bandwidth and as shown in the square waves, it has the slowest rise time and softest leading edge at 1khz and 10khz (in theory a more vertical rise time and sharper leading edge = faster transients and better high frequency extension) and pretty much equal at 100hz (less tilt = better bass response) with the Simple 45 having a slight edge but that uses a different OPT. To put things in perspective a 30hz-15khz +/- 1dB bandwidth is not a slouch if you refer to the table below.

I believe that good engineering aided by good ears is an important factor in building a musical sounding amplifier and cannot forget a post I read several years ago at a forum "...nice people build good sounding amps, bad sounding amps are designed by annoying ---..." and so it goes...kudos to the RCA engineer(s) in the 1930s who designed the Radiotron SE2A3, it is a musical amp!