Hi All,
I have almost finished my WAW speakers (Mark Audio Pluvia 7s [4 inch] and Monacor SPH 8M [8 inch] both nominally 8 ohm) which currently have 1st order series crossovers.
I thought, wouldn't it be nice to have a Class A amp to either drive the full-ranger or the whole speaker. Better still what about a 4 channel by-amped system. I currently have some hardware salvaged/re-purposed from some other equipment so it would be a shame not to use it.
I have at least 2 toroidal transformers that have dual 0-22V AC secondary windings. Don't know their VA ratings but they are 130 mm diameter and 65 mm thick. I also have at least 12x 22,000uF caps. I also have some handy chassis that this stuff is mounted on. The only hardware I don't have is adequate heat-sinking and of course the transistors etc.
So I've looked at JLH and Hiraga and I need to take a look at the Pass Labs stuff also.
Ideally I'd like a kit or PCBs with easily obtainable components.
So what do I need advice with, I suppose something that is fairly easy to set up, reliable, forgiving or whatever insight people might have.
Thanks
I have almost finished my WAW speakers (Mark Audio Pluvia 7s [4 inch] and Monacor SPH 8M [8 inch] both nominally 8 ohm) which currently have 1st order series crossovers.
I thought, wouldn't it be nice to have a Class A amp to either drive the full-ranger or the whole speaker. Better still what about a 4 channel by-amped system. I currently have some hardware salvaged/re-purposed from some other equipment so it would be a shame not to use it.
I have at least 2 toroidal transformers that have dual 0-22V AC secondary windings. Don't know their VA ratings but they are 130 mm diameter and 65 mm thick. I also have at least 12x 22,000uF caps. I also have some handy chassis that this stuff is mounted on. The only hardware I don't have is adequate heat-sinking and of course the transistors etc.
So I've looked at JLH and Hiraga and I need to take a look at the Pass Labs stuff also.
Ideally I'd like a kit or PCBs with easily obtainable components.
So what do I need advice with, I suppose something that is fairly easy to set up, reliable, forgiving or whatever insight people might have.
Thanks
The USSA-5 is maybe the best class A-amp you could get. The inventor (fab) is here on diyaudio and you would find much information about it here. I've read, that he has done a version with easier obtainable parts some time ago that isn't using the hard to find driver mosfets...
130 mm diameter and 65 mm thick, I think it is around 300VA transformer, dual 0-22V AC secondary windings can build around 30W/channel Class A amp
I remember reading about this amp in a Hi Fi magazine years ago. Is it available as kit/pcb?
If you don't want buy unavailable and expensive parts,for a class A amplifier ,i will HIGHLY recommend the Bonsai SX.
Ask him for the power supply voltage upper limit .
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Bonsai has a KX amp 25W Class A with +-26V~28V DC, so that the 22V AC supply is OK.
A FAST/WAW system with an 8in woofer has relatively low sensitivity once baffle step loss is considered. Typically 82dB to 84dB and 25w Class A amps simply don’t have enough power to drive them to their full potential.
I currently have a 10F/RS225 FAST/WAW system and find that an amp closer to 35w or 40w will provide a superior experience and sound quality.
Here is the amp I am using:
Alpha Nirvana 39w 8ohm Class A Amp
Parts are readily available and not exotic or expensive. 22v trafos are perfect but you will need at least 250VA to 300VA per channel.
The nice thing about this amp is that the transistors and the PCB are installed separately with Molex quick connect plugs - making installation or repair and access in a chassis, a snap.
The sound is perhaps the best I have heard for a DIYA Class A amp. You can read listening impressions in the thread.
Here is my FAST/WAW setup being driven by the Alpha Nirvana in the 4U Dissipante chassis.
Here is an example of the Alpha Nirvana by Vunce, as mounted in a 5U Dissipante chassis and also using an ultra low ripple SLB power supply.
One nice thing about this amp is that there are no adjustments for offset or bias and it maintains very close to 0mV DC offset automatically.
I currently have a 10F/RS225 FAST/WAW system and find that an amp closer to 35w or 40w will provide a superior experience and sound quality.
Here is the amp I am using:
Alpha Nirvana 39w 8ohm Class A Amp
Parts are readily available and not exotic or expensive. 22v trafos are perfect but you will need at least 250VA to 300VA per channel.
The nice thing about this amp is that the transistors and the PCB are installed separately with Molex quick connect plugs - making installation or repair and access in a chassis, a snap.
The sound is perhaps the best I have heard for a DIYA Class A amp. You can read listening impressions in the thread.
Here is my FAST/WAW setup being driven by the Alpha Nirvana in the 4U Dissipante chassis.
Here is an example of the Alpha Nirvana by Vunce, as mounted in a 5U Dissipante chassis and also using an ultra low ripple SLB power supply.
One nice thing about this amp is that there are no adjustments for offset or bias and it maintains very close to 0mV DC offset automatically.
Which amplifier is best will always be a subjective topic. If there was a "BEST" amplifier. we all would own it.
Your speakers will also influence the sound.
Your speakers will also influence the sound.
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I had a feeling this thread may cause more questions than answers.
I'm leaning towards the JLH 1969 because of its simplicity. I can use it to just drive the full-rangers to begin with (bi-amp). I can use the crossover cap instead of the 2500u electrolytic output cap. Then in future I can 'upgrade' and see what improvements can be made. Since the parts I've acquired so far have been free, going the JLH way will keep costs down to begin with. PCBs on ebay are a few quid.
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I would recommend choosing an amp that can run into Class AB on the peaks to give some headroom for the bass driver, plus you get to turn down the bias in the summer months. The Pass F4 may be a good choice. It needs a preamp, but that means more flexibility and fun.
You can not go wrong with the JLH; perhaps Class AB on the woofer.
You can not go wrong with the JLH; perhaps Class AB on the woofer.
That's what I could do with my current setup. I have a 60W integrated with a pre-out. It has a remote and a built in DAC so gives me flexibility and WAF. I could even use it just as a pre-amp but seems a bit of a waist, so driving the woofer with it seems ideal for now.
the pass f4 is probably a very good choice as you can bridge them and theyll deliver 100w into 8ohm if you do that, but as said previously you do need a specialist preamp. I built the impasse preamp which has balanced outputs on them specifiaclly for driving the f4. I only use my one unbalanced because i only have 1 amp. But my open baffles are really sensitive (well, ~94db). I will say that the 25w into 8 ohm does seem a very conservatively rated 25w. They really kick.
Theres also the F5 turbo which i believe puts out 50w per channel, but youll probably need BIG heatsinks on that.
Theres also the F5 turbo which i believe puts out 50w per channel, but youll probably need BIG heatsinks on that.
I built the F5 and was disappointed with it.
The Alephs are very very good.
I'm just building the Aleph J to compare against the Aleph 4.
The Alephs are very very good.
I'm just building the Aleph J to compare against the Aleph 4.
The KX amp is a very good amp imho. PCB's are available from jim's audio.
As has been said the Nelson Pass design are also very good. Current favourite is the M2. Also building one supports the forum.
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The jlh is well described here, can use lots of different transistors, I'm currently building one, and having a blast!
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If you build the Pass F4 you not only have a superb amp that’s capable of good headroom but you can drive it from the JLH. The JLH drives the mid-tweet directly and drives the woofer through the F4 as a power buffer. Endless possibilities.
You know, I really gotta build myself an F4, it seems to be a flexible option.
The F4 is a jewel... and seems underestimated
You know, I really gotta build myself an F4, it seems to be a flexible option.
The F4 is a jewel... and seems underestimated
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The kx-Amp will deliver 28W peak into 8 ohms and after that it gracefully transitions to class AB where it delivers c. 50 watts RMS into 5 Ohms and about 90 watts into 2 Ohms - this last figure short term peaks. There’s a cap multiplier PSU available for it as well.