I have started a new Phono Stage project. After watching Stephe's series and reading a lot of the discussions I decided to get one of the built up Chinese clones and then upgrade the critical components. I settled on the two chassis version with a volume control. I think that I have a plan!
In addition to Stephe's series I got a lot of ideas from the discussion here: https://www.lencoheaven.net/forum/index.php?topic=26658.0
I got a unit without tubes for $158 from AliExpress. Shipping via DHL was like 75 bucks. I was amazed that they got it to Pennsylvania from Hong Kong in four days!
It looks very nicely put together inside and out. These things are not available on Amazon and I don't think that they are really intended for the American market, but rather aimed at audiophiles in Hong Kong.
I auditioned it briefly as it came and it's not bad. There is plenty of gain and no noise or hum to speak of. The tonal balance seems pretty even and extended. The soundstage was not very wide or deep at all. Focus was okay on that miniature stage.
The first upgrade on my list is to add the choke to the power supply and I got that done this afternoon.
The replacement coupling caps should be here tomorrow. I ended up getting two Mundorfs and one Clarity Cap. Mundorf makes a 0.15 mf but I couldn't find them.
I have decided to go closer to Stephe's plan and not remove the subsonic filter between V2 and V3 as Thorsten's mods do. I am using Robert's RIAA values, however. I have ordered the precision mica caps and resistors to replace the RIAA filters. The parts here are just okay.
I have decided to also bypass the electrolytics on the signal board and ordered the film caps needed. While I'm at it I'm going to put caps across the tube heaters. These will go on the bottom of the board.
The power supply is marked 115v and the voltages are just a bit high with my 123ish wall voltage. Not out of spec but higher than ideal: B+ is around 297 and my heaters are at like 6.7 volts. The treatise that I linked above describes how to change the diodes to adjust B+ and which resistors to change for the 6.3 circuit, but I think that I'm just going to build a bucking transformer. It seems like a 6.3v heater circuit transformer would be just right.
I'll let you all know how it goes and how it sounds as I go.
Pete
In addition to Stephe's series I got a lot of ideas from the discussion here: https://www.lencoheaven.net/forum/index.php?topic=26658.0
I got a unit without tubes for $158 from AliExpress. Shipping via DHL was like 75 bucks. I was amazed that they got it to Pennsylvania from Hong Kong in four days!
It looks very nicely put together inside and out. These things are not available on Amazon and I don't think that they are really intended for the American market, but rather aimed at audiophiles in Hong Kong.
I auditioned it briefly as it came and it's not bad. There is plenty of gain and no noise or hum to speak of. The tonal balance seems pretty even and extended. The soundstage was not very wide or deep at all. Focus was okay on that miniature stage.
The first upgrade on my list is to add the choke to the power supply and I got that done this afternoon.
The replacement coupling caps should be here tomorrow. I ended up getting two Mundorfs and one Clarity Cap. Mundorf makes a 0.15 mf but I couldn't find them.
I have decided to go closer to Stephe's plan and not remove the subsonic filter between V2 and V3 as Thorsten's mods do. I am using Robert's RIAA values, however. I have ordered the precision mica caps and resistors to replace the RIAA filters. The parts here are just okay.
I have decided to also bypass the electrolytics on the signal board and ordered the film caps needed. While I'm at it I'm going to put caps across the tube heaters. These will go on the bottom of the board.
The power supply is marked 115v and the voltages are just a bit high with my 123ish wall voltage. Not out of spec but higher than ideal: B+ is around 297 and my heaters are at like 6.7 volts. The treatise that I linked above describes how to change the diodes to adjust B+ and which resistors to change for the 6.3 circuit, but I think that I'm just going to build a bucking transformer. It seems like a 6.3v heater circuit transformer would be just right.
I'll let you all know how it goes and how it sounds as I go.
Pete
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I have the same EAR834p clone. It sounds amazing, especially after I upgraded the 2 main caps (I did not touch anything in the RIAA section). I am using JJ 12AX7s in there.
I also eliminated the power switch on the back of the power supply, and instead installed a locking push button power supply with built in led. I rewired the 6.3VDC led lin to power the led in the power switch. It looks much nicer, and is far easier to use.
I also eliminated the power switch on the back of the power supply, and instead installed a locking push button power supply with built in led. I rewired the 6.3VDC led lin to power the led in the power switch. It looks much nicer, and is far easier to use.
In case you are interested. There is a huge thread on upgrading these boards on Lenco Heaven
https://www.google.com/url?sa=t&rct...usg=AOvVaw1wNSUtU8TXvmBVp7Z1YGt4&opi=89978449
Cheers
https://www.google.com/url?sa=t&rct...usg=AOvVaw1wNSUtU8TXvmBVp7Z1YGt4&opi=89978449
Cheers
DNic - yeah, my next revision will be to move the preamp stage to a new case, and replace the big electrolytics with big *** can caps (33uf and 100uf) for the side areas. I expect it to be more aesthetics than sound, but over time will be much better (less age drift).
That is a great link for all the possible mods tho.
Trying to decide how far I go down the rabbit hole....
That is a great link for all the possible mods tho.
Trying to decide how far I go down the rabbit hole....
I didn't measure before and after, unfortunately. I removed the resistor when I added the choke so I thought that it would be a wash.
There is a bit more hum afterwards, which I didn't expect! I didn't audition it between adding the choke and replacing the caps so I don't really know the cause. I did twist the leads to the choke.
Pete
Oddly enough, this different link takes us to the same discussion that I mentioned in the first post. Very interesting stuff!
Pete
I received and installed the replacement coupling caps today.
Spoiler alert: this thing is transformed!
I found a source for all Mundorf Evo caps but only the 0.01mf one is the oil filled version.
I unsoldered the first cap to remove it but pretty quickly I started just clipping the leads with my flush cutters as I wasn't using any of the same holes.
I tried it out after upgrading one channel but quickly decided to do the other side.
After the upgrade the phono stage is transformed. The high frequencies are much cleaner -- cymbals are less splashy -- but the biggest changes are to the soundstage. The stage is much wider and deeper, larger than the room itself. The images on that stage are much rounder and more full-bodied.
As received this was basically a mid-fi level product. The frequency response was reasonably flat and extended and it was quiet. It sounded "nice". It didn't really create a soundstage, the musicians sounded like cardboard cutouts strung in a line between the speakers. Some of the cutouts were a bit smaller than others but not really behind them.
After the capacitor upgrades this is starting to sound like a high end product. The frequency response is more refined but the change in the imaging capabilities has taken it to a different league. The soundstage is MUCH bigger, not just wider than the speakers but wider than the room and there is now a convincing illusion of depth, extending well farther away than the wall. The images of the musicians are now rounded, full-bodied people with air around them.
This improved separation makes it much easier to follow the individuals making the music. I have been playing the same Jeremy Steig record over and over again, and this time those guys were doing all sorts of subtle **** that they weren't doing yesterday!
The caps in the RIAA section have brand names on them but I wonder if they are authentic. It seems possible that it is a counterfeit WIMA part. In any event, even if it's real it isn't the highest quality. The same goes for the other one. It might be a Mica cap but I think that it's a 5% part . The replacement precision Cornell Dubilier Mica caps and Holsworthy resistors should really clean up this critical area.
So, so far so good. I'm very happy with the progress up to this point and I look forward to seeing what the next round does.
Pete
Spoiler alert: this thing is transformed!
I found a source for all Mundorf Evo caps but only the 0.01mf one is the oil filled version.
I unsoldered the first cap to remove it but pretty quickly I started just clipping the leads with my flush cutters as I wasn't using any of the same holes.
I tried it out after upgrading one channel but quickly decided to do the other side.
After the upgrade the phono stage is transformed. The high frequencies are much cleaner -- cymbals are less splashy -- but the biggest changes are to the soundstage. The stage is much wider and deeper, larger than the room itself. The images on that stage are much rounder and more full-bodied.
As received this was basically a mid-fi level product. The frequency response was reasonably flat and extended and it was quiet. It sounded "nice". It didn't really create a soundstage, the musicians sounded like cardboard cutouts strung in a line between the speakers. Some of the cutouts were a bit smaller than others but not really behind them.
After the capacitor upgrades this is starting to sound like a high end product. The frequency response is more refined but the change in the imaging capabilities has taken it to a different league. The soundstage is MUCH bigger, not just wider than the speakers but wider than the room and there is now a convincing illusion of depth, extending well farther away than the wall. The images of the musicians are now rounded, full-bodied people with air around them.
This improved separation makes it much easier to follow the individuals making the music. I have been playing the same Jeremy Steig record over and over again, and this time those guys were doing all sorts of subtle **** that they weren't doing yesterday!
The caps in the RIAA section have brand names on them but I wonder if they are authentic. It seems possible that it is a counterfeit WIMA part. In any event, even if it's real it isn't the highest quality. The same goes for the other one. It might be a Mica cap but I think that it's a 5% part . The replacement precision Cornell Dubilier Mica caps and Holsworthy resistors should really clean up this critical area.
So, so far so good. I'm very happy with the progress up to this point and I look forward to seeing what the next round does.
Pete
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jayme -- Here is the cap that I removed from that location. 103k is 0.01uf where I come from, I wonder if they used the wrong value when building your unit.
The schematic that Stephe posted shows 0.01uf in this location but I have seen versions that show 0.1 uf here.
Pete
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Huh. I will have to trace out my circuit. I see a couple different schematics. That cap couple be a couple different parts. Either a bypass cap per the bottom schematic, or in the signal path between tubes 2 and 3.
If it is just the 0.1uf bypass cap, I am not worried about it affecting the sound.
Disregard the purple / red circles and comments. Thats not mine. I just pulled an image from another thread.
.
If it is just the 0.1uf bypass cap, I am not worried about it affecting the sound.
Disregard the purple / red circles and comments. Thats not mine. I just pulled an image from another thread.
.
Humm, as I understand the circuit this is a high pass filter acting as a subsonic filter. I wonder if the reason Thorsten decided to remove it is that his amp had the higher value capacitor and the crossover point was too high.
The first schematic shows 0.012 uf in this location and the second one has the entire filter section removed and replaced with a 100 ohm resistor.
Pete
The first schematic shows 0.012 uf in this location and the second one has the entire filter section removed and replaced with a 100 ohm resistor.
Pete
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Not yet. I've been using a passive preamp and set the phono stage volume control to about 2/3 of the way up. Where do you have yours set?
Pete