Ampex 403 Preamplifier Service Manual
Ampex 403 Preamplifier Service Manual - In this site is not the similar as a answer manual you purchase in a sticker album heap or download off the web. AMPEX Model 400A, 401A, 402, 403, 404, 405 Manual.
1961 Ampex Signature Promotional Photo I’ve enjoyed Bryce's museum tour of his Ampex console collection for a few years now - and with some patience and persistence I finally found a very nice intact Ampex Signature for restoration - at a time that it finally fit the budget. In the interim I had been collecting all of the information, brochures, ads, photos etc.
That I could find. My most recent finds are the September-November 1960 Sunset Magazine ads (will repost when I find an original magazine) and the 1961 Ampex Signature promotional photo set. I will be happy to index and trade scans - and will otherwise gradually post those of manageable file size. I'm hoping this posting will inspire a continuing discussion of production dates, serial numbers and production variants of the Ampex Signature console - as there are apparently many different configurations under far fewer model numbers. I will compile any provided photos and details into a spreadsheet and repost at some future date.
My 'new' Signature ('8202-2' s/n 1094) was delivered to its Lake Balboa, Los Angeles owners on May 3, 1961. I received it with the original hand-signed manual and the original (perhaps unused) pair of microphones (with, for some reason, the cords cut at the base of the microphones). The console also has a protective glass top - I assume the addition of the owner. I wish I had taken the car to the truck scales before and after picking up this console.
It will remain a mystery for now as to how much this beast actually weighs. This console has the 40W EL-34 amplifiers (selenium rectifier) and the 403 preamplifier (though the outdated manual describes the 30W amplifiers and 402 preamplifier). I'm not sure if the owner's manual was ever updated as the features were revised - perhaps with the scan that Bryce shared of the 40W amplifiers being provided as an insert to the manual.
Ampex Amps
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(I’m grateful that you posted it, Bryce, as I could not find it elsewhere.) I haven't been able to find a schematic for the 403 preamplifier. Some schlocky work was done in 1968 by the authorized Los Angeles repair facility - mismatched output tubes on both sides, amplifiers swapped left for right in spite of being clearly labeled, atrocious cable reharnessing, nearly shorted speaker terminals and some cross-threaded and missing screws. The surprising lack of pride in workmanship still stands out 50 years later but fortunately can be addressed and forgotten. The company is long out of business.
Ampex 403 Preamplifier Service Manual
I will need to choose some electrolytics and coupler caps - and am interested in any (budget) recommendations. A while back I read somewhere that there are some high-quality cost-effective Russian-manufactured coupling caps on the market which are highly recommended. I'm much more familiar with electrolytics - having replaced many over the years. (I'm an electronics engineer, btw.) This 8202-2 console appears much as shown in the attached Ampex promotional photo, though with the dark gray variant of the 960 reel to reel rather than the 1250. Less noticeable in the photo is the six-door cabinet. Mine has the much more common three-door parquet inlay style cabinet.
Until I finally saw one of the six-door cabinets (minus components) advertised on Craigslist, I assumed that the six door cabinet in the promotional photos was only a prototype. During my search for Signatures I have encountered a couple of other units - each at a time that I could not make the investment - with each ultimately being parted out by the new owner. By the time I found this unit I had already resigned myself to building a custom vintage stereo from the first of these two empty cabinets, with existing similar quality components from my collection. I realized that without the speakers installed, the width of the cabinet openings for the speakers are each 19.25”W. Perfect for installing rack mount rails. The Signature cabinet is very well made and without the speakers can hold quite a bit of rack mount equipment. I really liked the Barzilay K61B - until I saw how much better the Signature cabinet is made.
There were apparently quite a variety of different driver configurations provided with over the roughly 1959-1961 production run. (Can this be confirmed?I'm trying to put these on a timeline. I haven’t seen any reference to the Stephens Trusonics drivers being optional upgrades (such as the Garrard 301 was for a measly $50 extra) but the Stephens drivers seem to be a similar level of upgrade. Either that or Ampex was looking at cost cutting after initial production with the Trusonics. My empty cabinet that originally housed the Trusonics (Model 8102 - s/n 1077 - re the 2014 'Ampex Signature in Los Angeles' thread) was of 1959 production.
My 1961 8202-2 appears to have a pair of Altec 803B 15” bass drivers, the Ampex 668-0022 8” midrange drivers (the deep basket drivers with the metallic brown painted baskets) and the ElectroVoice T35-B horn tweeters. (I haven’t disassembled anything; this judgment comes from comparing the appearance of the cones to other driver sets sold on eBay etc.). The LH tweeter sits on a plywood filler plate which causes the tweeter to be pointed off to the left. I would have assumed that filler plate just had not been seated properly in the faceplate inset - until I recently saw a picture of another console built the same. I have no idea yet whether the RH tweeter also points outward - as due to production variances the RH grille fits extremely snuggly and will require some further creativity to release the bullet latch and pull the grille without damage.
While waiting for this Signature to find me, I also came across a Signature speaker set which a craftsman clock builder had years ago salvaged from a Signature console and installed the drivers and faceplate with crossover in a set of custom cabinets of the same internal volume. This set of speakers uses a pair of Ampex 12” on each side, the 8” Ampex midranges (those with the “X” over the flat felt dust cover as opposed to the Ampex/JBL 8” midranges (D-216?) with the couple of small felt dots on the domed dust cover), and the T35-B tweeter. I don't know any more than that about their history, but the driver configuration seems to be the same as an early 1959 model 8002 s/n 024952 that I also ended up with the cabinet for. Which brings me to a question The Signature speaker set in custom boxes with the dual Ampex 12” drivers has gauze mesh covers over the back of the drivers to keep the cabinet damping material away from the back of the driver cones. I am assuming that the Signature console cabinet was originally filled with substantial damping material.
I have seen photos on the of the same configuration with only a couple of square feet of the traditional yellow fiberglass stuffed inside of the box (and without the cloth mesh over the back of the drivers). The configuration was otherwise the same other than the use of a dome tweeter versus the T35-B.
(see photo) The Signature cabinet which originally had the Stephens Trusonics before it was parted it out still had the remnants of the same gauze to protect the back of the driver. The speaker enclosures on this unit were packed with a surprisingly heavy mixture of white fiberglass or cotton (etc.) fiberfill mixed with something like sand (see photo). I still have the two heavy bags of that material that came with the empty Signature cabinet - but am not sure if that material was unique to the use of the Ampex/Stephens 15” drivers or if it was used in some but not all of the dual 12' enclosures. 2015 ford f350 air conditioner repair manual. Perhaps another cost-cutting revision along with the revision to the dome tweeter?
Q: Does anyone know if this dense acoustic dampening material is used in the dual 12” enclosure? Is it also used within the midrange sub-enclosure? Thanks!Much to share yet. Bob in San Diego.
As Ampex evolved the 402 preamplifier to the 403, It appears that Ampex made use of their existing stock of 402 faceplates by bonding a thin overlay panel to cover and move the location of holes. It seems that the company kept the 403 Model designation even as the cosmetics were further revised. The first photo is of a 1959 Model 402, photos 2-4 Are from two different units but represent an early Model 403, and the last is of a 1961 Model 403. Are there any Ampex experts here that can confirm the timeline or know of any other cosmetic variations on the 402 and 403 preamps?
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