Hello,
I built the tubelab se about a year ago.
I have been noticing way more distortion at slightly high listening levels, and even at 'normal' levels lately. If I turn it down, it sounds great, but not quite loud enough.
Is there a valid reason for this, or is it most likely psychosomatic or my ears getting more in tune for that sort of thing.
It's bad, though. every solid bass hit becomes a flabby mess... (dono why, but flabby seems like the correct description)
Every build up where many instruments are playing becomes unrecognizable. (not truly unrecognizable, but the definition between tones is lost)
And for a slightly more technical description.. My volume control goes to 20. I used to be able to turn it up to 15 and it would be loud, and I used to think it sounded great at that level. Now I can't go past about 10 w/out noticing distortion.
Is it me or my machine?!?
thanks
I built the tubelab se about a year ago.
I have been noticing way more distortion at slightly high listening levels, and even at 'normal' levels lately. If I turn it down, it sounds great, but not quite loud enough.
Is there a valid reason for this, or is it most likely psychosomatic or my ears getting more in tune for that sort of thing.
It's bad, though. every solid bass hit becomes a flabby mess... (dono why, but flabby seems like the correct description)
Every build up where many instruments are playing becomes unrecognizable. (not truly unrecognizable, but the definition between tones is lost)
And for a slightly more technical description.. My volume control goes to 20. I used to be able to turn it up to 15 and it would be loud, and I used to think it sounded great at that level. Now I can't go past about 10 w/out noticing distortion.
Is it me or my machine?!?
thanks
The honeymoon is over. You have listened to your gear long enough to notice it's shortcomings. You will now spend eternity building and tweaking gear in attempts to achieve the perfect sound. Welcome to the club 
I'm partially kidding, something may have (or not) changed electrically, but the only way to tell is to use test equipment and take measurements. If you plan to stay in this hobby, get a Oscilloscope, and download a PC based spectrum analyzer. I use a program called "Visual Analyser" which does a good job for freeware. You will also need some 8ohm dummy loads and some misc connectors and cables to hook everything up.
Flabby bass and rolled-off highs are typical plagues of SE amplifiers that use no feedback. It effects many, but not all.
Have you changed your speaker placement? What kind of speakers are you running and in what sized room?
I'm partially kidding, something may have (or not) changed electrically, but the only way to tell is to use test equipment and take measurements. If you plan to stay in this hobby, get a Oscilloscope, and download a PC based spectrum analyzer. I use a program called "Visual Analyser" which does a good job for freeware. You will also need some 8ohm dummy loads and some misc connectors and cables to hook everything up.
Flabby bass and rolled-off highs are typical plagues of SE amplifiers that use no feedback. It effects many, but not all.
Have you changed your speaker placement? What kind of speakers are you running and in what sized room?
Have you repositioned either your speakers or your seating location?
Do you have an extra set of tubes? You could conceivably put on 1800 hours over the course of a year if you are playing six hours a day, six days a week. While I would hope a pair of ($$$) 300B should last more than a couple thousand hours, maybe not all of them do.
Do you have an extra set of tubes? You could conceivably put on 1800 hours over the course of a year if you are playing six hours a day, six days a week. While I would hope a pair of ($$$) 300B should last more than a couple thousand hours, maybe not all of them do.
"The honeymoon is over. You have listened to your gear long enough to notice it's shortcomings."
That is sort of what I figured, but it is SO OBVIOUS now that I hear it. I'd really think something is wrong w/ the amp, except that at lower levels it still sounds great. I did test all the common points.. the voltages are in line, the current is where it should be.
I guess the only way to fix this is to go deaf or spend some money on building a more powerful amp.
-I did try different output tubes. Same thing.. I haven't tried switching the input tubes.. I guess thats a possibility, but I truly doubt those have gone out.
That is sort of what I figured, but it is SO OBVIOUS now that I hear it. I'd really think something is wrong w/ the amp, except that at lower levels it still sounds great. I did test all the common points.. the voltages are in line, the current is where it should be.
I guess the only way to fix this is to go deaf or spend some money on building a more powerful amp.
-I did try different output tubes. Same thing.. I haven't tried switching the input tubes.. I guess thats a possibility, but I truly doubt those have gone out.
I do have a pair of high efficiency fostex speakers. I do have 2 subs, but I'm not crossing over b4 the amp. That was my next thought.
Unfortunately, that opens a new set of issues. There are some very mixed and heated opinions out there about crossovers.
I'd like to xover at bout 80hz b4 my amp. I dont even need to cross over as my music source has multiple outputs, and already one output goes to the subs. I just need to highpass filter the signal going to my amp.
I thought that would be easy, but after researching it, I need to figure out the resistance of my amp first which looks quite complex!
Maybe Mr Tubelab knows... I dont care if its perfect! I just want to cut off the low lows.
Unfortunately, that opens a new set of issues. There are some very mixed and heated opinions out there about crossovers.
I'd like to xover at bout 80hz b4 my amp. I dont even need to cross over as my music source has multiple outputs, and already one output goes to the subs. I just need to highpass filter the signal going to my amp.
I thought that would be easy, but after researching it, I need to figure out the resistance of my amp first which looks quite complex!
Maybe Mr Tubelab knows... I dont care if its perfect! I just want to cut off the low lows.
My feeling is that a vacuum tube amplifier doesn't "like" to be presented with a passive crossover. You'll end up with a high impedance load beyond the crossover frequency, and vacuum tubes don't always handle high impedance loads gracefully. They would rather deal with a dead short.
If you want to bi-amp, I think you would be better off using an active crossover and filter out the lows before they even get into the amp. If you're really lazy, you might try making a simple RC filter on the input side of the Tubelab SE by adding a capacitor just upstream of R8. It'll only be first order, but maybe it'll work well enough for your purposes.
If you want to bi-amp, I think you would be better off using an active crossover and filter out the lows before they even get into the amp. If you're really lazy, you might try making a simple RC filter on the input side of the Tubelab SE by adding a capacitor just upstream of R8. It'll only be first order, but maybe it'll work well enough for your purposes.
My history w/ electronics comes from building a HUGE analog modular synthesizer, and I have a LOT of filters in that thing. Maybe I'll try running my audio through one of those, as a test. I've got just about every layout of active filter available. They were designed to color the sound, but only when Q is turned up. I've never done any tests to see how well they can cleanly filter a signal.
My initial idea was to make a simple first order passive filter for the amp, but if you say there could be issues w/ that, I guess I'll skip past that idea.
Ive even got spare PCB's for synth filters I've made sitting in a box..... I guess I'll do some testing to see how well they filter w/out changing the rest of the signal.
(AH shoot.. all that stuff is mono.. I guess i can still test it, and just build 2 channels worth if I need)
My initial idea was to make a simple first order passive filter for the amp, but if you say there could be issues w/ that, I guess I'll skip past that idea.
Ive even got spare PCB's for synth filters I've made sitting in a box..... I guess I'll do some testing to see how well they filter w/out changing the rest of the signal.
(AH shoot.. all that stuff is mono.. I guess i can still test it, and just build 2 channels worth if I need)
wicked1 said:
Shouldn't be any problems using a filter on the input signal to the amp. I'd just shy away from using a passive speaker crossover on the output side. I'm sure others will disagree, and cite particular installations where they have biamped into passive crossovers for years without issue.
Thanks!
Ty, do you know, is it really important to figure out the resistance of the amp, if I want to make a passive input filter, or is there a general figure I could use for a 300b se amp?
Like I siad, it doesn't need to be perfect. I can adjust the subs to fit. I'd like it at about 80hz +/- 20hz
Ty, do you know, is it really important to figure out the resistance of the amp, if I want to make a passive input filter, or is there a general figure I could use for a 300b se amp?
Like I siad, it doesn't need to be perfect. I can adjust the subs to fit. I'd like it at about 80hz +/- 20hz
I believe for a high pass filter, Fc = 1 / (2*pi*R*C). R is shown as 121K on the Tubelab schematic. For simplicity sake, I'll assume you do not have an input volume pot. Solving for C in your case gives C = 1 / (2*pi*121000*80) = 1.64E-8, or 0.016 uF.
Something like one of these might work. Just stick it in series with the input.
http://www.mouser.com/Search/ProductDetail.aspx?qs=0MjLoSXK18MdCixfzed3qQ==
http://www.mouser.com/Search/ProductDetail.aspx?qs=BgLWnqjd5YJLpbvhjUrgGA==
Somebody correct my math for me...
Something like one of these might work. Just stick it in series with the input.
http://www.mouser.com/Search/ProductDetail.aspx?qs=0MjLoSXK18MdCixfzed3qQ==
http://www.mouser.com/Search/ProductDetail.aspx?qs=BgLWnqjd5YJLpbvhjUrgGA==
Somebody correct my math for me...
A high pass before the amplifier would be best. Filtering the low frequency out of the music will give your amplifier some more headroom before clipping. That's because the high frequencies ride on the low ones, like AM.
As Ty recommended, a simple coupling cap on the input of the amp will do the job with excellent fidelity. Since it's a first order filter, I'd recommend setting cutoff to 100Hz since the slope is not steep.
I wouldn't recommend a synthesizer filter. Synthesizers typically use a low-pass VCF. You will need a high pass that isn't voltage controlled. Fidelity usually is not of concern in the world of synthesizers (there built to sound cool, not for sound reproduction).
As Ty recommended, a simple coupling cap on the input of the amp will do the job with excellent fidelity. Since it's a first order filter, I'd recommend setting cutoff to 100Hz since the slope is not steep.
I wouldn't recommend a synthesizer filter. Synthesizers typically use a low-pass VCF. You will need a high pass that isn't voltage controlled. Fidelity usually is not of concern in the world of synthesizers (there built to sound cool, not for sound reproduction).
"R is shown as 121K on the Tubelab schematic."
OH! I thought I had to calculate the resistance of the amp itself, from input to to output of the transformers. Really, I think the pages I was reading were talking about doing that, and it didn't sound easy. They were feeding test tones, and using the frequency of the test signal in their calculations. I didn't put a lot of though into it, but from skimming the pages, it seemed overly complex.
However, like I said, I don't care if it's perfect. I just want to cut some of the lows.
SO, to the workbench!
Thanks for all of your help.
OH! I thought I had to calculate the resistance of the amp itself, from input to to output of the transformers. Really, I think the pages I was reading were talking about doing that, and it didn't sound easy. They were feeding test tones, and using the frequency of the test signal in their calculations. I didn't put a lot of though into it, but from skimming the pages, it seemed overly complex.
However, like I said, I don't care if it's perfect. I just want to cut some of the lows.
SO, to the workbench!
Thanks for all of your help.
The input impedance of the grid is very large - I'm certain it is safe to ignore it for all practical purposes. Your source is effectively working into the grid resistor - R8 (and R19), or 121K in this case.
You'll need a non-polarized capacitor of some sort, most likely a film type. I suggested a Vishay Sprague Orange Drop - they get good press. You don't really need the 200V rating here, but I don't think they come in anything less. Generally, people seem to say the 716P is a better cap than the 715P. I'll remain silent on the issue, though I will say I've used the 715P in my own stuff.
You could also use any sort of exotic fancy stuff which pleases you as well. The 0.015 uF part should give a 87 Hz corner frequency, which ought to be close enough.
You'll need a non-polarized capacitor of some sort, most likely a film type. I suggested a Vishay Sprague Orange Drop - they get good press. You don't really need the 200V rating here, but I don't think they come in anything less. Generally, people seem to say the 716P is a better cap than the 715P. I'll remain silent on the issue, though I will say I've used the 715P in my own stuff.
You could also use any sort of exotic fancy stuff which pleases you as well. The 0.015 uF part should give a 87 Hz corner frequency, which ought to be close enough.
One channell or both?
Hey.
This degradation... is it one channell or both.. how is your rectifier?
What brand of 300b? My friend kept an eye on his 300b's with his AVO and found they degraded quite quickly.. which is another reason why I ditched my plans to build a pse version.. 300'bs too expensive and somewhat unreliable.. yes I know they sound great but maybe your tubes are calling it a day... dont suppose you have a few lying around to test?
Nick
Hey.
This degradation... is it one channell or both.. how is your rectifier?
What brand of 300b? My friend kept an eye on his 300b's with his AVO and found they degraded quite quickly.. which is another reason why I ditched my plans to build a pse version.. 300'bs too expensive and somewhat unreliable.. yes I know they sound great but maybe your tubes are calling it a day... dont suppose you have a few lying around to test?
Nick
So, I did put a capacitor on the input, and WOW.. It has made a HUGE difference. I haven't changed anything else, w/ my subs or anything..
From my listening position, I hear just as much tone, like, everything just as it should be, but that distortion is gone! (makes sense.. the bass still comes from the subs, but isn't being pushed through my tube amp now)
I'm using a Zune as my audio source. (it has a GREAT DAC, as far as most MP3 players go.. better than Ipods, that's for sure)
I started noticing this problem after an update to the zune. Maybe they changed something that is letting all sorts of super low frequency stuff through, I dono... but this has certainly helped.
From my listening position, I hear just as much tone, like, everything just as it should be, but that distortion is gone! (makes sense.. the bass still comes from the subs, but isn't being pushed through my tube amp now)
I'm using a Zune as my audio source. (it has a GREAT DAC, as far as most MP3 players go.. better than Ipods, that's for sure)
I started noticing this problem after an update to the zune. Maybe they changed something that is letting all sorts of super low frequency stuff through, I dono... but this has certainly helped.
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