That's what I think as well. The spike is always there and depends on the sample rate as you mentioned.
I have posted much more on the Behringer UMC202HD for measurements thread rather than the R.E.W. thread itself. I am considering some of the mods described in there at one point.
I have seen a few people with that kind of spike, but I believe not all of these units have them.
I can try Windowing and check the measurements.
I have posted much more on the Behringer UMC202HD for measurements thread rather than the R.E.W. thread itself. I am considering some of the mods described in there at one point.
I have seen a few people with that kind of spike, but I believe not all of these units have them.
I can try Windowing and check the measurements.
Thanks, I'll give this a try. But if I measure on a TRS between Tip and Shield, I need to multiply that by a factor right?
I just checked two frequency ranges, one small and one extended, and I don't get the numbers under the Distortion graph for the smaller range.
Anyone else gets that kind of issue sometimes?
So that's what was on the bench tonight, except it's the couch bench. Enough for tonight unless I get another bout of insomnia. If so, I might go to Lab Desk 1 again in the night.
I bought 4 bags of fake KOA BPR non inductive resistors from AliExpress. They were $5 a bag - an amazing deal as the genuines are $0.89ea and out of stock for another year.
the question is will these work well and can we use them as low distortion source/emitter resistors where low distortion performance is important? One requirement is that they need to be non inductive - basically not wirewound. However, they can be used as perfectly in CRC PSU where we actually don’t care about the inductance. We just need the thermal dissipation capability. These are nice in that regard and can take 5w.
First test is to smash one open to see if it has the labyrinth non inductive pattern in bulk metal:
That checks out great. Next test was to snip the leads and see if they are made of copper or some other material (steel?). It is definitely ferromagnetic.
Next test was to wire them up in series for a critical test as a low distortion dummy load for amp power testing. I used 16x 0.47R plus 2x 0.22R for nominal 8.0ohms. I have a tap for 4.0ohms. That’s 20x 5w or about 100w total capacity. Running these at 100% load is not advised as non heatsinked resistors generally will smoke and turn brown and burn up eventually at full load. I put a 1kHz 22Vrms sine wave into them for 60w and I could hear the resistors lightly buzz/whine at 1kHz. That’s not a good sign - it means there is some sort of non linear electro mechanical interaction. The IR thermometer showed 115C to 125C temps. Acceptable and not smoking but you could feel the heat radiating off.
The final test was to look at the distortion vs my reference standard: an EBG UXP-300 heatsinked low distortion 300w 10ohm thin film resistor. This resistor is silent and gives this FFT for 14.14Vrms (nominal amplitude for 25w into 8ohms):
THD is 0.0045% mostly third and second harmonic.
Now with the fake BPR’s we get this:
THD is 0.021%, not huge but lots of higher order odd harmonics. This would not be a good resistor to use in a critical spot like an output stage emitter or mosfet source resistor. I do have 20x of them in series and maybe this magnifies the effect by 20? If we divide the 0.021% effect by 20 we get 0.001%THD for a single resistor dissipating 3W each. This might not be bad I don’t know. To be fair, I have not connected 20 genuine KOA BPR’s in series (don’t have the luxury as they are unobtanium now). Maybe they would behave the same way? It’s tough to beat that EBG UXP-300 resistor. I have yet to find a lower distortion power resistor.
For now, I would say these are a great deal for use on CRC PSU’s. But be cautious using them for amplifier output stages. If dividing the effect of the distortion by 20 is technically sound, I would say 0.001% is not a huge deal. Maybe they will be fine. Certainly no worse than cheap wirewound 5W resistors. I have done similar tests and those are much worse.
You can find the fake BPR’s here:
https://a.aliexpress.com/_mN0G6NO
the question is will these work well and can we use them as low distortion source/emitter resistors where low distortion performance is important? One requirement is that they need to be non inductive - basically not wirewound. However, they can be used as perfectly in CRC PSU where we actually don’t care about the inductance. We just need the thermal dissipation capability. These are nice in that regard and can take 5w.
First test is to smash one open to see if it has the labyrinth non inductive pattern in bulk metal:
That checks out great. Next test was to snip the leads and see if they are made of copper or some other material (steel?). It is definitely ferromagnetic.
Next test was to wire them up in series for a critical test as a low distortion dummy load for amp power testing. I used 16x 0.47R plus 2x 0.22R for nominal 8.0ohms. I have a tap for 4.0ohms. That’s 20x 5w or about 100w total capacity. Running these at 100% load is not advised as non heatsinked resistors generally will smoke and turn brown and burn up eventually at full load. I put a 1kHz 22Vrms sine wave into them for 60w and I could hear the resistors lightly buzz/whine at 1kHz. That’s not a good sign - it means there is some sort of non linear electro mechanical interaction. The IR thermometer showed 115C to 125C temps. Acceptable and not smoking but you could feel the heat radiating off.
THD is 0.0045% mostly third and second harmonic.
Now with the fake BPR’s we get this:
THD is 0.021%, not huge but lots of higher order odd harmonics. This would not be a good resistor to use in a critical spot like an output stage emitter or mosfet source resistor. I do have 20x of them in series and maybe this magnifies the effect by 20? If we divide the 0.021% effect by 20 we get 0.001%THD for a single resistor dissipating 3W each. This might not be bad I don’t know. To be fair, I have not connected 20 genuine KOA BPR’s in series (don’t have the luxury as they are unobtanium now). Maybe they would behave the same way? It’s tough to beat that EBG UXP-300 resistor. I have yet to find a lower distortion power resistor.
For now, I would say these are a great deal for use on CRC PSU’s. But be cautious using them for amplifier output stages. If dividing the effect of the distortion by 20 is technically sound, I would say 0.001% is not a huge deal. Maybe they will be fine. Certainly no worse than cheap wirewound 5W resistors. I have done similar tests and those are much worse.
You can find the fake BPR’s here:
https://a.aliexpress.com/_mN0G6NO
X,
Thanks for testing.
Is there a way to retest but with a smaller number of resistors while watching heat dissipation? It would be worthwhile to see if the distortion truly goes down in a ratio.
Best, Anand
Thanks for testing.
Is there a way to retest but with a smaller number of resistors while watching heat dissipation? It would be worthwhile to see if the distortion truly goes down in a ratio.
Best, Anand
I believe 56 is 0.6mm lead diameter. 58 is 0.8 mm lead diameter. Both are 5 watt rated.
https://www.koaspeer.com/products/leaded-resistors/current-sense-leaded/bpr/
Best,
Anand
Your right! Plenty of 0r1, 0r22 and 0r47 in stock. Last I looked Mouser was out.
X, you are comparing the result of pushing 25w into a chain of resistors that is rated 10x 5w, vs 25w into a resistor that is rated 300w. Perhaps a more fair test is to compare with the real BPR with the same power rating.
I'd even volunteer to send you some if you give me ur address, for the good of learning and education. Happy to do so since I have learn a lot from your postings through the years. 🙂
I'd even volunteer to send you some if you give me ur address, for the good of learning and education. Happy to do so since I have learn a lot from your postings through the years. 🙂
Hi guys,
I just realized I can’t count. It’s 18 resistors in series. LOL!
Jmpsmash, if you have 18 KOA BPR’s to send me, I’ll repeat the test. I am curious too but don’t have any genuines to do it with.
I had a few genuine ones from Mouser and noticed that the text is printed in portrait not landscape. And legs are not ferromagnetic. I bet that is the prime contributor to the distortion. The ceramic body is also smoother on the KOA’s.
I just realized I can’t count. It’s 18 resistors in series. LOL!
Jmpsmash, if you have 18 KOA BPR’s to send me, I’ll repeat the test. I am curious too but don’t have any genuines to do it with.
I had a few genuine ones from Mouser and noticed that the text is printed in portrait not landscape. And legs are not ferromagnetic. I bet that is the prime contributor to the distortion. The ceramic body is also smoother on the KOA’s.
Doing some sine wave power tests on my amp with new Oscope. This thing is great.
Here are fan cooled 300w dummy resistors (10ohms or 5ohms parallel):
This is what clipped output looks like. Believe it or not, this measures only 8.5% THD! 🙂
Here is clipping with 1% THD. Rms Fluke measures 31.23Vrms and thus matches Oscope 88.8Vpp:
Here are fan cooled 300w dummy resistors (10ohms or 5ohms parallel):
This is what clipped output looks like. Believe it or not, this measures only 8.5% THD! 🙂
Here is clipping with 1% THD. Rms Fluke measures 31.23Vrms and thus matches Oscope 88.8Vpp:
On the bench is a proper set of Torx screwdrivers. I have been running into Torx screws more and more on commercial builds. I was actually making do with a Bondhus ball driver but it can only apply so much torque.
A new review of the Vanguard speakers that I designed for Vera-Fi Audio was just posted on SBAF. The reviewer did A/B comparison against his BBC spec Graham Chartwell LS3/5A’s.
https://superbestaudiofriends.org/i...-fi-audio-vanguard-speaker-impressions.11814/
https://superbestaudiofriends.org/i...-fi-audio-vanguard-speaker-impressions.11814/
There's a Torx I've been looking for, it must have a hole in the centre. It might be called a Security Torx. Does this set have one?
No, mine are regular Torx.
These have (tamper resistant) holes:
https://www.amazon.com/dp/B07Q21RPS2/ref=cm_sw_r_cp_api_glt_i_DTWJJ0Q5FC6FV7G1ECF2
These have (tamper resistant) holes:
https://www.amazon.com/dp/B07Q21RPS2/ref=cm_sw_r_cp_api_glt_i_DTWJJ0Q5FC6FV7G1ECF2
On the bench tonight is a remote controlled volume pot from China. Supposedly an Alps. I’ll be testing it out on one of my plank preamps I think.
Let us know what you think. I have one in my Aksa Lender preamp, and love the convenience of controlling the volume remotely. I had serious doubts about the Alps, given that the complete board with remote is cheaper than buying an Alps pot locally. But it sounds ok to me.
AliExpress special....... CS3310 preamp into ADAU1701 DSP into a TPA3255 4ch. I need to double 2 of the ADAU1701 outputs to go into the 4 channels of the 4ch amp, then make 2 RCA outputs to feed the other channels into a sub. This setup is just for general testing, but some version of it is eventually going into my kitchen. I kind of like the cutting board theme though. I might make a fancier version with all the high voltage stuff on the underside and small enclosures for everything.
Nice setup @cheapvega !
@twocents - the pot sounds great! Easy to use and nice smooth volume change. No scratchiness or noise when changing volume. Channel balance is good. Listening to ACP+ as headphone amp as test and I like it. The on/off works the open collector logic and I tested with an LED. It works well. Odd behavior of red LED is that it toggles on off with mute or on off but moment volume is changed it lights up and stays on. Volume control always works if DC power present. The pot appears to be a genuine Alps Rk168 (or very good sounding and looking copy) which costs about the same as the whole remote unit with the pot.
https://www.mouser.com/ProductDetail/Alps-Alpine/RK16812MG099?qs=uOLQ569YubvkId4TDNOKXQ==
@twocents - the pot sounds great! Easy to use and nice smooth volume change. No scratchiness or noise when changing volume. Channel balance is good. Listening to ACP+ as headphone amp as test and I like it. The on/off works the open collector logic and I tested with an LED. It works well. Odd behavior of red LED is that it toggles on off with mute or on off but moment volume is changed it lights up and stays on. Volume control always works if DC power present. The pot appears to be a genuine Alps Rk168 (or very good sounding and looking copy) which costs about the same as the whole remote unit with the pot.
https://www.mouser.com/ProductDetail/Alps-Alpine/RK16812MG099?qs=uOLQ569YubvkId4TDNOKXQ==
and -- shielded twisted pair or skinny coax like RG-174 -- both with leads that are as short as practical -- helps a lot.
i have an old illuminated magnifier/viewer with a fluorescent light -- it is sufficiently annoying that I have to remember to turn it off when measuring noise.