Acrosound Ultra-Linear II Mono Tube Amplifiers (Pair)
Archived listing from the original vintage-amplifier.com. Prices, seller details and purchase links have been removed; this page is a reference record, and nothing here is for sale. About this archive.
Very rare pair of Acrosound ultra linear
Transformers work fine, needs recap…
Pair of mono blocks EL output push pull
About this model
The surviving text is short: a very rare pair of Acrosound Ultra-Linear mono blocks, push-pull output, transformers in working order, needing a recap. It is the history behind the name that makes the pair interesting.
Acrosound was founded in Philadelphia in 1950 by David Hafler and Herb Keroes to sell output transformers. In November 1951 they published "An Ultra-Linear Amplifier" in Audio Engineering, coining the name for a connection in which the output tubes' screen grids are fed from taps on the output transformer. Amplifiers like these were built around that transformer. Hafler went on to co-found Dynaco in 1955.
The listing's "EL output" most likely refers to EL-series output tubes such as the EL34, but it does not say which.
| Maker | Acrosound, Philadelphia, USA |
|---|---|
| Type | Mono power amplifiers (pair) |
| Output stage | Push-pull, ultra-linear (listing) |
| Condition noted | Transformers working; needs recap (listing) |
| Company founded | 1950, by David Hafler and Herb Keroes |
Questions collectors ask
Who made Acrosound amplifiers?
Acrosound was the Philadelphia company founded in 1950 by David Hafler and Herb Keroes, best known for its ultra-linear output transformers.
What does ultra-linear mean on an Acrosound amplifier?
The output tubes' screen grids are connected to taps on the output transformer primary. Hafler and Keroes named the connection in 1951; it gives lower distortion than pentode operation with little loss of power.
Sources: Wikipedia: Ultra-linear; Wikipedia: Dynaco.
