The 14th Chapter of the Radiotron Designer's Handbook is "Fidelity and Distortion". By the fifth paragraph, the author ( who is the editor of the entire tome ) concedes that there is a strong subjective component to the concept of fidelity.
It's interesting and well worth reading ( or re-reading ) - the manual is rather old at this point, but still contains an extraordinary amount of useful information. I'm lucky enough to have a hard copy but someone stepped up to the plate ( pardon the pun ) and undertook the Herculean task of disassembling the book, scanning it, and putting it online.
I don't know if posting links to external sites is allowed, but googling "radiotron designers handbook 4th edition" puts the link to it as the first search result.
Win W5JAG
It's interesting and well worth reading ( or re-reading ) - the manual is rather old at this point, but still contains an extraordinary amount of useful information. I'm lucky enough to have a hard copy but someone stepped up to the plate ( pardon the pun ) and undertook the Herculean task of disassembling the book, scanning it, and putting it online.
I don't know if posting links to external sites is allowed, but googling "radiotron designers handbook 4th edition" puts the link to it as the first search result.
Win W5JAG
I glanced over the whole 14th Chapter. Lots of good information that is as important today as when publicized.
I think that would be Pete Millett's repository - all types of vintage Tube books there. He has a few interesting circuits as well, which have been improved upon by other contributors.
As for fidelity, it can be subjective - since hearing capability is not uniform, audiophilia is by default subjective. On the other hand, some measurements do help orient designs and getting measurable and repeatable results. However, there are all sorts of heated debates for all types of things in audiophile-land, one of which is the objective vs subjective one - best avoided.
Yes, I have come across his 'First Watt' material and other texts by him, really interesting stuff and aligned to the low-power + high-efficiency speakers/full-range drivers, although he is more concerned with SS amplification.
I think I definitely could get a higher B+ with the Edcor XPWR as it's 370-0-370, so it does seem that there's a big voltage drop along the way.
This said, perhaps it's then better to use another tube as well.
How's your SSE build going?
Forgot to add:
There are a few principles you can try to adhere to to maximise or diagnose fidelity and there's a kind of hierarchy to it (this is all according to me):
1. Defer or take as reference to the artist's perception of whether the equipment transmits the performance
2. Defer or refer to what you hear at the live event (even if that means acoustic or classical and you prefer electronic music like I do)
3. Defer or refer to what was originally captured on the Master Tape (or other original medium)
Lots of fun to be had in that area.
Mine is coming along fine (in my head).
The tubes arrived last week, the GL KT88s are enormous, and Edcor sent an email to say that my transformers have been dispatched.
I should have them next week.
I can't even look at the wiring diagrams until I have the stuff in my hands.
I have been looking at the charts and I downloaded that Radiotron book (it's also enormous) and it seems that the lowest distortion figures are for low B+ (350vcd) and higher impedance (5000 ohms).
Why then does the general recommendation be to go higher towards or above 450V?
Are there different qualities that people like at these voltages, or is it just for more power?
I will be using a standard setup with 375-0-375 Edcor GSXE OPTs and my line voltage is very close to 240AC so I am expecting a B+ around 450V.
I will also have a lowish impedance - I have bought 5K - 8ohm OPTs for my 4 ohm speakers because I want to change them in the future.
The DC resistance of the speakers is exactly 4 ohms. I downloaded the free arta software and made the little jig for my laptop sound card and it gave me the attached plot.
It is probably not that accurate but it seems reasonable given the DCR of the speakers and should give me a load impedance of around 3000.
I got the KT88s because they seem to be the best at these lower impedances.
This will put me in the higher distortion bracket, I think, but I'll be happy if I can hear the distortion that people are talking about.
I have various cathode resistors to try out and I might get that other rectifier tube that drops the 40 volts or so to see if I can hear any difference.
I don't have huge faith in my own ears.🙁
Attachments
Soon, soon, then!
Yes, I believe it's the power vs distortion equation. But higher power also equates to shorter lifespan for the tubes. Ideally, you would want to pair the output with highly-efficient speakers, and I've seen people recommend at least 94dB, so that the 'low power' is less of an issue.
My Totem Mites are faw below that but sound great in my room, but of course, the fact that I now don't have the ideal speakers to pair with the SET is nagging me.
Additionally, I would like to also optimise these two things in my setup:
- Use balanced interconnects (that would mean retrofitting Balun interfaces at both the DAC and Amp levels)
- Use a chip-less DAC with a tube filter/output
This would be bliss, especially with DSD256 and above.
What's the arta software you mentioned? Looks cool.
You can get it here:
ARTA Download
It will give you frequency response plots impedance curves etc.
I found this page to be the best to explain construction of the jig.
It's just a resistor and some plugs.
https://sites.google.com/site/amateuraudio/projects-1/arta-limp-and-or-room-eq-wizard-impedance-jig
Here is the jig I made, it only took a couple of munutes.
It's not pretty but it works.
Attachments
Thanks gcom, looks like it also provides estimations for all TS parameters as well, nice!
Hey Sprags,
I don't know if this is what you were thinking of? I got these plugs on ebay.
You can solder wires into them and plug the in and out of the tube sockets.
I got them because I had already soldered in the pcb mounted sockets and then thought I would use chassis mounted sockets but if I tried desoldering I would make a mess.
Turned out I didn't leave myself enough room anyway so I won't be using them for now.
An externally hosted image should be here but it was not working when we last tested it.
Sent from my HTC One_M8 using Tapatalk
A new sub-reddit named diytubes was just started on Reddit, it's small for now but quite cool, and I found this very interesting article from Tube Cad Journal there, great to start learning from the basics:
The Grounded Cathode Amplifier.
The Grounded Cathode Amplifier.
Thanks for that link.
I downloaded it the other evening, and was going to build an attenuator/matcher for my PC so I could put it to use, when the PC abruptly died. 😡
So, I guess I'm still stuck in the last century for analysis.
Win W5JAG
Loving the SSE amp as usual, especially with high-rate DSD through a native DSD DAC, up to DSD256.
I am thinking of how to use the subwoofer with the SSE: the Totem Mites I am currently using min out at around 50Hz, so there's a lot of room for improvement here.
Having fished for a frequency response curve for the Mites, I found a user showing measurements which start down-trending as from 170Hz towards 50Hz and below.
So, I am thinking of tapping the DAC output, diverting some of it to a DIY lowpass filter then going into the subwoofer.
The subwoofer is good for games and movies but nowhere near the quality of the SSE for audiophile music, so if I can either re-build a good cabinet for the driver or mod it in any way, I'll be looking to do that too.
I am thinking of how to use the subwoofer with the SSE: the Totem Mites I am currently using min out at around 50Hz, so there's a lot of room for improvement here.
Having fished for a frequency response curve for the Mites, I found a user showing measurements which start down-trending as from 170Hz towards 50Hz and below.
So, I am thinking of tapping the DAC output, diverting some of it to a DIY lowpass filter then going into the subwoofer.
The subwoofer is good for games and movies but nowhere near the quality of the SSE for audiophile music, so if I can either re-build a good cabinet for the driver or mod it in any way, I'll be looking to do that too.
Re-worked USB connection and Power supply for the DAC.
Loving the sound of the Tubelab SSE with my native DSD DAC, the iFi iDSD Nano.
I have been experimenting with USB cable geometries for a couple of years or so. Last year I temporarily disconnected the GND on the USB cable and had a great bump in SQ. I also experimented with choking the computer power lines with good results.
These past few days I have been re-visiting that USB connection several times to try and reach total galvanic isolation. In practice, it doesn't seem possible with my DAC. I have had to reconnect the computer GND.
In the meantime I had built a filter for the computer power line. Trying it out did remove all the glare from the sound - it's a pernicious thing as you can get used to it, but once it's removed, you ask yourself how you can listen to that kind of sound all the time. On the other hand, the filter also removed a lot of high-frequency detail in the audio band, so wasn't really usable like this.
So I built another little circuit for isolating the Ground and installed this and had a big bump in SQ again, most of the effect of total disconnecting but probably not up to it exactly.
I added my filter to the computer supply and turned it on - yet another bump in SQ, while powering the DAC with an external power using an iPhone charger to try and see if I could get the DAC to handshake and operate properly and safely.
I performed simple experiments with the shield and jack and shield termination and got much more out of this connection.
This morning I woke up early and finished my Low-Noise Linear Regulated Power Supply prototype with some great thinking by John Swenson and others, thus replacing the iPhone charger which is an SMPS.
Now, my DAC powers its clock and DAC chip by the internal battery. The USB receiver used to be through computer USB power. The bump in SQ with the iPhone charger was big, together with the other circuits and enhancements, but this Low-Noise Linear Regulated PSU is something else entirely.
The increase in the sense of space and definition from the mid-range down to the bass articulation is huge. Before today I certainly never heard or paid attention to a singer's tongue lifting from her mouth before she sings (Barbra Streisand - Memory). We hear new details in a lot of songs we know very well.
I'm quite satisfied with all the research/reading and guerilla-style experimentation which brought these results.
A Linear Regulated PSU is a must, all the goodies apparently also come with a blacker background. With my current implementation, it does appear the prototype is a little behind the SMPS concerning the rapidity and resolution of the higher ranges of transients, so perhaps I can tweak it further. The SQ in the high-range is otherwise quite smooth.
Overall, it is smooth, velvety, has a deep and wide soundstage, the presence of vocalists is real and uncanny. Bass-to-mid-range is stellar.
Packaging of the prototype re-engineered USB connection as well as the Low-Noise Linear Regulated PSU is a bit below expectations from a full Christmas gift, but Father Xmas was a bit tired after building it, especially after yesterday's excesses. Further tests and enhancements are possible now, but I am going to let it play for a good while before those. 😀
Loving the sound of the Tubelab SSE with my native DSD DAC, the iFi iDSD Nano.
I have been experimenting with USB cable geometries for a couple of years or so. Last year I temporarily disconnected the GND on the USB cable and had a great bump in SQ. I also experimented with choking the computer power lines with good results.
These past few days I have been re-visiting that USB connection several times to try and reach total galvanic isolation. In practice, it doesn't seem possible with my DAC. I have had to reconnect the computer GND.
In the meantime I had built a filter for the computer power line. Trying it out did remove all the glare from the sound - it's a pernicious thing as you can get used to it, but once it's removed, you ask yourself how you can listen to that kind of sound all the time. On the other hand, the filter also removed a lot of high-frequency detail in the audio band, so wasn't really usable like this.
So I built another little circuit for isolating the Ground and installed this and had a big bump in SQ again, most of the effect of total disconnecting but probably not up to it exactly.
I added my filter to the computer supply and turned it on - yet another bump in SQ, while powering the DAC with an external power using an iPhone charger to try and see if I could get the DAC to handshake and operate properly and safely.
I performed simple experiments with the shield and jack and shield termination and got much more out of this connection.
This morning I woke up early and finished my Low-Noise Linear Regulated Power Supply prototype with some great thinking by John Swenson and others, thus replacing the iPhone charger which is an SMPS.
Now, my DAC powers its clock and DAC chip by the internal battery. The USB receiver used to be through computer USB power. The bump in SQ with the iPhone charger was big, together with the other circuits and enhancements, but this Low-Noise Linear Regulated PSU is something else entirely.
The increase in the sense of space and definition from the mid-range down to the bass articulation is huge. Before today I certainly never heard or paid attention to a singer's tongue lifting from her mouth before she sings (Barbra Streisand - Memory). We hear new details in a lot of songs we know very well.
I'm quite satisfied with all the research/reading and guerilla-style experimentation which brought these results.
A Linear Regulated PSU is a must, all the goodies apparently also come with a blacker background. With my current implementation, it does appear the prototype is a little behind the SMPS concerning the rapidity and resolution of the higher ranges of transients, so perhaps I can tweak it further. The SQ in the high-range is otherwise quite smooth.
Overall, it is smooth, velvety, has a deep and wide soundstage, the presence of vocalists is real and uncanny. Bass-to-mid-range is stellar.
Packaging of the prototype re-engineered USB connection as well as the Low-Noise Linear Regulated PSU is a bit below expectations from a full Christmas gift, but Father Xmas was a bit tired after building it, especially after yesterday's excesses. Further tests and enhancements are possible now, but I am going to let it play for a good while before those. 😀
I have called back into action my DIY AC Filter box as well.
Looks like the iMac definitely needs to be on a filter line judging by the improvement in SQ I get this way.
Didn't find a proper place on either the main power strip in the AC Filter box, nor on a filter line for the DAC's new Linear Regulated PSU, but we felt putting it on a separate outlet is better for all SQ, including rapidity of transients.
Where we were rather shocked was also putting the TV on a filter line. In my setup, the iMac is linked so that it can mirror its screen onto the TV with a cable going into an HDMI port.
This is an avenue for ground plane pollution or what not, perhaps Leakage Currents, but in any case, putting the TV on a filter line too made a big change in SQ as well.
As an aside... I had the idea of re-using the AC Filter Box, and also plugging the UHD 4K Blu-Ray player into a filter line and found out we can't live without this, so looks like I also need to build us a new AC Filter box but for the video side too.
It's quite amazing how SMPSes and ground loops or leakage current can rob you both of SQ and Picture Quality. 😛
Looks like the iMac definitely needs to be on a filter line judging by the improvement in SQ I get this way.
Didn't find a proper place on either the main power strip in the AC Filter box, nor on a filter line for the DAC's new Linear Regulated PSU, but we felt putting it on a separate outlet is better for all SQ, including rapidity of transients.
Where we were rather shocked was also putting the TV on a filter line. In my setup, the iMac is linked so that it can mirror its screen onto the TV with a cable going into an HDMI port.
This is an avenue for ground plane pollution or what not, perhaps Leakage Currents, but in any case, putting the TV on a filter line too made a big change in SQ as well.
As an aside... I had the idea of re-using the AC Filter Box, and also plugging the UHD 4K Blu-Ray player into a filter line and found out we can't live without this, so looks like I also need to build us a new AC Filter box but for the video side too.
It's quite amazing how SMPSes and ground loops or leakage current can rob you both of SQ and Picture Quality. 😛
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