Is it possible to modify a vintage amplifier to a chip amplifier by replacing the transistors circuits with chip boards and keeping transformers with power supply and all front panel (preamp) circuits?
It is in theory possible, but it depends a lot on how your vintage amplifier is constructed. I have disassembled a number of vintage amplifiers and sometime they use basically one big board for power amplifiers, power supply, pre-amplifier circuits and speaker protection circuits. Then, you cannot with advantage remove a part and re-use the rest. Another issue is interface between new and old circuits which can be a bit awkward to solve compared to new circuits all together.
I always ended up taking out for re-use a lot of components that would cost me somewhat to replace. The rest ended up at the recycling center. If the design of the chassis is unique, you can re-use the chassis. Often you will realize along the way that re-use of a chassis puts a lot of constraints afterwards.
I always ended up taking out for re-use a lot of components that would cost me somewhat to replace. The rest ended up at the recycling center. If the design of the chassis is unique, you can re-use the chassis. Often you will realize along the way that re-use of a chassis puts a lot of constraints afterwards.
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If the power supply and heatsinking are suitable it could be a good idea since these and the chassis are the most costly, both monetarily and work wise, parts of an amplifier.
Yes Thank you. this is my idea.
I am thinking to find one in-order to use the chassis with all switches ans input selectors with analog VU meters, the power supply with the transformer. Which chip board would you recommend? should we start from there?
I am thinking to find one in-order to use the chassis with all switches ans input selectors with analog VU meters, the power supply with the transformer. Which chip board would you recommend? should we start from there?
I can't recommend anything specific I'm afraid, so many and not familiar enough with them. However when it comes to finding a suitable old amplifier you may find this site useful HiFi Engine - Owners and Service Manuals
Yes I am using this site already
I will be locking for old amp with good power supply and beautiful chassis
I will be locking for old amp with good power supply and beautiful chassis
Before finding a suitable chip you have to measure the output voltages from the power supply. The power supply design will point you toward certain chips to use. Dual- or single-rail?, and voltage levels are important to know.
The more that you wish to save and re-use, the more complex the problem. But YES it is certainly doable.
Using the vintage switches is not a good idea.
Using the vintage switches is not a good idea.
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It's certainly possible to re-use some parts but how many is a tough question depending alot on your amp.
- The case: no big problem usually.
- The heatsink: it would seem straightforward but usually isn't. For what dissipation was it rated ? For kind of transistors package ? Where are the mounting holes ? Do you have to tap new ones ? How much space do you have near it ? Would a typical rectangular pcb fit there ?
- The transformer: many older amps use transformers with high voltage/low current ratings. It would boost the power on 8r load and the power supply would sag on 4r loads, protecting the amp. That means few amps actually have a transformer really suitable for the common chip amps (which don't like high voltage usually, about +/-32vdc is a good aim). Maybe have a look at class-d amps too to widen the range of usable transformers.
- The power supply: here, it's simple. Scrap it. Diodes and caps have come a long way since the amp was built. It's best to rebuild anew.
- VU meters: not that easy. Can the driver stage be saved ? If not, how accurate do you want those meters ? If accuracy is the goal, some tinkering will be needed.
- Switches on the front panel: a real nightmare. First there are always much more than you need. Then the buttons and knobs tend to use all kinds of mounting systems which are never compatible with modern ones. On top of that, they are often mounted on a pcb (the awful lever switches...) and that pcb is never laid out like you'd wish. And of course, all that assumes that they are still clean and working.
I've once rebuilt an amp like this in which I glued all the switches/pots, refitting only a new selector switch and balance/volume pots.
- The case: no big problem usually.
- The heatsink: it would seem straightforward but usually isn't. For what dissipation was it rated ? For kind of transistors package ? Where are the mounting holes ? Do you have to tap new ones ? How much space do you have near it ? Would a typical rectangular pcb fit there ?
- The transformer: many older amps use transformers with high voltage/low current ratings. It would boost the power on 8r load and the power supply would sag on 4r loads, protecting the amp. That means few amps actually have a transformer really suitable for the common chip amps (which don't like high voltage usually, about +/-32vdc is a good aim). Maybe have a look at class-d amps too to widen the range of usable transformers.
- The power supply: here, it's simple. Scrap it. Diodes and caps have come a long way since the amp was built. It's best to rebuild anew.
- VU meters: not that easy. Can the driver stage be saved ? If not, how accurate do you want those meters ? If accuracy is the goal, some tinkering will be needed.
- Switches on the front panel: a real nightmare. First there are always much more than you need. Then the buttons and knobs tend to use all kinds of mounting systems which are never compatible with modern ones. On top of that, they are often mounted on a pcb (the awful lever switches...) and that pcb is never laid out like you'd wish. And of course, all that assumes that they are still clean and working.
I've once rebuilt an amp like this in which I glued all the switches/pots, refitting only a new selector switch and balance/volume pots.
Dual rail is not better, nor worse. Dual rail was used in the past because the amplifiers were expensive to make (many discrete components) so it was overall cheaper to make a more complicated power supply and only one amplifier per channel, thus two amplifiers for stereo.
With the availability of good monolithic amplifiers at cheap prices, making 4 amplifiers instead of 2 amplifiers in a chip (or more chips) didn't add much to the cost. Therefore, from then on it became cheaper to use 4 amplifiers (in BTL mode) and use a simpler single voltage supply.
That means, if you buy a good amplifier (>30W) with an age of 15 years or more, you are likely to find a dual rail power supply inside. With a dual rail power supply you should look for an amplifier chip that is intended for dual rail supply.
With the availability of good monolithic amplifiers at cheap prices, making 4 amplifiers instead of 2 amplifiers in a chip (or more chips) didn't add much to the cost. Therefore, from then on it became cheaper to use 4 amplifiers (in BTL mode) and use a simpler single voltage supply.
That means, if you buy a good amplifier (>30W) with an age of 15 years or more, you are likely to find a dual rail power supply inside. With a dual rail power supply you should look for an amplifier chip that is intended for dual rail supply.
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Thank you for all this information.
With a little search I did find the following amplifiers:
do you know anyone of those?
Luxman L-200 2χ45w - 8Ω
Technics SU-Z1 2x25w - 8Ω Year 1982 it has VU meters
AKAI AM-U01 20Wx2 -8Ω Year 1980
Pioneer SE42020W year 1980
Sansui AU555-A year 19972
I guess I should search for something mor powerfull
With a little search I did find the following amplifiers:
do you know anyone of those?
Luxman L-200 2χ45w - 8Ω
Technics SU-Z1 2x25w - 8Ω Year 1982 it has VU meters
AKAI AM-U01 20Wx2 -8Ω Year 1980
Pioneer SE42020W year 1980
Sansui AU555-A year 19972
I guess I should search for something mor powerfull
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Most of this type modification finishes as ruined working vintage amplifier.
Like this one:
Marantz PM310 Upgrade Project
It's good for learning, but result is always dissapionting.
Like this one:
Marantz PM310 Upgrade Project
It's good for learning, but result is always dissapionting.
A good post.
My thinking also is you should not mix the old amplifier with some chip amp.
Measure the power supply.
Then find some chip amplifiers that can take the voltage.
Then you have the case and power supply for your chip amplifier.
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