Vintage Tube Amp

1957 National Aztec Valco 1240T in great, original condition. Aztec, was a National designed amp manufactured by Valco and has a completely different large single speaker approach than earlier Aztec 3 speaker oval speaker type construction. This is the National design built by Valco with Orange identification for each tube socket. Multiple pre amp tubes (some NOS) are included, and offer shielded (can-type) or un-shielded socketing. Cabinet is 18x20x9 which tapers at the top on the back side to 8 inch depth where a mirrored panel provides 2 Regular Inputs, 1 Treble Input, and 1 Microphone Input. 1 Volume & Tone adjust the 3 Instrument Inputs, while 1 Mic Volume Control adjusts the single microphone Input. The “Tone Control” works across all channels, including the Microphone Input. The cabinet houses a single 15 speaker with a closely mounted output transformer mounted to the side of the cab. The upper deck houses the Controls and Power/Fuse/Indicator and other controls. There is a Tremolo footswitch and separate switchable Volume/Depth control with on/off. Power for the unit is operated by the Instrument Volume control. There are three Shielded Tubes also contained in the upper deck. The lower deck at the base houses the power supply and power output tubes, rectifier and transformer. Comes with original 9 foot 2 prong cord. (a three prong grounded adapter will be properly plugged-in). Designed and manufactured for 6L6-type tubes this amp has the higher output version, more closely matching the popular British KT-66. These 6L6 type are 7581A Tubes matched for this National. The 35 watt 7581 over the 30 watt 6L6 usually carry about a 20% higher cost. USA branded logo on the tube glass. Speaker is a 15 inch alnico type. 7581A spec design refers to the 5% higher output over 6L6 type, in all other ways, specification wise, they are functionally equivalent to 6L6 but closer to the KT-66. Speaker directly wired to a secondary off the stand alone mounted output transformer. All the small signal tubes are shielded. 2 are in Can-type octal-sockets and one has a surround shield in a 9-pin. Pictures in the upper deck show the tube type in Orange on a shielded frame under the top of the amp. The AMP base tubes are also are labeled in bright Orange. The amp is relatively quiet until about mid-volume when it begins to demonstrate its power. The Tone range is very broad and pleasant. Due to the typical higher amplification demands of a Microphone the gain seems higher on the MIC channel/Volume, and it is hotter and while the regular inputs bring solid strength to the sound, the Mic input really cuts through and offers and leans towards distortion at higher levels, with an edge. This model utilizes a permanent magnet as demonstrated by holding the knife on its edge in one of the photos. The tweed and faux wood grain have seen their share of loving use and a bit of abuse as well, with corners now well worn as is common for amps with over forty years of use. At this point, the tremolo will wobble about once or twice when the control is switched on, and then stops with no effect on the sound beyond the initial vibes. It has been this way for at least 10 years, and I really never use it anyway, so I never had it serviced, and I did not want the circuitry touched. (no irons have been laid it). I use a 2-3way grounded adapter with it to ensure it is plugged into AC correctly, reversed it’s capable of a shock. In a studio environment, the Aztec was always chassis grounded and’float’ not possible for side chain, and was run’cold’ chassis. The Instrument input uses a 5879 shared with the tremolo circuit, the regular inputs are direct coupled and the treble is. This is the warm tube used in Gibson’s Les Paul amp. The Mic input uses a 6SJ7 and has a grounded cathode without bypass and is de-coupled with a. 01uf capacitor at input. In schematic, it’s even easier to see, the “I” channel and the “M” channel meet up at the post amp before mains at a point where the “Tone Control” is designed to do it’s job. The versatility works great in studio settings. The smoother tone of the 5879 channel can fit many situations, while the hotter 6SJ7 overloads nice. This amp is best suited to anyone looking for’tone’ over distortion. Here is an observation from an individual talking about the 5879 pentode. A 5879 is used in Gibsons GA-40 of the late fifties. This pentode fits the same 9-pin socket as dual triodes (12AX7), but require very different circuitry. The 5879 is known for thick, robust sound and have higher gain factors than a 12AX7, but arent prone to distorting the way that dual-triodes can. A complete set of pre-amp t ubes matching this amp are included in boxes in addition to the ones currently in socket. Note: NO 7581A tubes and NO 6L6 are in ANY “boxed items ” – it ships with 2 7581′s in socket only. The boxed items are New original Old Stock pre amp tubes , and offer replacement for top level Pre-Amp section, one has both GT and CAN choice, for the 9-pin, one tube is used and good, and offers a NOS choice as well. Thanks for looking, and God bless you. Note: If considering for professional road work, I would match it with an Anvil case, have an isolation transformer mounted inside and earth ground the chassis. If the price is too high, then it’s not for you, but thanks for looking and your attention is very much appreciated. It will also have the phased (2-3 way) adapter properly connected to the amp’s original non-phased power plug for safe AC use. The item “Vintage ORIG 1957 National Aztec Tweed 15 Valco Guitar Amp 7581A Tubes (KT-66)” is in sale since Friday, October 13, 2017. This item is in the category “Musical Instruments & Gear\Guitars & Basses\Guitar Amplifiers”. The seller is “zzeon” and is located in Chelmsford, Massachusetts. This item can be shipped to United States.

• Brand: National
• Amplifier Type: Combo
• Amplifier Technology: Vacuum Tube
• Type: Electric Guitar Amplifier
• Number of Channels: 4
• Suitable For: Performance
• Model: Aztec1240T
• Country/Region of Manufacture: United States
• Impedance (ohms): on secondary side of transformer – .7 ohm