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Kay Vanguard 704 with Vibrato

Kay 704 Vanguard Vibrato

“A Briefcase Full of Blues” – The World’s First All Solid-State Guitar Amp

Quick Info

Summary: 1965 5-watt solid-state combo amp with built-in vibrato effect; 8-inch Alnico speaker; seven Germanium transistors and five Germanium diodes. Point-to-point hand soldered. Perfect little amp for practice or recording.

Pros: Vintage 60′s tone. Extremely compact and portable design. Vintage Germanium transistors and diodes. Simple chassis layout.

Cons: Cheap, lightweight construction and paper-thin fabric covering (but hey, it’s lasted this long already).

Surprises: This old school amp designed more like a tube amp than a solid-state amp. The 8-inch Oxford Alnico speaker sounds great! Awesome vintage vibrato circuit.

Value: Street prices vary by condition and demand, but the price of these continues to rise.

Similar Amps: Kay 700, 705 and 706 of similar vintage. It’s possible, but not certain, that there may be some similar Kay-built amps with a Truetone (Western Auto) label.

Introducing the Kay Vanguard Series

In 1962, the Kay Musical Instrument Company of Chicago introduced the Vanguard line of guitars and amps. That new line included the Kay Vanguard Amplifier with Vibrato, Model 704 (Model No. K-704). The Vanguard 704, along with other Vanguard amp models 700, 705 and 706, were the world’s first mass-produced all-transistor (solid-state) guitar amplifiers. While some transitional hybrid amplifier circuits had previously existed, which paired solid-state electronics with traditional vacuum tubes, Kay was the first company to offer a full line of exclusively solid-state amps to market in ’62. The Vanguard 704 was part of that line and was frequently seen offered with the Kay Vanguard solid-body electric guitar.

A marketing advertisement from 1965 says that the K-704 was built with seven transistors and five diodes.

A Compact Design

In contrast to the heavy, boxy, amplifiers of the 1950′s, the engineers at Kay set out to create a new series of amps styled for the Modern Space Age. The new Vanguard Series was designed to be compact, lightweight, sleek in appearance. Finished in a rad two-tone pattern, the tapered vertical design had a top mounted control panel, and a cabinet barely deep enough to house the speaker and chassis. The new look was unique for a guitar amp of the day and remains unique today. However, the lightweight cabinet materials made it more prone to excessive wear and tear. Therefore, not many of these amps have survived.

The Controls

The Vanguard 704 features three instrument inputs into a single channel; a volume control and a tone control. The power switch is built into the tone control knob. The vibrato controls include speed, strength, and a jack for a foot switch. A sturdy brass handle is ready to go places.

Old Germanium, New technology, Old Circuit Design

What really makes the Vanguard 704 interesting today is its 1960′s Class A amplifier design and chassis layout. Since solid state technology was still relatively new at the time, the Kay engineers built the preamp, vibrato and the output circuits similar to the old tube circuits, except using Germanium transistors and diodes substituted for vacuum tubes. Because of this design the K-704 sounds akin to its tube cousins of the day. Based on traditional tube amp design of that period, the vacuum tubes were replaced in the hand-wired circuits with seven Germanium transistors and four diodes. The old Germanium transistors sound a little “looser” than the newer Silicon versions, which make them perfect for these low wattage amps. However, Germanium never could handle the heat and raw power of higher watt amps. But Germanium still has a following and is used in low voltage applications, like custom built effects pedals.

According to the pots, it’s a 1965 model. Completely original. A 5-watt wonder. It’s circuits and layout are traditional for the period, but seven germanium transistors and four diodes in place of the traditional vacuum tubes. A single front-loaded 8″ Oxford Alnico speaker. Not a whole lot of lower mid-range. But then again, no low end speaker flab either. The tone kinda reminds me of Led Zep. Mild overdrive at full volume from my Gretsch 5120 humbuckers. Growling, howling overdrive from my Silvertone 1445 with Teisco single coils.

Vibrato, CCR, and The Midnight Special

The vintage Germanium powered vibrato circuit stirs up a deep swirly tremolo that simply sounds awesome. The Kay Vanguard with Vibrato is perfect for nailing that stirring, swelling, sound that Creedence Clearwater Revival played on songs like The Midnight Special and Run Through the Jungle, and other great CCR recordings.

If you are a fan of that vintage 60′s and 70′s tremolo, then this effect alone was worth the price of this unit.

Features

  • Compact, ready-to-go “suitcase” design.
  • Two-tone fabric over wood construction.
  • Five watts output.
  • 7 Germanium transistors.
  • 4 Germanium diodes.
  • 8-inch Oxford “Heavy Duty” Speaker with Alnico magnet.
  • One channel.
  • Three inputs.
  • Vibrato speed and depth controls; foot switch.
  • Volume and tone controls.

Specifications – Kay 704

KAY 704 – VANGUARD with VIBRATO
Model Number 704A
Serial Number 9366
Manufacture Date 1965
Type 8″ Combo Amp
Output (Peak or RMS) 5 Watts, Peak
Pre-Amp Transistors 2N2613, 2N408 and 2N591 Ge PNP BJT, RCA USA
Vibrato Transistors 2 ea. 2N408 Ge PNP BJT, RCA USA
Power Transistors 2 ea. 2N545 Ge PNP BJT, Motorola USA
Speaker Configuration 1 x 8″ Rear Loaded
Speaker Oxford 8ES-9 Alnico Magnet
Speaker Code 465-510 (10th month of 1965)
Baffle Board 1/4″ Plywood
Impedance 8 Ohm
On-Board Effects Solid-State Vibrato
Footswitch Yes
Controls Volume & Tone
Inputs 3 Instrument Inputs
Channels 1
Cabinet Construction 3/8″ Plywood
Cabinet Covering/Color Fabric
Dimensions (WxHxD) 14″x17″x6″
Weight 8 lbs.
Power 120V AC

Schematic Diagram and Parts List for the Kay 704A

Original factory schematic diagram as photographed from inside the 704 chassis.


Original factory Bill of Materials (or, “parts list”) as photographed from inside the 704 chassis. Notice that transistors Q1, Q2, Q3 and Q4 are all Germanium transistors made in the USA by RCA and Motorola, as well as diode D1.

Additional Resources

Links to additional information.

Photos: See more photos here.

Comments

weldon January 1, 2014 at 12:04 am

i had a 704 kay amp and kent guitar in the 60s they were new—–i had to pawn them to move away–i found a kent guitar and now looking for the amp-can you help thanks weldon bent

REPLY

alex January 1, 2014 at 9:13 am

Weldon,
Thanks for stopping by the website. 704 amps are hard to come by these days. Not many survived the 1960′s. Ebay is probably your best bet, as I see a few show up there each year. Craigslist another option. Good luck!
~alex

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big gee February 1, 2015 at 1:56 pm

I have one of these 704 Kay in great condition for sale make an offer

REPLY

Tom J April 7, 2015 at 4:28 pm

I have a Heater II reverb amp type 58 with the tag that says “Manufactured by beautiful girls in Milton, Wis.
under controlled atmosphere conditions”.
Can you help me get a schematic ?

REPLY

alex July 26, 2015 at 9:58 pm

Hi Tom.
That reverb unit was made by OC Electronics and was used in many amplifiers sold by Sears, Wards, etc. in the late 60′s early 70′s. I don’t know if a schematic is available, but you might try Schematic Heaven.

REPLY

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Silvertone 1420 (Sears 5XL)

Vintage Sears 5XL Silvertone 1420 Guitar Tube Amp


Welcome to our first review. Please consider Tone Gems a resource for vintage guitars, amps and gear of non-repute. We will strive to make each review rich with information and content, including inside gut shots, electrical schematics, audio, video, manufacturer specs and more. Since this is our very first review, please excuse any rough spots. We welcome your comments and feedback. Thanks ~alex.

Quick Info

Summary:  Five watts of hand-wired boutique tube heaven for a fraction of the cost. Lots of midrange growl and creamy overdrive. Great for  jazz, blues, classic and indie rock. Use as a practice amp or at small venues. Perfect for recording.

Likes:  Cheap! Lots of tube overdrive. Awesome speaker. Cheap! Point-to-point hand soldered. Cheap!

Dislikes:  Cheap cabinet materials and shoddy construction. Not loud enough. No safety fuse. Non-grounded power cord.

Surprises:  8-inch Alnico Speaker. Polypropylene caps (Orange Drops!).

Price:  $90.00 from Trade Up Music, Portland Oregon.

Similar Amps:  Silvertone 1420; Silvertone 1459.

The 5XL Review

At first glance the Sears 5XL guitar amp would be easy to disrespect, even considering it’s legacy in the line of original Danelectro/Silvertone guitars and amplifiers. And why not, it’s a Sears, right? Well, that’s where you’d be wrong. We recently discovered this 5XL at Trade Up Music, a local music shop in Portland (see posting: How It All Began…). It was dirty, dusty inside, and a little beat-up. It appeared to be all original, except for two replaced vacuum tubes, and was fully functional. Later, we discovered that someone must have upgraded the capacitors with new Orange drops (more on that later).

My son Jon, who likes to play alternative and indie stuff, thought this amp would be a perfect match for his 1950′s Gretsch Electromatic or his newer custom modified Telecaster. I was not initially impressed. But boy was I wrong, and he was right!

The 5XL is an all-tube amplifier producing a modest 5-watts of peak power through a single 8-inch speaker. It has one channel, two instrument inputs, and separate volume and tone controls. The cabinet is built from cheap pressed board and the speaker baffle is 1/8-inch thick Masonite. It is clad in an equally cheap, thin green vinyl that stretches and tears easily.

At lower volume this amp has a clear, clean sound and decent frequency response. But with only three tubes pushing 5-watts it’s more fun to dial this puppy to 10! At that level it’s easy for the player to control the output and vary the tone from clean to full distortion.

This amp is also friendly to effects pedals. It sounds really good with a decent analog delay or analog reverb pedal.

Video of the 5XL

How good does it sound? See and hear for yourself. Here is Jon playing his modified Squier thinline Tele through the 5XL. Hope you have a good set of speakers connected to your computer.

Who built the 5XL?

The tube version of the 5XL was sold by Sears in the United States from about 1969 through about 1972. It was Sears entry level into their line of guitar amps. But the original manufacturer of the Sears 5XL is hard to nail down. I have seen several different builds of the Sears 5XL amp on eBay and elsewhere on the web. Up until 1968 or so, the Silvertone line of electric guitar amps were built for Sears by the Danelectro company of Neptune, New Jersey. In fact, the 5XL is identical in electronics and appearance to the earlier Silvertone 1420 and 1459 amps that were built by Danelectro. But Danelectro was purchased by MCA in 1967 and was, unfortunately, out of business by 1969. This particular sample appears to have been built in December of 1968, so it’s possible that it could be a Danelectro original. But I suspect that even later models were built for Sears by others, maybe using leftover Danelectro parts?

UPDATE: I recently noticed that the schematic diagram for the Harmony H303A is nearly identical to the Silvertone 1420 and Sears 5XL. So it might be possible that these were built for Sears by Harmony. However, I thought Harmony was struggling to stay open around this time as well?

UPDATE 2: This basic amplifier design was used throughout the radio and musical instrument industries for decades. Which makes it even harder to pin point the factory of origin.

The 5XL Chassis

The amplifier is a hand-wired, point-to-point, single-ended Class A amp. The chassis layout and construction is standard to Danelectro/Silvertone design dating back to 1950’s. It is very similar to the Silvertone 1430 chassis, except that it has a separate tone control and a voltage isolation transformer which the 1430 lacks. Apart from some replaced tubes, this chassis has all its original parts including the big paper-oil-wax filter capacitor. Amazingly, this amp is still quiet while running. The three vacuum tubes (thermionic valves) used here are: one 12AU6 for pre-amp, 5OC5 output, and a 35W4 tube rectifier. Curiously, we believe someone replaced all the original capacitors with newer polypropylene film capacitors (Orange Drops!) which may have something to with the usually smooth tone of this sample.

A close up view of chassis showing the Orange Drop caps and volume pot. The stamped 7-digit code on the pot indicates it was manufactured by CTS (code 137) on the 48th month of 1968.

The Speaker

Sears used a lot of cheap parts. No exception here. But for some reason this original 8-inch speaker made by Fisher with an Alnico magnet sounds great!

Conclusion

Even though this little amp is as basic as it gets, it simply excels at what it does. And that qualifies the 5XL as a Tone Gem. Perfect for recording jazz, blues or rock. And perfect for the player looking for that alternative indie sound. But fare warning: manufacturing quality of this amp was inconsistent and not all samples found today will be built like or sound like this one.

Specifications – The Sears 5XL

SEARS 5XL
Model Number 257-1420(1100?)
Serial Number ????
Manufacture Date Dec. 1968
Type Combo
Output (Peak or RMS) 5 Watts, Peak
Pre-Amp Tubes 1 x 12AU6
Power Amp Tubes 1 x 50C5
Tube Rectifier 35W4
Speaker Fisher 8″ Alnico
Speaker Code 6392 (printed on cone)
Speaker Configuration 1 x 8″
Baffle Board 1/8″ Masonite
Impedance 16 Ohm (?)
On-Board Effects None
Footswitch None
Controls Separate Volume & Tone
Inputs 2
Channels 1
Cabinet Construction 3/8″ Pressed Board
Cabinet Covering/Color Vinyl / Olive Green
Dimensions (WxHxD) 16″x16″x6″
Weight 8 lbs.
Power 120V AC

Schematic for the 5XL

I’m working on a new schematic diagram for this amp which I will add here later. In the meantime the schematic of the Silvertone 1430 (shown below) is somewhat similar to the 5XL, except that the 5XL adds a tone control and has no safety fuse! Diagram courtesy www.freeinfosociety.com.

Silvertone 1430 Schematic

Additional Resources

Links to more info surrounding the 5XL…

 

{5 comments}

Ty Stites February 18, 2012 at 10:05 am

See also schematic for the Alamo Capri which is very similar. You might want to add that as an update. ( I can e-mail you one if you like).
I bought a “5 XL” on e-bay that needs to be repaired/restored. It does NOT say Sears on it anywhere (however, the back is missing…) but has a big Danelectro logo on the grille. It does say “5 XL” on the front panel but where you sometimes see a Sears logo on the front panel there is a logo that looks like an atom or something (???). Anyway, I was wondering if you ever found another schematic. Most of the wires in this one have been cut – I have no idea why as it appears that all the original components are still in place despite all the wires being cut (??!). Anyway, this one has TWO chassis mounted transformers (wires cut) which appear original which I do not see in your pics. It has the output transformer on the speaker like in your pics. Three trannys total. (??…)
Any help would be greatly appreciated!!
Love your site. Keep up the good work!
Thanks.

alex February 18, 2012 at 12:47 pm

Ty,
Thanks for stopping by and leaving your comments. What you are describing sounds odd to me. To the best of my knowledge, Danelectro did not market a 5 XL amp with a Danelectro badge on it (that would be news to me). The logo that looks like an atom is actually a Sears-Roebuck (SR) logo from that era. I have two amps with that logo. It sounds like you have a mixture of things going on there (a frankenamp?). Could it be possible that someone before you took it apart and added the Danelectro logo? The transformers you describe definitely sound to me like someone’s custom modification. Could you email to me some photos? That would be great. ~alex

alex February 18, 2012 at 12:59 pm

Also, thanks for the tip about the Alamo Capri. The schematic does look similar, and it uses the same tubes. I will research that further. Thanks!. ~alex

Scott June 7, 2016 at 11:47 pm

I have been slowly hot rodding one of these little amps for a while now. I have recapped/potted, traded out the OT with a Hammond, and replaced the cheapy 8″ speaker with a Jensen p10r. I’ll tell you what, for blues harmonica it is a tone monster. To play with a band I just stick a microphone in front of my speaker and let the PA do all the heavy lifting. I have a few big tube heads and combos, but I still plug into the hot rod 5xl every time.

alex June 10, 2016 at 10:18 pm

That sounds awesome! Thanks Scott for sharing that info about your 5xl.

~alex

 

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DOD FX10 BiFET Preamp

DOD Bi-FET Preamp FX10[This is an update to an earlier post. Since then we have done some more testing of this unit with different instruments and amplifiers.]

I was looking for a good analog pedal to overdrive my tube amp without loosing that “great Gretsch sound” of my Electromatic. The DOD FX10 was originally built as a preamp for acoustic guitars, but I had read some pretty good things about using the FX10 as a clean boost, so thought I’d give it a try. I ordered this one online from Studio 1525 (BTW: Studio 1525 has a huge selection of vintage pedals). According to the America’s Pedal web site, the FX line of pedals was first introduced by DOD in 1982, and the FX10 was part of the first group of FX pedals released that year. It remained in production through the mid-1990’s. According to the date code on this FX10’s pots, it was made in 1983. This sample is the original version that has the really cool larger knobs, similar to some other respected DOD pedals of that era.

DOD FX10 SpecificationsDOD Bi-FET Preamp FX10 DOD Bi-FET Preamp FX10

  • Gain of +17 Decibels
  • Controls: Level and Tone (CTS pots)
  • Jacks: ¼” In and Out
  • Construction: Die Cast Metal Box
  • IC: TL062 Dual Op Amp, TI Malaysia
  • JFET: Two J113’s
  • Bypass Switch: CMOS 4007
  • Power: 9-volt battery or PS125 (10VDC)
  • Mfrd: 1983 in USA
  • Dimensions: 3″x5″x1½”
  • Serial No: FX216329

How does it sound?

Others have reported more success with this pedal than I have been able to achieve. It does perform OK on a guitar amp when both controls are kept between 0 and 6 (up to about 2 o’clock on the dial). But above those levels it will add a significant amounts of noise.

Originally, I tested this unit with an old Silvertone tube amp. Initially I was disappointed, because, even though the pedal boosted the amp into overdrive, it was pretty noisy and thickened my guitar’s tone more than desired. But that could have been due to the minimal (or no) shielding in the old tube amp. So I took the pedal out of chain and set it aside for awhile.

Later, I tested this pedal on a solid-state Univox bass amp and it really did a good job of boosting the signal without changing the original tone of the guitar. And unlike before, it barely added any signal noise into the chain of effects. So obviously the combination of equipment makes a big difference.

More photos…

Additional online resources for the DOD 10FX:

Shop: Studio 1525 Preamps
Shop: Search ebay for DOD FX10
More Info: America’s Pedal
More Info: DiscoFreq’s Effects Database

Posted on

A Briefcase Full of Blues

Kay 704A Guitar Amp with Tremolo

1965 Kay 704 Vanguard Vibrato

Find the full review here: Kay 704 Review

The Kay 704 Vanguard with Vibrato was the world’s first all transistor solid-state guitar amp, introduced by Kay Musical Instruments in 1962. Based on traditional tube amp design of that period, the vacuum tubes were replaced in the hand-wired circuits with seven germanium transistors and four diodes.

I bought this from a guy on eBay. According to the date codes found on the potentiometers, it’s a 1965 model. Completely original. A 5-watt wonder. A single front-loaded 8″ Oxford Alnico speaker. Not a whole lot of lower mid-range. But then again, no low end speaker flab either. The tone of this amp makes me think of Led Zep. Mild overdrive at full volume from my Gretsch 5120humbuckers. Fantastic OD howl from my Silvertone 1445 with its Teisco single coil pickups. The solid-state vibrato circuit is simply amazing! The vibrato effect alone was worth the price.

See more photos of the Kay 704 Vanguard Vibrato here.

Comments

tomas March 29, 2011 at 4:37 pm

glad you are enjoying it!

nice site, added it to my RSS reader….

REPLY

alex March 30, 2011 at 8:07 am

tomas, thanks for visiting the site! ~alex

glassdog March 2, 2012 at 4:27 pm

I have the same vanguard amp was wondering Its worth having someone look at it. It has some issues with the sound. It mostly crackles It was given to me by a relative. thanks

REPLY

alex March 2, 2012 at 4:59 pm

@glassdog, thanks for visiting the site. Personally, I like these amps a lot, and they are getting much harder to find. I do my own repairs to save $. I would definitely recommend having someone look at it to at least estimate the damage and repair cost. But I wouldn’t recommend spending very much to repair it. $75 to $100, max, and that’s pushing it. Unless yours is in pristine physical condition – and most are not! Good luck! ~alex