Treble is playing bass?!

[Vinyl and Tube Dude]

Long story short: Changed my tube preamplifier out with an Audiolab 8200Q transistor with variable gain which is now paired with my SE KT88 14 watt amp and Klipsch RB61 and B & W 608 sub. I have some LPs with heavy bass that I used to play loud with deep bass and clear treble. I have only had the pre amp for 1 ½ month now and have first played one of those LPs loud today. But now I cannot play loud without the treble distorts pretty much when the heavy bass kicks in. I have checked the LPs’ through my Grado RS1 through the amplifier headphone jack. I turned the volume up high for a moment (much more than normal listening levels) and there were no distortion, so I don’t think it's the cartridge that’s creates resonance. I have tested the Klipsch with LP music with very high pure tones and little bass and played it loud and it was an absolutely clean treble. So the tweeters are not blown. The new preamplifier is sonically superior the old one: Better resolution, faster and deeper bass and a wider stereo perspective. So you could say that my tube power amp had more potential than the old preamp could deliver. Is it just so that my Klipsch cannot deliver what the pre/ amplifier are sending out, that signal are "too good" for the speakers? If so, not to worry, I will upgrade the speakers in the near future anyway. If not, what just happened since the treble obviously start playing bass? At normal volume these bass heavy LP’s sounds just fine. I've tried this with different gain setting with the same result.

[Alec124c41]

The tweeters should be fed through a capacitor, to limit the bass. It sounds like they need to be replaced.

Cheers,
Alec

[Vinyl and Tube Dude]

Short lifetime for the capacitors The speaker is only 3 years old. But then again, it's not the most expencive ones. Well, as long as it's not the amplifier, then I'll just aviod bassheavy tracks untill I buy new and better speakers. Next time I'll go for 3 way with 10'' woofers. I can that see the 6,5'' in the RB61 is working mutch harder with the new pre amp than with the old one. Not sure they were build for that
Buy the way, I have fallen in love with these babies


You can buy them in Denmark now

[duficity]

Have you checked the input voltage requirement for your tube amp to make sure your preamp output is not overdriving the amp input? that would cause the distortion you are experiencing. You say your preamp has a variable output. If it doesnt distort at low volume, that could be the problem.

[Vinyl and Tube Dude]

Have you checked the input voltage requirement for your tube amp to make sure your preamp output is not overdriving the amp input? that would cause the distortion you are experiencing. You say your preamp has a variable output. If it doesnt distort at low volume, that could be the problem.

Well.. you just burst my bubble of denial there ´cos I know you're right. The pre is running a 3 db gain, even at 6 db gain the sound starts to compress at slightly higher volume. I was just not ready to face the truth: I have to change my power amp too

[Vinyl and Tube Dude]

I found the specs on my KT 88 tube amp
2x14 or 2x16w in 4 or 8 ohm.
20 Hz to 70 Kz. + /- 0,6 db.
Input impedance 47 Kohm.
sensitivity 07 volt

The specs on my pre amplifier is:
Frequency Response: 10 Hz-20 kHz±0.2 dB; 1Hz-75 kHz -3dB
Total Harmonic Distortion & Noise: Less than 0.007% ref7.7V rms, 20Hz - 20 kHz
Channel Balance: Within 1dB
Channel Separation: Better than100dB@1 kHz any input, any setting
Pre-amp Output: Max. Output>7.7V RMS (20dBm); Output impedance 75Ω

It really does not make sense to me. Is there any one who can read from the specs if the pre and power is a totally mismatch?
If so, I give up on tubes alltogether (must find a new user name then) and go for a new transistor power amp. Then I must wait with speaker upgrade then. I must have the amp source to work first.

[Alec124c41]

Check the capacitors in the speaker crossovers. They are easy to replace.

Cheers,
Alec

[vexorgtr]

Alec's theory of crossover caps failing is a possibility, and also the "too high of input" therory is good too.

I have lots of tube amps here, but they are for guitars.... when we get distortions out of them, it's because we put the input signal too high... the higher we put it the more it "Cranks"... and we call it Rock and Roll... although it's a nemesis of high fi.

Tube amps usually have more gusto for driving speakers than do transistors, but I have NOTHING bad to say about the big classic solid state monster amps.

[duficity]

Your preamp will put out a certain voltage. Your amp will accept that voltage and amplify it and requires a certain amount to meet its output specs. you dont list your amplifiers input sensitivity. If your preamp's output is greater than your amp's input sensitivity, you could be overdriving your amp, thereby causing distortion. see if you can find the input sensitivity of your amp. If it is .07 vrms and your preamp is putting out 7.7vrms, then it seems to be a mismatch. are you sure you are reading the right specs?

[Tako]

I understand that the problem did not manifest itself immediately after changing to the new pre-amp? And there is no distortion through the Audiolab's headphone output OR when connecting a headphone amp to its pre-out?

If so, maybe one of the tubes in your power amp is on its last legs?

A voltage mismatch between pre and power amp seems highly unlikely, and with your Audiolab you can easily check it by setting the gain to "0dB" effectively turning it into a passive pre-amp, if it IS a voltage mismatch the distortion should dissappear.

Edit: When I did some googling to find if the Audiolab still had the "0dB" setting (I owned the same pre-amp under the TagMclaren brand) This: viewtopic.php?f=85&t=45832 was one of my first hits. I'm confused now: Did the distortion problems show up recently, or did they also manifest with your old tube pre as described in your old thread?
Sounds to me like your power amp has a problem, not your pre-amp. (Or your loudspeakers)

[Vinyl and Tube Dude]

Thank's for the answers. First about the tube amp / Audiolab specs. It's all I can find on it and I did a "copy/paste". My tube amp /pre is build by a small danish firm and the problem is, I think, that is a kind of a "feinsmecker product" meaning that the original pre amp and power amp is tuned in to each other and supposed to be used to listning sessions with certan brands of speakers. I know most of the customers use Audio Note /Snell speakers. So I think the amp is not very flexible with other gear and not meant to be used with backgrown music and movies, like I allso used my hi-fi for. I started to get drop outs in one channel at low volume when I got the Klipsch (95 db 8 ohm)and they just could'nt fix it and had no problems with drop outs on their tests.
About the the distortion problems: No problems with the old preamp and no problems with rock, jazz, pop etc. But when I put on some electronic music with heavy bassline and crank up the volume, then you have the problem with the new pre amp/ power amp. I could play heavy bassline with the old pre amp, but it was not as deep as it is now. I have just tried with 0 gain. The distortion is mutch lower at higher volumue, but off cause I can stress the speaker to distort in the tweeter. So I quess it is a cobination of high input and offcause speakers who reatch thier limtis? So the bottom line is, that I think the amp and speakers is not just suited for a certain kind of music, and I do love a good bassline sometimes. This year I'm planning speaker and subwoofer upgrade and next year TT upgrade. But I'm close to start with the power amp instead. Because i have had the tubes for 3 years now and been fighting with various problems for the last 2. So maybe it's just time to face the fact that is was not the right gear for me and sell it.

[duficity]

You only have 14 watts of power, Are you running your sub off that amp, or does it have its own amplifier. If so, use the crossover on the sub to remove deep bass notes from the main speaker and amp. Your amp is not made to cleanly produce deep bass at high volume.

[Vinyl and Tube Dude]

The sub is an active one. Now that I'm totally aware of the power amp's "bass problem", I only choose music whith moderate bass. Yesterday I listened to Budos Band on LP as loud as I used to with no problems. No doubt that my new pre amp is feedning a signal with deeper bass than my tube power can handle. I'll blow the budget next month and buy a new power amp. At least I can try and sell my pre / power tubes since they work fine together.

[thespirit3]

Pre-amp Output: Max. Output>7.7V RMS

7.7V RMS? For a pre-amp? That seems crazily high to me. I think most line level outs are 1 or 2V peak to peak, certainly not ~8V RMS. You mention the pre-amp was part of a matching pre/power combo; it seems likely the higher output of the pre was designed to lower overall SNR. Even with the gain of the pre at modest levels you'll still be clipping on transients although (I'm guessing) a tube amp will be driven into less noticeable compression rather than the harsh distortion you'd associate with a solid state amp. Remember, it's generally the bass that carries the power, during powerful bass passages your amplifier will be driven to the limits, the treble distortion is less likely "bass making its way to the tweeters" (if this was the case they'd fail within minutes if not seconds) but rather your poor tube amp begging for mercy whilst being pounded to within an inch of it's life by a ~8V beefcake wielding a baseball bat.

I'd suggest perhaps changing the pre or borrowing an integrated amp with a pre-out just to test driving the tube amp at 'normal' levels.

Of course, I may have misunderstood the situation, read the specs incorrectly or just be plan wrong. I'm sure someone more knowledgeable than myself can confirm/deny my concerns over input/output levels