Ok, so I did the test with my Alpha 20 running 1.35amp bias with R131=0.47R and R132= 0.22R.
I used two 270ohm (5W) resistors in series for the high impedance case for 3.52vrms or 9.96vpp.
Then with a 10.0ohm 2% 10W resistor I measured 3.39vrms or 9.59vpp.
So (1-9.59/9.96)=0.0368 or 10ohm/0.0368=27.2 DF - fairly close to the 30 DF Hugh predicted for the Alpha 20 running 1.93amps bias.
So one thing that is important is to use very low impedance speaker cables. They do make a difference. 16ga stranded copper zipcord is not as good as solid copper 12ga Romex. So back goes the Romex into the speaker setup.
I used two 270ohm (5W) resistors in series for the high impedance case for 3.52vrms or 9.96vpp.
Then with a 10.0ohm 2% 10W resistor I measured 3.39vrms or 9.59vpp.
So (1-9.59/9.96)=0.0368 or 10ohm/0.0368=27.2 DF - fairly close to the 30 DF Hugh predicted for the Alpha 20 running 1.93amps bias.
So one thing that is important is to use very low impedance speaker cables. They do make a difference. 16ga stranded copper zipcord is not as good as solid copper 12ga Romex. So back goes the Romex into the speaker setup.
Nice !
Directly after the theory to see the realworld measurements and that they match
An example of the technique I used can be downloaded from Bob Cordell's website.
It's SPICE Tutorial Examples\Figure 19_7\Damping factor
It puts an ac analysis signal at the node of interest: between 8R Rload and ground.
Vin2 is the voltage between the new ac analysis signal and Rload.
Don't forget to remove the ac analysis signal from V1, the sine wave voltage source at input.
I think once you have a damping factor above 100 you don't hear a difference.
So now the Alpha20 can be configured for two different damping factors, a low and a high, just by connecting the fb resistor on another place.
This Alpha20 is a very flexible design,
DF, gain and 8R/4R easily adapted to personal preferences.
Congratulations Hugh for this !
Directly after the theory to see the realworld measurements and that they match
An example of the technique I used can be downloaded from Bob Cordell's website.
It's SPICE Tutorial Examples\Figure 19_7\Damping factor
It puts an ac analysis signal at the node of interest: between 8R Rload and ground.
Vin2 is the voltage between the new ac analysis signal and Rload.
Don't forget to remove the ac analysis signal from V1, the sine wave voltage source at input.
I think once you have a damping factor above 100 you don't hear a difference.
So now the Alpha20 can be configured for two different damping factors, a low and a high, just by connecting the fb resistor on another place.
This Alpha20 is a very flexible design,
DF, gain and 8R/4R easily adapted to personal preferences.
Congratulations Hugh for this !
Attachments
Last edited:
Yes, JT, you will hear a clear difference with different DFs, particularly on high efficiency speakers.
IN fact, in one Pass amp Nelson uses a way to move DF from low to high by taking a variable fb point from a pot connected left and right of the output resistor (0.12R on the ALPHA).
Cheers,
HD
IN fact, in one Pass amp Nelson uses a way to move DF from low to high by taking a variable fb point from a pot connected left and right of the output resistor (0.12R on the ALPHA).
Cheers,
HD
Well, my 15" bass/mid is something like 96db/w/m so there will be audible diffirence. Gab and I actually share very similar systems altough Gap's version is much nicer looking. Interesting to see what will be preferred. I can imagine that with metal music bigger might be better, some genres maybe otherwise.
What I understand now is with Alpha you can also change DF but it might effect sound quality?
Theres quite bad internet connection, so difficult to read previous posts from here. Answer is probably there already.
altough Gap's version is much nicer looking. Interesting to see what will be preferred. I can imagine that with metal music bigger might be better, some genres maybe otherwise.What I understand now is with Alpha you can also change DF but it might effect sound quality?
Theres quite bad internet connection, so difficult to read previous posts from here. Answer is probably there already.
xrk971
Belden DIY audio cables
Belden DIY audio cables
-> Low-Inductance DIY Braided Hi-Fi Speaker Cables
-> The Importance of Star-Quad Microphone Cable - Benchmark Media Systems, Inc.
DIY speakers cable with star quad geometry I think is a good idea. Something like these commercial cables:
XTZ XTZ Star Quad NLP 2x2,5mm 2,8 m - XTZ,Swedish Design, speaker cable
Audiophile idea: made with Neotech SOCT.
-> http://www.audiocircle.com/index.php?topic=137288.msg1493866#msg1493866
Talking about cables (impedance, capacity, inductance and RF interferences: star quad geometry) maybe someone is interested:
Belden DIY audio cables
Belden DIY audio cables
-> Low-Inductance DIY Braided Hi-Fi Speaker Cables
-> The Importance of Star-Quad Microphone Cable - Benchmark Media Systems, Inc.
DIY speakers cable with star quad geometry I think is a good idea. Something like these commercial cables:
XTZ XTZ Star Quad NLP 2x2,5mm 2,8 m - XTZ,Swedish Design, speaker cable
Audiophile idea: made with Neotech SOCT.
-> http://www.audiocircle.com/index.php?topic=137288.msg1493866#msg1493866
Last edited:
To finish,
Some days ago, by mail, Magico speakers use Canare 4s11. After a search:
magico speakers canare 4s11 - Google Search
-> Speaker Cable for Old Quad Loudspeaker (aka 57) -
Audionirvana.org
Off topic:
Talking about expensive Magic speakers...
NRC Measurements: Magico S5 Loudspeakers
SoundStageNetwork.com | SoundStage.com - NRC Measurements: Magico S5 Loudspeakers
[URL]https://www.soundstage.com/images/stories/loudspeakermeasurements/magico_s5/thd_95db.gif[/URL] !!!!!!!
[quote][B]Total Harmonic Distortion + Noise[/B]
Chart A: @ 90dB, 50Hz - 10kHz (measured @ 2m)[/quote]
[COLOR=green][B]f > 70 Hz nothing[/B][/COLOR] !!!!
[URL="https://www.stereophile.com/content/magico-s5-mkii-loudspeaker-measurements"]Magico S5 Mk.II loudspeaker Measurements | Stereophile.com[/URL]
Some days ago, by mail, Magico speakers use Canare 4s11. After a search:
magico speakers canare 4s11 - Google Search
-> Speaker Cable for Old Quad Loudspeaker (aka 57) -
Audionirvana.org
********* ********
Off topic:
Talking about expensive Magic speakers...
NRC Measurements: Magico S5 Loudspeakers
SoundStageNetwork.com | SoundStage.com - NRC Measurements: Magico S5 Loudspeakers
[URL]https://www.soundstage.com/images/stories/loudspeakermeasurements/magico_s5/thd_95db.gif[/URL] !!!!!!!
[quote][B]Total Harmonic Distortion + Noise[/B]
Chart A: @ 90dB, 50Hz - 10kHz (measured @ 2m)[/quote]
[COLOR=green][B]f > 70 Hz nothing[/B][/COLOR] !!!!
[URL="https://www.stereophile.com/content/magico-s5-mkii-loudspeaker-measurements"]Magico S5 Mk.II loudspeaker Measurements | Stereophile.com[/URL]
Maty,
I have not tried star braided cables but my experiment with regular OFC 16ga stranded zipcord vs 12 ga solid copper Romex was quite disturbing.
http://www.diyaudio.com/forums/parts/315971-belden-diy-audio-cables-8.html#post5380201
I never believed that cables had much of an effect but it’s easy to measure and know for sure. The FFT and output impedance test doesn’t lie.
I am not sure $50k unicorn breath infused cables make a difference - but pure solid copper thickness sure seems to make a difference.
I changed the cable from my amp to my front loaded horn subwoofer to a as short as possible (0.5m) dual pair of 16ga stranded zip and it made a huge impact on bass articulation since damping factor went up massively from previous 4pair Cat5 (long length). That was an obvious change that I had put off since I used whatever wire I had at the time to make a connection.
http://www.diyaudio.com/forums/parts/315971-belden-diy-audio-cables-8.html#post5380201
I have not tried star braided cables but my experiment with regular OFC 16ga stranded zipcord vs 12 ga solid copper Romex was quite disturbing.
http://www.diyaudio.com/forums/parts/315971-belden-diy-audio-cables-8.html#post5380201
I never believed that cables had much of an effect but it’s easy to measure and know for sure. The FFT and output impedance test doesn’t lie.
I am not sure $50k unicorn breath infused cables make a difference - but pure solid copper thickness sure seems to make a difference.
I changed the cable from my amp to my front loaded horn subwoofer to a as short as possible (0.5m) dual pair of 16ga stranded zip and it made a huge impact on bass articulation since damping factor went up massively from previous 4pair Cat5 (long length). That was an obvious change that I had put off since I used whatever wire I had at the time to make a connection.
http://www.diyaudio.com/forums/parts/315971-belden-diy-audio-cables-8.html#post5380201
Cables - Benchmark Media Systems, Inc.
[URL]https://cdn.shopify.com/s/files/1/0321/7609/products/Cable_NL2toBan_full.JPG?v=1417637929[/URL]
[QUOTE][B]Star-Quad Construction[/B]:
This top-quality Benchmark cable features Canare Star-Quad Speaker Cable. [B]Four heavy-duty 14 AWG stranded[/B] conductors are combined into two pairs arranged in a star-quad configuration. The combined conductors are [B]equivalent to 11 AWG[/B], but the [COLOR=Green][B] star-quad configuration reduces magnetic radiation and interference by about 20 dB[/B][/COLOR], making this cable superior to 2-conductor cables.
[/QUOTE]Maybe would be a good idea [B]ALPHA[/B] with [B]SpeakON speaker connectors[/B] like PA amplifiers. And the preamp too. ALL with [B]SpeakON from Neutrik[/B].
-> Benchmark Speaker Cable - NL2 to Banana - 2 pole - Benchmark Media Systems, Inc.
[URL]https://cdn.shopify.com/s/files/1/0321/7609/products/Cable_NL2toBan_full.JPG?v=1417637929[/URL]
[QUOTE][B]Star-Quad Construction[/B]:
This top-quality Benchmark cable features Canare Star-Quad Speaker Cable. [B]Four heavy-duty 14 AWG stranded[/B] conductors are combined into two pairs arranged in a star-quad configuration. The combined conductors are [B]equivalent to 11 AWG[/B], but the [COLOR=Green][B] star-quad configuration reduces magnetic radiation and interference by about 20 dB[/B][/COLOR], making this cable superior to 2-conductor cables.
[/QUOTE]Maybe would be a good idea [B]ALPHA[/B] with [B]SpeakON speaker connectors[/B] like PA amplifiers. And the preamp too. ALL with [B]SpeakON from Neutrik[/B].
Last edited:
Those are very reasonable prices for the Benchmark cable with locking banana and Speakon connectors. Raw 25ft 12 ga 2-conductor plus GND (inflexible) Romex was $15, no connectors and looks like pre-drywall construction material.
That Benchmark amp has some impressive specs. Will be interested to hear your subjective comparisons once built.
Hi Hugh, X,
A question about a small capacitor.
In the original Alpha20 schematic there's the C4 18p capacitor,
with the 22k fb resistor it makes a lowpass fb (<400khz) to Vvas (I think).
But in the BB and the 4R version that capacitor is omitted.
Is it of no importance ?
Regards,
Danny
A question about a small capacitor.
In the original Alpha20 schematic there's the C4 18p capacitor,
with the 22k fb resistor it makes a lowpass fb (<400khz) to Vvas (I think).
But in the BB and the 4R version that capacitor is omitted.
Is it of no importance ?
Regards,
Danny
Last edited:
Hi Danny_66,
Perhaps you have not seen the definitive BB schematic (version Beta v1) that was just produced, since I have not yet posted it until now. It has a larger 47pF NP0 or silver mica C111/C1110 capacitor on the feedback upstream of the the Aleph sense resistor(s) R151-153 and only an 18k carbon film downstream of the sense resistor. This was the circuit that Hugh gave us to produce and I am sure it was after careful analysis of the stability margins.
Quite a simple amp though isn't it?
There is also the associated PWM controller, which I would not worry too much about as we can also get standalone COTS PWM fan contollers with temp sensors for $6ea.
Perhaps you have not seen the definitive BB schematic (version Beta v1) that was just produced, since I have not yet posted it until now. It has a larger 47pF NP0 or silver mica C111/C1110 capacitor on the feedback upstream of the the Aleph sense resistor(s) R151-153 and only an 18k carbon film downstream of the sense resistor. This was the circuit that Hugh gave us to produce and I am sure it was after careful analysis of the stability margins.
Quite a simple amp though isn't it?
There is also the associated PWM controller, which I would not worry too much about as we can also get standalone COTS PWM fan contollers with temp sensors for $6ea.
Attachments
Last edited:
Yep, still quite simple, almost the same as the Alpha20 except for the ground lift.
I see that the C4/C105 18p resistor is also omitted here.
Yes, ali/ebay is your friend for cheap PWM fan controllers.
I would definitely use a complete separate power supply with a little transformer for powering the fans and the PWM controller.
So both circuits/grounds are completely separated.
Regards,
Danny
I see that the C4/C105 18p resistor is also omitted here.
Yes, ali/ebay is your friend for cheap PWM fan controllers.
I would definitely use a complete separate power supply with a little transformer for powering the fans and the PWM controller.
So both circuits/grounds are completely separated.
Regards,
Danny
Last edited: