Hi,
the schematic of your Pre Looks interesting.
Whats about the gain and the PSU voltage?
Tanks & Chefs
Thorsten
Simple and effective topology. Please browse through the thread "A headphone transconductance amp for change". The schematic in Headphone 007. pdf is a simple preamp/attenuator. Food for thought!
The schematic of my pre is from Juma actually, I just switch from BD139 to D44H11.
The gain of this is about x2.
PSU is a symmetrical +/-18v based on LM317/337 with a BDX33/34C gyrator on the LMs inputs.
Greg.
You may first consider using the Amp Camp Amp [as a preamp] as designed; afterall it is already optimized by Mr. Pass. It has an impressively low 100 uV output noise; which is due to the switching power supply. Add an input 25 K volume control like B1 and hear what happens! Can only be awesome.I'm thinking scaling down the Amp Camp Amp would make a nice pre
From all amps I have seen, where it stands out is from the low power supply being used. 19V single ended for 5W...
ADD: PLH is similar to the Amp Camp's Amp#1, where IRF610 is used instead of K170. But the power supply is 40V for the PLH.
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Great catch. I see your point. Charging and discharging this cap by the input resistance of F5 willl be long. Load the [Amp Camp Amp] with a 33-100 Ohm resistor. I read it somewhere that Mr. Pass prefers any amp to do some work. Or resize the ouput cap!
R14?
Thanks flg. The existing R14 = 1K Ohm [in amp] is to discharge the output capacitor. I see this Amp Camp Amp [ACA for short] doing double duty. A switch at its output to select either 'power amp' or 'pre-amp'. Either way, a volume control at its input is needed. Music Source to ACA to loudspeaker or music source to ACA to F5 or other to loudspeaker.
Your analysis may well be correct in the end. Still, your [bolded] statement is nonetheless a hypothesis. Prove it either way by doing the experiment. Maybe you [or others] have already built other low power Pass amplifiers of topology [opposed drains of output stage] like ACA [Zen, Aleph etc.]. Your hypothesis can then be easily/readily tested, and/or this experiment was already done.
There was an earlier request for a headphone ACA. I have a simple and painless method to do so for any amp devoid of a headphone port. Please visit the last 4 threads in Headphone Systems entitled "Does anyone make their own headphones". Best
Yeah, the ACA#1 looks suitable for headphone amp. Actually, it seems also suitable for power amplifiers (strictly with high impedance speakers), but may be not. I'm curious myself with this topology. I cannot find anything wrong except visually, i.e. use of N-N that forces feedback resistor to connect input to output.
I'm building the ACA#1 with IRFP460 (which gives better simulated performance than IRFP240), starting today and hope to be completed tomorrow (today I have finished the chassis, PCB, simulation and parts gathering). Unfortunately this is for a friend so I will not be able to review its performance (It needs time to review the performance as I guess there will be some kind of "boring effect", even tho the current drive is good).
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