I'm looking for a relatively small inexpensive decent quality amplifier that can put 15-20 watts into a 16 ohm load.
The amplifier can be mono or it can be stereo provided it can be bridged.
I cannot use anything with any digital amp circuitry (class D, class T ETC...) nor can it use a switch mode power supply or voltage regulator as the amp will be used at work around a sensitive unit where RFI can affect the test results.
The amp can either have a built in volume control or require a passive preamp.
I'd also be interested in amplifier kits such as something from this site or one of the low cost boards on Amazon.
The amplifier can be mono or it can be stereo provided it can be bridged.
I cannot use anything with any digital amp circuitry (class D, class T ETC...) nor can it use a switch mode power supply or voltage regulator as the amp will be used at work around a sensitive unit where RFI can affect the test results.
The amp can either have a built in volume control or require a passive preamp.
I'd also be interested in amplifier kits such as something from this site or one of the low cost boards on Amazon.
Stereo =or= mono? Is this for music or some sort of servo amp? So you want mono, stereo only if it can be bridged to mono? Obviously an analog amplifier. I understand no switching supply and corresponding EMI, but no voltage regulator? Even a linear regulator that produces no EMI? What supply voltage or power supply are you willing to use- a linear wall-wart, or direct AC power with linear power supply? The amp for the job really depends upon your power availability/topology. There are a lot of linear BTL amplifiers out there on Amazon.
I only have one speaker so the amp needs to be mono. If the amp is stereo it needs to be able to be bridged whether by a switch on the amp or connecting a balanced signal to the right and left input jacks.
Only a linear voltage regulator.
Either a linear wall wart or built in linear power supply.
For a kit I'd use a toroidal transformer.
Only a linear voltage regulator.
Either a linear wall wart or built in linear power supply.
For a kit I'd use a toroidal transformer.
Hi Tube Radio,
Okay, I'll assume you have decided you want only tube based. That's fine. 15 to 20 watts means a 6L6GC normally, 7591A are expensive although a 6CA7 based amp is good (replace EL14 with 6CA7 - plug in).
Tube amplifiers cannot be bridged. What you do is connect the two channels in parallel at one lower tap, so the 8R tap for a 16R speaker. Maybe a 6BQ5 (EL84) based amplifier might work. Given you are connecting two channels in parallel, the amplifier must be rebuilt and the two channels very close in gain, feed a mono signal (not from a stereo control). Heathkit and many early tube amplifiers were mono, Eico, Paco and many others. I have a bunch of mono amplifiers. Of course McIntosh made many mono amplifiers, MC30, MC40 and so forth. Expensive but vey good.
Avoid junk like Pioneer. They ran 6189 or 6BQ5 really hard and claimed 30 watts. No. The output transformer has a lot to do with sound quality, and larger cores are better. Dynaco amps were very inexpensive and can sound okay, but they are cheap and others are better at the end of the day. Some Bogen PA amps are actually pretty good. I had a CHA-75 as a teenager, it was awesome! 4 - 6AV5 sweep tubes I think.
Okay, I'll assume you have decided you want only tube based. That's fine. 15 to 20 watts means a 6L6GC normally, 7591A are expensive although a 6CA7 based amp is good (replace EL14 with 6CA7 - plug in).
Tube amplifiers cannot be bridged. What you do is connect the two channels in parallel at one lower tap, so the 8R tap for a 16R speaker. Maybe a 6BQ5 (EL84) based amplifier might work. Given you are connecting two channels in parallel, the amplifier must be rebuilt and the two channels very close in gain, feed a mono signal (not from a stereo control). Heathkit and many early tube amplifiers were mono, Eico, Paco and many others. I have a bunch of mono amplifiers. Of course McIntosh made many mono amplifiers, MC30, MC40 and so forth. Expensive but vey good.
Avoid junk like Pioneer. They ran 6189 or 6BQ5 really hard and claimed 30 watts. No. The output transformer has a lot to do with sound quality, and larger cores are better. Dynaco amps were very inexpensive and can sound okay, but they are cheap and others are better at the end of the day. Some Bogen PA amps are actually pretty good. I had a CHA-75 as a teenager, it was awesome! 4 - 6AV5 sweep tubes I think.
I have a heathkit A9C amp to restore that at one point I had intended to use with the speaker, but it's rather large so I will have to go with solid state.
Would the F5M amp kit work for this or does it require a rather large heatsink?
https://diyaudiostore.com/pages/project-f5m
I love the simplicity of the circuit.
I would just use one board.
Would the F5M amp kit work for this or does it require a rather large heatsink?
https://diyaudiostore.com/pages/project-f5m
I love the simplicity of the circuit.
I would just use one board.
Okay (I have one too). Excellent amplifier.
Solid state, great choice. Poor solid state sounds bad. Most low power amplifiers are not designed that well (despite claims they are). I would highly recommend a SymAsym, I've built them and they perform extremely well, and are compact. Pretty inexpensive to build and very high sound quality. It is rated for more power, but you don't need to drive it to full power. The headroom is actually good to have. Don't run it at much lower voltages as that (and any amplifier) will not allow it to operate properly. Yes it will make noise, but not what you want.
Chip amps seem to be missing something from my own experience. High currents and tiny wires don't mix.
Solid state, great choice. Poor solid state sounds bad. Most low power amplifiers are not designed that well (despite claims they are). I would highly recommend a SymAsym, I've built them and they perform extremely well, and are compact. Pretty inexpensive to build and very high sound quality. It is rated for more power, but you don't need to drive it to full power. The headroom is actually good to have. Don't run it at much lower voltages as that (and any amplifier) will not allow it to operate properly. Yes it will make noise, but not what you want.
Chip amps seem to be missing something from my own experience. High currents and tiny wires don't mix.
I currently use two single supply TDA2050 amp boards running them bridged without the speaker coupling caps.
While that works, it's real sketchy as if one speaker wire touches ground one 2050 chip gets damaged.
I'll keep the SymAsym in mind.
Another reason not to use the tube amp at work is I don't know what safety would think of tubes out in the open as there's a burn risk there.
While that works, it's real sketchy as if one speaker wire touches ground one 2050 chip gets damaged.
I'll keep the SymAsym in mind.
Another reason not to use the tube amp at work is I don't know what safety would think of tubes out in the open as there's a burn risk there.
lol!
Yeah, I get it. Plus if you break the glass you have full plate potential until the fuse blows.
I service audio professionally. The easiest thing to do is simply buy a kit and build it. Those should be robust, although no amplifier likes a shorted output. If you want something really easy, have a look on AliExpress or Amazon for kits. Post a link if you think something would work well.
On those single supply chip amps, I always include an output DC block capacitor. I also serviced car amps for years, the "25 watt" amps were pretty much exactly what you have. One short and the chip is blown, possibly the speaker too. They had about 7 VDC on each output terminal.
Yeah, I get it. Plus if you break the glass you have full plate potential until the fuse blows.
I service audio professionally. The easiest thing to do is simply buy a kit and build it. Those should be robust, although no amplifier likes a shorted output. If you want something really easy, have a look on AliExpress or Amazon for kits. Post a link if you think something would work well.
On those single supply chip amps, I always include an output DC block capacitor. I also serviced car amps for years, the "25 watt" amps were pretty much exactly what you have. One short and the chip is blown, possibly the speaker too. They had about 7 VDC on each output terminal.
Will do.
I found out the hard way with the TDA2050 amps why the cap is needed even when operating in bridged mode.
I'll look on amazon after lunch.
Only real thing there I saw last night in a brief search was a plethora of class D amps and chip amps.
Now its possible to go with a dual supply kit provided the amp can be used about 12' away from the speaker with the speaker wire not affecting the amp at all.
Another thing I discovered about the chip amps.
Since they are basically a power OP-AMP they just like regular OP-AMPs don't really like driving capacitive loads.
The TDA2050 amps showed a bit of oscillation at a decent listening level with the 12' of speaker wire connected, but when I moved the amp to the speaker that no longer was a problem.
Here's the speaker I am driving with the amp.
I found out the hard way with the TDA2050 amps why the cap is needed even when operating in bridged mode.
I'll look on amazon after lunch.
Only real thing there I saw last night in a brief search was a plethora of class D amps and chip amps.
Now its possible to go with a dual supply kit provided the amp can be used about 12' away from the speaker with the speaker wire not affecting the amp at all.
Another thing I discovered about the chip amps.
Since they are basically a power OP-AMP they just like regular OP-AMPs don't really like driving capacitive loads.
The TDA2050 amps showed a bit of oscillation at a decent listening level with the 12' of speaker wire connected, but when I moved the amp to the speaker that no longer was a problem.
Here's the speaker I am driving with the amp.
Here's a couple photos of the finished speaker.
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Bipolar power supply, you want a decently designed amplifier. Buy one rated for more power just to get a decent design, 50 watts is reasonable. 12' away is zero problem.
That looks like a piezo electric tweeter, basically a capacitor. Amplifiers do not like capacitive loads. So a decent kit will have an output inductor that will help. Speaker lead length should never be an issue unless it is insanely long. A series resistor for a piezo tweeter will also help by raising the cutoff frequency and isolate the amp from the tweeter. Piezo tweeters do need a crossover, they aren't happy being feed a full range signal. If it is dynamic my comments don't apply.
That looks like a piezo electric tweeter, basically a capacitor. Amplifiers do not like capacitive loads. So a decent kit will have an output inductor that will help. Speaker lead length should never be an issue unless it is insanely long. A series resistor for a piezo tweeter will also help by raising the cutoff frequency and isolate the amp from the tweeter. Piezo tweeters do need a crossover, they aren't happy being feed a full range signal. If it is dynamic my comments don't apply.
The speakers are:
Two 12" 8 ohm RCA woofers wired in series for a 16 ohm load with zobel network on the woofers.
One 15 ohm Goodmans Midax.
One 8 ohm tweeter from a Klipsch KG-4 speaker.
One Goodmans three way crossover network.
Definitely will get an amp with more power.
Two 12" 8 ohm RCA woofers wired in series for a 16 ohm load with zobel network on the woofers.
One 15 ohm Goodmans Midax.
One 8 ohm tweeter from a Klipsch KG-4 speaker.
One Goodmans three way crossover network.
Definitely will get an amp with more power.
Okay, good.
Those original amplifiers needed an output zobel to stabilize them. An output inductor if they didn't have one.
Yep, something close to 50 watts might be more appropriate. Not to go loud so much, just for the headroom if a good song comes on.
Those original amplifiers needed an output zobel to stabilize them. An output inductor if they didn't have one.
Yep, something close to 50 watts might be more appropriate. Not to go loud so much, just for the headroom if a good song comes on.
Plus given most solid state amps don't list a power into 16 ohms a 50 watt rating will ensure I have plenty of power available to the 16 ohm speaker.
A board I found on Amazon doing a quick search.
https://www.amazon.com/TDA7292-Amplifier-Effect-TDA7293-TDA7294/dp/B09MMFG5CK
I also have one of these amps, but need to open it up and see what amp chip it uses.
https://www.pyleaudio.com/manuals/LA120.pdf
Also if I wanted to spend some money this amp would work for sure.
https://www.schiit.com/products/gjallarhorn-f
I'd need a preamp that converts an unbalanced signal to a balanced signal. Something like this would work, but I'd need to build a +/- supply for it.
https://www.amazon.com/Channel-Unbalanced-Balance-Balanced-Amplifier/dp/B0DJNFSZV8
A board I found on Amazon doing a quick search.
https://www.amazon.com/TDA7292-Amplifier-Effect-TDA7293-TDA7294/dp/B09MMFG5CK
I also have one of these amps, but need to open it up and see what amp chip it uses.
https://www.pyleaudio.com/manuals/LA120.pdf
Also if I wanted to spend some money this amp would work for sure.
https://www.schiit.com/products/gjallarhorn-f
I'd need a preamp that converts an unbalanced signal to a balanced signal. Something like this would work, but I'd need to build a +/- supply for it.
https://www.amazon.com/Channel-Unbalanced-Balance-Balanced-Amplifier/dp/B0DJNFSZV8
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Not one of those are what I would call good. A car amp will draw a lot of current from a 12 volt supply, expect efficiencies to run 40% at best.
I guess you want built. Why not then buy a used amplifier, or used car amplifier (I wouldn't go the car amp route). You could buy a decent used stereo and run one channel only. Your 16 ohm power will be lower than rated of course by about 1/2. I'm sure you could find a used decent integrated amplifier, and it would sound better. I might need some service, but you would be way further ahead.
You only need the converter to drive bridged (built in with most car amps anyway). Don't do that. Just run one channel. Don't get fixated on running bridged or both channels. A low powered amp bridged will not sound as good as an amplifier that same power using one channel. Up to you though.
I guess you want built. Why not then buy a used amplifier, or used car amplifier (I wouldn't go the car amp route). You could buy a decent used stereo and run one channel only. Your 16 ohm power will be lower than rated of course by about 1/2. I'm sure you could find a used decent integrated amplifier, and it would sound better. I might need some service, but you would be way further ahead.
You only need the converter to drive bridged (built in with most car amps anyway). Don't do that. Just run one channel. Don't get fixated on running bridged or both channels. A low powered amp bridged will not sound as good as an amplifier that same power using one channel. Up to you though.
Had wanted a kit as those can often be relatively compact.
I do have a Kenwood KA-5002 amp I had forgotten about that I think is not being used.
Would that be a good amp to use?
I do have a Kenwood KA-5002 amp I had forgotten about that I think is not being used.
Would that be a good amp to use?
After replacing a bad transistor on the speaker protection board the amp works great.
The speaker sounds good as well.
The speaker sounds good as well.
Fantastic!
This worked out better than you might have hoped. Less work too.
This worked out better than you might have hoped. Less work too.