300b lovers

Hi @lynn_olson

I use EAR834p schematics in my current DIY phonostage.

The second ecc83 miller capacity for RIAA equalization.

It is also using small capacitors in the RIAA equalizer. So I use air capacitors in this RIAA.

I also use the LCLC power supply filter plus 2x 0A2 voltage regulators.

In general I like the sound of this phonostage.

The main drawback of this schematics is output cathode follower that drives feedback and output RCA cable. When I tried different ECC83 tubes in this position - speed, dynamics and bass were changed dramatically.

If I reuse this schematics for the new project I am thinking about adding an output buffer. It can be 6SN7 with the output transformer.

https://www.diyaudio.com/community/threads/ear834p-is-not-what-it-seems.313042/

I did something more similar to this (just without a fixed bias for the second ECC83):

http://www.romythecat.com/Forums/ShowPost.aspx?PageIndex=2&postID=9161#9161

Still out in the weeds dept.;

Many phono preamp designers over the last 70 years have ignored the significance of a magnetic cartridge whose output is in parallel with the capacitance of the tonearm cable.

Any time an inductor is in parallel with a capacitance there is an associated resonance whose frequency is set by the values of the cap and the inductor. With high output MM cartridges this peak is generally about 20dB and centered just inside or just above the audio band. If the phono section does not have good HF overload characteristics, this peak will overload the input of the phono section resulting in ticks and pops.

Just to boggle your mind a bit more, cutting a lacquer master from the two-track master tape meant the engineer "riding the controls" as the cutterhead neared the center of the record.

We never had to do this with any of the LPs we cut. We used the Westerex 3D cutter with 1700 series electronics, all stock. We found that the old myth about loss of bandwidth towards the end of the LP was just that. We cut 30KHz tones in the inner grooves that played back fine on our Technics SL1200 with Grado Gold (we used that setup to know if the groove we'd cut was playable on an average machine). I think a lot of that myth got started in the 1960s when stereo cartridges really just weren't all that good.

Well, keep in mind most LP’s were cut with spherical styli in mind ... specifically, the Stanton 681A with spherical styli. Over in Europe, it was the Ortofon SPU with a spherical stylus. Both were used to play the lacquer once for quality control, then off to the plating plant.

Ellipticals were fairly rare in the Sixties and often poorly cut, with obvious asymmetries. In college, I had an ADC elliptical cartridge that destroyed several of my records until I wised up and bought the Stanton (as recommended by the early Stereophile magazine).

We didn’t see Shibata or Fine-Line profiles until CD-4 quadraphonic records, with their 30 kHz FM carrier on each groove, required for adequate CD-4 playback. That was 1971 or so, if memory serves. The trick with Fine-Line profiles is azimuth needs to be *exactly* right, within one degree, or mistracking gets pretty bad. With sphericals, azimuth hardly matters, and even ellipticals are moderately tolerant of misalignment. But not Fine-Line profiles. They need to be exactly on the money.

One of my minor inventions with the Shadow Vector quadraphonic decoder (Patent #4,018,992) was an electronic crosstalk cancellation scheme, which electronically rotated the axis of the two generators so they were precisely at 45/45 degrees. That gave about 45 dB of measured separation, with an optional second-order corrector which operated above 10 kHz. That corrected for cantilever twisting at high frequencies, a problem I noticed happening with many cartridges.

Shadow Vector quadraphonic decoder

I was not thrilled to discover many $2000 to $15,000 cartridges had visibly rotated cantilevers ... not by much, but by about 2 or 3 degrees, which made azimuth adjustments extra tricky. With a Fine-Line stylus, nearly mandatory at that price point, you have to get the stylus exactly square in the groove, regardless of the generator axis. Which is where electronic compensation comes in ... if the generator is not at 45/45, you can rotate it electronically, and get the separation back with no penalty.

P.S. The crosstalk cancellation is very simple. Each channel has an adjustable amount of crosstalk from the other channel, with plus-phase crosstalk on one side of the pot, and minus-phase crosstalk on the other side. In the center of rotation, zero crosstalk. One pot for each channel, a test disc, two quick adjustments with a meter, and off you go. 45 dB or better separation from any record or cartridge.

P.P.S. That EAR schematic looks kinda sketchy to me. I would not use it. I suspect the errors and the wonky drawing style are intentional.

Both were used to play the lacquer once for quality control, then off to the plating plant.

Usually you don't want to play the lacquer at all- any playing degrades it. But you can cut outside the 12" diameter since the lacquer is 14"; in this way if there is a troublesome cut you can test that part of the recording by cutting it there and then playing it to see how it went. If OK then you can proceed with the regular cut.

I found that if we spent enough time with a project there was usually no need for processing of any kind; there is usually a way to cut a playable groove, even with out of phase bass (if its not too bad). Compression is really only used to speed up the mastering time; mastering time is expensive.

Hi, I used the "shunt regulator" to replace the RC cathode self bias circuit in my 45, 2A3, 300B, and 845 SE power amps. The sonic improvement is exceptional. My friends tried it and they all agreed it is real worth to try. 

I haven't try using fixed bias in my amps as it is a bit difficult for such modification.

Johnny