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Highs

I've seen a lot of posts asking how to get bass, or what components effect bass in a se tube amp, but what should I be looking at if I think highs are lacking?

I just finished a tubelab se 300b amp, and it sounds really good, but I think some highs are missing. I don't hear any silibance in vocals, and cymbals don't have the 'shimmer' in the decay.

My comparison is a 6v6 PP amp I restored in which my initial impression was that the highs were exaggerated. I've since pulled out my solid state amp, and it's right in the middle of the two, so I'd say maybe the 6v6 was exaggerated, and this new amp is muted in the highs.

The bass is definitely better in this amp. I HAD to use a sub w/ the 6v6, and other than a little bit of highs missing in the tubelab amp, it's perfect w/out the sub.

So, to wrap this up, I'm using cheap chinese 300B tubes, some fairly nice Angela poly/foil caps in the signal path, and O'Netics output tx's. My source for music for this testing is an mp3 player.

Any idea what components I should check out first when trying to get more high frequency??

thanks!
 

kevinkr

Administrator
Paid Member
First figure out whether or not you actually have flat frequency response out to 20kHz or so - once you know that then you will be able to determine whether or not a real issue exists.

What sort of test equipment do you have?

You might just find that your other two amplifiers are artificially emphasizing the highs and this one is not. Hard to tell though until you know whether or not the amplifier is at least electrically flat.

Should you find that the amplifier is in fact rolling off, then you can determine whether or not it is the output transformer, choice of coupling cap (some are quite inductive) or a mistake somewhere else.

FWIW I have found paper caps to be somewhat soft sounding in the highs and now use teflon almost exclusively for coupling - and the cause was not obvious in swept frequency response measurements out to 20kHz, but I did not investigate further.
 
I've got a synthesizer which will make whatever sort of waveform I want at whatever frequency I want.
I've also got a scope. That might be all I need to do some testing. It will definitely show me distortion, but the scope is old and inaccurate (I mainly use it to check waveforms, or check for obvious problems when building my synth, and it's good enough for that).
I'm not sure if I'll be able to notice subtle differences in level. If the highs drop off sharply, I'll certainly be able to see that.

Hmm.. guess I'll do some tests tonight.

I'm guessing I just feed it a saw or square wave, then go up through the frequencies and see if I loose some gain.
If there is a better way to test w/ the equipment I've got, let me know.

thanks!
 
At this time, I'm just using the volume control from my MP3 player. I do have a "blue velvet" pot, but Im not sure of the value. It's downstairs on my workbench right now, not hooked up for these tests. I'll check it out before I build my case, but that isn't the issue at the moment.

To be honest, I think i just got used to the exaggerated highs from the 6v6 amp Ive been using, so now these sound muted. I listed to some new music that I hadn't been playing for weeks on the 6v6 amp, and it sounds great. the music I had been playing a lot on the 6v6 sounds muffled, but... thats probably just mental. I'll try to do some tests tonight to get the facts.

thanks!!!!!!

Also, and now this is probably the couple of beers I had at lunch loosening me up to say this, but I've got much respect for you. I think I read somewhere that you got your degrees later in life, and just the fact that you're into music and rockin', and you hold down a real job and also have time to do this tubelab stuff amazes me. My biggest problem in life is motivation, and I know you must have a lot of it (or figured out how to manage the natural human tendency to be lazy) to keep up with all the things you are doing. It's definitely something for people like me to try to live up to.
Thanks for all your help!
 
I've got much respect for you. I think I read somewhere that you got your degrees later in life

Thanks. Yes, I finally started college when I was 37 years old. Finished my masters degree at 49. The college professors thought I was crazy for tinkering with tubes. One of them found me an old tube manual that had been lying around since the '60's.

My biggest problem in life is motivation, and I know you must have a lot of it (or figured out how to manage the natural human tendency to be lazy)

We all have our bouts with laziness, maybe I just win a few more of them than the average guy. The events of today have a way of instilling the desire to chug a beer and watch some stupid TV. I walked into work today (the same job that I have worked at for 35 years). At first I read an email concerning the break up of the company. Then I saw 350 of my friends and coworkers laid off. What do you think that does to your motivation!
 
. I walked into work today (the same job that I have worked at for 35 years). At first I read an email concerning the break up of the company. Then I saw 350 of my friends and coworkers laid off. What do you think that does to your motivation!

Whoa. That's a reality check there. I hear the US is undergoing tough times at the moment; sincere wishes for you and any other tube-heads who are in the gun...

Back on topic- My 6B4G SE amp initially sounds muted in the highs compared to my PP efforts. I'm convinced that it is due to the harmonic distortion profile rather than limitations of the parts. My hearing only goes out to 17KHz (only 29 but used to be into loud dance music!) but the SE sound is different, the treble is definitely there but it is gentler and non-fatiguing somehow??
 

kevinkr

Administrator
Paid Member
tubelab.com said:

<snip>
We all have our bouts with laziness, maybe I just win a few more of them than the average guy. The events of today have a way of instilling the desire to chug a beer and watch some stupid TV. I walked into work today (the same job that I have worked at for 35 years). At first I read an email concerning the break up of the company. Then I saw 350 of my friends and coworkers laid off. What do you think that does to your motivation!

I can relate to that, my employer, a large ATE company laid off several hundred workers a few weeks ago in order to remain competitive. Several of my friends were amongst the not so lucky. My last ATE company went bankrupt two days after Christmas of 2006 and I was in that last wave having watched the company shrink to less than a 1/4 of the size when I got there. Very few cradle to grave jobs left in this country.. I'm impressed you "survived" 35yrs so far in one place, not sure I'd want or be able to.. ;)