Pictures from the Fish Ladder

We've been hammered with snow here in the great wilds of Grand Rapids, MI. I thought it would be a good time to take some pix from the fish ladder located on the Grand River. This is a favorite locale for my family to visit, but it is usually a little more pleasant in the spring and summer!




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Threshold S/500 amplifier review

I've been a tube guy ever since 1989 when I first heard a pair of Quad ESL-63 speakers driven by a heavily customized McIntosh 240 amplifier. The glow of the vintage Genalex KT66s were magical as was the sound coming out of the electrostatic speakers. It was that day that I became an audiophile for life - a man obsessed with wringing the last bit of detail and realism from my favorite recordings.

So far it has been an interesting journey - filled with tubed gear from Dynaco, Harman Kardon, Eico and my own DIY creations. Over the years I've also dabbled with solid-state, owning at various times a SAE preamplifier, a McIntosh 250 amplifier, an Adcom 565 preamplifier and even building a kit or two. But in my heart of hearts I still remained a tube guy. To my ears tubes always came out on top for sheer musicality. But I've always kept an interest in the industrial art solid-state 'super' amps - brands like Threshold, Krell and Mark Levinson still hold some magical awe for me. These were the amplifiers that only the rich and well-heeled reviewers used with their uber-expensive exotic loudspeakers. However I've never actually known anyone who has owned any of these 'super' amps so I never had the opportunity to hear one. Surely they couldn't compare to a good tube amp!

Recently I've started to have an interest in purchasing a pair of Magnepan 1.6QR speakers. The problem was the low efficiency. I didn't trust my refurbished and upgraded Dynaco Mark IIIs to provide enough power, so I started thinking about getting a more powerful McIntosh solid state amplifier. I love the sound of my vintage MC250 and if I could capture that sound in a higher wattage model then I would be rather pleased. Well a chance conversation led me to buying a used Threshold linestage and amplifier instead.

The Nelson Pass designed Threshold S/500 was built from 1983-1988 and boasts 250WPC into 8 ohms. The power doubles into 4 ohms and the amplifier still has the grunt to even drive a 1 ohm load. This kind of power was needed for driving Apogee and other high end speakers of yore. Even today, some manufacturers build speakers with difficult and punishing loads that require arc-welding amplification.

For a sense of history the original Stereophile review of the S/500 can be read here.

The S/500 amplifier is huge and weights in at a portly 92 pounds. Removing the top panel reveals a massive toroidal power transformer, four huge power supply capacitors and ten pairs of output transistors per channel. The input/driver board is gold plated but to my jaded eyes some of the passive parts certainly look a little pedestrian. But you have to realize that this amplifier was made before the days of ultra-tweak parts.

It is rather funny how bias works - and I'm not talking about Class A versus Class B operation here - but human expectations. My mind was biased against this amplifier for several reasons - it doesn't have tubes, it is some 25 years old and it is high powered. I told myself that solid state design has surely improved over the years and low-powered amplifiers always sound better than their big brothers. And take a look at the insides there - it is just a bunch of silicon parts - where is the mystery and romance of the vacuum tube? A nice black-plate Tungsol 6550 or a Western Electric 300B output tube must be the only way to sonic nirvana. At best I was hoping a tube preamplifier could tame some of the solid state nastiness.

With low expectations I hooked the S/500 up to the Threshold linestage and as I switched it on, I was greeted with a small thunk through my KEF C-75 speakers. I turned up the volume, sat back in my sofa and gave it a listen.

The S/500 simply dominates any speaker it drives. The sheer power, low impedance and high damping factor controlled my KEF speakers more so than any of my tube amplifiers. But yet the sound had a refinement that was totally unexpected from such a monster. Treble was light and airy with incredible extension. Not only was it clean, but it was also free of etch. Based on my past experiences with silicon amplification this is the total opposite of what I had predicted. The midrange was glare and grit free, reminding me of some of the best tube amplifiers I have heard. Not exactly like a tube amp mind you, but very similar with warm musicality and excellent body. And the bass - the bass! - I cannot accurately describe the bass except to say it is the best I've ever heard. Not only is it low and controlled, but it is extremely musical. I can hear different bass shades and musical interactions that were just hints when coming through a tube amplifier output transformer. I never knew a KEF C-75 8" woofer could go so low!

This amplifier is really a high definition piece, besting my old McIntosh 250 by leaps and bounds when retrieving detail. I also feel it is an improvement over my Dynaco Mark IIIs, offering more bass, detail and drive. In some way the clarity reminds me of my SE EL156 amplifiers. But my EL156 amplifiers certainly can't drive difficult low impedance loads like the S/500 can.

Is this the best amplifier in the world? I don't know about that, but I'm certainly interested in seeing how it sounds with my UREI 813A and future Magnepan speakers. The S/500 has forever changed my mind about solid-state amplifiers. They can sound very good indeed and money permitting, I'm curious enough to try out some more upscale solid-state pieces in the future.

If you're interested in trying out a Threshold S/500 for yourself (or any vintage amplifier for that matter), you may want to consider a replacement of the aging power supply capacitors done by an experienced technician. That and some passive parts upgrade will not only increase the longevity but it could also improve the sonics. Right now my S/500 is running completely stock but I will be upgrading once I can.


System:
Source: Phillips DVD player with RAKK DAC
Preamplifier: Threshold FET-10HL
Amplifier: refurbished Dynaco Mark IIIs or Jenison Audio Ultra SE-1 monoblocks
Speakers: KEF C-75 or PSB Stratus Bronze
Wire: Cardas 300-B Microtwin interconnects and Canare Starquad speaker cable

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Speaker Review Updates

I gave the PSB Stratus Bronze and KEF C-75 speakers another listen using some solid-state amplification. I added my findings to the bottom of each review.

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Threshold FET-10/HL linestage review

The past few days I've been listening to the Threshold FET-10/HL linestage. This is an 'old' stereo unit built back in the late 1980s by the great Nelson Pass. It uses discrete FETs throughout with no op-amps in sight. It has tape outputs, selector switch for five inputs, a stepped Nobles balance and volume control. Be warned that there is no phono stage - that was available by purchasing the stand alone FET-10/Pc.

Opening the case of the 10/HL reveals an amazing layout - all discrete components, gold plated circuit boards and an attention to detail that would make a mil-spec electrical engineer gawk in admiration. Output capacitors are basic ERO polypropelenes and the resistors appear to be very nicely made metal-films. There is also an outboard power supply that keeps hum down to near zero.

In all honesty I wasn't expecting much from this linestage. I had faith that my trusty 6N6P based unit could trounce anything commercially made. After all I had MIT RTX coupling caps, all wirewound resistors, a SMD Goldpoint volume control and a choke-based tube rectified power supply. Surely some great parts combined with a simple topology would beat out an 80s produced solid-state piece!

Well, I'm prepared to eat a healthy helping of crow now. The FET-10HL is a wonderful performer and makes me question the need for ultra trick parts. I never knew that solid-state could sound this good.


First of all, it has the ability to resolve the smallest details in the recording. The brush of the cymbal, the breath against the microphone, the way the stick hits the drum and a myriad of other audiophile tricks that I crave in a high performance preamplifier. This is one high resolution piece of gear and on everyone of my recordings I heard details that I never knew existed before. But this resolution does not lose out in musicality. There is a natural sweetness to the treble and the midrange is remarkably grain free. The bass is deep and well defined, adding even more control to my EL156 single ended vacuum tube amplifiers. Instruments have body - maybe a bit less than the best vacuum tube preamplifiers - but more than enough to satisfy me. I wish the gain could be just a little higher for the use with a non-OS DAC, but it hasn't been a problem with my transformer-coupled RAKK DAC.

Considering the performance, a used FET-10/HL is an audio bargain. Prices vary since this was never a mass produced unit. However consider a power supply capacitor upgrade as part of the overall price. This will help for long-term reliability and if you're not handy with a soldering iron, have this work done by an experienced technician. Also a coupling capacitor upgrade may improve the sonics even more, but for now I'm quite happy with the stock caps.


System used:
Source: Philips DVD player and K&K RAKK DAC with passive output
Speakers: KEF C-75 or PSB Stratus Bronze
Amplifier: Threshold S/500 or Jenison Audio Ultra-SE1 EL156 monoblocks
Wire: Cardas 300-B Microtwin interconnects, Canare Quad speaker cable

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U.S. source for the EL156 tube

For anyone interested in making my Singled Ended Ultralinear amplifier, Antique Electronic Supply is now carrying the EL156 output tube. Price is a bit higher than a Chinese supplier, but at least you can try to return the tube if you have a problem with it.

I've been buying from Antique since 1990 and continue to do so because of their great customer service. Plus this year for Christmas they sent me a small tin of mints shaped like a 2A3! Of course Front Panel Express sent me some chocolate shaped like a laser cut panel. I guess being a 'big spender' has its perks. Heh.

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The C3m pentode

The C3m is a loctal socket metal-shielded pentode use by the German Post for audio repeater amplifiers in long distance telephone lines. They are extremely linear and were rated for 10,000 hours of use.

The use of this tube was popularized by Thorsten Loesch in his 'Legacy' 300B amplifier. There are also a few commercial pieces of gear (eg Ayon Audio has a full function preamp) that use this tube. I have experimented with these connected as a triode and my experiences reflect this use.

Breaking a defunct one open and removing the mesh shield, I found a black plate inside with beefy construction. There are no side supports on the mica, which leads to one of many issues with these tubes - microphonics. They are extremely microphonic - reminding me of an old 71A globe linestage I built many moons ago. The switch bounce from my Goldpoint stepped volume control was easily picked up and amplified by the C3m. I tried many brands of C3m tubes (Valvo, Siemens, Lorenz, Philips) and got varying results but some microphonics always remained. So if you do use this tube, I strongly suggest using an extremely heavy case.

Another issue is the loctal socket and 20V/125mA filament requirements. This puts them in the realm of DIY use. I used a 24V transformer with an regulator board using a 7820. The more rare (read expensive) C3o uses 6.3V filaments but is an equivalent.

Another concern is fragility. When making my linestage, I once fired it up for 2-3 minutes to take some voltage readings. I pulled the C3ms out, made some changes and put in the C3ms back in. The movement of the heated tube was enough to make one stop working - ie, it would no longer draw current. I don't suggest ever 'hot-switching' tubes, but it is something to consider if doing some work on a C3m equipped unit. Let them cool down for a few minutes before moving.

Ok - how do they sound? Connected as a triode and used in a linestage, I found them to be very neutral. No glare or grain, they are even-handed from top to bottom. They reminded me more of a really good 6SN7 'type of sound' than (let's say) a 6DJ8.


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