Power Amp advice needed, for my JBLs 4312 power thirsty...

Zen Mod said:
believe me , I'm even happier that way :cheers:
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Yes, but you didn't tell my why marantz 22** series is a venerable piece of drek 😀

I understand that the audiophools gave them an aura and glare of sanctify, but actually, technically, why are they a piece of drrerek?
Damping factor marantz 40 f4 20
 
Probably nothing wrong with the circuit but they didn’t invest in a power supply capable of allowing the amp to sing.

Kind of like putting a 125cc motorbike motor in a Ferrari and expecting it to be good.


Edit: Damping factor of F4 is 40 not 20. Output impedance of 0.2 Ohms gives a damping factor of 40.
 
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One Caveat about F4. F4 may be a good choice for the power output and sound quality that you need. While your source can output 56vrms, what is the gain. It is one thing to have a large maximum voltage output but that does not mean you have the gain necessary to swing that voltage. If you have a gain of 10 in your preamp it will need almost 3vrms input to get your F4 up to the 100w/8 ohm power output. A system without enough gain always seems to feel like it is running out of power when you need to turn the volume up near maximum to get good volume levels. Perhaps that could be an issue with your current system as well. If you want it loud with 91 dB speakers then at least 50 solid high current watts and preferably 100 would be what I would aim for.
 
This is what I discussed right at the beginning, I was under the impression he understood my questions and was saying it actually outputs 60 V rms not that it is capable of outputting 60V
 
It just seemed unlikely to me that a typical home audio system would have the gain structure needed to output that kind of voltage. It is a point that many system owners don’t understand.
 
Bfpca said:
It just seemed unlikely to me that a typical home audio system would have the gain structure needed to output that kind of voltage. It is a point that many system owners don’t understand.
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Tube preamp has a gain of over 23dB, it can output 60V RMS.
It is a 6sn7 srpp tube preamp
 
Bfpca said:
It just seemed unlikely to me that a typical home audio system would have the gain structure needed to output that kind of voltage. It is a point that many system owners don’t understand.
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I agree.
I think his preamp is 0 feedback so I was starting to think it might be possible.
 
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2 picoDumbs said:
So you have a MM or MC Cartridge?
Then the output of the cartridge goes direct into tube preamp?
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tube phono preamp, MM gain of 44 dB; MC 65dB, all scope measured;
these go to tube preamp, another little over 23 dB gain. again, measured. it has no feedback
 
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Michelag said:
tube phono preamp, MM gain of 44 dB; MC 65dB, all scope measured;
these go to tube preamp, another little over 23 dB gain. again, measured. it has no feedback
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Cool.

So MM Cartridge has between 3mV to 6mV output. Let's call it 4.5mV

With 44dB of gain we get to 720mV

Then 23dB of gain gets you to 10V rms

Another 6 to 10dB of gain could possibly be useful.
We can add a BA3 front end if necessary later. Just proceed as is for now.
 
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2 picoDumbs said:
Cool.

So MM Cartridge has between 3mV to 6mV output. Let's call it 4.5mV

With 44dB of gain we get to 720mV

Then 23dB of gain gets you to 10V rms

Another 6 to 10dB of gain could possibly be useful.
We can add a BA3 front end if necessary later. Just proceed as is for now.
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I'm seriously tempted adding balanced output to this tube preamp... and let the two f4 monoblocks swing more and fly together...
what'd you say ?
 
marconi118 said:
post the schema of your preamp,I am curious
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2 picoDumbs said:
Have the long term goal of going balanced, but first do single ended.
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yes... let the wife accept a double BoM more than a single BoM twice....
til yesterday this was a long term project, i was just gathering info, do you remember?

oh, wait, for a single ended I'll add two vu meters, for two monoblocks they'll be four... but for balanced mono how are they working? just one moving for each block?
 
For balanced mono you still only need one VU per channel (ie monoblock)

So you have 2 monoblocks.

You start by adding one F4 pcb per monoblock. Then later you add an additional F4 pcb per monoblock to make balanced monoblocks.

The wife will never know the changes you made internally to the amp, on the outside it looks the same to her.
I think your "friend" will ask to repair it for you (he is so kind). Then some how when you "get it back" from "him" it will be magically now balanced monoblocks not just single ended mono blocks.
 
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You need 1 VU meter per channel, for regular single ended mono blocks.
You need 2 total.

Nothing changes when you go to balance. You still need just 2.
 
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