@DrewsBrews said:
I give it a trial run. Inserted it between my AT turn table with built-in preamp and my stereo receiver. Slapped on Dark Side of the Moon and let 'er rip.
Well. It makes sound. Heavily weighted to one channel and sounded pretty meh.
Being rather underwhelmed, I decided to chance the GE tubes. Holy cow what a transformation! Much more balanced L/R and that tooby holographic effect like I could reach out and grab whatever was making the sound. Those clock alarms....omg...
They cost as much as the kit, which is still pretty cheap. But you get way more than double the sound IMO. Definately worth it if you are springing for all the other "fixins" anyway.
Then I took it out of the signal path and listened again to compare. So with the tube preamp in-line you lose a bit of crispness, but gain that whole depth of soundstage. Like comparing the feeling of a nice form fitting stiff starched shirt to a warm bath that you feel the water swirling around as you move. Pick your poison. Probably mood dependant on which is most pleasing. But I noticed one nice side effect of that loss of crispness is it does neuter the majority of the subtle vinyl crackles.
It's good to know this kit responds favorably to different tubes. Even with the 'matched' pair of Voskhod tubes center is still right of center and the soundstage is much smaller than the diy 4s preamp. Supposedly, the RCA tube to have is the one with 6ak5 as the sole identifier printed on the end of the RCA box. Have a pair in the cart but they are $40. Think I'll try those you linked, and a TungSol, Raytheon, Mullard cv4010, ... already spent more than the kit cost on better kit parts, now it's getting bloody ridiculous. Cheap simple tube linestage???
That should be fine, as long as your B+ does not exceed your 470uF cap ratings. What is your B+ running at? Are you using the 50V 470uF caps or the 35V 470uF caps?
Tubes are very forgiving, +/- 10%, so heater voltages between 5.67 and 6.93 Vac are totally acceptable. I would never add series resistance if the heater voltage at the tube socket is in that range. Plus these are reasonably priced tubes so if you only get 8,000 hours of service out of them instead of 10,000 hours not a huge deal. Now if these were NOS Western Electric 300B tubes... I'd sharpen my pencil a bit more. Just my $0.03
@4thtry said:
That should be fine, as long as your B+ does not exceed your 470uF cap ratings. What is your B+ running at? Are you using the 50V 470uF caps or the 35V 470uF caps?
Using the 50v caps + the suggested 25v cap on C13. I didn't end up measuring it. If I pull it back apart again I'll try to remember to do so.
@PWRRYD said:
Tubes are very forgiving, +/- 10%, so heater voltages between 5.67 and 6.93 Vac are totally acceptable. I would never add series resistance if the heater voltage at the tube socket is in that range. Plus these are reasonably priced tubes so if you only get 8,000 hours of service out of them instead of 10,000 hours not a huge deal. Now if these were NOS Western Electric 300B tubes... I'd sharpen my pencil a bit more. Just my $0.03
Good to know it isn't such a big deal.
The higher VA transformer outputs 14v (no load). The stock board comes with a 2.2ohm on the heater supply line to get 12.6v. I ended up just installing a 10watt 5.1ohm resistor under the board so I could re-solder the slightly displaced parts flush with the board. Now I can assemble the acrylic case. Squeezes on the caps a bit. Not ideal if a cap does happen to blow, but at least it should be contained.
A pair of TungSol 6096/6ak5w, grey plates, d-getter, came in yesterday. Stubby little buggers compared to the Voskhods. At $25, they were a bit pricey but it appears some care was taken in the matching process. Fingers crossed they are better than the 'matched' pair of Voskhods from Amazon where center stage is always to one side of center. Trying to stay awake long enough today to give them a listen.
Cool - those were actually matched by a human! I'm curious to hear how they sound.
The 5654w "Matched Pair" I got on Amazon all seem to have the exact same sticker slapped on the box.
It bugs the beetlejuice out of me how the last 'matched' pair pulls the center to the sides. Good news, the Ukrainian tubes made it to the US. Any easy way to go about matching them?
I've experienced that off center too with tweeters. One pair of RS28AS were so bad my wife even heard it. She asked why the girl singing was off to the left. Turns out that tweeter was almost 1 dB more sensitive than the other. I was quite surprised such a little difference was so audible. Adding an extra ohm to that side's padding resistor centered the stage nicely.
The Ukrainian tubes came in and with the glass indentions, diamond, and otk stamp )Russian military stamp of approval?) they appear to be the 'rockets'.
Is it possible to do at least a rough matching with basic gear before sending them out?
@Tom_S@a4eaudio@ani_101@4thtry pm your shipping addresses. It may be some time before getting these tubes in the mail as I'd like to do some kind of matching before shipping them and my work hours are KraZy.
I think you could put a 400Hz sign wave into the preamp and see if you have any pairs with the same voltage at the output. Just make sure the input level doesn't change and it's the same on both grids. That will probably get us fairly close.
@Kornbread said:
The Ukrainian tubes came in and with the glass indentions, diamond, and otk stamp )Russian military stamp of approval?) they appear to be the 'rockets'.
Is it possible to do at least a rough matching with basic gear before sending them out?
@Tom_S@a4eaudio@ani_101@4thtry pm your shipping addresses. It may be some time before getting these tubes in the mail as I'd like to do some kind of matching before shipping them and my work hours are KraZy.
PM sent. One thing you could do to match tubes is to simply use the voltage drop across the heater filaments as a proxy for the micromhos (or GM) of each tube. Since the tube heaters are connected in series, the voltage drop across the filament will be higher for higher gain tubes. So when the voltage drop across the two tubes in circuit match, you have a matched set of tubes! Pins 3 and 4 on each tube socket are the heaters. Use two DMM's. Connect one DMM with minigrabbers to the left channel tube socket. Connect the other DMM with minigrabbers to the right channel tube socket. Power it up and compare voltages. Should be that simple. Below are how my 4 tubes measured on my Heathkit TT-1 tube tester a while back. Notice how the heater voltage drop follows the micromhos measurement. @Tom_S when you tested your tubes, did you also notice that the filament drop followed the gain measurement? Maybe you could double check this to see if this simple test will work. I also have a set of matched JAN5654W tubes that I have not tested yet. When I get some free time tomorrow, I'll put them on my tester and see if the gain follows the filament drop.
Kit 1, Tube A: 2800 micromhos: 0.379v drop across 200 ohm cathode resistor (1.89ma) Heater: 5.8vdc
Kit 1, Tube B: 3550 micromhos: 0.466v drop across 200 ohm cathode resistor (2.33ma) Heater: 6.15vdc
Kit 2, Tube A: 4500 micromhos: 0.538v drop across 200 ohm cathode resistor (2.69ma) Heater: 6.25vdc
Kit 2, Tube B: 3450 micromhos: 0.488v drop across 200 ohm cathode resistor (2.44ma) Heater: 6.15vdc
No tube rolling for a while. Swapped a couple tubes around and apparently didn't get them seated correctly. Now the amplifier power supply cycles on/off. Unhooked the lead from the power supply to amp board and the power supply stays on, but it makes a weird tickle-tic sound when it powers up, which was not its normal turn on sound. Fingers crossed, it was just coincidence and the Meanwell power supply stb. If not, I'm out a gremlin amp board.
The matched set of TungSol are nice. Bass, it goes low with a lot more weight than the Rockets or RCA. Voice is smoother, further back in the mix than the RCA or Rocket. Highs are smooth, maybe a bit laid back, but there, and extended. Largest yet best detailed soundstage of all the tubes so far. The TungSol is smooth, laid back and with a big bottom. It's a nice big bottom.
The RCA gives a grittiness to voice that is pretty nice. Brings it forward in the mix. Definitely less bass than the TungSol, maybe even lean compared to the TungSol. Sounstage is more compact than TungSol with sounds emanating from a straight line between and slightly outside the speakers. There is depth, just not like the TungSol. Stuff is well placed What bass they have is higher up in freq and controlled. Bit more emphasis on the mid and up region. Not a spotlight, just more there. Even with this clarity, or emphasis on the mid and up, they don't seem harsh. Even with this good mid and up, I'm not sure they are as extended as the smoother with big bottom TungSol. One tube is smooth and heavy, the other more lively and there. Pick your poison.
The Rocket. Soundstage is more compact. Decent placement. Decent depth, every bit as much depth as the RCA. Not sure how to describe it, things are a bit more sterile. Not as smooth or as much bass as the TungSol but bass is still deep and better than the RCA. Voice more forward than TungSol, further back than RCA. Voice, and sounds in general, do not float free as easily as the RCA, or even the TungSol. Out of the three pairs, I guess this one is the middle ground. It maybe seems more balanced than the other pairs, but it just feels sterilized?
For what it's worth, I do not think the RCA pair was very well matched.
As you can see from the attached spreadsheet, I was only able to get a total of four matched sets of the OTK1 stamped tubes from the group of 10. I will be carefully listening to ALL of these tubes tomorrow to see how much of a difference the matching actually makes. Since I will be able to listen and compare all sets, I am going to keep the unmatched OTK1's for myself and ship out the tighter matched pairs for others to hear. In this way, everyone will be able to listen for themselves and hear just how much of a difference this matching process really makes. Here is how the matching breaks out:
We can get three matched sets out of the group as follows:
1) One 1% tolerance matched set at 4750 and 4800 (test #10 and #14)
2) One 2% tolerance matched set at 2350 and 2400 (test #15 and #16)
3) One 5% tolerance matched set at 2900 and 3050 (test #11 and #9)
Or we can get four matched sets out of the group as follows:
1) One 1% tolerance matched set at 4750 and 4800 (test #10 and #14)
2) One 2% tolerance matched set at 2350 and 2400 (test #15 and #16)
3) One 8% tolerance matched set at 3050 and 3300 (test #9 and #12)
4) One 9% tolerance matched set at 2650 and 2900 (test #17 and #11)
When it comes time to put these in the mail, I'll need to ship out four matched sets; one for Tom, David, Ani, and Kornbread. Will also be returning Kornbread's RCA 6AK5's and Voskhod Rockets after I get a chance to listen to them. Will probably flip a coin to see who gets the closest tolerance OTK1 sets. Let me know if this makes sense. Bill
I kind of call this a bust. If you guys want a better match but don't mind waiting again, and @4thtry is willing, I'll order a lot of 22pcs. and maybe we can get some decent matching tube sets.
Sending out matched pairs? Guess that means I'm in, just let me know how much $ I'm in for.
I've got this pair of GE tubes I'm pretty happy with sofar. But I have been secretly mulling over trying a point to point version of this also. More tubes fill more sockets
No problem. I can match them up for you when you get them in. I saw that essues curve tracer a few years ago on Blueglow. Seems like a well made unit, but it's kind of pricy.
Up to the group. Do we want 3 </=5% matched pairs to go out and the rest of us wait for the next batch to arrive, or do we want to get 4 lesser matched pairs out?
22pcs are on order. The last order took <4 weeks to arrive.
@4thtry said:
No problem. I can match them up for you when you get them in. I saw that essues curve tracer a few years ago on Blueglow. Seems like a well made unit, but it's kind of pricy.
One of the best ways to find an inexpensive tube tester would be to visit one of the local hamfests in your area. That is how I found mine. They always have used testers for sale at these events. Some in good shape, some in not so good shape. You can also dig through all the used and NOS tube vendor stashes while you are there, looking for diamonds in the rough.
@Kornbread said:
Up to the group. Do we want 3 </=5% matched pairs to go out and the rest of us wait for the next batch to arrive, or do we want to get 4 lesser matched pairs out?
22pcs are on order. The last order took <4 weeks to arrive.
I think the best thing would be to hold off mailing anything out until all the tubes have arrived. I can then do the matching from the entire set of 32 tubes. With that many tubes, we should be able to come up with several good sets. Also, before mailing, I can give each matched set a quick listen to weed out any tubes from the batch that measure good but have very high fluttering type noise levels (hiss).
Today I have been listening to Kornbread's matched pair of RCA 6AK5's (test #7 and #8). I have to say, they certainly sound quite a bit better than my matched pair of Chinese 6J1's (test #2 and #4). The soundstage appears to be a little off center on both the RCA's and my Chinese 6J1's.
Part of the problem is the lack of a stereo balance pot. It's not just the tubes, resistor and pot tolerances are also partly to blame.
Test of perfectly balanced 800mv rms sine wave fed into the right and left channels:
4000 umhos RCA tube in right channel: 1.10Vrms output
4450 umhos RCA tube in left channel: 1.35Vrms output
Swap tubes:
4450 umhos RCA tube in right channel: 1.16Vrms output
4000 umhos RCA tube in left channel: 1.27Vrms output
Comments
It's good to know this kit responds favorably to different tubes. Even with the 'matched' pair of Voskhod tubes center is still right of center and the soundstage is much smaller than the diy 4s preamp. Supposedly, the RCA tube to have is the one with 6ak5 as the sole identifier printed on the end of the RCA box. Have a pair in the cart but they are $40. Think I'll try those you linked, and a TungSol, Raytheon, Mullard cv4010, ... already spent more than the kit cost on better kit parts, now it's getting bloody ridiculous. Cheap simple tube linestage???
I pulled the 4ohm resistor and installed a 5.1ohm. Heater voltages are down to 6.25v and a hair over 6v.
Both seem to glow happily still so is this ok to run with?
That should be fine, as long as your B+ does not exceed your 470uF cap ratings. What is your B+ running at? Are you using the 50V 470uF caps or the 35V 470uF caps?
Tubes are very forgiving, +/- 10%, so heater voltages between 5.67 and 6.93 Vac are totally acceptable. I would never add series resistance if the heater voltage at the tube socket is in that range. Plus these are reasonably priced tubes so if you only get 8,000 hours of service out of them instead of 10,000 hours not a huge deal. Now if these were NOS Western Electric 300B tubes... I'd sharpen my pencil a bit more. Just my $0.03
From what I gather these are interchangeable, but roll at your won risk. Will add more as the research continues.
6J1, 5654, 6ak5, ef95, 6hm5, cv4010, m8100, 6096, 403a/b
Using the 50v caps + the suggested 25v cap on C13. I didn't end up measuring it. If I pull it back apart again I'll try to remember to do so.
Good to know it isn't such a big deal.
The higher VA transformer outputs 14v (no load). The stock board comes with a 2.2ohm on the heater supply line to get 12.6v. I ended up just installing a 10watt 5.1ohm resistor under the board so I could re-solder the slightly displaced parts flush with the board. Now I can assemble the acrylic case. Squeezes on the caps a bit. Not ideal if a cap does happen to blow, but at least it should be contained.
A pair of TungSol 6096/6ak5w, grey plates, d-getter, came in yesterday. Stubby little buggers compared to the Voskhods. At $25, they were a bit pricey but it appears some care was taken in the matching process. Fingers crossed they are better than the 'matched' pair of Voskhods from Amazon where center stage is always to one side of center. Trying to stay awake long enough today to give them a listen.
Have you checked out TubeDepot.com? They have NOS 6096's for $4.95. They are geat to deal with. Give them a call and see what brands they have.
Ordered quite a bit from them over the years and they are only 3hrs away. Do they match tubes?
Cool - those were actually matched by a human! I'm curious to hear how they sound.
The 5654w "Matched Pair" I got on Amazon all seem to have the exact same sticker slapped on the box.
They do matching for an extra couple bucks.
It bugs the beetlejuice out of me how the last 'matched' pair pulls the center to the sides. Good news, the Ukrainian tubes made it to the US. Any easy way to go about matching them?
I've experienced that off center too with tweeters. One pair of RS28AS were so bad my wife even heard it. She asked why the girl singing was off to the left. Turns out that tweeter was almost 1 dB more sensitive than the other. I was quite surprised such a little difference was so audible. Adding an extra ohm to that side's padding resistor centered the stage nicely.
The Ukrainian tubes came in and with the glass indentions, diamond, and otk stamp )Russian military stamp of approval?) they appear to be the 'rockets'.
Is it possible to do at least a rough matching with basic gear before sending them out?
@Tom_S @a4eaudio @ani_101 @4thtry pm your shipping addresses. It may be some time before getting these tubes in the mail as I'd like to do some kind of matching before shipping them and my work hours are KraZy.
I think you could put a 400Hz sign wave into the preamp and see if you have any pairs with the same voltage at the output. Just make sure the input level doesn't change and it's the same on both grids. That will probably get us fairly close.
PM sent. One thing you could do to match tubes is to simply use the voltage drop across the heater filaments as a proxy for the micromhos (or GM) of each tube. Since the tube heaters are connected in series, the voltage drop across the filament will be higher for higher gain tubes. So when the voltage drop across the two tubes in circuit match, you have a matched set of tubes! Pins 3 and 4 on each tube socket are the heaters. Use two DMM's. Connect one DMM with minigrabbers to the left channel tube socket. Connect the other DMM with minigrabbers to the right channel tube socket. Power it up and compare voltages. Should be that simple. Below are how my 4 tubes measured on my Heathkit TT-1 tube tester a while back. Notice how the heater voltage drop follows the micromhos measurement. @Tom_S when you tested your tubes, did you also notice that the filament drop followed the gain measurement? Maybe you could double check this to see if this simple test will work. I also have a set of matched JAN5654W tubes that I have not tested yet. When I get some free time tomorrow, I'll put them on my tester and see if the gain follows the filament drop.
Kit 1, Tube A: 2800 micromhos: 0.379v drop across 200 ohm cathode resistor (1.89ma) Heater: 5.8vdc
Kit 1, Tube B: 3550 micromhos: 0.466v drop across 200 ohm cathode resistor (2.33ma) Heater: 6.15vdc
Kit 2, Tube A: 4500 micromhos: 0.538v drop across 200 ohm cathode resistor (2.69ma) Heater: 6.25vdc
Kit 2, Tube B: 3450 micromhos: 0.488v drop across 200 ohm cathode resistor (2.44ma) Heater: 6.15vdc
No tube rolling for a while. Swapped a couple tubes around and apparently didn't get them seated correctly. Now the amplifier power supply cycles on/off. Unhooked the lead from the power supply to amp board and the power supply stays on, but it makes a weird tickle-tic sound when it powers up, which was not its normal turn on sound. Fingers crossed, it was just coincidence and the Meanwell power supply stb. If not, I'm out a gremlin amp board.
Odds and ends ...
The matched set of TungSol are nice. Bass, it goes low with a lot more weight than the Rockets or RCA. Voice is smoother, further back in the mix than the RCA or Rocket. Highs are smooth, maybe a bit laid back, but there, and extended. Largest yet best detailed soundstage of all the tubes so far. The TungSol is smooth, laid back and with a big bottom. It's a nice big bottom.
The RCA gives a grittiness to voice that is pretty nice. Brings it forward in the mix. Definitely less bass than the TungSol, maybe even lean compared to the TungSol. Sounstage is more compact than TungSol with sounds emanating from a straight line between and slightly outside the speakers. There is depth, just not like the TungSol. Stuff is well placed What bass they have is higher up in freq and controlled. Bit more emphasis on the mid and up region. Not a spotlight, just more there. Even with this clarity, or emphasis on the mid and up, they don't seem harsh. Even with this good mid and up, I'm not sure they are as extended as the smoother with big bottom TungSol. One tube is smooth and heavy, the other more lively and there. Pick your poison.
The Rocket. Soundstage is more compact. Decent placement. Decent depth, every bit as much depth as the RCA. Not sure how to describe it, things are a bit more sterile. Not as smooth or as much bass as the TungSol but bass is still deep and better than the RCA. Voice more forward than TungSol, further back than RCA. Voice, and sounds in general, do not float free as easily as the RCA, or even the TungSol. Out of the three pairs, I guess this one is the middle ground. It maybe seems more balanced than the other pairs, but it just feels sterilized?
For what it's worth, I do not think the RCA pair was very well matched.
Tube measurements are done and attached. Tomorrow I will re-connect my two 6J1 preamps to my bench speakers and give them a listen. Stay tuned.
As you can see from the attached spreadsheet, I was only able to get a total of four matched sets of the OTK1 stamped tubes from the group of 10. I will be carefully listening to ALL of these tubes tomorrow to see how much of a difference the matching actually makes. Since I will be able to listen and compare all sets, I am going to keep the unmatched OTK1's for myself and ship out the tighter matched pairs for others to hear. In this way, everyone will be able to listen for themselves and hear just how much of a difference this matching process really makes. Here is how the matching breaks out:
We can get three matched sets out of the group as follows:
1) One 1% tolerance matched set at 4750 and 4800 (test #10 and #14)
2) One 2% tolerance matched set at 2350 and 2400 (test #15 and #16)
3) One 5% tolerance matched set at 2900 and 3050 (test #11 and #9)
Or we can get four matched sets out of the group as follows:
1) One 1% tolerance matched set at 4750 and 4800 (test #10 and #14)
2) One 2% tolerance matched set at 2350 and 2400 (test #15 and #16)
3) One 8% tolerance matched set at 3050 and 3300 (test #9 and #12)
4) One 9% tolerance matched set at 2650 and 2900 (test #17 and #11)
When it comes time to put these in the mail, I'll need to ship out four matched sets; one for Tom, David, Ani, and Kornbread. Will also be returning Kornbread's RCA 6AK5's and Voskhod Rockets after I get a chance to listen to them. Will probably flip a coin to see who gets the closest tolerance OTK1 sets. Let me know if this makes sense. Bill
Since I already have a few pairs to play with, I'll take the least close pair. I think I may even have one that came with one of my kits.
@a4eaudio @ani_101 @Tom_S @4thtry
Am I forgetting anyone? Seems like I'm forgetting someone???
I kind of call this a bust. If you guys want a better match but don't mind waiting again, and @4thtry is willing, I'll order a lot of 22pcs. and maybe we can get some decent matching tube sets.
Ordered them anyway. Been looking at tube testers on ebay, and then there's this https://essues.com/index.php/etracer-1
Sending out matched pairs? Guess that means I'm in, just let me know how much $ I'm in for.
I've got this pair of GE tubes I'm pretty happy with sofar. But I have been secretly mulling over trying a point to point version of this also. More tubes fill more sockets
No problem. I can match them up for you when you get them in. I saw that essues curve tracer a few years ago on Blueglow. Seems like a well made unit, but it's kind of pricy.
Up to the group. Do we want 3 </=5% matched pairs to go out and the rest of us wait for the next batch to arrive, or do we want to get 4 lesser matched pairs out?
22pcs are on order. The last order took <4 weeks to arrive.
There's also this and it looks to be capable and cheaper https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
One of the best ways to find an inexpensive tube tester would be to visit one of the local hamfests in your area. That is how I found mine. They always have used testers for sale at these events. Some in good shape, some in not so good shape. You can also dig through all the used and NOS tube vendor stashes while you are there, looking for diamonds in the rough.
https://www.arrl.org/hamfests-and-conventions-calendar
I think the best thing would be to hold off mailing anything out until all the tubes have arrived. I can then do the matching from the entire set of 32 tubes. With that many tubes, we should be able to come up with several good sets. Also, before mailing, I can give each matched set a quick listen to weed out any tubes from the batch that measure good but have very high fluttering type noise levels (hiss).
Today I have been listening to Kornbread's matched pair of RCA 6AK5's (test #7 and #8). I have to say, they certainly sound quite a bit better than my matched pair of Chinese 6J1's (test #2 and #4). The soundstage appears to be a little off center on both the RCA's and my Chinese 6J1's.
Part of the problem is the lack of a stereo balance pot. It's not just the tubes, resistor and pot tolerances are also partly to blame.
Test of perfectly balanced 800mv rms sine wave fed into the right and left channels:
4000 umhos RCA tube in right channel: 1.10Vrms output
4450 umhos RCA tube in left channel: 1.35Vrms output
Swap tubes:
4450 umhos RCA tube in right channel: 1.16Vrms output
4000 umhos RCA tube in left channel: 1.27Vrms output