AMPLIFICATOR MCINTOSH MC 250 - RARITATE VINTAGE

Putere MCINTOSH MC 250. Aparatul este al unui prieten in varsta care nu foloseste net-ul. Anuntul se adreseaza doar celor ce isi doresc un McIntosh in stare originala asa cum a fost fabricat in 1967, baietii desteptii fiind rugati sa incerce la Media Galaxy sau sa astepte urmatorul Black Friday.

Va rog cititi cu atentie tot anuntul inainte de a licita.

Manual: 

Un scurt istoric: 

History: The McIntosh MC-250 was McIntosh's first foray into the field of solid-state amplification. They certainly held off for awhile since the amp did not come into production until 1967. Most of the hi-fi companies about that time had left vacuum tubes forever. It could be argued that this sudden shift of technology led to the downfall of many of these companies. Early solid-state technology was tenuous at best and the first generation amplifiers were not known for their reliability. McIntosh wanted to get it right the first time. Of course McIntosh is a company that continues to follow the beat of their own drum. The MC-250 has proven to be a reliable beast, having survived the tortures of time with its own unique circuitry - notably the Autoformer and the Sentry Monitor which continue to be used in their top-of-line models.

Here is how Roger Russell explains autoformer -

from 

Transistor power output circuits can match 8-ohm loads directly. This eliminates the need for the output transformer for most manufacturers. However, output stages that are designed to operate into an optimum load of 8 ohms can double or quadruple heat dissipation when operating into 4 or 2 ohm loads. At some frequencies, speakers rated at 8 ohms can dip as low as 4 ohms. Some 4-ohm systems can dip even lower. This mismatch can cause the amplifier to exceed its thermal dissipation limits.

On the other hand, if an amplifier is designed for an optimum load of one or two ohms, a low impedance load would be no problem. However, less power would be available for a speaker having 4 or 8 ohms impedance.

The unique McIntosh output autoformer was the answer. Since McIntosh output stages were connected in a single ended push-pull circuit, one side of the output was always connected to ground. They were typically designed to work into an optimum load of 2.1 ohms. The matching autoformer was connected directly to the output. In the MC2505 amplifier, the matching output was for 4, 8 and 16 ohms. Other impedances became available in later amplifiers. Full continuous amplifier power could be delivered to each of these loads. There was no danger of exceeding safe limits or overheating.

The autoformer also protected the speakers from damage in the event of amplifier failure. Should a direct current component appear at the amplifier output, it was shunted by the low DC resistance of the autoformer, instead of passing through the speaker voice coil, which could damage the speaker or even cause a fire.

McIntosh autoformers continued to be used in the "top-of-the-line" amplifiers. They were all designed and manufactured by McIntosh. Although the autoformers added extra cost, weight and took up extra space, they assured a safe, optimum match to a variety of speakers and speaker hook-ups. They were constructed and performed in the McIntosh tradition of excellence.

Although the autoformer provided an efficient match between the power transistor output and a variety of load impedances, a short circuit at the amplifier output or a load that was much lower than the selected autoformer tap could cause excessive current to flow in the output transistors. To complement the new transistor amplifiers, the McIntosh Sentry Monitor circuit was developed which prevented destructive current levels from occurring under any conditions. This circuit sensed the dynamic operating time, voltage and current of each amplifier output stage and controlled the current flow, confining it to non-destructive limits. The arrangement assured complete circuit reliability for all load conditions. The Sentry Monitor did not limit the rated power output available from the amplifier in any way. McIntosh power amplifiers continue to use the Sentry Monitor circuitry.

Conclusion: So if you're looking for some cheap and reliable amplification, check out the McIntosh 250 or its big brother the 2100. The metered versions (2505 and 2105) look prettier, but my manly (ha!) instincts prefer the industrial look. A perfect piece for any mancave or swinging bachelor pad. This amp now sits on my living room bookcase providing hours of daily musical enjoyment.

McIntosh is an American icon and they continue to make their amplifiers at their Binghamton, New York plant. The new ones are bloody expensive, but you can own one of their older amplifiers for a decent price. Do your ears a favor and check 'em out.

Aparatul este adus acum mai multi ani din SUA si este alimentat la 110-117 V. Starea aparatului este originala, existand urme de trecere a timpului vizibile in poze care sunt reale. Reflexia suprafetelor cromate este destul de buna, observandu-se imaginea si detaliile suportului pe care au fost facute pozele.

Functionarea este foarte buna, sugestia mea fiind ca viitorul proprietar sa efectueze o mica cosmetizare si curatare a potentiometrelor si comutatorilor.

Aparatul se vinde asa cum este, pretul afisat este FIX, nediscutabil. Nu licitati decat daca sunteti de acord cu toate conditiile din acest anunt.

Livrare personala in Bucuresti, nu trimit in alte localitati decat cu plata 100% in avans. 

Va multumesc pentru intelegere si astept orice intrebare pe forumul licitatiei.