So in prep for B.B. arriving in 3 days, I just ordered a full set of Vishay Dale resistors. A pair of 5.6uF Clarity Caps (purple ones). I have the heatsink CPU coolers. Also ordered all the PWM SMT parts for the fan controller. Each has its own temp sensor and variable speed control. The dual 400VA 25v trafos. And finally monster IXYS MOSFETs. Missing a case but can’t do that until I see that it all looks like bolted together. Should I do dual true monoblock cases?
Sounds like you got the right pieces to make a great amp, X!
I'm thinking about mono-blocks when I build the BB version.
Monoblocks defentily imo.X,
Sounds like your going to be ready to build once DHL delivers
I’m thinking along your way Pcgab.... MONOBLOCKS!
Looks like a good project.
I'm intrested but have to finish my 6channel amp first. I mean the case work & protection sections wiring etc.
Both channels up and running using CPU coolers and fans. Still on test loudspeakers, but I am impressed with the quality. I have made a quick comparison with my usual amplifier and think the Alpha sounds more detailed, but I will need more time for long listening tests.
With this in mind I want to investigate passive cooling further as I am not a fan of fans.
Regards
Alan
With this in mind I want to investigate passive cooling further as I am not a fan of fans.
Regards
Alan
Just the logistics of each having it’s own 400VA trafo and CRC board and two CPU coolers with fans seems to make more sense as a mono.
Now just need to figure out a nice looking but cost effective case. Note that it no longer needs fins. Just either grille plate top and bottom or a low profile 3U with cutouts for CPU coolers/fans sticking out.
Maybe an open frame ATX case with tempered glass front?
Seems that a toroidal transformer and CRC board plus the main amp and two CPU coolers could be hung on all the available aluminum panels with holes/slots in them.
This costs the same as a Ho-hum 5U steel Pessante case from DIYA store (Modushop).
PAEAN M Open frame M-ATX Chassis - Newegg.com
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Any comments on the open frame glass front PC cabinet? Both my 400VA 25v toroidal Antek’s came now. They have to be shipped separately to stay within weight limit. Everything is here but the PCBs and big IXYS MOSFETs.
How do you guys all feel about an optional “smart” amplifier controller with micro controller, turn on delay, soft start circuit, temp sensor, auto shutdown of amp power in case of overtemp, fan controller, OLED display, adjustable temp fan speed settings, 12v PSU separate from amp for safety and low noise, all TH components, and beautifully designed and affordable since a JPS64 Special? A special big amp like the Alpha B.B. deserves a special bit of high tech flair. If we wanted to, I’m sure even a web accessible smartphone control app could be added
How do you guys all feel about an optional “smart” amplifier controller with micro controller, turn on delay, soft start circuit, temp sensor, auto shutdown of amp power in case of overtemp, fan controller, OLED display, adjustable temp fan speed settings, 12v PSU separate from amp for safety and low noise, all TH components, and beautifully designed and affordable since a JPS64 Special? A special big amp like the Alpha B.B. deserves a special bit of high tech flair. If we wanted to, I’m sure even a web accessible smartphone control app could be added
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I think the smart amplifier controller is a great idea! Especially if it is designed as a standalone board that the user can then use on another amp.
And a good idea would be to use an off the shelf microcontroller board such as an arduino micro, this will keep cost down and programming easy
And a good idea would be to use an off the shelf microcontroller board such as an arduino micro, this will keep cost down and programming easy
All of the ideas sounds great . What can you see from OLED-display, temperatures etc? Like the display idea really much.
I think it's a good and easy way to get really nice cabinet! I like the open design also.
. What can you see from OLED-display, temperatures etc? Like the display idea really much.I think it's a good and easy way to get really nice cabinet! I like the open design also.
Lower gain version ?
Hello,
The Alpha20 has plenty of gain, too much for my system with 2v sources and 93db speakers,
and to throw that gain away in an attenuator is not that good.
Thanks to Hugh for posting the ltpsice simulation files, I tried to simulate an Alpha20 version with less gain.
In the ltspice simulation files I named the resistors like in the first schematic of the first post.
To lower the gain I added more feedback.
R7 is the feedback resistor but this one can't be changed much, because otherwise the Vout DC offset is messed up.
Lucky there's also the R6 resistor that shunts some feedback to ground.
I've changed the R6 820R to 2k7, this lowers the gain a lot:
with 820r: 0.68 Vin gives 17 Vout
with 2k7: 2.05 Vin gives 17 Vout
But in the FFT H2 and H3 were on the same level with 2k7,
but with changing the R13 ccs fb resistor to 560 I got the same nice declining H2 H3 as the original Alpha20.
So R6 2k7 and R13 560r gives lower gain with the same declining H2 H3 in FFT.
I also tried 3k9 for R6, with 3k9 there was no need to change ccs fb R13,
the FFT looked great with R13 680r
Hugh, X,
Is this lower gain version OK or did I miss something ?
In the attachments you'll find:
ALPHA20-8R_KSA992.asc the original Alpha20
ALPHA20-8R_LG1_KSA992.asc the lower gain trial with 2k7
ALPHA20-8R_LG3_KSA992.asc the lower gain trial with 3k9 (matches the FirstWatt F5 gain)
In the ltspce files the dynamic current labels are resistor bound, the Vin is set for 12Vout
Regards,
Danny
Hello,
The Alpha20 has plenty of gain, too much for my system with 2v sources and 93db speakers,
and to throw that gain away in an attenuator is not that good.
Thanks to Hugh for posting the ltpsice simulation files, I tried to simulate an Alpha20 version with less gain.
In the ltspice simulation files I named the resistors like in the first schematic of the first post.
To lower the gain I added more feedback.
R7 is the feedback resistor but this one can't be changed much, because otherwise the Vout DC offset is messed up.
Lucky there's also the R6 resistor that shunts some feedback to ground.
I've changed the R6 820R to 2k7, this lowers the gain a lot:
with 820r: 0.68 Vin gives 17 Vout
with 2k7: 2.05 Vin gives 17 Vout
But in the FFT H2 and H3 were on the same level with 2k7,
but with changing the R13 ccs fb resistor to 560 I got the same nice declining H2 H3 as the original Alpha20.
So R6 2k7 and R13 560r gives lower gain with the same declining H2 H3 in FFT.
I also tried 3k9 for R6, with 3k9 there was no need to change ccs fb R13,
the FFT looked great with R13 680r
Hugh, X,
Is this lower gain version OK or did I miss something ?
In the attachments you'll find:
ALPHA20-8R_KSA992.asc the original Alpha20
ALPHA20-8R_LG1_KSA992.asc the lower gain trial with 2k7
ALPHA20-8R_LG3_KSA992.asc the lower gain trial with 3k9 (matches the FirstWatt F5 gain)
In the ltspce files the dynamic current labels are resistor bound, the Vin is set for 12Vout
Regards,
Danny
Attachments
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@Juntuin
MMI not developped yet but roughly:
- main power on
- "I´ll BB..." on 1.3" OLED display
- following by "... testing" (fans tested)
- following by "... power on" or "fan failure"
- if ok then displaying temperature and fan speed of all fans; if nok then following
- if problem occurs, like high temperature (value to define) or fan failure, message displayed on OLED display, secondary DC supplies immediatly disconnected before disconnecting main power
- "please power off before servicing"
I´ll put the schematics and developement datas later online for comments.
JP
MMI not developped yet but roughly:
- main power on
- "I´ll BB..." on 1.3" OLED display
- following by "... testing" (fans tested)
- following by "... power on" or "fan failure"
- if ok then displaying temperature and fan speed of all fans; if nok then following
- if problem occurs, like high temperature (value to define) or fan failure, message displayed on OLED display, secondary DC supplies immediatly disconnected before disconnecting main power
- "please power off before servicing"
I´ll put the schematics and developement datas later online for comments.
JP