Gaston is my Idol!
In the Netherlands he is called Guust Flater.
Guust/Gaston and Monty Phyton: it doesn't get any better then that!
myleftyear, that's a theoretical calculation. The idea is that with a certain max output digital source and an amount of gain, you will get at most +/-17V swing at the output. And you can only achieve this with source material giving max output, and with the volume wide open. At all pot levels, your output signal by design, is well in the linear region. You will never clip you amp voltage wise.
I like the F4 but I used to worry that my source/preamp combos cannot drive it to full output. Then I realized I really don't listen that loud, and so all's good.
But as ZM stated, if you want to drive the F4 to full output, just crank up the voltage and increase the gain.
Cheers,
Dennis
I like the F4 but I used to worry that my source/preamp combos cannot drive it to full output. Then I realized I really don't listen that loud, and so all's good.
But as ZM stated, if you want to drive the F4 to full output, just crank up the voltage and increase the gain.
Cheers,
Dennis
I have 25V rails, stock gain setting, the 6db autoformer and live happily ever despite "leaving some on the table". More gain in my case means "throw more signal away to ground with the attenuator at my preferred listening levels..." I would rather not do that. But it's very good to know what needs to be done to get everything she's got, if that's what is required for some reason... I remember something about an orange vegetable doing that....
Andy, just for my better understanding, those final, unclean 3V ... does that mean that you're going to stop your attenuator at 17/20 (the rest of the attenuation been prone to unclean amplification)? Or does it mean that you are using 17/20 of the PSU to feed the stage?
And, your Fynes have some excellent 91dB sensitivity, that's almost twice as loud as mine… so you should be able to get in trouble with your neighbors already? (Maxing out f4 would mean to invoke a renovation-team I guess…)
I am not afraid that it won’t be loud enough. Just trying to get my head around the tech behind it all. Plus there is something about having a thought through gain structure, planned beforehand. That said, I might get even more sensitive speakers, so perhaps not that nescessary?
Choky: even if a setup requires not so much gain, will the F4 still take advantage of extra swing at the preamp?
Hugz and kissez,
Andy
Andy - if you want to try F4, merely drive the BA3 output stage directly from your BA2018. The lack of buffer won’t bother the BA2018 at all, and you’ll see what kind of volume you can get with only that gain.
speaking of gain structure - most important thing is having volume pot maximized, for loudest you'll use
does you have headroom in amp itself, and in preamp itself, that's another issue
let's phrase it differently :
-amp, say F4; you must be sure that 25W@8R (50W@4R) is enough for your speakers in your room @ your ears; if yes, that part is done
-preamp - is it capable of 40-ishVpp swing without clipping, so you can feed F4
-what position of volume pot is to get that (40-ishVpp or less, if you need less for preferred SPL) with regular source?
as I wrote ooomphteen times (me being Ara, not smart) - always go in direction shown above - room, speakers, amp, preamp, source
solve first step, then next one is easy
does you have headroom in amp itself, and in preamp itself, that's another issue
let's phrase it differently :
-amp, say F4; you must be sure that 25W@8R (50W@4R) is enough for your speakers in your room @ your ears; if yes, that part is done
-preamp - is it capable of 40-ishVpp swing without clipping, so you can feed F4
-what position of volume pot is to get that (40-ishVpp or less, if you need less for preferred SPL) with regular source?
as I wrote ooomphteen times (me being Ara, not smart) - always go in direction shown above - room, speakers, amp, preamp, source
solve first step, then next one is easy
Thanks a lot for the advice, Jim!
I will certainly consider it. Thing is I hade a one-use store coupon with some greenies to spare, so I ordered the F4 boards along. And realized I have all the parts I need except for a few resistors, diodes and voltage references iot build the F4.
But I also have all I need to redo my BA-3 with original Toshiba parts with golden IDSS for that exact amp.
Only thing is I find the gain of the BA-3 a bit high, making it less flexible wrt preamp choice vs high sens speakers. Right now it is perfect with my Fynes. But sorta wanna go the high sens way in time...
The choice is complicated further as my new PSU parts have arrived, for 24v rails. And I wonder if the F-4 is more suited for that than the BA-3 (FE distortion specs and all). But those are affected by the output stage need for swing, so I guess removing the FE just moves the problem to the preamp.
I am probably overcomplicating things. Turns out swapping a high gain amp for a unity gain one, brings to the table issues of it’s own =)
One solution is to use the BA-3 FE as preamp. That will enable more class A bias in the power amp, while at the same time enabling higher voltage rails in the preamp to provide swing =)
Room is given, I’m afraid. But speakers are up for reconsideration. The insane impedance swings of my Fynes, 8 ohms nominal but 3R5-ish through the whole bass region, needs watts and threatens class A operation at high levels. So the Fynes are under consideration to be sold and replaced with Zu. Now Zu’s, I can prolly drive with my phone. Or an ACP... so I guess gain won’t be an issue with those. One of the biggest challenges will be the opposite, I suppose: ensuring it is in fact possible to listen at low volumes.
Now that I, in an uneducated and very low tech technical way, have some understandig of how gain structure and voltage swing works, I wonder what math could help provide insight wrt how loud a speaker will play with a given input.
The Zu DW’s are 12R nominal and 97 db sens. Meaning 1 watt will provide 97db at one meter. I don’t think I’d need much more than that 😀
And with the WLS on roughly standard values - maybe a bit extra gain - and 20v rails, I should be able to get around 10 watts into 8 ohms with the F4, right Dennis?
That should bring them how loud? I do not know that math. But enough to go half deaf I presume...
I don’t know if all that has been shed light on here today had been discussed 1,2 or 1000 times in this forum. But I feel enlightened and that I have learned a lot. Thank you, guys!
Regards,
Andy
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Andy:
If you can find a way to swing it, consider the Elsinores. They are very well suited to a wide range of First Watt amps -- mine are usually paired with F5 Turbo V3s but, at the moment, they're rocking hard with a VFET P 10 watt amp. Stellar performer, easy load.
Regards,
Scott
If you can find a way to swing it, consider the Elsinores. They are very well suited to a wide range of First Watt amps -- mine are usually paired with F5 Turbo V3s but, at the moment, they're rocking hard with a VFET P 10 watt amp. Stellar performer, easy load.
Regards,
Scott
Thanks a lot, Scott! I checked out the website. Looks like bloody fantastic speakers. Only things stopping me at the time is lack of WAF, at least as far as my wife is concerned (Ireally like the looks myself), somewhat lacking woodwork skills and equip, and the price which at the moment is beyond my limits.
But do tell, how do you find them, and have you tried anything comparable in the past?
Regards,
Andy
But do tell, how do you find them, and have you tried anything comparable in the past?
Regards,
Andy
Gentlemen, a probably not surprising discovery, but in the name of learning I post it.
I had some issues with my WLS right channel. After redoing more or less the whole board, I finally got rid of some intermittent crackling noise. Solution was replacing some allready replaced JFETs, discovering some dirty pads under there...
Anyways, it looks dead quiet on the scope now.
The «discovery», mind you - probably a discovery only for me and not you experienced greedy boyz, was that voltage drop over R13/14 increased from approx 1R8 to 2R9 by changing JFET grade from GR to BL. Meaning from 12mA (per rail/phase) to 19mA, if my math is correct.
Now, this redone board is now in the categoty «test board». I’ll prolly put it to use anyways, though.
What this seems to indicate is that the CCS current increased in going from GR to BL, and as such the bias is now higher. Is that reasoning logical?
A few questions:
1: Is it too high for the standard parts in there? I guess no, and bias is always good, no?
2: Anyone know/want to explain the basic tech behind what I am seeing?
3: Zardoz is cool.
Regards,
Andy/Viking gone from axe to soldering iron
I had some issues with my WLS right channel. After redoing more or less the whole board, I finally got rid of some intermittent crackling noise. Solution was replacing some allready replaced JFETs, discovering some dirty pads under there...
Anyways, it looks dead quiet on the scope now.
The «discovery», mind you - probably a discovery only for me and not you experienced greedy boyz, was that voltage drop over R13/14 increased from approx 1R8 to 2R9 by changing JFET grade from GR to BL. Meaning from 12mA (per rail/phase) to 19mA, if my math is correct.
Now, this redone board is now in the categoty «test board». I’ll prolly put it to use anyways, though.
What this seems to indicate is that the CCS current increased in going from GR to BL, and as such the bias is now higher. Is that reasoning logical?
A few questions:
1: Is it too high for the standard parts in there? I guess no, and bias is always good, no?
2: Anyone know/want to explain the basic tech behind what I am seeing?
3: Zardoz is cool.
Regards,
Andy/Viking gone from axe to soldering iron
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Haha. There you go... you aren’t confused, you are disappointed and angry that I don’t live up to your Zardoz standards. Point taken!
1V8dc RMS and 2V9 RMS, equals total current of 24mVdc on GR side and 38 og BL side. No?
1V8dc RMS and 2V9 RMS, equals total current of 24mVdc on GR side and 38 og BL side. No?
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Vdc is by definition RMS already 🙂, so writing that is not critical, but arising question what else you don't understand
current usually defined with A
handy to have units written properly, so we can use our two brain cells to deduce worthy part of puzzle, not to fall short right in explanation stage
hardly that I'm angry..... while drinking first morning coffee (mid of day), there are just few things which can move me to really care 🙂
tell me DC voltages across R1 and R2 (which will tell how good your JFets are matched, besides giving info about actual Iq)
also voltages across R7 and R11
these 4 voltages are enough (if you set DC offset closest to 0 you can) to have all info
all ref. to schm in post #1
current usually defined with A
handy to have units written properly, so we can use our two brain cells to deduce worthy part of puzzle, not to fall short right in explanation stage
hardly that I'm angry..... while drinking first morning coffee (mid of day), there are just few things which can move me to really care 🙂
tell me DC voltages across R1 and R2 (which will tell how good your JFets are matched, besides giving info about actual Iq)
also voltages across R7 and R11
these 4 voltages are enough (if you set DC offset closest to 0 you can) to have all info
all ref. to schm in post #1
Copy, will measure as soon as I have a few minutes in the workshop. Plus my lab PSU arrives soon, that will make things even easier. Thank you very much!
PS: I have not done any matching, but have ensured all active devices are from the same reel.
I know current is defined with A, and voltage with V, ref my first post of the day. The cause for messing it up this time is a bit much on my plate, ergo no time, and too little surplus brain capacity compared to knowledge... Should save my postings for when I actually have time to think before I write. Sorry! Will make proper effort when giving the numbers I am tasked to give. But hey, I am just an amateur. Make mistakes all the time...
=)
PS: I have not done any matching, but have ensured all active devices are from the same reel.
I know current is defined with A, and voltage with V, ref my first post of the day. The cause for messing it up this time is a bit much on my plate, ergo no time, and too little surplus brain capacity compared to knowledge... Should save my postings for when I actually have time to think before I write. Sorry! Will make proper effort when giving the numbers I am tasked to give. But hey, I am just an amateur. Make mistakes all the time...
=)
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Correction: Reading of 2V9 was across R7 and R13, the 150R resistors. They were the same, presumably since offset was zeroed. I’ll get back to you with all requested measurements later.