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Post by myles on Dec 6, 2005 9:48:00 GMT -7
I have done a bit of experimentation by changing the bias on the Delta 88. I looked at the data sheets for the KT88S, SC, and SV. These tubes are very strong, stronger than any 6550 as an example. These tubes are rated at 50 watts on the plates and 8 watts on Grid 2 (screen). The book design spec allows for 59 watts (this is not a typo) per tube in class A/B. On a Marshall Major we easily get over 120 watts per duet or 250 or so watts out of the quad in the amp. The plate voltage max is 800 and the screens are rated at 600 volts. In a typical Z Delta 88 with about 500 plate volts, 50% idle dissapation setting would be 50mA per tube, or almost two times what the amps may be set at from the factory. This would be general accepted spec for a KT88S, SC, or SV in this application. If you reset the bias to 50mA you will notice quite a bit more clean headroom and overall output. The amp will be a "different" amp in many regards and give any "100 watt Marshall type amp" a run for it's money to say the least. The Delta 88 will also perform better with any pedals than your typical cascade gain amp such as the Marshall, Mesa, Bogner, etc., to many folks ears. This amp is quite a monster when unleashed. I do not know if this may void any type of warranty so you may want to check with the good Doctor first (the tubes would be warrantied by the way if they are the stock GT tubes). The data sheet on the output tube used in the Delta 88 can be downloaded or viewed at: www.guitaramplifierblueprinting.com/Tube/KT88S.pdf
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Post by myles on Dec 6, 2005 11:37:28 GMT -7
On Harmony Central I saw and replied to this post:
The Delta 88 used to have less clean headroom than the KT-45 (which had as much or close to a Fender Twin ... while still being able to also do the Vox AC-50 tones and Hiwatt tones) with the factory Delta 88 bias. Now you will find it has even more clean headroom than a KT-45 and more than a Marshall 100 watter 1959 but also loves pedals even more due to the pentode front end and it also utilizes an ultra linear output section which is not the case on the KT-45. I measured well over 100 watts in these amps. They are more defined and articulate than the Marshall as there is not as much in the signal path ... only ONE preamp tube before you hit the phase inverter ... and not a lot of "pots" to pass signal through .... only bass and treble ... no presence or mid control and no cascading gain topology. Yet, if you want more front end gain just jack up the two tone controls and drop down the volume (sort of like a master volume amp).
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Post by billyguitar on Dec 6, 2005 14:09:06 GMT -7
That probably explains why when I tried out a new Delta 88 in the store it didn't seem to ever be clean.
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Post by myles on Dec 6, 2005 16:29:59 GMT -7
That probably explains why when I tried out a new Delta 88 in the store it didn't seem to ever be clean. My Delta 88 was biased at a point where there was a lot of crossover notch distortion. This is not bad actually. On Marshall amps it is a prime characteristic of their tone and folks that run them too hot will find them sort of sterile. The Delta 88 really responds nicely to bias changes, much more so than many other amps. This is a very cool "tuning tool" or feature. Take a guy like Michael Burks: At times he runs TWO of these monsters and a MAZ Sr to boot. In smaller blues clubs he would blast the ashtrays off of tables that still allow ashtrays on tables at any setting other than dead low. I have been told he runs his amps with the volume below 9:00. Well, in this case having that crunch at rational levels could be "just what the Doctor ordered", or in this case what Michael and his manager Tim wanted. By the way, Tim is also a Doctor but the MD type. So a pair of these were built by the Doc for the Doc and Mr. Burks and they work great for his hard blues application. So, here we have an amp with tremendous range all at the twist of that little bias pot. The fact that those tone controls can also vary the front end drive and that the EF86 front end loves pedals more than most any other amp is just more icing on the cake. Oh yes .... before somebody shouts ERROR .... those KT-45 panels on Michael's Delta 88's are there because the Delta panels were not available yet .... these may have been the first two of these. Collectors items! Sort of like the first Stingray or RxES with the old Rx panels!
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Post by Jim Fairbairn on Dec 7, 2005 6:58:42 GMT -7
Speaking of Michael Burks, I've tried to find information on the Celestion G12H100 which Michael uses in his cabs. Does anyone have any info or links for that speaker? I couldn't find it on the Celestion website.
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Post by myles on Dec 7, 2005 8:29:32 GMT -7
Speaking of Michael Burks, I've tried to find information on the Celestion G12H100 which Michael uses in his cabs. Does anyone have any info or links for that speaker? I couldn't find it on the Celestion website. I do not think they make that speaker anymore. The ones I have are from the late eighties.
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Post by billyguitar on Dec 11, 2005 15:22:37 GMT -7
I have a G12H100. I put in a Boogie Mark 3 hardwood combo instead of the EV. It saved a little weight and was less punchy than the EV which made the Boogie easier to live with. I loved that amp when I first got it but grew to hate it. Every room it sounded different. After that I got into tweed Bassmans and deluxes. I learned that a good amp sounds good everywhere and that a boogie rarely sounds good. Z amps sound good everywhere. That's one way to know they'll be classics. Back to our program already in progress:
The G12H100 is a terrible sounding speaker. Highs are attenuated but spikey, and has a cardboardy midrange. A very colored sounding speaker. It's the high wattage voice coil that hurts the sound. The upside is I don't think you can blow one.
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Post by myles on Jan 10, 2006 19:59:54 GMT -7
I have a G12H100. I put in a Boogie Mark 3 hardwood combo instead of the EV. It saved a little weight and was less punchy than the EV which made the Boogie easier to live with. I loved that amp when I first got it but grew to hate it. Every room it sounded different. After that I got into tweed Bassmans and deluxes. I learned that a good amp sounds good everywhere and that a boogie rarely sounds good. Z amps sound good everywhere. That's one way to know they'll be classics. Back to our program already in progress: The G12H100 is a terrible sounding speaker. Highs are attenuated but spikey, and has a cardboardy midrange. A very colored sounding speaker. It's the high wattage voice coil that hurts the sound. The upside is I don't think you can blow one. I think your assessment is very accurate from my own personal taste.
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