So glad you built it!
Hello all, first post here. Am interested to know if this can be used to drive an F7 if built. Specifically, will it deliver +10-11V into 10K Ohms or 9bd of gain into this impedance? I cannot figure this out from the information in the thread, probably because I am an idiot. I would be using it as more of a linestage gain device than as a full preamp. Headphones not so important. Interested in getting some more gain to my F7 and it would be interposed between the F7 and a DAC + digital preamp that can output 4.5V from its variable ouputs. If not, are there modifications that could be made to optimize it for output into 10K Ohms as opposed to 32. I believe Mark Johnson had alluded to an Edcor power supply on P81.... not sure I need 50V. Another 10bd of gain over what I have now would be sufficient.
Sorry for the elementary questions...
Sorry for the elementary questions...
if you have 4V5 on output of your source, there is no need for preamp with gain at all
that's more than sufficient to drive F7 to full clip
@Autodidactosaurus, Welcome!
Your questions are not silly, nor is it likely that you're an idiot. You've received some great answers; even one from Nelson himself re: your specific questions.
However, why are you asking them, in general? Some of your questions may be derived from incorrect assumptions.
Knowing that 4V5 is more than sufficient to take the F7 to clipping (Input sensitivity is 2V7 per a quick Google search), why are you looking for more voltage <=> gain? Are you thinking that it will play louder? If we know what you're trying to accomplish, in general, you may get better guidance to achieve your overall goal vs. getting answers to specific questions.
Your questions are not silly, nor is it likely that you're an idiot. You've received some great answers; even one from Nelson himself re: your specific questions.
However, why are you asking them, in general? Some of your questions may be derived from incorrect assumptions.
Knowing that 4V5 is more than sufficient to take the F7 to clipping (Input sensitivity is 2V7 per a quick Google search), why are you looking for more voltage <=> gain? Are you thinking that it will play louder? If we know what you're trying to accomplish, in general, you may get better guidance to achieve your overall goal vs. getting answers to specific questions.
Thanks to those who answered, including Papa, whose beautiful F7 I am enjoying. To answer your question, which is a good one: what I have going on now is this: My DAC+ digital preamp is a Marantz ND8006. It is the only source I need or want at the moment as it contains a CD player and of course handles all digital media, including the ability to up-convert computer files to DSD resolution. Bottom line: it sounds amazing.
It features fixed and variable outputs. The variable ouput supposedly (per spec) outputs up to 4.5V (marantz does not list an impedance and their tech dept is utterly useless) - enough theoretically to drive any normal amplifier and that was one of the features I was interested in, wanting to get rid of my existing preamp. However, I do not believe this is actually happening. My existing equipment (the plate amp in my SVS PB-13 and my high-bias 200WPC Class a/AB amp, are clearly not being driven to full power by the ND. Listening to music at 70-80db, my digital volume control is at 70 out of 100. With the F7, I need to drive it to almost 90-95 for the same 70-80db. This result is not surprising given the lower gain of the F7. So I suspect, but cannot confirm, that the ND probably puts out up to 2V or whatever it's line level output is, but not much more than that. I did push to 100% volume with the F7 and there was is no audible distortion as far as I can hear. That gave me 80-82 db continuous at my listening position, which is consistent with my system sensitivity as I understand it (3M away from 88db speakers). So the F7 was probably being driven to between 1 and 2 watts.
So what I really want to do with the ACP+ is interpose a high quality Class A gain stage between the ND and the F7. Being lazy, I would prefer to run the ND's digital volume control from my couch, as an option, as I can control the ND from my Iphone and the HEOS app.
Given Nelson's response, and if I am understanding correctly how these things work, there is a new concern - the total gain of the ND + ACP+ combination without going into distortion. Do I understand correctly that, regardless of the input voltage being delivered to it, the ACP (like any amplifier device) can only deliver so much absolute voltage (in this case 8V into 32 Ohms or slightly more into 10K Ohms) without significant distortion? Then again, it sounds like what Zen is telling me is that the ACP+ has more than enough power to drive the F7. Getting back to my question about the output impedance.... does it make any sense to add a resistor to the RCA out so that the ACP+ "sees" a 32Ohm load, or is that not a concern when driving an amplifier (as opposed to a set of headphones).
Thanks all. As you can see I am a total noob on all this stuff. Either way, the ACP+ is neat little device. Finding a good preamp these days that doesn't cost thousands, is tough! Seems like I should build one?
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Autodidactosaurus - If you turn your volume up to 100%, is the volume more than you want to listen to?
EDIT: Also, looking here on pg.101, there is a setting for max volume from the variable outputs, can you verify that this is set to Off?
https://www.marantz.com/-/media/files/documentmaster/marantzna/us/nd8006u_eng_cd-rom_ug_v00.pdf
EDIT: Also, looking here on pg.101, there is a setting for max volume from the variable outputs, can you verify that this is set to Off?
https://www.marantz.com/-/media/files/documentmaster/marantzna/us/nd8006u_eng_cd-rom_ug_v00.pdf
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Wow 6L6, you are fast!
The answer to the second question is YES. Volume limit is OFF and the ND confirms it is at "96+db" whatever that means.
To the first question... this is adequate for most of my listening, but there are orchestral passages which may exceed 90db from time to time (beethoven's 9th or cannons of the 1812 overture). This particular test was a CD recording of Handel's Dixit Dominus which is a very quiet CD with some areas of significant dynamic power, such as when the choir sings. My concern is that at "100%" volume, is the ND going into distortion? I couldn't hear any, but that doesn't mean it's not there.
The F7 is such a clean and beautiful amp with soundstage and clarity. I want to make sure I am driving it with the clean signal it deserves.
Part of my issues are that I do not understand how these digital output devices work. The Marantz uses HDAMs in a "Class A output topology" which sounds like product jargon for a bunch of discrete output devices. So when the volume is at "100%" does that mean all the devices are outputting clean at low distortion (let's say less than 1% THD) or are they being over driven.
Either way, I could use a few more db of gain to cover all my musical bases, so to speak.
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The output will be at stated distortion. It’s not bad just because you have the volume “up” all the way. (Which is actually minimum/no attenuation…) You are driving with a good signal.
It appears you have all the pieces you need, you merely have to get used to running the volume at large numbers.
It appears you have all the pieces you need, you merely have to get used to running the volume at large numbers.
no harm including preamp of few times amplification factor (say 6db) in cases when sources itself are having enough voltage swing for direct feed of power amp ...... dunno exact root of phenomena, but - in this context - with proper preamp sound is in many cases better than without
however, including gain stage wiith more gain than that is simply leading to too much attenuation in signal chain and that leaads to deterioration of sound, practically plonking down from possible performance
read this article ( even of somepics are missing, think about written .......... https://www.diyaudio.com/community/threads/what-is-gain-structure.186018/
however, including gain stage wiith more gain than that is simply leading to too much attenuation in signal chain and that leaads to deterioration of sound, practically plonking down from possible performance
read this article ( even of somepics are missing, think about written .......... https://www.diyaudio.com/community/threads/what-is-gain-structure.186018/
Thanks Zen Mod I will read this and get educated.
I don't think there are any issues downstream of the ND. I have a Peachtree Nova Pre (the preamp I was hoping to remove from the chain) and that thing can drive my old amp and the SVS PB-13 to full power and in fact it is way too much: I am getting 90db volume at something like 9 O'clock volume on the PTree. This is the typical excessive gain scenario Papa has referred to in prior writing on the subject. I have not connected the PTree to the F7 but I have no doubt it would drive it to full output and then some by 1 O'clock on the dial.
Whatever the Marantz is doing, I suspect it is not outputting a sufficiently strong signal to drive the amps to full power. It is, however clean as far as I can tell. The Marantz actually sounds fantastic and I'd like to keep it in my system as a source at the very least.
Not sure what the output impedance is on the marantz, but you could also look at iron as an option. Edcor have a nice selection that are chassis mount with QC terminals. You could put two of those in a box (or not) and call it a day.
something like this: https://edcorusa.com/collections/ma...-matching-transformers?variant=41117605232827
something like this: https://edcorusa.com/collections/ma...-matching-transformers?variant=41117605232827
digital sources by default, when volume set to 0db, are having least compromised SQ, so no possibility to even think of overdrive
now, all you need is just simple procedure - connecting Marantz to F7, with volume on min;
play, dial volume up ; when loud enough - see what's written on screen
if there is still some headroom left, nice box with buffered volume attenuator is solution (so no additional gain needed)
if maxed on Marantz and you need more, choose preamp with moderate gain ......... taking in account logic explained in linked article
now, all you need is just simple procedure - connecting Marantz to F7, with volume on min;
play, dial volume up ; when loud enough - see what's written on screen
if there is still some headroom left, nice box with buffered volume attenuator is solution (so no additional gain needed)
if maxed on Marantz and you need more, choose preamp with moderate gain ......... taking in account logic explained in linked article
Thanks 6L6 and, I agree. I just spoke with marantz tech and he confirmed that Var Putput is 4.5V RMS max and that it is designed to drive "virtually any amp" to full power.... not just Marantz stuff. There is no output impedence stated but the headphone amp, which is separate but uses the same circuitry, has 32 Ohm output impedance. He has no explanation for the lower output and there is according to him no other adjustment settings in the unit that could affect Var power output. . Maybe I need to start by returning the player.
Anyway, don't want to gum up the thread on the ACP with my issues...
from UM of Marantz:
Unbalanced output (FIXED):2.2 V RMS
Unbalanced output (VARIABLE):4.5 V RMS (variable maximum)
F7: 20W@8R, gain 14db
going backwards, 20W@8R means 12V65 RMS; gain of 14db is 5V/V
divide 12V65 with 5, that says that F7 needs to be driven on its input with 2V53 RMS, for full blast
that 2V53 RMS is way lower than declared 4V5 RMS of Marantz
introducing any gain stage in between Marantz and F7, so being in situation to first attenuate it heavily, then amplify some again ........ is waste of signal energy, and insult to simple logic
Unbalanced output (FIXED):2.2 V RMS
Unbalanced output (VARIABLE):4.5 V RMS (variable maximum)
F7: 20W@8R, gain 14db
going backwards, 20W@8R means 12V65 RMS; gain of 14db is 5V/V
divide 12V65 with 5, that says that F7 needs to be driven on its input with 2V53 RMS, for full blast
that 2V53 RMS is way lower than declared 4V5 RMS of Marantz
introducing any gain stage in between Marantz and F7, so being in situation to first attenuate it heavily, then amplify some again ........ is waste of signal energy, and insult to simple logic
all you need is either test disc or image of it or just single file - one or both channels , 1KHz 0db
play it, all interconnects removed, and you need semidecent multimeter - set to Vac
it must show something as 4V5, as DMM is presenting Vrms at display
that's easier than returning it , then getting another, just to get same problem
from your post #1943, I have impression that you have several ideas ( from where or whom?) but main problem stays unclear ............ do you have wanted SPL , or not
try what I wrote in #1956
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