I'm sorry, I completely misunderstood the R22 (1M) resistor's purpose as a parallel load on the volume control's wiper, to the positive terminal of C15.
One slightly confusing thing is that there are two R22 resistors (for each channel) on the schematic. One in parallel from input to ground, before the volume control. The other from the volume control wiper to the junction of the 'top' of R24 and the positive terminal of C15. Are they both necessary for bleeding down the capacitors' charge?
One slightly confusing thing is that there are two R22 resistors (for each channel) on the schematic. One in parallel from input to ground, before the volume control. The other from the volume control wiper to the junction of the 'top' of R24 and the positive terminal of C15. Are they both necessary for bleeding down the capacitors' charge?
I am currently working out the chassis mechanicals for this project. I will be mounting the tubes horizontally enclosed inside the aluminum chassis. I've been looking everywhere for information on the best pin alignment to use when operating 6V6 horizontally. I asked AI and it said to align pins 2 and 7 horizontally. But horizontal pin alignment specifications usually name what pins to align vertically, not horizontally, so AI might be dubious here. Does this sound like the best pin alignment to least stress the elements? I couldn't find mention in the data sheets either.
Hello Windcrest77:
My RCA-22 says mount in any position.
I guess that means what it says any position that makes thing work for you.
I hope this helps
My RCA-22 says mount in any position.
I guess that means what it says any position that makes thing work for you.
I hope this helps
Finally have assembled my two Salas HVSS2 and gathered the associated 6V6 circuit parts.
Looking to build the power supply next.
Will SS diodes with a simple CRC filter be adequate to supply the shunt regulators for a clean/quiet B+? Or is the tube rectified CLC circuit as in the original schematic the way to go?
Looking to build the power supply next.
Will SS diodes with a simple CRC filter be adequate to supply the shunt regulators for a clean/quiet B+? Or is the tube rectified CLC circuit as in the original schematic the way to go?
Both ways will do and both will sound different. They have different impedance and loss. Choke input configuration is best in any case. Vacuum rectifier soft start is a benefit. Some views in this old thread: Tube vs. Semiconducter rectification
Is it possible to use a 100Kohm vol. Pot in the feedback version. Can the circuit be modified to suite the high Pot value? Maybe less feedback?
Hi, its a matter of properly driving the input impedance of the preamp. Higher value pots have higher insertion impedance. They reach maximum Zo (representing 1/4 their value) at half division point.
Ri is 56k Rf is 470k in the preamp and you should keep about that ratio. Maybe Ri 100k and Rf 1Meg can work with 100k pot. Not sure if as well as with smaller pots, the bandwidth could shrink enough.
Ri is 56k Rf is 470k in the preamp and you should keep about that ratio. Maybe Ri 100k and Rf 1Meg can work with 100k pot. Not sure if as well as with smaller pots, the bandwidth could shrink enough.
Testing with 100k pot you should lose 0.75dB gain and 8% bandwidth as it is. Subjectively I don't know how it will feel because I tested only up to 50k pot that keeps a 10dB gain figure. If you go 100k Ri, 1Meg Rf, and 100k pot, expect plus 0.75dB gain but 50% bandwidth loss. Since double the Ri makes twice lower an HF filter with the tube's input capacitance. It should have an impact on 10kHz squarewave testing.
It sounds like, it is a small penalty on specs to use the standard circuit, and keep feedback resistors as they are. If I understand correctly, I will go for that, else I can change potentiometer later, when I see everything else is working. I might also start with a simpler PSU, I don´t think the shut regulator is so easy to make hardwired.
Sounds like a plan. In any case see with gen and scope that the -3dB HF response goes at least 100kHz for satisfactory 10kHz squarewave risetime.
Practical input capacitance of the tube is higher than predicted in its datasheet. Because socket, wiring, etc. contribute some extra pF.
Measure for worst case circuit output HF response when with the test signal at 1/2 attenuation after the pot.
Practical input capacitance of the tube is higher than predicted in its datasheet. Because socket, wiring, etc. contribute some extra pF.
Measure for worst case circuit output HF response when with the test signal at 1/2 attenuation after the pot.
I'd like to build this linestage, but I lack the skills to make my own PCBs for Salas's SSHV2. What is the next best thing?
That looks good, thanks. However, I plan to use one regulator per channel and the Neurochrome costs $169 each, too much for my shallow pockets.
Just curious, has anyone tried rolling 6W6 or 6F6 tubes here in the circuit unchanged? Presuming you built the preamp with enough heater current headroom. I'm planning my chassis to have a both pair of octal and a pair of 9 pin sockets real close to each other to roll 6AQ5's or 6V6's. And so close as to prevent insertion of all 4 tubes. I'm thinking of tweeks that could make this project a universal "tube roller" kind of platform for preamp pentodes.
I built the Salas 6V6 pre-amp but then eventually went on to his DCG3 which I like more. I also had been thinking of the 6W6 substitution at the time when I originally built the 6V6 pre-amp but never got around to it. I did get some advice for the 6W6 conversion and it is copied below from another forum, suggestion provided graciously by danlaudionut.
Frank
I would use the 6W6 which is much more linear.
It also sounds better - it has been compared to a 45.
Unless you want the extra warmth of the 6V6.
Gain Mode
330R on the cathode 7.5K on the plate
30mA at 3.5W dissipation
340V B+
Unity Mode
(Cathode Follower)
9V Ni-Mh in series with Hammond 126C on Cathode
100V B+
DanL
Frank
I would use the 6W6 which is much more linear.
It also sounds better - it has been compared to a 45.
Unless you want the extra warmth of the 6V6.
Gain Mode
330R on the cathode 7.5K on the plate
30mA at 3.5W dissipation
340V B+
Unity Mode
(Cathode Follower)
9V Ni-Mh in series with Hammond 126C on Cathode
100V B+
DanL
Thanks fmena,
OK B+ is the same, I'd just need a method in the chassis to swap the plate/cath resistors to accommodate either 6V6/6AQ5 or 6W6 I guess. Assuming people found these are the optimal operating points for each tube. I'm installing parallel 7 pin miniature sockets for 6AQ5 rolling. Some say 6CU5 and 6EH5 miniatures come close to the 6W6 family but unfortunately doesn't have the same pin base as the 6AQ5 sockets. 50C5 is interesting as a 6W6 analog, it seems to have a monster sized cathode, but 50 volts heater. Making this into a tube rolling platform is getting complicated.
OK B+ is the same, I'd just need a method in the chassis to swap the plate/cath resistors to accommodate either 6V6/6AQ5 or 6W6 I guess. Assuming people found these are the optimal operating points for each tube. I'm installing parallel 7 pin miniature sockets for 6AQ5 rolling. Some say 6CU5 and 6EH5 miniatures come close to the 6W6 family but unfortunately doesn't have the same pin base as the 6AQ5 sockets. 50C5 is interesting as a 6W6 analog, it seems to have a monster sized cathode, but 50 volts heater. Making this into a tube rolling platform is getting complicated.