Kutztown Radio Show Spring 2022

All pictures taken with a Fuji X-E3 camera + W-Nikkor 35mm f2.5 LTM lens

It's hamfest and radio show season!👏

 

On Friday, May 13th, I drove through the back roads northwest of Philly towards Kutztown with Ding, who attended this event for the first time.

The weather wasn't very cooperative. Soon after we got there, this vendor had to move to the pavilion due to a heavy downpour.

There weren't as many vacuum tubes compared to the past years, but Ding found enough 5U4Gs to replenish is stash.

A pair of Utah Celeste 12" co-axials driven by a DIY 6CK4 SE amps in para-feed mode provided nice tunes.

A clean Rek O Kut belt drive turntable + Grado tonearm

A well worn ROK B12 Rondine with a Borg "death cube" motor

I've never been a JBL fan, but here's a pair of 4311B monitors + a Harman Kardon receiver.

Green Altec 802D + 806A!👍 

Unfortunately, the diaphragms were fried.😥

Fisher mono receiver + a Scott stereo integrated

Art Deco and Noveau speakers

Hifi guys

A nice monophonic hifi system could be built around this University 6201 co-ax housed in a nice mid-century modern cabinet!

A pair of Heathkit W-7 PP EL34 monoblocks + a DIY tube amp

When stuff I used to see at Circuit City, Crazy Eddie, J&R Music World, The Wiz, etc. are considered vintage, we can only guess what that means.😆

A pair of PPP 6L6 amps

Technics SP15 + a mixing console and a cool art deco TV

Stereo Lab of Columbus Ohio demo'ing brand new Wharfedale speakers driven by a Leak integrated amp fed by a Leak CD player.

Visit the Delaware Valley Historic Radio Club website for more info.

Before leaving, I spotted this '56 Chevy Bel-Air.

My paternal grandparents had one, albeit, black and white, 235 cid "blue flame" straight six + three on the tree. It was in service until 1981. 

See you in September!

Snell Type JIII Part 2: $25 foam vs $40 Euro foam

Re-foaming the 8" woofer found in various incarnations of the Type E, J and K Snell speakers is a very contentious issue exacerbated by their cult-like status amongst audiophile admirers. 

Vifa M21WN-07-04 woofer
Left = $25/pr. foam (yellowish tint), Right = $40/pr. Euro foam

In this day and age of marketing hype, spending $100 or so to import a pair of alleged original foam from European sources is, IMHO, not justifiable. How does one determine which retailer is being truthful?

Given that I wanted to give this project my best shot, when I noticed that Simply Speakers* added a Euro version to their website for $40 a pair/shipped, I placed an order. This is just one of the many reasons why this installment has been delayed. 

*No affiliation, just a satisfied customer!

WARNING!

In Part 1, I re-foamed my pair of Vifa M21WN-07-04 woofers using the $25 foam kit. I specifically mentioned that the dust cap and cone are just one piece. 

I've seen discussions in audio forums suggesting the removal of the dust cap to center the voice coil. I have to reiterate that the removal of the dust cap = a DESTROYED woofer!

After using both these foam kits, I can confirm that the voice coil on this particular Vifa woofer is self-centering. If you encounter voice coil problems, it's either the foam you used is suspect or you seriously deviated from the instructions.

RTA Traces

$25 foam vs. $40 Euro foam

Only one Vifa M21WN-07-04 was fitted with the Euro foam so I could compare them.

Die-hard Snell aficionados and "specialist" retailers contend that "generic foam" will kill the bass response of the Vifa M21 woofer. Given the RTA traces below, which foam is generic?

Snell JIII with Simply Speakers $25 foam

This trace pretty much tracks the original specs at hifiengine.com. 

Snell JIII with Simply Speakers $40 Euro foam

If we split hairs, this $40 Euro foam trace looks just a touch more ragged. 

Euro foam serial number

FWIW, unlike the $25 foam, the Euro foam has a serial number. Does that give it more credibility?

Listening to Foam 

$25 foam vs. $40 Euro foam

Evaluations were conducted in full dimensional mono! 

The sonic dissimilarity was very subtle. It only became obvious in A/B comparisons in which I was consciously listening for a difference. Also, as usual in audio, better metrics don't necessarily = better sound because audio tests (in this case, pink noise) are static while music is very dynamic! 

Listening to Billie, Ella, Julie, Frank, Tony and Johnny H, it was relatively easy to discern better midrange presence from the unit fitted with the Euro foam. When I pulled out my Ray Brown, Curtis Counce, Charlie Haden and Mingus CDs and LPs, I heard more tuneful and articulate bass lines from the Euro foamed woofer. The woofer with the $25 foam had a tendency to sound boomy while the midrange was just a touch veiled. 

That said, if your Vifa M21s are already fitted with the $25 foam replacement and you're not very DIY savvy, it's nothing to lose sleep over. IMHO, you're still listening to a pair of very decent classic speakers. However, if you're a seasoned DIYer restoring an unmolested pair of Type Js or Es with rotten Vifa foams, go for the $40 Euro foam!

 Is the $40 Euro foam the original foam?

The Time Tunnel

I wish I could travel back to the early 90s to find the honest-to-goodness truth.

Instead of worrying about matters beyond my control, I'm going to replace the $25 foam on the other Vifa M21 with Euro foam so I can listen in full dimensional stereo!

Go to Part 3 or back to Part 1

MC step up transformer redux + Hashimoto HM-7

When I ordered this pair of MC step up transformers from Mr. Isao Asakura of tube-amps.net (highly recommended👏) for my cousin's system, he suggested the use of high-quality 24-gauge stranded copper wire. I also took note of his MC step up page, in which he discussed his chassis mounting experiments.

Taking the cue from my buddy Nate aka Redboy at HifiHaven.com, who’s a prolific audio DIYer and MC step up builder, I ordered a cast aluminum project box + 24-gauge stranded tinned copper wire from Amazon.

Hashimoto HM-7 - specs

Upon inserting the freshly mounted and wired HM-7 into my hifi set up, my Tamura TKS83 and Altec 4722 sounded comparatively hard and mechanical...🤔

I had to retrace my steps.

Tamura TKS83

Those who are familiar with my Homebrewer article in Sound Practices #17 will remember that the TKS83 was mounted on an aluminum plate + wooden base while the Altec 4722 + others were on plastic project boxes. These were also wired using 99.999% 19-gauge solid-core silver wire + Teflon sleeving, Kimber TCSS or a combination of both. 

In hindsight, whether commercial or DIY, all the Japanese MC step up transformers I've seen in the metal or in MJ Radio Experiment and Stereo Sound Tube Kingdom magazines, were always housed in all metal enclosures or chassis.

Altec/Peerless 15095A + 4722

Before doing further listening comparisons, I remounted all my MC step up transformers on cast aluminum chassis and used 24-gauge tinned stranded copper for wiring. Since we're dealing with very delicate signals at tenths of a millivolt, very fine strands of high purity copper wire + maximum shielding make a lot of sense!

Hashimoto HM-7

After the playing field had been leveled, the Hashimoto HM-7 no longer outclassed my beloved MC step up devices. However, I'm pleased to say that the HM-7 sound falls somewhere in between the detailed and dynamic TKS83 and the organically rich and spacious airiness of the classic 4722!

Alas, these cast aluminum boxes weren't available when I started experimenting with microphone transformers as MC step up devices in the late 90s. Otherwise, I would've used them since I love the industrial vibe of unfinished aluminum!

Altec 756B + 32C + 806 + 23744 = mini 757

The WE756A is the middle child in the Western Electric series of wide range drivers introduced in the late 40s.

I've seen and heard a couple of WE/Altec 728Bs + a dozen or so pairs of 755As, but I've never heard a WE756A and have only seen one in the metal at a radio show many years ago. Although still quite scarce, its Altec 756B brother isn't quite as elusive.

Back: Blonde + Mahogany Altec Melodist 700A
Front L-R : WE728B, Altec 755A/pr. + Altec 756B

The few Altec 756Bs I've encountered all came out of the Altec Melodist 700A. It's a compact bass reflex speaker system loaded with the 756B, supplemented on top by a 3000A horn tweeter via an N3000B crossover. The 700A belonged to the Melodist monaural hifi system line, which Altec targeted at apartment dwellers in big cities of midcentury America.

 Subsequently, the 756B was replaced by an 8" Altec 401A and was re-designated as the Melodist 700B. With the introduction of stereo for the mainstream market in 1958, the Altec Melodist line quietly faded into oblivion.

 If found in good condition, the Altec Melodist 700A is a fine looking midcentury modern artifact! Unfortunately, the < 1.5 cf ported box doesn't allow the 756B to shine sonically, IMHO. Since it shares similar proportions to its more successful contemporaries like the Acoustic Research AR-1 and the Jensen Duette, the cabinet design may have been dictated by market positioning rather than sound engineering.

My once-in-a-lifetime lucky find 700A above has lived a hard life. The lower front edge of the cabinet was missing while the sweet and airy but very fragile 3000A horn tweeter element had been replaced by a tiny ferrite magnet dome tweeter.😏 A "mod" that has been circulating in the internet, so watch out.  

 

Fortunately, the 756B is very well preserved. If memory serves me right, the WE756A frame is more substantial than the Altec 756B. That’s probably the reason why the back handles were omitted in the Altec. The 756B has an 8 ohm voice coil, while the WE756A is 4 ohms.

J-Rob's Altec 756B at 
Capital Audio Fest 2016

Joe Roberts has already done a great job of describing the sonic qualities and proper implementation of the Altec 756B in his (Geekstar) "My big ten inch --Altec 756B" post at the Altec User's Board. He also gave insight on the shifting Asian market for vintage Western Electric and Altec gear. A guaranteed fun and informative read!

Since I don't have Joe's networking skills, I resigned myself to the reality that my Altec 756B will be the main speaker of my monophonic hi-fi set up, just as Altec intended.

Click for a videoclip

Meanwhile, I repurposed (sealed) a Heathkit AS10 (almost 2 cf) cabinet to familiarize myself with the 756B. I listened to it as a wide range driver with and without top end assistance from either a 32A/802/34852 + an XO based on this schematic or 3000H with an L-Pad + 0.5 uf - 1 uf paper in oil cap. The simplest XO I used was a 0.22uf paper in oil cap in series with the + terminal of the 3000H, no L-pad needed. That also sounded good, albeit, with slightly less sparkle.   

JE Labs mini 757
inspired by the Western Electric 757A

After extensive listening in wide range mode, I determined that a mono hifi set up will benefit from a wider baffle + the dispersion pattern of the Western Electric-derived 32 horn. So I sketched a slant front ~ 2.5 cf infinite baffle that has a provision for an Altec 32C horn + 802 driver and sent it to John Piro of Hommage Audio.

728B vs. 756B

As expected, the 756B is more extended at the top end than the 728B with almost, but not quite, equal bass extension. However, music through the 728B held my attention appreciably longer without my reaching for a clip-lead to fill in the top octaves with the 32/802 horn/driver for more harmonic overtones above 5 kHz. 

RTA = Altec 756B in a ~ 2.5 cf infinite baffle 

I confirmed this during one of my shop talks with J-Rob, who also found it more rewarding to listen to 728Bs in wide range mode than to his 756Bs. It makes me wonder if the 756B and its WE756A brother were designed with a middle-child syndrome gene in their sonic DNA.🤔

After many years of collecting Altec 1" compression drivers, I've only landed a single Altec 23744 "light" aluminum diaphragm, which was fitted to an 806 motor that was used in the Altec 9849 monitor speaker.

Things started to crystalize when my friend Dave V. aka Salectric,🙏 sent me his spare .085 mH choke. It was a proprietary part found in the EQ circuit of the Altec 9849 crossover, which is an 8 ohm speaker system. This EQ circuit shapes and boosts the response of the 32/806 horn/driver combo. Incidentally, Dave's "Last PAS" articles written for The Audio Amateur contributed to my 80s Dynaco hacking activities.

RTA = Altec 32C + 806 + 23744

 The 4 uf paper in oil capacitor serves as a first order high pass filter hinged around 5 kHz with a gentle 6dB/octave slope, while the variable 8 ohm L-pad shapes and controls upper frequency overtones to taste. 

inside the mini 757

John P did a great job of building a very rigid cabinet, which saved me the time and trouble of having to experiment with damping. I just lined the interior panels with Kimpak and I was ready to listen.

RTA = JE Labs mini 757

This project transpired as an opportune moment to assemble all the singleton Altecs from my collection - 756B + 32C + 806 + 23744 - into a formidable monaural hifi speaker system.😊

JE Labs mini 757

My ears hear close to half an octave of bass extension from the mini 757 compared to the 755A in a Silbatone or 618 cabinet. Due to its greater efficiency, it plays louder while dynamics at micro and macro levels are less compressed. The larger cone area of the 756B + wide baffle + 90° horizontal x 60° vertical dispersion of the 32C horn, portray a bigger sense of scale. All of these were achieved without compromising the midrange realism I enjoy from my beloved 755A. 

However, the Altec 753C is perceptibly more efficient, offers at least an octave lower of extension with more authority. It also produces higher SPLs. 

Alas, we can't defy the physics of sound...

JE Labs monophonic hifi

...so I focused on the aesthetics by spicing it up with a touch of Charles Eames and Dieter Rams! 😉

Analog LP Playback + Film Photography

Combining my passion for two obsolete technologies

Thorens TD124 MKII with heavy platter + Alfred Bokrand AS309 tonearm
Canon P + Canon 50mm f1.8 LTM 
Ultrafine eXtreme 100 in Kodak HC110 

Late last year, I acquired the classic AS309 tonearm for my Thorens TD124 MKII from Alfred Bokrand. I really can't hear a difference between the AB309 and AS309, even if I'm forced to split hairs. I'm just happy to own both!

Garrard 301 + Ortofon RMG309 + SME 3012 in JE Labs plinth
Tower 3 (Leica copy) + Leitz Summitar 5cm f2
Ilford FP4+ in Kodak HC110

This was my main turntable for over twenty years. Now the duty is shared with the Thorens TD124 MKII above, and the Garrard 401 below.

Garrard 401 + Alfred Bokrand AB309 tonearm
Bessa R + Canon 50mm f1.8 LTM
Ilford FP4+ in Kodak HC110

A couple of blog readers and Instagram contacts have reached out regarding long delivery times from Alfred Bokrand. All of my transactions with him were done through eBay and on the average, delivery was within two months. I highly recommend that buyers order via eBay since it has a buyer protection guarantee.

emails from Ukraine, was Radiotron SE2A3

Bach Chaconne
from
Partita No. 2 in D minor for Solo Violin

An important lesson I learned as a classically trained violinist was that music theory evolved from the analysis and study of great masterpieces from Bach to Bartok. Great composers broke theory to reach new heights in musical expression. Just like any artistic pursuit, music continues to evolve through individuals who are not afraid to go against convention for a greater good!

Tube load line simulator
from Trioda.com

On the other hand, audio engineering, for the most part, has always been theory driven. Audio design simulators are significant modern conveniences but don't guarantee musical-sounding circuits even if the metrics look great. Creativity in audio design is when human ears are still the final arbiter, at least in my experience and opinion, which is why my hifi system is a hodgepodge of mostly obsolete technology, some of which date back to almost a century ago.

Last year, a Juilliard-trained pianist turned lawyer visited my man cave and listened to various amps + a couple of speakers I built. On his second visit, he brought his amps for comparison. At the end of that session, he commissioned a pair of Altec 753C speakers, the second pair I built in collaboration with John Piro of Hommage Audio, who crafted the speaker cabinets.

The chosen amp was the Radiotron SE2A3 - a topology from the pre-WWII Radio Designer's Handbook, 3rd edition. This circuit was from an era in which calculators were but a dream and engineers computed complex equations aided by a slide rule. 

!!!WARNING!!!

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

Although this pentode-driven circuit sounded fine as is, to my ears, its fullest potential was only realized after I adjusted the plate and screen grid voltages to achieve a 2:1 ratio as suggested by my Ukrainian internet buddy, Sergey Didkovsky in the winter of 2007. 

"Try please, to increase the cathode resistor (1,2k-1,5k ohm) and reduce anode resistor (to75k-82k). It will allow to increase Ua up to 150V and to receive 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. I use TCC Visconol. I think oil caps in the grid - adds bass. Reduction of the anode resistor - improves the hi range a little."

Click here for the 2007 Radiotron SE2A3 article 

I'm pretty sure the 2:1 ratio wasn't a number crunched by a simulator, it was a figure painstakingly chosen by Sergey's ears because of his love for music!

 

Sergey, wherever you are, I pray that you and your family are safe. Freedom-loving people around the world are very grateful, yet very sorry that Ukraine is all alone in shielding the free world from the atrocities of a megalomaniacal autocrat!