
Home  Forums  Rules  Articles  The diyAudio Store  Gallery  Blogs  Register  Donations  FAQ  Calendar  Search  Today's Posts  Mark Forums Read  Search 
Pass Labs This forum is dedicated to Pass Labs discussion. 

Please consider donating to help us continue to serve you.
Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving 

Thread Tools  Search this Thread 
20th December 2012, 08:33 PM  #681 
diyAudio Member
Join Date: Aug 2008
Location: Toronto

This is what I am thinking of building:
1) 4 devices per channel 2) 0.63 amps/device (total 2.52 amp bias) 3) 36 VAC transformer (approx. 46 volt rails) using a 1.5 KVA transformer. This gives about 118 wpc class A. If you use a 24 VAC transformer, I figure that 1Kva ought to do a stereo amp at this bias current, and give you about 80 wpc. 
20th December 2012, 10:17 PM  #682 
diyAudio Member
Join Date: Aug 2008
Location: Toronto

I think my numbers show peak Class A watts. RMS would be about 60 and 40.
Last edited by BigE; 20th December 2012 at 10:34 PM. 
21st December 2012, 12:11 AM  #683  
diyAudio Member
Join Date: Apr 2006
Location: MA

I am currently collecting parts for a V2. Could someone expand on the section of the F5T article below about the diodes? I am not 100% clear what is need to be done. I am thinking 32V rails and not sure of the bias.
Quote:


21st December 2012, 02:25 AM  #684 
diyAudio Member
Join Date: Aug 2008
Location: Toronto

AndrewT, I have a spreadsheet for this now.
It says that an amp can be made with these parameters: 1) Vsec : 40 VAC 2) Vrail : 52 VAC (1.3* Vsec) 3) Ib : 0.7 A per device 4) Ibt : 5.6 A ( 8 devices * Ib ) 5) VAbias : 582.4 ( (2 * Ibt) * ( 2* Vsec) ) 6) VAcool: 1164.8 ( 50% transformer load at idle ) 7) Wpeak: 291.2 ( Vrail * Ibt ) 8) Wrms: 145.6 ( Wpeak/2 class A) 9) Wab: 291.2 (twice Wrms) 10) VAab: 582.4 (twice Wab, not 1.5) 11) Total VA: 1164.8 ( VAbias + VAab) Note that this is the identical figure to VAcool  that level of VA to allow the transformer to run cool. It is also exactly 8*Wrms. So, you can make A 145.6 Watt mono amp with 8 Fets, 52 volt rails, 40 volt secondaries biased to 0.7 A per device with a 1.2Kva transformer. Or this could be a stereo 72.8 watt class A amp. It dissipates 582 watts at idle. If you have a 34 Volt secondary, and get 44.2 V rails, 0.7A, you can make a 123.76 watt monoblock or 62 watt stereo amp from a 1Kva transformer. It dissipates 500 watts at idle. A 1A bias and 34 VAc secondary will need a 1414 VA transformer for a 176 W monoblock or 83 watt stereo amp. It dissipates 707 watts at idle. A 1A bias and 36 Volt secondary will need a 1.5KVA transformer to produce a 98.6 watt stereo amp, or 187.2 watt monoblock. It dissipates 750 watts at idle. The dissipation is VAbias. I think these numbers are OK, but as usual, I will take NO responsibility for their accuracy. Last edited by BigE; 21st December 2012 at 02:29 AM. 
21st December 2012, 02:51 AM  #685 
diyAudio Member
Join Date: Feb 2009

0.7A bias pr device, and 4pairs = 2.8A bias. 52V*2.8A*2=291W dissipation.
this will give you about 125W Class A power at 8ohms. transformer need to be a minumum of 600VA pr ch. 
21st December 2012, 03:26 AM  #686  
diyAudio Member
Join Date: Sep 2002
Location: India

Quote:
I'll be using similar capacitance level (though my rails are lower)  22000uF x 8 and 10000uF x 8. The first bank will be as per the V2 power supply recommendation, the second bank is twice as beefy. I am not sure that with the higher rails a similar capacitance will be sufficient. Yes. 25V minus the margin of error for mains voltage, which is never 230V. Quote:
Will be glad to see where I went wrong in this calculation. 

21st December 2012, 03:36 AM  #687 
diyAudio Member
Join Date: Aug 2008
Location: Toronto

According to this, with 2 devices ( 1 N and 1 P ) each device biased at 1.3 A ( so the pair has 2.6 amps) my spreadsheet shows 27 watts , 108 Watts dissipation and a 216 VA transformer ( For one channel ) 16 VAC secondary and 20.8 V rail.
http://www.firstwatt.com/pdf/prod_f5_man.pdf In your example, if you calculate using 8 devices at 0.7 A each ( 5.6 A) you get a 250 Watt peak = 5.6 * 5.6 * 8 , which is 125 Watts RMS. The dissipation is 582.4 watts which is 5.6 * Vrail_to_rail as in Andrew's example. 
21st December 2012, 03:46 AM  #688 
diyAudio Member
Join Date: Aug 2008
Location: Toronto

Sangram
According to the spreadsheet, you are exactly correct. 24 V secondaries 31.2 V rails 1 Amp/Device * 4 devices = 4 Amps draw. Gives 64 Wrms per channel, using a 1Kva transformer. (1024 VA would be exact) It will double in A/B and idle at 50%. Ignore my previous post. It is exactly the right size. Last edited by BigE; 21st December 2012 at 03:50 AM. 
21st December 2012, 03:54 AM  #689 
diyAudio Member
Join Date: Feb 2009

1A pr device, 2pairs =2A bias. dissipation =2A*32V*2 = 128W pr ch. so minimum 250300VA transformer pr ch.

21st December 2012, 03:59 AM  #690 
diyAudio Member
Join Date: Sep 2002
Location: India

:whew:
I am aiming for more voltage swing, so the 'stereo' is only indicative. In reality I will be running in balanced configuration (this 8device/1A bias/1KVA supply is for 1 channel) with another exact monoblock for the other channel. The power output target is ~80W in Class A and maybe 120130W total. Also, during summer as is my practice with the F5, the bias will be lowered to prevent me from bursting into flames. 
Thread Tools  Search this Thread 


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
F5 Turbo Circuit Boards  chchyong89  Pass Labs  2347  14th July 2014 02:19 PM 
B1 builders thread  Bas Horneman  Pass Labs  696  14th July 2014 12:57 PM 
F5 Turbo is posted  Nelson Pass  Pass Labs  635  6th April 2014 10:51 AM 
F5 turbo problems  Rob Dingen  Pass Labs  17  11th January 2013 08:38 PM 
F5 Turbo ............. if only !!!!!!  a.wayne  Pass Labs  23  21st January 2012 02:24 AM 
New To Site?  Need Help? 