Go Back   Home > Forums > Amplifiers > Pass Labs

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
Reply
 
Thread Tools Search this Thread
Old 15th September 2009, 06:11 PM   #1
NV&H is offline NV&H  United States
diyAudio Member
 
Join Date: Feb 2005
Location: Charlotte, North Carolina
Default What input voltage produces maximum output with the F5?

Driving an experimental transducer with an F5 and driving the F5 with an iTouch. I think the iTouch has a maximum out put of 2V or so, which doesn't give me all that much volume.

So, what input voltage is needed to drive the F5 to full-tilt boogey mode?
__________________
NV&H
  Reply With Quote
Old 15th September 2009, 06:48 PM   #2
pro is offline pro  Italy
diyAudio Member
 
pro's Avatar
 
Join Date: Feb 2004
Location: Milano
The gain is 15 dB or 6 times, so, for 20V out you need about 20/6 Volts
__________________
Michele
  Reply With Quote
Old 16th May 2010, 01:54 AM   #3
ichiban is offline ichiban  United States
space charged
diyAudio Member
 
ichiban's Avatar
 
Join Date: Oct 2004
Location: Tonawanda
Default Is this right ?

I ran a 1000Hz 0dB test signal from a Denon test cd
and measured the F5 output, using a Fluke 8060A true rms meter,
into a 4Ohm power resistor.
The meter reading was 10v4.
So, 10v4 / 4R = 2A6 , 10.4 * 2.6 = 27.04 Watts rms

10v4 rms = 14v7 peak (10v4 * 1.414)

14v7 / 4R = 3A675 , 14v7 * 3A675 = 54 Watts peak

That jibes with what the F5 should output with 24 volt rails.

Does all that look right?

So, I measured the voltage at the input (101k ) and the meter
reading was 0v57 ? But, if the voltage output is 10v4 and the amp
gain is 6 then the input should have measured 1v733 ?
I'm I measuring the input voltage correctly? What's missing.
__________________

  Reply With Quote
Old 17th May 2010, 10:43 AM   #4
RIP
 
Join Date: Oct 2005
Location: Central Florida
The F5 can output more when it crosses into AB. Your numbers are OK but really don't tell you anything about the Class A power or sensitivity.

Best, Bill
  Reply With Quote
Old 17th May 2010, 04:35 PM   #5
ichiban is offline ichiban  United States
space charged
diyAudio Member
 
ichiban's Avatar
 
Join Date: Oct 2004
Location: Tonawanda
Quote:
Originally Posted by Bill Fuss View Post
The F5 can output more when it crosses into AB. Your numbers are OK but really don't tell you anything about the Class A power or sensitivity.
Best, Bill
Thanks for the reply.

Any comment on
[So, I measured the voltage at the input (101k ) and the meter
reading was 0v57 ? But, if the voltage output is 10v4 and the amp
gain is 6 then the input should have measured 1v733 ?]

Don't understand why I got an input voltage measurement of only 0v57,
the source is an Twisted Pair Sabre32 dac which I believe should have
an output of 2v0 when it has a 0dB signal off a cd. That would be close
to what the back calculation of the F5s output (10v4) divided by its gain (6).

Again, thanks for your reply above and I'm not expecting to be tutored.
__________________

  Reply With Quote
Old 17th May 2010, 06:32 PM   #6
Jen-B is offline Jen-B  United Kingdom
diyAudio Member
 
Join Date: Jan 2010
Location: UK
Check the input and output at the same time. Make sure that you have 0.57 RMS in when you have 10.4 RMS out.

Check the gain setting resistors in your F5. (Refer to Firstwatt service literature). The overall gain is 6, which seems to be set by R1 and (the parallel combination of) R5//R7. (And obviously matched by R2, R8//R6). I think it is actually defined as 1 + [ (R5//R7) / R1 ]

J.
  Reply With Quote
Old 17th May 2010, 07:25 PM   #7
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Make sure your meter reads correctly when trying to measure two absolute voltages that are quite different from each other.

If you expect the amplifier to have a gain of 6times then fit a divide by 6 attenuator at the F5 input.

Now measure the voltage at the input of the attenuator and the voltage at the output of the F5. Do not convert anything to average power.

Adjust the attenuator until the input voltage exactly equals the output voltage.

Now, find out what attenuation the switched attenuator was set to. That should exactly equal the gain and the voltage inaccuracy of your meter has no effect on the measured gain.

That's one of the uses for my homebuilt 0dB to -61dB attenuator in steps of 0.05dB
The steps are -20, -20, -10, -5, -2, -2, -1, -0.5, -0.2, -0.2, -0.1, -0.05.
Twelve switches for 1220 steps. Not expensive to buy in the bits.
__________________
regards Andrew T.
  Reply With Quote
Old 17th May 2010, 08:08 PM   #8
Jen-B is offline Jen-B  United Kingdom
diyAudio Member
 
Join Date: Jan 2010
Location: UK
Quote:
Originally Posted by AndrewT View Post
If you expect the amplifier to have a gain of 6times then fit a divide by 6 attenuator at the F5 input.

Now measure the voltage at the input of the attenuator and the voltage at the output of the F5. Do not convert anything to average power.

Adjust the attenuator until the input voltage exactly equals the output voltage.

Now, find out what attenuation the switched attenuator was set to. That should exactly equal the gain and the voltage inaccuracy of your meter has no effect on the measured gain.
Or...

If you expect the amplifier to have a gain of 6 times then fit an attenuator at the F5 output.

Now measure the voltage at the input of the F5 and the voltage at the output of the attenuator. (Do not convert anything to average power).

Adjust the attenuator until the output voltage of the attenuator exactly equals the F5 input voltage.

Now, find out what attenuation the switched attenuator was set to. That should exactly equal the gain and the voltage inaccuracy of your meter has no effect on the measured gain.

: )

Last edited by Jen-B; 17th May 2010 at 08:29 PM. Reason: Because I like editing things? : )
  Reply With Quote
Old 17th May 2010, 10:24 PM   #9
diyAudio Member
 
carlomar's Avatar
 
Join Date: Dec 2004
Location: lisbon
Quote:
Originally Posted by ichiban View Post
I ran a 1000Hz 0dB test signal from a Denon test cd
and measured the F5 output, using a Fluke 8060A true rms meter,
into a 4Ohm power resistor.
The meter reading was 10v4.
So, 10v4 / 4R = 2A6 , 10.4 * 2.6 = 27.04 Watts rms

10v4 rms = 14v7 peak (10v4 * 1.414)

14v7 / 4R = 3A675 , 14v7 * 3A675 = 54 Watts peak

That jibes with what the F5 should output with 24 volt rails.

Does all that look right?

So, I measured the voltage at the input (101k ) and the meter
reading was 0v57 ? But, if the voltage output is 10v4 and the amp
gain is 6 then the input should have measured 1v733 ?
I'm I measuring the input voltage correctly? What's missing.
Hi,
I do the same:
0 db Cd output 2,15V
2,12V at the input R10 (100k)
12,3v at output into a 5,1ohm resistor

i think your 0,57V measured is not correct
  Reply With Quote
Old 18th May 2010, 02:47 AM   #10
ichiban is offline ichiban  United States
space charged
diyAudio Member
 
ichiban's Avatar
 
Join Date: Oct 2004
Location: Tonawanda
AndrewT, my mind boggles! "That's one of the uses for my homebuilt 0dB to -61dB attenuator in steps of 0.05dB" Wow, perhaps I can do this with a pot and do the calc. to a rough estimate.

carlomar Yes, I think the 0,57V measured is not correct also. But, why I'm not sure.

Jen-B Check the input and output at the same time. Make sure that you have 0.57RMS in when you have 10.4 RMS out.
Thought I did, but I will try again.

Spent my free time today revisiting tubes & vynil. Next couple of days are already filled. I know I'm making excuses, but you know reality some times intrudes. Darn.

And, thanks to all for the help. Will report back, soon I hope. This all came about because I wanted to know if the TP ESS dac was pushing the F5 to its max output when the control was full up with a 0dB signal.
__________________

  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Maximum Voltage for Mosfet Output Stage? Xoc1 Solid State 12 6th September 2009 02:26 PM
Capacitors and maximum voltage ratings hilbert_mostert Tubes / Valves 13 9th May 2009 09:05 AM
2A3 maximum plate voltage alexg Tubes / Valves 11 9th March 2008 05:39 AM
Maximum voltage for LM4780 G.L. Tirebiter Chip Amps 5 6th March 2005 09:06 AM
Maximum input voltage of LT1085 & LT1033 chengtaw Solid State 2 8th January 2003 03:27 PM


New To Site? Need Help?

All times are GMT. The time now is 09:39 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2