SRPP SE2A3 Circuit Redux

Back in the late 90s, I dismissed the hi-mu/low-gm SRPP input/driver because I found that the circuit had a tendency to sound tiring over extended listening. However, my memorable encounter with the Morikawa SE2A3 amp owned by my buddy Jose was haunting. I had to revisit this circuit just to make sure I left no stones unturned. 

Earlier this year, Steve of Angela Instruments shipped me the "shop mule" SRPP SE2A3 amp for a check up. After replacing the leaky coupling caps, the amp was as good as when I delivered it to the shop over two decades ago.  

My hotter operating point = slightly more power compared to Prof. Morikawa's SRPP 2A3 amp.

!!!WARNING!!! 

The voltages in this circuit are potentially lethal! Build at your own risk!

Click here if you'd like to try the SRPP 45 triode circuit.

Use a Hammond 302AX power transformer instead of T1 + T2 A&B

Click here to see the "cleaner" 10kHz square wave from the Morikawa SE2A3 amp

In spite of the 10 kHz square wave spike from the budget Hammond 125ESE output transformers, it was a very refreshing musical reunion with the Angela SRPP 2A3 amp. 

During its residency in the man cave, the amp powered my back up Altec 2-way system above, Altec 755As and Altec 755Cs in Silbatone cabs below. It was totally devoid of the listener fatigue I previously ascribed to the circuit. Even with the brightest and harshest software and/or hardware thrown into the listening chain, I couldn't induce the unpleasant quality which bothered me in the past. 

Then it dawned on me that I started doubting the SRPP's musical abilities when my Altec 2-way project commenced. Sorry SRPP, it wasn't your fault...😟

YMMV!😉

Hub City Vinyl

We took a long drive to visit relatives in Western Maryland for Memorial Day weekend.

I made sure we checked out Hub City Vinyl in downtown Hagerstown, MD. This really cool record store is housed in an Art Deco structure that served as a car dealership in its previous life.

I was based here from the latter part of the 90s till the late 2000s and never imagined a well-stocked record store of this size could thrive in this town.

Notice da boss patiently waiting in the listening lounge?

The Zu Omen speakers driven by Schiit Audio electronics with Steely Dan's "Gaucho" spinning on a Technics turntable made the atmosphere even more endearing!

Towards the back of the building is another room full of LPs and CDs.

The left hand corner of that room had stacks of classic hifi gear!

 This Gates CB1200 3-speed idler driven turntable + Gray 206 viscous damped tonearm definitely caught my eye. But I've run out of space and need to unload to pacify the boss.😉 

So I hope a blog reader will buy the above set up and enjoy it!🍻

I like the black out aesthetics of this 70s Plainview NY era Harman Kardon 330C receiver, which sported technically innovative circuitry. The rack mountable Tandberg tuner is also interesting!

How about a custom tube amp using 6BL7 tubes?

One of the sales associates told me that the back end of the building will eventually be transformed into a live music venue as the pandemic winds down. This is really great news for the cultural life of Washington County!

If you're a record collector and/or audio buff driving through the junction of I-81 and I-70, this place is a must-see!

Welcome, summer! Safe travels!

Fidelity Research FR64fx - dead channel fix

After many years of service, my FR64fx tonearm dropped one channel. 

I started sleuthing by studying the vertical pillar.

By peeling off the tonearm height scale (essentially an aluminum backed sticker), the set screws are exposed.

I loosened the set screws to carefully pull out the 5-pin DIN terminal + horizontal bearing housing from the vertical pillar. The unsoldered wire was instantly visible. 

After soldering the broken connection, I re-assembled in reverse order. I used rubber cement to secure the tonearm height scale back to the groove in the vertical pillar. 

Happy listening!

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!