JimS boards
Hi Jim, good to hear!!!
@ people they are interested in electrolytic caps. I'm on vacation for the next two weeks. After arriving home then I'll send a quote for the caps I placed a link earlier in this thread. I'm fancy building this amp
and I hope that I can get the few parts i still need.
Cheers Ernst
Hi Jim, good to hear!!!
@ people they are interested in electrolytic caps. I'm on vacation for the next two weeks. After arriving home then I'll send a quote for the caps I placed a link earlier in this thread. I'm fancy building this amp
and I hope that I can get the few parts i still need.Cheers Ernst
R-core group buy
Hi,
I'm looking to find out how many would be interested in getting involved in a group buy for an R-core transformer for this amplifier.
It would seem the best avenue would to get a transformer made with four individual secondaries to provide both front-end and output-stage supplies in one transformer.
To get enough quantity to get a good group price break, I would assume the transformer should be designed to handle one channel alone, to accomodate those wishing to build monoblocks without having to pay for two large transformers sized for a two-channel supply. This would be a 250-300VA transformer with 120v/240v primary 50/60Hz for maximum world-wide use. Since this transformer would not be big enough for a stereo supply, wo would have to be bought for a single-chassis stereo supply, unless the price breaks and quantities allow for two different sizes to be ordered.
We have an unconfirmed ballpark figure of about $115 for such a transformer with electrostatic shield(s), not including shipping. While not cheap, it may be cheaper than getting two off-the-shelf toroids, if you can even find suitable ones.
Therefore, so that we may get an idea of what quantities we're looking at for price breaks, please indicate your interest here.
Hi,
I'm looking to find out how many would be interested in getting involved in a group buy for an R-core transformer for this amplifier.
It would seem the best avenue would to get a transformer made with four individual secondaries to provide both front-end and output-stage supplies in one transformer.
To get enough quantity to get a good group price break, I would assume the transformer should be designed to handle one channel alone, to accomodate those wishing to build monoblocks without having to pay for two large transformers sized for a two-channel supply. This would be a 250-300VA transformer with 120v/240v primary 50/60Hz for maximum world-wide use. Since this transformer would not be big enough for a stereo supply, wo would have to be bought for a single-chassis stereo supply, unless the price breaks and quantities allow for two different sizes to be ordered.
We have an unconfirmed ballpark figure of about $115 for such a transformer with electrostatic shield(s), not including shipping. While not cheap, it may be cheaper than getting two off-the-shelf toroids, if you can even find suitable ones.
Therefore, so that we may get an idea of what quantities we're looking at for price breaks, please indicate your interest here.
Re: R-core group buy
Roender has already told us to use 4 separated secondaries for a 2ch amp or use two dual secondary transformers if building a pseudo monoblock.
It's probably down to having the main Audio Ground on the PCB.
you cannot use a two secondary transformer for stereo (2channel) use.pooge said:
Roender has already told us to use 4 separated secondaries for a 2ch amp or use two dual secondary transformers if building a pseudo monoblock.
It's probably down to having the main Audio Ground on the PCB.
You are not being clear on how you count the number of secondaries; i.e., whether you count a 50vct as one secondary, or two separate secondaries that are intended to be connected together as one or two secondaries. If you are talking about an an individual supply of voltage/rectification/regulation for each board section, then you would need eight windings, which I don't think there is enough interest in for a price break.
What I am specifying is a two independant-winding primary (2 x 120v) primary and a four independant-winding secondary (2 x 25v, 2 x 34v) at 50/60Hz on a 260VA core, probably with electrostatic shields.
In any event, it appears that we have enough interest to make a go of this. I am still trying to get more info from a couple of suppliers. What details does everybody need to know to make a decision on quality, etc., that would be needed to make a decision on whether to purchase?
As several of us have already ordered parts, I would like to stay within the designated voltages.
What I am specifying is a two independant-winding primary (2 x 120v) primary and a four independant-winding secondary (2 x 25v, 2 x 34v) at 50/60Hz on a 260VA core, probably with electrostatic shields.
In any event, it appears that we have enough interest to make a go of this. I am still trying to get more info from a couple of suppliers. What details does everybody need to know to make a decision on quality, etc., that would be needed to make a decision on whether to purchase?
As several of us have already ordered parts, I would like to stay within the designated voltages.
a centre tapped has one secondary with a tap at the centre.
A dual secondary has 2 separated secondaries that are isolated from each other.
To build a two channel amplifier with separated Audio Grounds you need 4 isolated secondaries. These feed 4 rectifiers. The rectifiers are paired to create two isolated Audio Grounds. These separate grounds will probably need two Disconnecting Networks to connect back to the Safety Earth.
The 4 secondaries can be wound on one bigger transformer or can be a pair of dual secondary transformers.
I think the RMI with it's on board Audio Ground is better suited to monoblock use, particularly since the heatsink has to dissipate ~ 71W when built as a 100W into 8r0 amplifier.
The RMI PCB has a combined power Ground. This can be fed from a centre tapped or dual secondary transformer. But two PCBs need two centre tapped secondaries or 4 secondaries, just as Roender has pointed out.
The extra secondaries for the regulated supplies are a separate issue.
A dual secondary has 2 separated secondaries that are isolated from each other.
To build a two channel amplifier with separated Audio Grounds you need 4 isolated secondaries. These feed 4 rectifiers. The rectifiers are paired to create two isolated Audio Grounds. These separate grounds will probably need two Disconnecting Networks to connect back to the Safety Earth.
The 4 secondaries can be wound on one bigger transformer or can be a pair of dual secondary transformers.
I think the RMI with it's on board Audio Ground is better suited to monoblock use, particularly since the heatsink has to dissipate ~ 71W when built as a 100W into 8r0 amplifier.
The RMI PCB has a combined power Ground. This can be fed from a centre tapped or dual secondary transformer. But two PCBs need two centre tapped secondaries or 4 secondaries, just as Roender has pointed out.
The extra secondaries for the regulated supplies are a separate issue.
There is nothing wrong with your Group buy specification.
I am pointing out that there is little point in considering a larger version for two channel power. It would become too specialised and not transferable to other projects.
Similarly to power two channels from this dual secondary transformer is at odds with Roender's advice.
I am pointing out that there is little point in considering a larger version for two channel power. It would become too specialised and not transferable to other projects.
Similarly to power two channels from this dual secondary transformer is at odds with Roender's advice.
I don't remember seeing that advice, but I do agreed that eliminating all potential ground loops is a good thing.
Since there is enough interest to get a price break of 10 or more, the cost looks pretty good, and probably a good bit better than the mentioned $115. So it's time to lock in the specification details.
I prefer to have a bridge rectifier for each winding, while others may prefer a bridge rectifier for a pair of winding connected in series with a "center cap" to ground. So the transformer should accomodate both schemes, provide the necessary rectified voltages for the proper voltage difference between the front end and output for light loads, full loads (e.g., regulation), and mains voltage variations.
Since there is enough interest to get a price break of 10 or more, the cost looks pretty good, and probably a good bit better than the mentioned $115. So it's time to lock in the specification details.
I prefer to have a bridge rectifier for each winding, while others may prefer a bridge rectifier for a pair of winding connected in series with a "center cap" to ground. So the transformer should accomodate both schemes, provide the necessary rectified voltages for the proper voltage difference between the front end and output for light loads, full loads (e.g., regulation), and mains voltage variations.
OK, I'm looking to finalize the specifications for the group buy transformer. I'm considering whether or not to add more primary taps. Right now, I'm considering 2 x 0,110,120 volt primary. This would serve 110, 120, 220, and 240 volt AC mains voltage. Would anyone considering being a part of this group buy require 115 or 230 volts? If not, I'd rather not add the extra leads to save clutter. However adding more taps will not cost extra, other than the clutter.
Never mind my previous post. 230V mains can use a 110v and a 120v tap to get 230v, so this set up should accommodate just about everyone in the world, no problem.
I am concidering some extra taps on the secondary HV windings to make any adjustments to the input of the regulator if necessary to reduce overheating there. To be determined after all other considerations are met, such as possibly raising the voltages to get the most benefit out of this amp. Stay tuned.
I am concidering some extra taps on the secondary HV windings to make any adjustments to the input of the regulator if necessary to reduce overheating there. To be determined after all other considerations are met, such as possibly raising the voltages to get the most benefit out of this amp. Stay tuned.
WIKI
Added a Wiki for this GB. Have a look. Not perfekt, but a start
Cheers Ernst
RMI-FC100 Parts Wiki
Added a Wiki for this GB. Have a look. Not perfekt, but a start
Cheers Ernst
RMI-FC100 Parts Wiki
Ernst,
Had no trouble getting to the Wiki page from your link, but wasn't able to find it going through the Wiki page and "Everything Else" index.
Regarding the transformer buy, it is still in progress. Finally got some info on core sizes that we need to help specify one. It may take a bit to get it finally resolved, but since they cannot be made before Chinese New Year is over anyway, there is plenty of time to twiddle with it to optimize it for the specified output and/or for higher output.
Had no trouble getting to the Wiki page from your link, but wasn't able to find it going through the Wiki page and "Everything Else" index.
Regarding the transformer buy, it is still in progress. Finally got some info on core sizes that we need to help specify one. It may take a bit to get it finally resolved, but since they cannot be made before Chinese New Year is over anyway, there is plenty of time to twiddle with it to optimize it for the specified output and/or for higher output.
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