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Post by ldm on Sept 5, 2010 6:04:44 GMT -5
Kt88s came and I installed the pair and then broke off the base! Its the center piece with the guide  I installed anyway and fired up to bias. It seems to still work,but I could not bias as low as I needed to. 69ma is as low as I could go. I must be doing something wrong. I did play with it a little and I do like the sound I'm getting. 1st off it lost the farting out I was getting with the EL34bs. Tighten up the bottom bigtime. I'm just kinda pizz about this whole thing. $154 for tubes to have the base break off 2 mins after I got em,can't get a good enough bias reading,and I've own this amp about 6 months and having to retube the whole thing. If anybody has a ideal about whats going on with the bias ,please let me know. What were these tubes rated at? Did you check the resistor to make sure it was the proper value (with and ohm meter)? What brand of tubes did you buy? I have had locator pins break easily but not too often. As long as you line-up the tube properly in the socket you are fine, just make sure you line it up properly or you will cause damage to your amp! |
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Post by MetalHeart on Sept 5, 2010 9:35:50 GMT -5
Tubes are Gold Lion KT88s rated at 31 ma. I'm buying another muti-meter today( I'm starting to think its malfunctioning and start over again.(new resistor)
Sorry if I seem to hi-jack thread.
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Post by MetalHeart on Sept 5, 2010 14:23:45 GMT -5
Finally things coming together. I got a new multi-meter and soldiered a new resistor in place and I got to bias down to about 51 ma .
Letting tubes cool down before putting chassis in headbox and then I'm going to fire it up.
Yesterday was for sh1t,I mean I left the iron plugged in all night! The room is covered in foam and could have went up in smoke in no time.
What little I heard yesterday sounded alot better. Now that its bias proper it should sound better . I also installed a new JJ803 in V3.
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Post by MetalHeart on Sept 5, 2010 16:55:52 GMT -5
Love these KT88s ;D Nice and full. Somebody else said it but the KT88s seem a perfect match for SuperComp(Nitro). I'm no expert but I can tell a huge difference between the 2 sets of tubes. I just wish I had the money for a full quad  but at half power mode this amp is punishing. |
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Post by bubbastain on Sept 5, 2010 17:32:36 GMT -5
Cool. Glad things are working better now. Is 51 as low as you could get it? If so, when you do get another set you could just ask for a some colder ones. I remember reading when you first got you Super Comp and how much you loved it. Seems like your stock tubes went south really quick. What did the 803 do to the sound? Thats the PI right? I'm selling my Nitro(I love the tone) when my Mako preamp get here. IF for some strange reason the Mak4 doesn't do it for me(i doubt) I'll be getting a Super Comp to replace the Nitro. Have you done any clips with your amp?
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Post by MetalHeart on Sept 6, 2010 9:34:29 GMT -5
Cool. Glad things are working better now. Is 51 as low as you could get it? If so, when you do get another set you could just ask for a some colder ones. I remember reading when you first got you Super Comp and how much you loved it. Seems like your stock tubes went south really quick. What did the 803 do to the sound? Thats the PI right? I'm selling my Nitro(I love the tone) when my Mako preamp get here. IF for some strange reason the Mak4 doesn't do it for me(i doubt) I'll be getting a Super Comp to replace the Nitro. Have you done any clips with your amp? No,I went as low as 49 but stop. I wanted to get in the target range before something else went wrong I did love the sound from my amp when I 1st got it no doubt. But not long after, I kept hearing this annoying woofing sound. Like my speakers were farting out. I tried to dial it out but with no luck. Changing pre-amp tubes help some but then I had problems with volume going up and down so I had to replace the power tubes. Here's where I think I went wrong with the mod,1st I did not have a proper working multi-meter,2nd I don't think I was getting a good enough connection between the 2 resistors. But one thing I did do was after I remove the 47k resistor I installed the EL34bs one last time and bias up with no problems. Rated at 24 ma and the same tubes came with the amp. I played thru and again I'm sure that was my problem  That same woofen sound,muddy etc.  My two sons both agreed that before the sound was way to muddy . I don;t have any clips or I would have let you guys hear what I'm talking about. In the future when I have extra $cash I would like to try some different EL34s SEDS or Mullards but for now we are happy with the 88s. |
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Post by DonaldDemon on Oct 20, 2010 23:04:22 GMT -5
Any idea what resistor value to get if you need to get the bias lower? I can't get my Pro Mod below 58ma and I think that's too hot because it sounds a little muddy now. Do I need to completely replace the resistor?
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Post by racerevlon on Oct 24, 2010 19:25:31 GMT -5
Drew--thanks for posting this! It is truly appreciated--I'm glad you consulted Scott on this as well. If I decide to "KT88" my Nitro, I'll do before/after clips and post them.
Cheers,
Race
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Post by bubbastain on Oct 25, 2010 1:26:10 GMT -5
Ahh, you found it. I was just about to forward this thread to you. Very easy to do. I did it to my Competition. I was running KT77s and I loved it. Now I'm running KT88s and I love it still. I haven't tried EL34s in my Comp. but I might sometime down the road. There is enough sweep in the bias pot now that all I have to do is get a "warm" set of EL34s and I'll be able to bias them right up without having to undo the mod. Glad your liking the Nitro.
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Post by DonaldDemon on Oct 25, 2010 8:05:14 GMT -5
I talked to Scott and he said to get a lower range the resistor has to be completely replaced. Anyone else do this or is it always people changing from 34s to 88s?
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but at half power mode this amp is punishing.
