Can you tell me what value Idss are you matching on BF861C? Or, how much current is one BF861C conducting in tgis phono?
I could connect LSK389 in parallel with two source resistors to give about the same current and would have less 'noise'.
If you know what I mean.
Regards
I didn't ask you about matching, but what value Idss is necessary or optimal for this phono?
15, 20mA?
Regards
My BigBottle Build
I’ve wrapped up my build of the BigBottle and have been sitting here enjoying it for the past few hours, something that rarely happens in my household. I think I’m getting a special pass because of Father’s Day and it couldn’t have come at a better time with the completion of this project! First of all, thank you to Bigman80 and Vivant for bringing this project to diyaudio, it’s been a joy and has provided a well needed distraction from 2020. I wanted to spend some time going through the details of my build and results.
When I first saw this project, I knew I wanted to build it to show off the tubes, wanted to keep the casing minimal only the tubes showing on top. I also wanted the chassis to be easily serviceable without needing to dismount or disconnect components to get to the PCB. The base chassis for this build is Takachi’s SRDSL-10HS (http://www.takachi-enclosure.com/data/c16-17/SRDSL.pdf). Takachi is distributed though Misumi who conveniently has one of their main distribution centers less than an hour away from me. At ~$115, not the cheapest option, but I wanted something that would come nicely finished, the other chassis I’ve gotten from them are always super high quality, and this one really hit the old school tube amp aesthetic.
I have a CNC router at home that I’ve been honing my skills on over the past 3 years (an upgraded Shapeoko 3 XL) and I was able to precisely mill the holes on the top of the case to snuggly fit all 3 Belton VT9-PT tube holders and mounting screws. I used 10mm standoffs between the PCB and chassis which perfectly sit the tube holders flush with the bottom of the lid.
As part of construction, I also finally learned how to use my sheet metal box and pan brake. I wanted additional shielding of the transformer from the audio circuit and I needed a way to mount the transformer to the top of the case without a screw showing (my own requirement to keep the top minimalistic). I took a piece of 20 gauge steel, and created a mounting bracket that all of the mains wiring and transformer would be seated in. I could then mount the transformer and a quick disconnect distribution block for wiring up the neon lamp, power switch, and transformer without any screws on the top of the case. I used a step bit and cut an opening for a rubber grommet to wire the secondaries to the PCB. It was a tight fit with clearances in the case. I had to trim down the transformer bolt and just barely had the width for the PCB and the bracket so I had to find some narrow 5.08mm pluggable terminal blocks that used crimp connectors to get the right clearance. It was worth the effort and I’m super happy with how it turned out.
Hopefully most of the other construction details will be obvious from the pictures. Per Bigman80’s suggestion, I have the transformer shield and mains ground run to a bolt on the chassis and the turntable ground to another post on the chassis. All RCA’s are isolated and ran with twisted pair 20 AWG directly soldered to the PCB. I put headers on the loading pads and will play with the best loading for my cartridge later. I’m using Clarity Cap CSA’s for the output caps since I already had 2.2uFs laying around. For tubes I am using a matched pair of NOS Valvo PCC88s and a Northern Electric 12AX7 (Northern Electric 12AX7 Audio Tubes - www.thetubestore.com). I have some Tungsram PCC88s in mail to try out as well.
This is one of my first tube projects and without the schematics available it is hard to determine if my voltages are on point. For my voltages, I expect these to be a bit high since my mains run at 116-117Vac, and the transformer was spec’ed at 115. I’m not sure if this will cause issues. The secondaries measured with load are 10.4-0-10.4 for the low voltage and 0-183 for the high voltage. From ground to D5P (positive pad), I have 239 Vdc.
The tubes have the following voltages relative to ground for each pin. Sorry for the verbosity, but I’m not sure which are the critical voltages here. Voltages are listed from pin 1 to pin 9 relative to ground (taken at ground point next to tube socket):
That said, I believe it sounds like its working correctly and measuring with a 5.41mVrms 1khz signal, I’m getting 593mV output which translates to ~110x gain or ~41dB gain. This was mentioned earlier by Bigman80 as the correct amount for MM.
I haven’t been able to test MC yet since I don’t have a generator that can reliably output within the 0.5mV range. I have however designed and manufactured a version of Hifisonix’s Inverse RIAA (An Accurate Inverse RIAA Network). I just need to get the PCB soldered and assembled and do some reading on the measurements to perform. I will post further measurements once I get that project finished.
I’m not one to wax poetic about listening impressions, I truly don’t believe I have the ear to identify small nuances or the right words to describe them. However, I will say that I am very delighted at how quiet this preamp is. I had issues with hum and noise at higher amp gain with my previous phono preamp that I don’t have here. Quiet passages in music are strikingly quiet and quite a joy. If nothing else, I have really been enjoying listening so far, it gets my foot tapping, and that is what makes these projects a success for me.
Please let me know if you have any questions about my build, I would love to answer them. In the meantime, back to listening (Pink Floyd - Pulse box set if you are curious)!
Greg
I’ve wrapped up my build of the BigBottle and have been sitting here enjoying it for the past few hours, something that rarely happens in my household. I think I’m getting a special pass because of Father’s Day and it couldn’t have come at a better time with the completion of this project! First of all, thank you to Bigman80 and Vivant for bringing this project to diyaudio, it’s been a joy and has provided a well needed distraction from 2020. I wanted to spend some time going through the details of my build and results.
When I first saw this project, I knew I wanted to build it to show off the tubes, wanted to keep the casing minimal only the tubes showing on top. I also wanted the chassis to be easily serviceable without needing to dismount or disconnect components to get to the PCB. The base chassis for this build is Takachi’s SRDSL-10HS (http://www.takachi-enclosure.com/data/c16-17/SRDSL.pdf). Takachi is distributed though Misumi who conveniently has one of their main distribution centers less than an hour away from me. At ~$115, not the cheapest option, but I wanted something that would come nicely finished, the other chassis I’ve gotten from them are always super high quality, and this one really hit the old school tube amp aesthetic.
I have a CNC router at home that I’ve been honing my skills on over the past 3 years (an upgraded Shapeoko 3 XL) and I was able to precisely mill the holes on the top of the case to snuggly fit all 3 Belton VT9-PT tube holders and mounting screws. I used 10mm standoffs between the PCB and chassis which perfectly sit the tube holders flush with the bottom of the lid.
As part of construction, I also finally learned how to use my sheet metal box and pan brake. I wanted additional shielding of the transformer from the audio circuit and I needed a way to mount the transformer to the top of the case without a screw showing (my own requirement to keep the top minimalistic). I took a piece of 20 gauge steel, and created a mounting bracket that all of the mains wiring and transformer would be seated in. I could then mount the transformer and a quick disconnect distribution block for wiring up the neon lamp, power switch, and transformer without any screws on the top of the case. I used a step bit and cut an opening for a rubber grommet to wire the secondaries to the PCB. It was a tight fit with clearances in the case. I had to trim down the transformer bolt and just barely had the width for the PCB and the bracket so I had to find some narrow 5.08mm pluggable terminal blocks that used crimp connectors to get the right clearance. It was worth the effort and I’m super happy with how it turned out.
Hopefully most of the other construction details will be obvious from the pictures. Per Bigman80’s suggestion, I have the transformer shield and mains ground run to a bolt on the chassis and the turntable ground to another post on the chassis. All RCA’s are isolated and ran with twisted pair 20 AWG directly soldered to the PCB. I put headers on the loading pads and will play with the best loading for my cartridge later. I’m using Clarity Cap CSA’s for the output caps since I already had 2.2uFs laying around. For tubes I am using a matched pair of NOS Valvo PCC88s and a Northern Electric 12AX7 (Northern Electric 12AX7 Audio Tubes - www.thetubestore.com). I have some Tungsram PCC88s in mail to try out as well.
This is one of my first tube projects and without the schematics available it is hard to determine if my voltages are on point. For my voltages, I expect these to be a bit high since my mains run at 116-117Vac, and the transformer was spec’ed at 115. I’m not sure if this will cause issues. The secondaries measured with load are 10.4-0-10.4 for the low voltage and 0-183 for the high voltage. From ground to D5P (positive pad), I have 239 Vdc.
The tubes have the following voltages relative to ground for each pin. Sorry for the verbosity, but I’m not sure which are the critical voltages here. Voltages are listed from pin 1 to pin 9 relative to ground (taken at ground point next to tube socket):
Code:
V1: 90.1, 0, 1.91, 63.8, 56.2, 90.2, 0, 1.9, 0
V2: 123.8, -2.2mV, 0.88, 62.6, 62.6, 118.1, -1.5mV, 0.935, 56.3
V3: 225.3, 121.4, 127.5, 64.0, 56.4, 225.5, 116, 122.1, 0That said, I believe it sounds like its working correctly and measuring with a 5.41mVrms 1khz signal, I’m getting 593mV output which translates to ~110x gain or ~41dB gain. This was mentioned earlier by Bigman80 as the correct amount for MM.
I haven’t been able to test MC yet since I don’t have a generator that can reliably output within the 0.5mV range. I have however designed and manufactured a version of Hifisonix’s Inverse RIAA (An Accurate Inverse RIAA Network). I just need to get the PCB soldered and assembled and do some reading on the measurements to perform. I will post further measurements once I get that project finished.
I’m not one to wax poetic about listening impressions, I truly don’t believe I have the ear to identify small nuances or the right words to describe them. However, I will say that I am very delighted at how quiet this preamp is. I had issues with hum and noise at higher amp gain with my previous phono preamp that I don’t have here. Quiet passages in music are strikingly quiet and quite a joy. If nothing else, I have really been enjoying listening so far, it gets my foot tapping, and that is what makes these projects a success for me.
Please let me know if you have any questions about my build, I would love to answer them. In the meantime, back to listening (Pink Floyd - Pulse box set if you are curious)!
Greg
Attachments
Very nice build there Greg, glad you are enjoying the performance.
You may find it gets a bit warm inside the case as I see you don't have any ventilation holes, I personally would add some.
All voltages are correct on the valves, around 180V AC is about optimal for the high voltage secondary.
The 165V spec came from an originally used Chinese C core transformer that was consistently high on the voltage, so 175-180 is perfect.
You may find it gets a bit warm inside the case as I see you don't have any ventilation holes, I personally would add some.
All voltages are correct on the valves, around 180V AC is about optimal for the high voltage secondary.
The 165V spec came from an originally used Chinese C core transformer that was consistently high on the voltage, so 175-180 is perfect.
Its a 230v primary, but I'd ship to the US.
Its an Audiophonics.fr traffo for the Bigbottle Phonostage
It´s Playing now,with my Denon 103 II (I thinks it name is)no hum or noise at all.
The load I have on 1K with less it tends to be darker sounding.
The one thing that bodders me is that when is switch over (No power to the relays)to MM I get no sound at all,I mean I shuold at least hear a little music.
Not even with a scope and a tonegenerator I get some signal throgh it.
I have the relays mounted on top of the pcb should that matter?
The load I have on 1K with less it tends to be darker sounding.
The one thing that bodders me is that when is switch over (No power to the relays)to MM I get no sound at all,I mean I shuold at least hear a little music.
Not even with a scope and a tonegenerator I get some signal throgh it.
I have the relays mounted on top of the pcb should that matter?