Simply Another Utter Novice's Amp Build - 300B

Also just a reminder that gain is going to go way, way down. I suspect you'll lose 18dB of gain by doing this and you'll definitely need ~3V or so of output from your preamp, but that's not that big of a deal in a modern hifi system.
 
Way late to this party -- but I just noticed/realized that this thread's title is an acronym:

Simply Another Utter Novice's Amp Build 300B...

SAUNA

ok... ok... maybe...

SAUNAB



:confused: :smoke
 
paulbottlehead said:
Also just a reminder that gain is going to go way, way down. I suspect you'll lose 18dB of gain by doing this and you'll definitely need ~3V or so of output from your preamp, but that's not that big of a deal in a modern hifi system.
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I think that is what held me back the first go around.
 
I guess the question I ask is how much input sensitivity you need? As it is now, you can put maybe 300mV RMS into the input of that driver stage before the amp will clip, and that (to me at least) is unreasonably sensitive. Usually, you'll see power amps structured to provide full power for somewhere around 1.5-2.5V of input, while integrated amps will tend to have a bit more gain than that.
 
Can I measure the output of my preamp with pink noise or a 1kHz sine wave played off of a record? I do 90+ of my listening with vinyl sources. Currently, with the new 3C24 amps I need the preamp around 40/63 steps to get where I usually listen.
 
Sure, you can measure a 60Hz tone. Do also keep in mind that your attenuator may have a couple of big steps close to where it's all the way up.
 
Do I need to run the preamp into the load of the amps or can I just measure the unloaded preamp output with a multimeter to make sure I can reach ~3V?
 
So you need to get to 70V peak, which is 50V RMS, and I think you could get there with maybe 2.8V RMS from the preamp.
 
Well, that was not successful. I played a 1KHz test track off a record and at max volume on the preamp I measured only a smidge over 1 volt AC with my Fluke multimeter. I'll look for a test track at 60Hz but I'm not hopeful.
 
Any thoughts as to that measurement of only ~1V at the input to the amps? Is 1KHz not accurately measured on a typical DMM?
 
Try a streaming service with your phone. Tidal for example has a Stereo Test recording with various tones and pink noise from Bunker Analog. I expect Spotify or Pandora have something similar.
 
Yes I could do that with ease but I was trying to measure the total level from TT to amplifier.
 
If you only have a 1kHz tone, then measuring the waveform with a scope is the way to go.
 
Did a few measurements. All with 1KHz test tones. All at max preamp output.


CD player - 10.9V P-P = 3.85V RMS
Phono Stage#1 - 3.12V P-P =1.1V RMS
Phono Stage#2 - 4.88 P-P = 1.7V RMS

Clearly seems like I'll have problems with vinyl playback unless I can increase output of the phono-stages (unlikely) or the Gadget pre-amp.
 
Are you on the 40dB or 60dB gain setting on the phono? Or are you using the Salectric one?
 
I used both my K&K (Phono#2)with it's internal SUTs as well as the Saulectric (Phono#1) one with the 40:1 plug-in SUTs.
 
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