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Post by rocknrolla on Jul 12, 2011 10:51:24 GMT -5
I'm having a strange problem with my KT88 Nitro. After it warms up (about 5 minutes into playing) it starts making strange noises on both channels. It sounds just like if you were to brush up against a microphone, like a swishy/crackly sound. So far I have switched guitars, inst. cable, speaker cable, and preamp tubes. I don't have a bias meter or spare power tubes yet but I switched it to 1/2 power and swapped the inner tubes with the outer tubes with no change. I have also engaged and disengaged the loop with and without a jumper cable connecting the send and return. I'm going to take it in to a tech but before I do that I thought I'd ask if anyone had a similar problem of any advise. Thanks guys!
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Post by Lewis on Jul 12, 2011 14:16:15 GMT -5
Have you tried swapping out preamp tubes?
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Post by rocknrolla on Jul 12, 2011 15:22:04 GMT -5
Yup.
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Post by splawndude on Jul 12, 2011 16:32:02 GMT -5
have you tried contacting Scott?
if you take it to a tech - i suggest a Splawn Auth Dealer
FYI - i had a preamp tube pin arc one time on a different amp and it make that sound
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Post by stompboxfreak1972 on Jul 12, 2011 16:47:36 GMT -5
Im sure its minor but I know how annoying those things can be. Email scott first. He has saved me a lot of time just via email.
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Post by rocknrolla on Jul 12, 2011 17:18:04 GMT -5
Yeah, I'm sure it's a simple fix. I'll have to call Scott. He seems reluctant to answer his emails from me on this subject.
I wonder if having the bias too hot may cause this.
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Post by banenis on Jul 12, 2011 21:21:03 GMT -5
Have you tried calling? I'm sure they get a bazillions emails every day. But when you call, somebody answers the phone.
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Post by rocknrolla on Jul 13, 2011 8:04:23 GMT -5
Have you tried calling? I'm sure they get a bazillions emails every day. But when you call, somebody answers the phone. Not yet. It's hard for me to get away from work long enough during the day. |
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Post by snappinnecks on Jul 13, 2011 8:21:31 GMT -5
Power tubes do that when they are on the verge of going nuclear. I had some KT77s in my first Nitro that did that before a meltdown and blown fuse.
I would try a new quad of tubes and bias them on the lower side of the recommended bias range. You can also try biasing by ear (I highly recommend this, but be careful). When I say bias by ear I mean bias with a Weber or TAD meter to the recommended range (50MA I think on KT88s). Then plug your guitar in and start doing some palm muted riffing. If the tone is more round and loose then back the bias off a bit until you get that tight woody tone we all love. If the tone is really fizzy and less reactive then crank the bias up a bit. Use half turns on the bias adjustment screw as you are setting your preferred tone. I have found that the bias range on say a set of tubes rated at 32 and say a set rated at 25 biased the same will sound/react different in the same amp. Thus biasing by ear will help remedy the difference.
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Post by rocknrolla on Jul 13, 2011 9:39:38 GMT -5
Thanks for the great info. I think before I go and pay a tech to tell me I have bad tubes I'll just replace them myself. KT88's are f@#$ing expensive!
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Post by splawndude on Jul 13, 2011 12:24:33 GMT -5
I know Scott is pretty busy but calling is always an option.
you can also email Josh. He often answers the phone anyway. josh@splawnguitars.com
what snappingnecks recommended is pretty good - I would only caution to not play your amp with the probe connected - you can fry the resistor in the probe (at least in the cheaper ones).
biasing your amp is always a good idea.
i know you did this but make sure your preamp tubes are seated real well and maybe spray some contact cleaner on all you tube pins.
if it still makes this noise after doing these things - then it is time to consider taking it to a tech.
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Post by rocknrolla on Jul 13, 2011 13:22:54 GMT -5
I'm ordering a bias probe from Bob at Eurotubes. Trying to decide if I want to get his JJ's or go with the Ruby STR's. I'm sure anything will be better than the crappy Sovteks in there now. I'll start from scratch again tonight. New pre's, cables, contact cleaner, etc, and see what happens. Still noisy=tubes and a bias. Still noisy after that=tech.
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Post by splawndude on Jul 13, 2011 16:46:05 GMT -5
I got my probe from Bob and it died pretty quick. Granted I was playing thru the amp while the probe was installed. JJs are pretty good bet but I've heard some good things about those STRs. If you want some other sources for tubes I highly recommend www.dougstubes.com and www.valvequeen.comAlso - there is a biasing tutorial in the FAQ section if you need any help with that. |
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Post by stompboxfreak1972 on Jul 13, 2011 19:47:51 GMT -5
Laura aka the valve queen recommended Rubystrs for me and I really like them in the Nitro. Get a Ruby ac5 for v1 and thank Laura for that also.
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Post by rocknrolla on Jul 14, 2011 0:34:49 GMT -5
I've never tried Ruby pre's before. I have JJ's, Mesa branded JJ's, Sovteks, and am currently running all Tung Sol's. I'll give the AC5+ a shot in V1.
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