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Post by gtrgriff3 on Apr 16, 2019 8:58:33 GMT -7
I've had my Therapy for a long time, but just recently I've been using it more and I've found a tone that I REALLY love out of it... except this super high (like, 7K or higher) fizzy frequency that I get.
Bringing the treble down obviously attenuates it, but at the expense of some lower treble that I want to keep.
In an experiment, I slaved the amp so that I could put a parametric EQ between the head and SS power amp and found that a low pass at about 8.5-9K seems to do the job. I don't know the Q of the EQ so it's likely affecting frequencies lower than 8.5-9K, but that's what works.
I'm thinking maybe there are some tubes I can try or possibly a simple mod to kill some of that super high end.
I run the amp nearly wide open... gain and master close to all the way up. Bass is low and mids and treble around 1pm. The feel is fantastic, it responds perfectly to volume changes on the guitar, and there are infinite tones available without a single pedal in sight. I played almost all night at Saturday's gig and only stepped on a tube screamer once or twice.
Sorry if this has been covered before and I just can't find it. I looked for a couple of hours last night.
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Post by headshrinker (Marc) on Apr 16, 2019 9:04:25 GMT -7
What speaker are you using. You might try a speaker change along with the tube change. I wouldn't modify the amp.
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Post by premiumplus (Dave) on Apr 16, 2019 9:22:30 GMT -7
Welcome to the forum! I'm curious about the speaker too, but if it is a symptom that has just cropped up I would try swapping the two preamp tubes. Put V2 into V1 and vice versa, and see what happens. I'm sure you know that V1 is the first tube in the amp to see the guitar signal, so that may reveal some useful info. How old are your tubes?
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Post by gtrgriff3 on Apr 16, 2019 10:45:12 GMT -7
I'm sorry, I should have mentioned that this is through several different speakers. Some are better some are worse, but none solve it entirely. The darker speakers like my WGS Vet30 are better, but even in my G12-65s with the larger dust cap it is very apparent. And I often use a 1x12 Mojotone with a Celestion Lead 80, or a Matchless 2x12 with G12M and G12H combo.
Tubes are stock, which means 3-4 years old, but probably 30 hours in all that time. When I first got the amp I was underwhelmed and it didn't do what I was looking for at the time, so i let it sit in the studio for a couple of years.
I've only recently been back to it and that's just the last couple of weeks.
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Post by gtrgriff3 on Apr 16, 2019 10:46:36 GMT -7
I should probably also mention that I realize one man's harsh and fizzy is another man's cut through the mix. I don't think the amp is broken or performing sub-par by any means. This is just my personal preference.
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Post by gtrgriff3 on Apr 16, 2019 10:48:42 GMT -7
For tube options, are there any that are known to be a little darker? I tend to buy JJs simple because they are readily available and cost effective (I use 10-12 amps so it adds up.)
But if you all have experience with something that works particularly well, I'm all ears!
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Post by Ridgeback on Apr 16, 2019 12:11:33 GMT -7
If you have access to that many amps, I'd have a preamp and power tube rolling party. Just start pulling different (appropriate) tubes from your other amps until you find ones that solve the problem. The therapy can take several types of power tubes without rebiasing and preamp tubes are a free for all. Have some fun and let us know the results. I rolled a bunch of preamp tubes in mine when I first got it looking for the right gain profile. I have not yet tried power tubes but I have several very nice sets of old 6V6s that I'll get around to some day (maybe).
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Post by gtrgriff3 on Apr 16, 2019 12:44:42 GMT -7
Well see, that's just it... like I said they all have JJs in them, not much swapping to be done
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Post by Ridgeback on Apr 16, 2019 12:48:50 GMT -7
Tubes vary, even if they are the same brand. Good luck.
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Post by dcarver on Apr 16, 2019 13:55:10 GMT -7
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Post by headshrinker (Marc) on Apr 16, 2019 14:16:34 GMT -7
I personally don't like JJ 12AX7s. They have this upper mid peak that I don't like and may be what you are talking about. Elecroharmonix and Sovtec,which are essentially the same, are darker sounding, but maybe too dark.
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Post by daddyelmis (Greg) on Apr 16, 2019 14:50:30 GMT -7
Doc uses JJs for v1 and the 6v6s, and I still have the stock preamp tubes and I’m not hearing the fizzle - but as you correctly point out it’s subjective.
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Post by purpletele on Apr 16, 2019 15:05:19 GMT -7
Didn't Frank run KT66's or 88"s and love the tone with those tubes.
That might be an option
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Post by premiumplus (Dave) on Apr 16, 2019 15:08:46 GMT -7
I've had excellent results with KT77 output tubes in my Therapy.
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Post by helmi on Apr 16, 2019 16:32:09 GMT -7
Didn't Frank run KT66's or 88"s and love the tone with those tubes. I have Franks Therapy. It had 6v6's in it when I got it. I thought the therapy could use, 6l6, 6ca7, 6v6,, el34, and kt77. kt77's are the only ones I haven't tried, but plan to.
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Post by helmi on Apr 16, 2019 16:33:05 GMT -7
I've had excellent results with KT77 output tubes in my Therapy. Dave, tell us about the kt77 tone in the therapy?
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Post by daddyelmis (Greg) on Apr 16, 2019 16:58:08 GMT -7
I’ve run KT77s and EL34s in my therapy. For cleanish tone I really like the KT77s - big, sort of “muscular” 6L6 tone. I read somewhere the KT77 was like a 6L6 but “more,” and that’s a pretty good description.
The EL34s definitely bring the British, Marshally flavor. That’s what I’ve got in there now to provide some Brit tone alongside my ZPlus and Z28.
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Post by premiumplus (Dave) on Apr 16, 2019 19:10:37 GMT -7
I've had excellent results with KT77 output tubes in my Therapy. Dave, tell us about the kt77 tone in the therapy? Well, for me it gave the amp more presence and clarity in the high midrange and top end. I always felt like the Therapy was a little on the dark side and the KT77 swap cured that. They sound great clean but I really like the way they break up too. Great tubes. Every so often I'll put some good 6L6GC tubes in it and I end up putting the KT77 set back in. I've run a Celestion V30 in it quite a bit, and right now the Celestion Gold is in there. Open back Z 1x12 convertible cab.
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Post by purpletele on Apr 16, 2019 20:04:11 GMT -7
Such a nice amp! It will really be nice with an FX loop
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Post by markT on Apr 17, 2019 4:36:23 GMT -7
I would suggest trying some different tubes in V1.....
However, a new set of JJ 6L6’s may be in need and solve your problem. 3-4 years of heavy use in a cathode biased amp is a long time...
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