Yes, true. However, they may also have a capacitative element (don't know for sure but have read this).
It's an active system; the ribbon amps are directly connected to the ribbons.
That's a very good point - thanks, Andrew.
So my 80w into 8 ohms nominal power probably needs to be 200w!
I saw some graphs of a sine wave output into 0.1 ohms, in an article by NP. Yes, I was surprised too - but, sorry, I can't remember where I found it.
Andy
80W into 8r0 is equivalent to 320W into 2r0 (+25dBW),
That's 35.8Vpk and 17.9Apk
What is the specified sensitivity of your ribbons?
say 84dB/W @ 1m would give 84+25 = 109dB @ 1m, or about 101dB @ 2.5m listening distance.
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Sure - they were simple and crude but, to me, showed that the amp I am using ... has a problem. Please tell if you would've come to a different conclusion.
This is a 3-way active system; using my signal generator I put a signal directly into the ribbon amp and then the mid amp (which are the same), and measured the voltage at the driver terminals.
See attachment for my results - if the amps were doing the right thing, I would've expected to measure the same voltage at all frequencies.
Regards,
Andy
From many years using my sig-gen, I know that it has only very minor differences in output, moving across those frequencies.
I'm not interested in getting 100% accurate figures - only in getting an indication showing the amp is - or is not - producing a lot less output at HFs than it does at 6Khz.
Andy
sure , but "he know's" it's not like " he measured it"
what does it cost ??
if you give an amp an steady voltage in at every frequency you should see ( measure) the amp gain at the output , dont you , so how can you understand whats is going on if you miss the input value ( measured) , he and you think it's steady , ok , measure it
and if it is , next step
.
what does it cost ??
if you give an amp an steady voltage in at every frequency you should see ( measure) the amp gain at the output , dont you , so how can you understand whats is going on if you miss the input value ( measured) , he and you think it's steady , ok , measure it
and if it is , next step
.
sure , but "he know's" it's not like "he measured it"
what does it cost ??
if you give an amp an steady voltage in at every frequency you should see ( measure) the amp gain at the output , dont you , so how can you understand whats is going on if you miss the input value ( measured) , he and you think it's steady , ok , measure it
and if it is , next step
Sure, Fabrice - you are absolutely right that measuring the voltage at the output of the sig-gen (or the input of the amplifier) produces a 100% solid conclusion.
But I know - from having done repeated measurements with my CRO on the output of phono stages - that the output of my sig-gen is nearly constant from 6Khz to 30Khz. Yes, it varies slightly (so when I am measuring the output of a phono stage, I always do a direct feed of the sig-gen to the CRO, to adjust the signal at that frequency back to my reference level, before measuring the output of the phono stage) ... but these small variations would not cause the radical difference in amp output (driver input) that I saw at HFs.
Andy , like you I am just trying to understand
I made the same measurement few days ago on my Pass F6
Oh dear - so is your F6 showing an inability to produce HFs at a constant output level?
Andy
Andy, if you wanna build an Pass amp , do an F6 (not the cheap version !!) with PCF, your ears will tell you what
"With PCF" ... what is this?
Re. F6 - according to the table here: FIRST WATT PRODUCTS
... the F6 has a Zout of 0.5 ohm ... whereas the F5 (the one I am interested in) has a Zout of 0.1 ohms. I am thinking this lower Zout will be a better match for 2 ohm ribbons?
Andy
Andy , i made measurement of my F6 up to 20 k , and I havent seen any significant variations , i will do some more measurements for you tomorrow .
my speakers are 3.5 ohms , not that far from yours
PCF mean , positive current feedback , ask Mr Nelson Pass for more details , I wont be surprised if it's ( PCF) helps ( if done properly ) with low Z speakers
.
my speakers are 3.5 ohms , not that far from yours
PCF mean , positive current feedback , ask Mr Nelson Pass for more details , I wont be surprised if it's ( PCF) helps ( if done properly ) with low Z speakers
.
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I'm very glad to hear that, Fabrice!
(As I have always assumed an amp should provide constant output voltage until it approaches its HF roll-off.my speakers are 3.5 ohms , not that far from yours
Mmmm, I think 2 ohms is a significantly harder load to drive than 3.5 ohms.
PCF mean , positive current feedback , ask Mr Nelson Pass for more details , I wont be surprised if it's ( PCF) helps ( if done properly ) with low Z speakers
thanks - and thanks to pD - I will have to research PCF.
Andy
The Maggie true-ribbon is specced to 40khz. It is supposed to be a constant resistive load (of 2 ohms, for my version - 3 ohms for the later version) ... with perhaps some capacitance as well. No I've never seen an impedance plot for one.
Andy
No, it's not "full range". The Maggie true-ribbon (5' long) is a tweeter - so the models that have them, also have mid-range panels and 1 or more bass panels.
I cross over to my mid panel at about 3.5Khz.
Aaah, OK, pD. The F5T has 2 output devices, yes? (I hope so, as I have already ordered the PCBs!)
Andy
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