For me, it is 2/3rds as well. All the way open is a bit too bright at higher volumes.
Since the pot is on the output, you can use it to vary the output resistance.
I love threads like this...I learn so much.
Since the pot is on the output, you can use it to vary the output resistance.
I love threads like this...I learn so much.
I imagine that the optimal setting would depend on the input impedance of the next stage. I'm using this in a low-budget secondary system so I'm just driving a Shiit-y passive preamp.
Pete
I have a Conrad Johnson Evolution 20se in the main system but I haven't taken the Clone out there. I have a borrowed Rogue Ares that I have compared it with and after the upgrades the Clone is at least able to play in the same league. The Rogue soundstage is HUGE but focussed. The Clone at least has one, now.
Pete
Pete
I do have questions about this circuit.
I have not done Thorsten's mods that delete the subsonic filter between V2 and V3. My understanding is that the change to the 68k cathode resistor on V3 is part of the same modification and so I have left it as is.
My questions are:
Is this correct? Is 68k the correct value for a 12AX7?
What value would be needed to try a 12AU7 here?
Thanks,
Pete
I have not done Thorsten's mods that delete the subsonic filter between V2 and V3. My understanding is that the change to the 68k cathode resistor on V3 is part of the same modification and so I have left it as is.
My questions are:
Is this correct? Is 68k the correct value for a 12AX7?
What value would be needed to try a 12AU7 here?
Thanks,
Pete
I tried a 12AU7 in that spot without subbing that resistor. It sounded shrill.
My understanding is that these values are appropriate with the rumble filter stuff removed. In the schematic that you posted that section just has a 100 ohm resistor.
Elsewhere in that discussion there is a suggestion of removing the subsonic filter and running a 12AU7 with the stock 68k in place. I think that the point is to optimize the operating point of the tubes but I don't know enough about it to figure it out for myself. I have some 12AU7s on hand and don't need all of the gain that a 12AX7 provides.
Pete
Tube #3 is a cathode follower. Swapping in a 12AU7 there wont change gain. It will potentially be a good option for driving more current at the output. I may need to try it again as well, I recall I tried that swap before I replaced the big caps.
UPGRADES STEP 2
I have replaced the RIAA networks with precision parts. While I was at it I reoriented the coupling cap that I had backwards.
I was hooking it up when I remembered that I forgot.
I had to take it back out to the shop to remove the cover again and install the tubes. It's now warming up a bit before I spin the record again. I'm going to add the bypass caps later so I can get an idea of how much they help separately.
Stay tuned!
Pete
I have replaced the RIAA networks with precision parts. While I was at it I reoriented the coupling cap that I had backwards.
I was hooking it up when I remembered that I forgot.
I had to take it back out to the shop to remove the cover again and install the tubes. It's now warming up a bit before I spin the record again. I'm going to add the bypass caps later so I can get an idea of how much they help separately.
Stay tuned!
Pete
Well, that was not an unqualified success. The better parts sound cleaner and clearer but the tonal balance is now screwy. I couldn't hear the bass over the cymbels!
I thought that the tweaked RIAA values didn't depend on the changes that I didn't make. I don't think that this is the "improvement" intended!
I think that I have 750k resistors on hand but I don't have caps. I'm not going to reinstall the cheap parts that I removed! I don't know how to calculate these values, if afraid. I think that the best plan is to go back to the values that were previously installed, just higher quality.
Pete
I thought that the tweaked RIAA values didn't depend on the changes that I didn't make. I don't think that this is the "improvement" intended!
I think that I have 750k resistors on hand but I don't have caps. I'm not going to reinstall the cheap parts that I removed! I don't know how to calculate these values, if afraid. I think that the best plan is to go back to the values that were previously installed, just higher quality.
Pete
I played as well. That middle stage 0.01u cap might be too much cutoff with your change. Without unsoldering it, try to add a bigger cap in parallel to create a larger value there.
I no longer want to remove the 0.1uf cap in that spot in my preamp.
After my online research, the original EAR834p has the 0.1uf there. It was reduced later to provide a subsonic filter.
I no longer want to remove the 0.1uf cap in that spot in my preamp.
After my online research, the original EAR834p has the 0.1uf there. It was reduced later to provide a subsonic filter.
I did some upgrades on my HIFI Split EAR 834P Clone, but before I started I made sure the Phono preamp didn't have any hum issues by itself, it does have a slight hum only when the turntable is connected. Has to do wit possible way the ET-2 arm is grounded. With a SUT connected shorting plugs and connected with the EAR Clone its still quiet.
Anyways, I did change the 0.15uF caps and the 1.0uf caps to Mundorf EVO Oil for the 0.15uF caps and AudioCap Theta for the 1.0uF. Sounds way better and can hear the bass fine, all instruments blend way better now and sound more balanced.
I do need to find out why my table is humming when connected to the EAR when the EAR is quiet with shorting plugs in it. I do have another ET-2 Wand that I'm repairing the clips on it and will hook up a Sumiko Ametyst cartridge to the table. This will give me a good idea if its the Cartridge or the arm that is the culprit. Right now I'm running a Grado Timbre Reference III. Also will move the gear around on the rack so the table is not close to any RFI/EMI interference.
I did try a different wand with NO cartridge installed and I still got the buzz/hum but louder than with the cartridge plugged in. Some here suggested on another thread to connect the interconnects without connecting the table to the other end see what happens. I will try that experiment later today. Hopefully it is still quiet.
BTW, if I can get this faint hum/buzz to go way when I have my Pot on the EAR at 2 on the pot knob I will have a really nice sounding Phono preamp/table combo that will rival some really nice Phono preamps. I can hear that musicality everyone always talks about with the EAR 834P phono preamps.
Anyways, I did change the 0.15uF caps and the 1.0uf caps to Mundorf EVO Oil for the 0.15uF caps and AudioCap Theta for the 1.0uF. Sounds way better and can hear the bass fine, all instruments blend way better now and sound more balanced.
I do need to find out why my table is humming when connected to the EAR when the EAR is quiet with shorting plugs in it. I do have another ET-2 Wand that I'm repairing the clips on it and will hook up a Sumiko Ametyst cartridge to the table. This will give me a good idea if its the Cartridge or the arm that is the culprit. Right now I'm running a Grado Timbre Reference III. Also will move the gear around on the rack so the table is not close to any RFI/EMI interference.
I did try a different wand with NO cartridge installed and I still got the buzz/hum but louder than with the cartridge plugged in. Some here suggested on another thread to connect the interconnects without connecting the table to the other end see what happens. I will try that experiment later today. Hopefully it is still quiet.
BTW, if I can get this faint hum/buzz to go way when I have my Pot on the EAR at 2 on the pot knob I will have a really nice sounding Phono preamp/table combo that will rival some really nice Phono preamps. I can hear that musicality everyone always talks about with the EAR 834P phono preamps.
I have been using the EAR834P with a Project turntable, but I have a Maplenoll in my main system. It has an air-bearing arm very similar to the ET-2 and any grounding scheme that I have tried is worse than just letting the 'table float.
I am going to install the bypass caps this afternoon. I'm using this phono stage in a secondary system with Maggies which aren't terribly efficient so any hum is only apparent at much higher than normal volume settings. I will report if the bypass caps help with the noise level.
Pete
I am going to install the bypass caps this afternoon. I'm using this phono stage in a secondary system with Maggies which aren't terribly efficient so any hum is only apparent at much higher than normal volume settings. I will report if the bypass caps help with the noise level.
Pete
@PeteAugello That is so weird as I too have confirmed that it's best to let the Arm float. My table is a Teres 255 Rosewood so the only things to ground is the platter spindle/bearing and the arm shield. Every time I tried to add the shield ground the hum got worst, Bruce told me the shield on the wand is connected internally to the ET-2 arm's spindle.
So I wrote this a little while ago on the LH site so I will just copy it here. It's what I found out earlier today doing the interconnect experiment. here is is below.
"Someone either here or on DIY site gave some recommendations on how to determine where the Hum is coming from. Today I double checked with shorting plugs it was not coming from my EAR 834P from Hi Fi Split clone after confirming the 834P was quiet with shorting plugs I went and connected some interconnects without connecting the table side, I was getting interference hum/buzz. I shorted the open end and greatly reduced the hum but when I started to move the interconnect around I found out where my Hum/interference was coming from the strongest. It was my Furman P-1800AR Voltage Regulator/Power Conditioner. Its was two shelf down but could still be picked up with the interconnect up where the cartridge is. This is a valuable test to track down exactly where the interference is coming from which I had always wondered but now got my confirmation.
So today and tomorrow will be dedicated to moving my Furman and other gear around to get the least interference and to move that gear the farthest away from the table/phono preamp. I wonder if some ceramic caps are in order to help remove this grunge on the signal return lines within the EAR Phono preamp? If so wonder what will be the best value for this type of cap?
I thought I would share this here to help others as I know how this hum/buzz issues can drive some crazy trying to track it down.
I will report back to give the results after moving the gear around."
I hope this helps others here with Hum issues. The Shorting plugs and interconnect test work really well and help quickly show what was going on within my systems environment.
So I wrote this a little while ago on the LH site so I will just copy it here. It's what I found out earlier today doing the interconnect experiment. here is is below.
"Someone either here or on DIY site gave some recommendations on how to determine where the Hum is coming from. Today I double checked with shorting plugs it was not coming from my EAR 834P from Hi Fi Split clone after confirming the 834P was quiet with shorting plugs I went and connected some interconnects without connecting the table side, I was getting interference hum/buzz. I shorted the open end and greatly reduced the hum but when I started to move the interconnect around I found out where my Hum/interference was coming from the strongest. It was my Furman P-1800AR Voltage Regulator/Power Conditioner. Its was two shelf down but could still be picked up with the interconnect up where the cartridge is. This is a valuable test to track down exactly where the interference is coming from which I had always wondered but now got my confirmation.
So today and tomorrow will be dedicated to moving my Furman and other gear around to get the least interference and to move that gear the farthest away from the table/phono preamp. I wonder if some ceramic caps are in order to help remove this grunge on the signal return lines within the EAR Phono preamp? If so wonder what will be the best value for this type of cap?
I thought I would share this here to help others as I know how this hum/buzz issues can drive some crazy trying to track it down.
I will report back to give the results after moving the gear around."
I hope this helps others here with Hum issues. The Shorting plugs and interconnect test work really well and help quickly show what was going on within my systems environment.
@PeteAugello I'm still going to upgrade all the Power supply caps on the Preamp board after I finally get this hum issue resolved, and make sure its not any of the upgrades that caused/causing it. I have the Nichicon 100uF 400V caps in the spare EAR Clone pcb I was doing a few years back but I do have some 47uF 400V caps I can use too. I will also be replacing that Alps pot with a TKD 50K pot 2511 series, that is a step up in SQ big time as I have done this in other preamps too.
I have been wondering if the Plate resistors placing 2 to 3 in parallel to make the same value as the one resistor will add any benefit to the circuit. I have seen this in Allen Wrights Preamp Cookbook and Counterpoint's Mike Elliot did it on some of his preamps as well like the SA-5000 and SA-3000 preamps. I'm trying to remember of the top of my head what those benefits were but it was so long ago. Eddie Current keep coming to mind but I could be on another planet with this. 🙂
I have been wondering if the Plate resistors placing 2 to 3 in parallel to make the same value as the one resistor will add any benefit to the circuit. I have seen this in Allen Wrights Preamp Cookbook and Counterpoint's Mike Elliot did it on some of his preamps as well like the SA-5000 and SA-3000 preamps. I'm trying to remember of the top of my head what those benefits were but it was so long ago. Eddie Current keep coming to mind but I could be on another planet with this. 🙂
Bypass caps installed.
The replacement RIAA components should be here on Monday so I think that I wait until then to reassemble and audition.
Pete
The replacement RIAA components should be here on Monday so I think that I wait until then to reassemble and audition.
Pete
Ok, I went ahead and turned off and unplugged the Furman and that reduced the noise but I was still sensing some noise still from the turntable area and it was coming from a lamp that I use for the table at night when I play LP's it was off but still creating some noise (LED). This with the Furman dropped the hum noise even further and eliminated the buzzing that was riding with the hum.
Then I turned to my Transcendent Sound Masterpiece 300b preamp that when I used the interconnects earlier as a Antenna it got louder by the the tubes. The preamp also has the Filament and Power Transformers for those supplies unshielded and sitting out on top. So I moved the Preamp to the floor and the hum noise was almost completely gone, I had the VC all the way up to around 3 on the control of the TS preamp and around 2 on the EAR 834 pot before I started to hear the hum again but with more hiss due the hum becoming more lower in level.
So it turned out to be 3 different things adding to this Hum/Buzz issue and I'm glad they were all external. Now i will have to order some transformer cover to eliminate the rest of the noise hum which is very low and I will not be having the VC that high during my listening sessions. This only happens on the Turntable side all the rest of the sources are quiet.
Again, I wonder is a cap on the input to ground will help remove the rest of that noise without me having to move my preamp so far away from the rack due to this noise. Can anyone help with what size cap will work for removing RF or EMI noises from the outside the Phono preamp. My Interconnects are Mogami 2534 and have the good shielding from the table to the Phono preamp right. I want to be able to insert my Mogami 2497 interconnect that are lower capacitance and are good for Turntable/Phono amp use.
Then I turned to my Transcendent Sound Masterpiece 300b preamp that when I used the interconnects earlier as a Antenna it got louder by the the tubes. The preamp also has the Filament and Power Transformers for those supplies unshielded and sitting out on top. So I moved the Preamp to the floor and the hum noise was almost completely gone, I had the VC all the way up to around 3 on the control of the TS preamp and around 2 on the EAR 834 pot before I started to hear the hum again but with more hiss due the hum becoming more lower in level.
So it turned out to be 3 different things adding to this Hum/Buzz issue and I'm glad they were all external. Now i will have to order some transformer cover to eliminate the rest of the noise hum which is very low and I will not be having the VC that high during my listening sessions. This only happens on the Turntable side all the rest of the sources are quiet.
Again, I wonder is a cap on the input to ground will help remove the rest of that noise without me having to move my preamp so far away from the rack due to this noise. Can anyone help with what size cap will work for removing RF or EMI noises from the outside the Phono preamp. My Interconnects are Mogami 2534 and have the good shielding from the table to the Phono preamp right. I want to be able to insert my Mogami 2497 interconnect that are lower capacitance and are good for Turntable/Phono amp use.
I'll let you know if they do anything, lol. They are between one leg of the heaters and the center taps. Presumably they could lower the noise floor.
I got these mods from the Lenco Heaven thread.
Pete