|19th October 2005, 08:19 PM||#1|
Famous Brazilian Amplifiers
I'm starting with Gradiente STR-1250.
This is a small history of this.
This vintage Gradiente Model 1250 was made in the seventies... people turns
crazy with it’s panel ligths and colors, and the power was the average power
for those days..something alike 30 Watts RMS each channel over 4 ohms.
It was a result of agreement with JVC, as those days Gradiente was constructing
JVC models in my country.
The supply is not simetrical, voltage around 45 volts and condenser was used in
People fast increase the output electrolitic condenser to 6800uF and a 100n
capacitor was placed in parallell with it....also the input condenser was increased
Quiescent current, bias current, stand by current was increased to 50 miliamperes,
and some guys modified the transformer to 60 volts DC including another transistor
pair in the output.
Brazilian home parties where made with those units....normally connected to bass
reflex speakers, and also there was one unit with an active speaker and the other as
a passive sound damper.
I will post in this post, some Brasilian amplifiers...
Felipe – Mod Evil
|19th October 2005, 09:21 PM||#7|
In this Post, i send to you the Gradiente HA-II Schematic... The amp consists in two monoblocks... This is tested for the biggests Brazilian audiophiles...
A photo of Gradiente HA-II
The Techical Specifications:
Potência de saída por canal
170W RMS (8 Ohms, 0,04% THD, 20Hz - 20kHz)
250W RMS (4 Ohms, 0,06% THD, 20Hz - 20kHz)
180W (8 Ohms, Pot. máx. contínua*)
290W (4 Ohms, Pot. máx. contínua*)
210W (8 Ohms, Pot. máx. dinâmica**)
370W (4 Ohms, Pot. máx. dinâmica**)
500W (2 Ohms, Pot. máx. dinâmica**)
Potência de saída (BTL) mono
500W RMS (8 Ohms, 0,09% THD, 20Hz - 20kHz)
Impedância de saída
4 a 16 Ohms
Resposta de Freqüência
10Hz - 20kHz ( 1 Watt, 8 Ohms) +/-0,2dB
5Hz - 100kHz ( 1 Watt, 8 Ohms) -3dB
Distorção Harmônica Total (THD)
0,04% (8 ohms, 20Hz a 20kHz)
0,06% (4 ohms, 20Hz a 20kHz)
0,09% (BTL, 20Hz a 20kHz)
Distorção por Intermodulação
0,03% SMPTE, 8 Ohms (60Hz, 7kHz 4:1)
0,05% SMPTE, 4 Ohms (60Hz, 7kHz 4:1)
0,02% IHF, 8 Ohms (19kHz + 20kHz)
0,04% IHF, 4 Ohms (19kHz + 20kHz)
Fator de Amortecimento (Damping)
150 (1kHz, 8 Ohms)
30V/us (20kHz, 8 Ohms)
Separação entre canais
80mV para 1W (?)
1V para 170W
Impedância de entrada
452 x 167 x 374 mm (LxAxP)
The Schamatic of the HA-II
|20th October 2005, 08:13 AM||#8|
Join Date: Feb 2004
Location: Recife - Brasil Northeast
Nice thread Felipe, go ahead, there are many things to show
And not only Netlist will be happy to see foreign equipments, there are many others that will be happy to observe those things.
I suggest you to inform, not needed too much precision, more or less precised the manufacture year.
This HII....hummmm, 1987 to 1994 could be the period of manufacturing.
The A1 is older....gone near 1972 and up.
The Model 900 and Model 1250, those receivers, started 1970.
Those units where manufactured, in some period that importation was not allowed in our country...was an effort to create the capacity to produce everything, without the dependence of foreign countries...and we did that, but costed "zilion" dollares that we are still paying.
Very good thread Felipe.
Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
|20th October 2005, 09:16 AM||#9|
Join Date: Feb 2001
Looks a lot like the Harman Kardon gear of that vintage too.
Circuitry looks a bit like an HK630, cosmetics a bit like the HK430.
|20th October 2005, 11:11 AM||#10|
Join Date: Mar 2001
It looks like an excellent project, that could benefit from some upgrading (main supply caps, better DC servo, regulated front-end) if it could be found in the second hand market.
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