Weill I took the AZ shot at the end of March. I am now wondering about taking the second AZ, not for the reason of clotting etc. However, the way forward looks to the mRNA tech. That means that if a third shot is required, will ONLY mRNA be developed?
As much as I took my first shot and will take the second which is the question, the question of these new vaccines long term safety is a real one and should not be disqualified in my mind. For ME the benefits outweigh the risk because I am old geezer though my looks betray that too well ! For younger people and kids that could be a real question and is debatable with no conclusion.
Then there was the thought of therapeutics which has all but disappeared but apparently exist.
I kept up on this covid thing since December 2019 and watched it all unfold before the Mainstream news started reporting. A year ago, it was pretty evident that it was likely a lab leak because of 4 letters. PRRA. More people are put into jail on weaker evidence. but there were greater forces at play.
Then COVID became political football.....and a money making scheme....people 's lives became the price of commercial and political gains.
Anyways, my sound system has changed over this time and I am finally homing into a resting spot.
I've been busy so I am unable to finish my Phono amp section so I ordered and Ifi ZEN phono. The price is reasonable hope it is all it has been written up to be!
I'd be interesting in seeing (and hearing) some of the projects that you guys have built.
Would a guitar amp be of interest to anyone? I've built an ax84 high octane but changed the power supply a bit. Put in a 20H choke and the first smoothing cap (47 uF) was replaced by a 1300 uF electrolytic cap paralleled with a 80 uF run motor cap. Made the amp real quiet and changed the tone slightly....
Working on a engineers amp monoblock but it'll be a while before it's finished....
Got my first Pfizer shot a month or so ago and my second one is scheduled for late August.
Would a guitar amp be of interest to anyone? I've built an ax84 high octane but changed the power supply a bit. Put in a 20H choke and the first smoothing cap (47 uF) was replaced by a 1300 uF electrolytic cap paralleled with a 80 uF run motor cap. Made the amp real quiet and changed the tone slightly....
Working on a engineers amp monoblock but it'll be a while before it's finished....
Got my first Pfizer shot a month or so ago and my second one is scheduled for late August.
That's great! The only 2 amps I've heard are the MOD102+ and the AX84. I really don't have anything to compare it to.
I've just posted a few pictures of it in the instruments and amps folder. It'd be nice to get some feedback on the tone and constructive feedback on my build. I'm all ears and am keen to learn & improve....
I've just posted a few pictures of it in the instruments and amps folder. It'd be nice to get some feedback on the tone and constructive feedback on my build. I'm all ears and am keen to learn & improve....
Really high power resistive load. With some creative arithmetic, shouldn't be hard to take a dozen 10-watt wire-wounds wired in series-parallel and make any load you need, at least for one channel.
Aside from that (and some cables), REW should be all you need. Piece of cake. But if you want to truly plumb the depths of low distortion, not sure REW and related bits can assess a modern amp.
I think much is lost by not actually looking at the waves rolling in on an oscilloscope esp square waves - not sure if the REW or software apps work like a hard-wired oscilloscope.
B.
Aside from that (and some cables), REW should be all you need. Piece of cake. But if you want to truly plumb the depths of low distortion, not sure REW and related bits can assess a modern amp.
I think much is lost by not actually looking at the waves rolling in on an oscilloscope esp square waves - not sure if the REW or software apps work like a hard-wired oscilloscope.
B.
I have that equipment in my lab here at home. An RTX 6001 audio analyzer.
Anyone who wants a test can swing by. I use industry standard 8R 1% 250W non-inductive dummy loads. You'll see a spectrum for both THD and IMD tests. I can then send you the files.
I'm sorry, but with everything it is connected to, I can't really bring it out to a meet.
-Chris
Anyone who wants a test can swing by. I use industry standard 8R 1% 250W non-inductive dummy loads. You'll see a spectrum for both THD and IMD tests. I can then send you the files.
I'm sorry, but with everything it is connected to, I can't really bring it out to a meet.
-Chris
You can use a half decent sound card and an attenuator pad with (free) software like REW (room eq wizard) or ARTA.
How To - Distortion Measurement with REW
For the most simplistic test - get a patch cord and connect your sound card output to sound card input to get a loopback measurement of any sound card you have and that will also tell you what the noise floor of your measurement system is.
8903 or sound card or whatever, you'll still need a dummy load for testing a power amp
How To - Distortion Measurement with REW
For the most simplistic test - get a patch cord and connect your sound card output to sound card input to get a loopback measurement of any sound card you have and that will also tell you what the noise floor of your measurement system is.
8903 or sound card or whatever, you'll still need a dummy load for testing a power amp
Last edited:
Dummy load that I use - I have a pair of the 100W 8R loads. I don't build anything that approaches 50W but you can always parallel/series them if you need better power handling
PartsExpress Dummy Loads
If you want a cheap sound card that performs pretty well, I have used the Behringer UCA222 ($24 on Amazon) and with a good quality 1KHz source, I get a noise floor about -110dB below the fundamental. The Focusrite Scarlett can do better than -120dB.
It's true that you still need a scope to measure square wave response but if that's all you're going to do with the scope then you can really cheap out on that potentially if you don't already have one
PartsExpress Dummy Loads
If you want a cheap sound card that performs pretty well, I have used the Behringer UCA222 ($24 on Amazon) and with a good quality 1KHz source, I get a noise floor about -110dB below the fundamental. The Focusrite Scarlett can do better than -120dB.
It's true that you still need a scope to measure square wave response but if that's all you're going to do with the scope then you can really cheap out on that potentially if you don't already have one
Last edited:
Hi twitchie,
Better than nothing for sure. However it is too easy to blow the inputs of a sound card up. Most handle 5 V maximum at around 10 K before damage. Plus, they aren't differential like purpose built audio analyzers.
The best way to do this without the real thing is to use a distortion meter as a front end and plug your sound card into the monitor out. One channel at a time.
This is an example - random. The last thing I built, an "HDAM" preamp kit off Ebay. Its performance is pretty good (really good actually, and it sounds great!). The source signal is part of the instrument. Here is a loop back test.
So using a really good distortion analyzer like Rick's Amber, and a good sound card ($100 +) will get you closer to this. I know an analyzer is expensive, and that is why I am offering to test anyone's equipment here if you want to make the trip to my place at any point.
-Chris
Better than nothing for sure. However it is too easy to blow the inputs of a sound card up. Most handle 5 V maximum at around 10 K before damage. Plus, they aren't differential like purpose built audio analyzers.
The best way to do this without the real thing is to use a distortion meter as a front end and plug your sound card into the monitor out. One channel at a time.
This is an example - random. The last thing I built, an "HDAM" preamp kit off Ebay. Its performance is pretty good (really good actually, and it sounds great!). The source signal is part of the instrument. Here is a loop back test.
So using a really good distortion analyzer like Rick's Amber, and a good sound card ($100 +) will get you closer to this. I know an analyzer is expensive, and that is why I am offering to test anyone's equipment here if you want to make the trip to my place at any point.
-Chris
Attachments
Hi Chris,
I definitely agree that you don't want to connect any amp directly to a sound card input and that's where I referred to having an attenuator in front of the sound card. I've built and tried the super simple one from the Akitika site and have been using a Linear Systems Autoranger but that is far from cheap.
I think an analyzer would be the best route as well but I'm just trying to suggest low cost alternatives for Koja until it's safe for folks to get together again.
If anyone in the GTA is looking for an 8903A - Toronto Scientific Surplus has a couple left but only 1 with the front panel mounted connectors. Fun fact - the owner Mike looks and sounds exactly like Jeff Daniels (the actor) and once you recognize this, you cannot unsee it or unhear it when he talks.
@Chris, the RTX looks like a super sweet piece! I know there was a group buy here many years ago and it looks like it's almost doubled in price since then but the performance certainly speaks for itself.
Cheers,
Stephen
I definitely agree that you don't want to connect any amp directly to a sound card input and that's where I referred to having an attenuator in front of the sound card. I've built and tried the super simple one from the Akitika site and have been using a Linear Systems Autoranger but that is far from cheap.
I think an analyzer would be the best route as well but I'm just trying to suggest low cost alternatives for Koja until it's safe for folks to get together again.
If anyone in the GTA is looking for an 8903A - Toronto Scientific Surplus has a couple left but only 1 with the front panel mounted connectors. Fun fact - the owner Mike looks and sounds exactly like Jeff Daniels (the actor) and once you recognize this, you cannot unsee it or unhear it when he talks.
@Chris, the RTX looks like a super sweet piece! I know there was a group buy here many years ago and it looks like it's almost doubled in price since then but the performance certainly speaks for itself.
Cheers,
Stephen
That company is in my neighborhood, and I was always wondering what makes them stay in business. Pricing is outrageous, mostly double of what you can get from an equivalent local (Toronto) or US dealer (with the exception of those strictly focused on the "price no objection" business market). Definitely not a place for the enthusiast amateurs.
I have an 8903B (among other audio analyzers) and payed for it USD450 shipping included, about 5 years ago. He's asking USD750 for an 8903A (which is significantly inferior in performance), go figure... Mike is also a hard bargainer, you can't hope of anything under 10% off the list price.
I have an 8903B (among other audio analyzers) and payed for it USD450 shipping included, about 5 years ago. He's asking USD750 for an 8903A (which is significantly inferior in performance), go figure... Mike is also a hard bargainer, you can't hope of anything under 10% off the list price.
Last edited:
Member
Joined 2009
Paid Member
I assume somebody eventually turns up and buys it - that's his business model. There’s a guy on eBay selling tubes at outrageous prices, I heard he gets banned and just turns up again under a different name, I think it’s Bangy Bang these days. There must always be somebody willing to pay or these sellers would close shop.
That jives with my recollection of dealing with Mike as well. Although, I just bought a pair of Tek 7000 series scope plug-ins and they weren't expensive. About market value. I just hope they work. I'm trying to get a cheap scope together for a very good friend. About 100 MHz, dual trace.
I would love an 8903B, but then I collect HP equipment. An 8902 would also be great (measuring receiver - non-audio).
I would love an 8903B, but then I collect HP equipment. An 8902 would also be great (measuring receiver - non-audio).