I'll differ to your expertise. But the original circuit has those voltage divider resistors and cap already. I've also seen people completely eliminated those parts by directly coupled to the grid of cathode follower, which increases open loop gain, without changing the feedback network values.
That network in the 834 is for DC bias of the cathode follower, and does not affect the open loop gain,
since the series resistor is bypassed at signal frequencies.
Direct coupling to the previous stage would therefore not change the open loop gain at all.
However, the cathode follower performance would be degraded, since its carefully designed
DC bias conditions would be altered.
since the series resistor is bypassed at signal frequencies.
Direct coupling to the previous stage would therefore not change the open loop gain at all.
However, the cathode follower performance would be degraded, since its carefully designed
DC bias conditions would be altered.
Rayma, you're right the direct coupling would not increase gain much because 3.3M is too minute to matter to load it down. I assume people who modified it into direct coupling compensate on the DC relationship with the cathode follower. At least, I hope! Perhaps lowering the value of 2nd stage plate resistor, also with cathode resistor adjustment, can lower the gain slightly. But that's changing its operating point which is changing the design. I guess the safest approach is adding trimpot to output.
So the 5751 which many people have had good luck with in this circuit couldn't possibly actually work?
If I absolutely have to stick with 12ax7's, I will likely replace the current Psvanes with Mullards.
This thing is too bright! I am going to rip the silver micas out, but replace them with what?
I am also going to replace the outlying Mylars (coupling caps?) with Russian oil caps.
Any recommendations for improving the amount of bass this thing produces?
If I absolutely have to stick with 12ax7's, I will likely replace the current Psvanes with Mullards.
This thing is too bright! I am going to rip the silver micas out, but replace them with what?
I am also going to replace the outlying Mylars (coupling caps?) with Russian oil caps.
Any recommendations for improving the amount of bass this thing produces?
This is not about good luck but the accuracy of RIAA curve ... and that is not subjective .
You can use a tone corrector after this circuit if you are not happy with the sound
The EAR uses NFB and if tubes with less gain is used it will not have the correct riaa correction.
If the amp delivers to high output then use a voltage divider at it's output, that is the correct solution.
The EAR has a fairly correct RIAA correction, if you want more bass then turn your bass-control up.
People are getting too much output with a medium gain cartridge!
Try to match your cartridge to its phono corrector ....less ear ache...ie " This thing is too bright! "
My cartridge is completely neutral. What I am hearing is the effects of the silver mica, combined with too much gain.
My turntable is a Micro-Seiki BL-51 with a Grace 707 II tonearm and a Signet TK7e cartridge.
My phonostage runs thru a vintage Numark eq (for bass correction), then thru an otl single-ended triode tube headphone amp driving a set of JVC HA-D990 headphones.
Original EAR 834p has quite high gain (~49dB) compared to passive RIAA 12AX7 stages, which typically would be around 40dB. So we'll assume most, if not all clones have the same high gain.
Your cartridge output is on the low side, so on paper looks to be a good match for the 834p.
jeff
"The cartridge output at a velocity of 3.5 centimeters (cm/sec) was 3.65 millvolts - about average for a good quality magnetic cartridge -"
That appears to be a good match for your EAR at 49dB......
I would look at the overall gain structure of your set-up.
Never mind ...you can always build another phono preamp....diyAudio is great.
Never stop building!
Something to consider...Is your new phono preamp making you aware of the issues you've highlighted further up the chain?
Yes our hobby will do your head in sometimes!! But how glorius the sound when it tickles the ear.
Good luck and keep building.
That appears to be a good match for your EAR at 49dB......
I would look at the overall gain structure of your set-up.
Never mind ...you can always build another phono preamp....diyAudio is great.
Never stop building!
Something to consider...Is your new phono preamp making you aware of the issues you've highlighted further up the chain?
Yes our hobby will do your head in sometimes!! But how glorius the sound when it tickles the ear.
Good luck and keep building.
This, of course, is problematical. Statements without proof or even logical explanations aren't generally useful.
Not to be harsh, but RIAA equalization is difficult to achieve and is always conditional on an understanding of the relationship between the tracing (mechanical) response (which would include the vinyl compliance x stylus effective (referred to contact) mass) and the electrical LC ultimate rolloff, which typically falls somewhere in the top octave of human hearing (not mine (too old - all gone). The stylus' moving mass "indents" the vinyl contact points at pressures peaking at tons per square inch (in Regal Thumb units) and this compliance resonates with the effective (stylus plus some proportion of cantilever plus some proportion of generator) mass. This resonance is a classic second order resonant peak which is added to the second order LC rolloff of the usual generator mechanisms.
We only care about the response of the the whole system, so our only figure of merit can be the accuracy of translation from some (historically) intended magnitude response. Without some independently agreeable (at least blinded, at best well thought out) testing, who's opinions have any validity? Mine? I certainly wouldn't think so.
I'm sorry if this is harsh, but we humans are very sensitive to small variations in amplitude response over octave sized regions, so it someone says that they (he, because it's always he) says that that they (he) says that they (he) can hear the difference between similar (not defective, not polar electrolytics or weird ceramics or such) I think that they should first be certain that the simple magnitude response is comparable (within some reasonably stringent tightness) and then test themselves blinded. Then talk. If we don't include our human strengths and faillibilties we learn nothing. If we ignore them, we deceive ourselves. Cleave to the truth, as possible.
All good fortune,
Chris
I have spent years getting to know the other components in the chain using world renouned phonostages, so it is unlikely except for a new tonearm cable that isn't quite broken in yet.
This phonoclone did sound better today, but still a bit rough around the edges. It has been running continuously for 100 hours so far.