I am trying to build an L20 in a fisher BA6000 chassis.
I have a 58V dc in that amp - I removed the power amp boards due to some problems.
Its only a 6.3 ampere supply.
Will this power supply for this amp work ?
Will it sound good ?
Will it blow more easily ?
and what will blow ? the fuse or the amp ?
Thanks.
Srinath.
I have a 58V dc in that amp - I removed the power amp boards due to some problems.
Its only a 6.3 ampere supply.
Will this power supply for this amp work ?
Will it sound good ?
Will it blow more easily ?
and what will blow ? the fuse or the amp ?
Thanks.
Srinath.
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You will need 2 pairs of output transistors per channel as already pointed out a few times.
A 2x40VAC transformer rated 6.3A RMS, for 2x58VDC rails, is likely 500VA.
That is a substantial transformer, plenty big enough for 2x135W 8R or 2x 230W 4R
provided the output stage and heatsink(s) are adequate to supply that safely.
However, If the BA6000 used 100W/8R rated hybrid modules, I think there is something odd in the transformer rating there.
A 2x40VAC transformer rated 6.3A RMS, for 2x58VDC rails, is likely 500VA.
That is a substantial transformer, plenty big enough for 2x135W 8R or 2x 230W 4R
provided the output stage and heatsink(s) are adequate to supply that safely.
However, If the BA6000 used 100W/8R rated hybrid modules, I think there is something odd in the transformer rating there.
it will work whatever transformer you use,important is the power for driver stage thats at least 40vdc ,then your choice.mine is running on center tapped 54Vdc > 2 x 6A
so i cant get more than 45% volume in my room ,it will blow my 120w 6ohm speakers
and its very loud,integrated dac.
Help biasing more into class A,50w if possible
-i have big heatsink from both sides,doesnt even get warm
so i cant get more than 45% volume in my room ,it will blow my 120w 6ohm speakers
and its very loud,integrated dac.
Help biasing more into class A,50w if possible
-i have big heatsink from both sides,doesnt even get warm
I got +/- 58 vdc.
The BA6000 has a 7 amp main fuse, and 6.3 X 2 in the 58v B+ outputs from the trafo.
One of the things about this amp was that it has a huge hefty toroidal transformer. It simply is a monster.
It also has a 12 v 1 amp for lights, and 65v X 2 1/2 amp to run the tone/meter/AC/DC control board.
They put the stk0100ii in the amp it had. 100 watt output lets say it uses 200, that is 2 ohm in +ve circuit and 2 ohm in the -ve. 6.3 amp fuse means some major available extra power.
Cool.
Srinath.
The BA6000 has a 7 amp main fuse, and 6.3 X 2 in the 58v B+ outputs from the trafo.
One of the things about this amp was that it has a huge hefty toroidal transformer. It simply is a monster.
It also has a 12 v 1 amp for lights, and 65v X 2 1/2 amp to run the tone/meter/AC/DC control board.
They put the stk0100ii in the amp it had. 100 watt output lets say it uses 200, that is 2 ohm in +ve circuit and 2 ohm in the -ve. 6.3 amp fuse means some major available extra power.
Cool.
Srinath.
Hello,
Last week I put two L20 boards into an old Samson Servo 240 amp case and used the original heat sink for the boards. I'm running a transformer that I pulled out of a Sony stereo receiver which puts out 68 volts DC after the bridge rectifier, so a combined voltage of 135VDC is running to each board. I have two 10,000uf 71volt caps on the supply that also came out of the sony receiver which seems to be enough as the voltage doesn't sag much when at full volume.
I powered up the boards and they sound great! No hum or hiss when the input is muted and the heat sinks are staying cool at this time. The only trouble is a lack of power. It seams that the L20 boards could use a pre amp as the line level doesn't seem to be high enough and I can't get the amp boards to clip at full volume. When I connect a 60watt speaker up to the amp and I can barely get it to distort at full volume and a 100 watt speaker will not distort at all. I tried a larger transformer (same voltage, but higher wattage) and had the same result so a small pre amp is going to be placed inside next week to see it it will boost the volume level.
So far I'm really happy with the sound and hope that the new pre amp will give it some more volume.
Dale P.
Last week I put two L20 boards into an old Samson Servo 240 amp case and used the original heat sink for the boards. I'm running a transformer that I pulled out of a Sony stereo receiver which puts out 68 volts DC after the bridge rectifier, so a combined voltage of 135VDC is running to each board. I have two 10,000uf 71volt caps on the supply that also came out of the sony receiver which seems to be enough as the voltage doesn't sag much when at full volume.
I powered up the boards and they sound great! No hum or hiss when the input is muted and the heat sinks are staying cool at this time. The only trouble is a lack of power. It seams that the L20 boards could use a pre amp as the line level doesn't seem to be high enough and I can't get the amp boards to clip at full volume. When I connect a 60watt speaker up to the amp and I can barely get it to distort at full volume and a 100 watt speaker will not distort at all. I tried a larger transformer (same voltage, but higher wattage) and had the same result so a small pre amp is going to be placed inside next week to see it it will boost the volume level.
So far I'm really happy with the sound and hope that the new pre amp will give it some more volume.
Dale P.
Well, that's fine and perfect for your project - you certainly dont need a 24A or 2kVA
rated transformer for 2 x 130W 8R etc, if that's what you were asking.
The other questions about blowing fuse(s) depend on the amplifier's rated requirements. Each amplifier should be fused separately so that its current draw is curtailed when the amp's power limit is exceeded for a particular period of time. It can all be calculated precisely but I suspect that within typical broad F/Blow fuse tolerances, a ROT figure is appropriate. 5A fuses should be OK as a conservative start for 8R loads, 8A for 4R.
The 6.3A transformer secondary rating is a max, continuous current rating whilst audio is anything but continuous power output. Transformers can deliver vast currents many times their rating for brief periods until they heat up. This comfortably allows smaller transformers than continuous ratings might suggest.
Will it sound good? About as good as other posters here say. This is a general purpose, low cost design as I see it. I don't think throwing money at it in the form of boutique parts is going to turn it into a Goldmund or any kind of audiophile amplifier, if that's what you hope for, but you can make it clean and sweet by (for starters) ensuring your power wiring is properly twisted and routed away from signals as per any worthy guide to amplifier construction.
OK digesting these 2 posts ...
So the 60v 1/2 supply in my amp going to the front board - its doing nothing other than power the meters ? cos the switching of input from DC to AC/subsonic works fine without even powering up the amp (I mean chassis ... I mean trafo ... I mean carcass) Whatever its called.
So what does the 60v supply do ?
Cool.
Srinath.
So the 60v 1/2 supply in my amp going to the front board - its doing nothing other than power the meters ? cos the switching of input from DC to AC/subsonic works fine without even powering up the amp (I mean chassis ... I mean trafo ... I mean carcass) Whatever its called.
So what does the 60v supply do ?
Cool.
Srinath.
So, you need to work out how the BA6000 is arranged first, before you transplant the L20 modules which is fair enough, but a long O/T subject for this thread. FWIW, the indicator board is a small discrete peak indicator circuit run from ~25V and an IC for the meters, run from 22/-18V rails. It appears to derive from the main 57V power rails supply as the only low voltage secondary supply is solely for light bulbs.
I assume you are also talking about the input switching that bypasses the input cap and HF filter. This is a really bad idea for a DIY amp, period. Don't try to incorporate in the L20s.
The schematic I found is fragmented and very hard to follow so the reply is sketchy, sorry.
I assume you are also talking about the input switching that bypasses the input cap and HF filter. This is a really bad idea for a DIY amp, period. Don't try to incorporate in the L20s.
The schematic I found is fragmented and very hard to follow so the reply is sketchy, sorry.
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DC/AC subsonic
Sorry about the schematic. I will try to find a better one.
But I was not going to use the input cap+HF filter switch in that DC/AC subsonic switch, I was going to send say the DC to the power amp boards, but send the AC one into a pre out jack ... so you can use this with input controls etc as a pre, yea crappy idea, but it saves me having a knob that does nothing cos its disconnected.
Thanks.
Srinath.
Sorry about the schematic. I will try to find a better one.
But I was not going to use the input cap+HF filter switch in that DC/AC subsonic switch, I was going to send say the DC to the power amp boards, but send the AC one into a pre out jack ... so you can use this with input controls etc as a pre, yea crappy idea, but it saves me having a knob that does nothing cos its disconnected.
Thanks.
Srinath.
Yes, it would seem a neat arrangement but the DC connection to the input transistor pair, with no filter or isolating capacitor is still the bad idea. If you want trouble, just try DC connection to the L20 in the manner that the Fisher amp is, without a proper analysis of what else needs to be altered in the amplifier and this will probably include a DC Servo opamp to maintain a minimal and steady offset at both input and output. It's not a simple change at all, unless it is intended to be connected to a particular preamp that is already AC coupled at it's output (Seems stupid but that's the only safe way other than a servo.)
To keep it simple, forget the DC connection idea, perhaps try that for the 'Pre-out" connection and simply use the L20 as the per the instruction notes with it. Anyways, if i read you correctly this just to be additional input circuitry to that already in the L20 which will remain and won't make any odds. If so, thats fine since you don't need to add a second, series input cap.
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Ah cool I send the dc part to the pre out.
I however think that AC/DC switching was only sending output to 2 different parts on the amp board, the DC and AC parts were in the power amp board.
The volume+ac/dc+meter range board has an opamp in it JRC1105 45580x - whatever that means. That board gets the 60v supply, I suspect the 60v power is to the meters ... Its labelled as B+ E and B- too.
The AC/DC switch works without even powering up this amp. The meter will not however, so I suspect the meters need the 60v.
Let me get to fiddling with it in a day or 2.
Cool.
Srinath.
I however think that AC/DC switching was only sending output to 2 different parts on the amp board, the DC and AC parts were in the power amp board.
The volume+ac/dc+meter range board has an opamp in it JRC1105 45580x - whatever that means. That board gets the 60v supply, I suspect the 60v power is to the meters ... Its labelled as B+ E and B- too.
The AC/DC switch works without even powering up this amp. The meter will not however, so I suspect the meters need the 60v.
Let me get to fiddling with it in a day or 2.
Cool.
Srinath.
Well, I've already described the operation as you say and the input switch operation is pretty clear on the schematic. Essentially, the switch bypasses the amplifiers' input cap and that also includes part of the input HF filter. Plain and simple.
Remove the connection to the DC input point at the base of the input transistor and reconnect that to your pre-out via another similar cap, preferably. You need to avoid getting noise on that lead - It's like dangling a wire to pick up unwanted noise, so you need shielded leads to any new panel sockets. Even so, I doubt you will get good results trying to use the amplifier and the pre-out together. Try it and see what differences there are to amplifier noise, if any, when you switch off the pre-out connection. Check with and without a lead from there to another device.
I got weirdness ... I better look in the manual again ...
The pink and white pairs without the ground wire sending out nothing ...
The pinks - 2 of em, are both right only and only work in AC ...
The whites - 2 of em are both left only and only do in the dc setting ...
I thought never mind ... I better look in the schematic.
Cool.
Srinath.
The pink and white pairs without the ground wire sending out nothing ...
The pinks - 2 of em, are both right only and only work in AC ...
The whites - 2 of em are both left only and only do in the dc setting ...
I thought never mind ... I better look in the schematic.
Cool.
Srinath.
You need to read the thread and the schematic for the BA6000 power amplifier section. It has 2 switchable input routes. One is conventional, via an on-board input cap. A second option, DC, is direct to the first transistor and leaves the amplifier prone to a number problems. This has nothing to do with the L20 amplifier.
The OP is planning to use that input selector switch for another purpose when replacing the original power amplifier with an L20.
Sorry for confusing you
Hey man, Ian Finch has been trying to help me, with the fisher BA600, the only connection to the L20 is that in future I am hoping to put an L20 amp in that chassis.
I have long since hijacked this thread ...
Sorry.
Cool.
Srinath.
Hey man, Ian Finch has been trying to help me, with the fisher BA600, the only connection to the L20 is that in future I am hoping to put an L20 amp in that chassis.
I have long since hijacked this thread ...
Sorry.
Cool.
Srinath.
100V power rails should tell you something about the component changes and likely schematic changes such as cascoding to scale anything say, x5 in power terms. It is possible to do anything radical and then say it works. It is more likely you will only get it to survive in real use at 500W+ if it is designed from the ground up to do so.
One of the features of high power amplifiers is the size of the PCB traces to admit the massive currents without burning up or incurring big losses. By the time you lay out and build the output stage for this monster, any skimping on size or parts for the front end will be just irrelevant at best and otherwise a really bad decision. This is a basic, low cost amplifier, even at the rated power it is specified for. I think it's already at its limit of sensible use, whatever the possibilities are with risky increases.
If you want high power, why not look at Anthony Holton's (The Saint) boards in the commercial sector. They not only save laying out the output stage but probably deliver much more reliably too. If you are only counting on the cost of a cheap front end PCB module and the power transistors, I think you will be in for a nasty surprise how much a working final assembly with the necessary safety, cooling and control circuits will really cost.