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Post by leeophonic on Oct 20, 2019 17:34:12 GMT
Michael of greater interest, tell us about the audio valve amp you have on your side board  Lee |
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Post by Michael Messer on Oct 21, 2019 7:45:05 GMT
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Post by Pickers Ditch on Oct 21, 2019 9:17:24 GMT
Aha! KT88s, the bass players dream. Back last century Tony Merrill built a prototype ELGEN 40W bass head containing 2 x KT88s and a thumping great Partridge output transformer which he let me use for a long while. Through a modified Vox T60 speaker cabinet, using a Precision bass, I had tone and volume which could keep up with Marshalls of the day, nae problemo. Tonnes of headroom and grunt. It was pretty good with my Dansette plugged into it, too. My son is now into a very slow process of trying to build a copy:  I love KT88s me. Attachments:
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Post by Michael Messer on Oct 21, 2019 10:39:48 GMT
This is interesting. Well, the bits I can understand are!
From Wikipedia
The KT88 is a beam tetrode/kinkless tetrode (hence "KT") vacuum tube for audio amplification.
The KT88 fits a standard eight-pin octal socket and has similar pinout and applications as the 6L6 and EL34. Specifically designed for audio amplification, the KT88 has similar ratings to the American 6550 which was designed for use as a servo amplifier. It is one of the largest tubes in its class and can handle significantly higher plate voltages than similar tubes, up to 800 volts. A KT88 push-pull pair in class AB1 fixed bias is capable of 100 watts of output with 2.5% total harmonic distortion or up to about 50W at low distortion in hi-fi applications. The transmitting tubes TT21 and TT22 have almost identical transfer characteristics to KT88 but a different pinout, and by virtue of their anode being connected to the top cap have a higher plate voltage rating (1.25 kilovolt) and a higher power output capability of 200 watts in class AB1 push–pull.
The screen grid is sometimes tied to the anode so that it becomes effectively a triode with a lower maximum power output.
History
The KT88 was introduced by GEC in 1956 as a larger variant of the KT66. It was manufactured in the U.K. by the MOV (Marconi-Osram Valve) subsidiary of G.E.C, also labelled as IEC/Mullard, and, in the U.S., Genelex Gold Lion.
As of 2018, KT88 valves are produced by Shuguang (China), JJ Electronic (Slovakia), Svetlana (Russia), and New Sensor Corporation (Russia). NOS examples in good condition are extremely rare. Due to its availability and characteristics, the KT88 is popular in hi-fi production amplifiers.
Historically, it has been far more popular with high fidelity stereo manufacturers than guitar amplifier builders, given its characteristics of high-power and low-distortion. Due to these characteristics, it is regularly used to replace 6550 tubes by end users seeking a guitar amplifier tone with less distortion. Some of the amplifiers which shipped with the KT88 power tube include the Hiwatt Custom 200 and 400 Bass Heads, Sound City L/B 200, 200 watt Marshall Major,[2] Mesa-Boogie Bass Strategy Eight:88 (465 Watt) and Bass Prodigy Four:88 (250 Watt), Orange Thunderverb, Reeves Custom 225 bass, Fryette (formerly VHT) Two/Ninety/Two power amp, Pittbull Ultra-Lead, Sig:X & Deliverance, McIntosh MC2102, McIntosh MA2275, McIntosh MC2301, Splawn Nitro, Pro Mod, Competition & Superstock, Blackstar Series One 200, Carlsbro 200 TC, Bogner Shiva 20th Anniversary, Egnater Tweaker 88 and the Marshall 2203KK Kerry King Signature JCM800.
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The KT88s in my amp are made by PSVANE, which apparently are the best KT88s around. I'm not going to question that, or try any others because I know that David Shaw knows his stuff and if he puts them in his amps, then that's good enough for me.
Shine On
Michael
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Post by Deleted on Oct 21, 2019 12:19:43 GMT
Beautiful amplifier. I will look it up. So it is an integrated amp...preamp section is octal, not 12AX7/ecc83 which is quite unique...what are they? (I looked it up...they are 6SL7/6SN7 dual triodes. I dont know if they are presently manufactured. The ones in your photo with the reddish bases look like Mil Spec JAN versions...premium grade)
I believe most vacuum tubes are (unfortunatly) only made in those 3 factories...what differentiates most brands is the screening and burn-in process. I heard that for example someone buys 100 tubes from factory X, and of those 100, only 5 or 10 qualify to become, say, Ruby tubes, maybe 25 become, say, Sovtek, and the rest are junk...who knows where they go...
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Post by Michael Messer on Oct 21, 2019 22:18:07 GMT
Fred, I think that David Shaw has the 6SN7/6SL7 driver valves made for him with the old style brick coloured base. Prior to this I had a pair of Quad II amps and a Quad 22 controller from the 60s. They were excellent, but as the years went by they became like owning a vintage car and needed constant care. I decided to sell the Quad system and get the Icon Audio and I am very pleased that I did. The sound is superb, as you would expect from a handbuilt valve/tube amp. I run it through a pair 1971 Kef Cadenza speakers and it sounds amazing.  Shine On Michael |
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Post by leeophonic on Oct 21, 2019 22:40:28 GMT
Thanks Michael, I knew it was not just me that has an appetite for this stuff.
Of note I coined a term "shelfie" a few years back where as much as it is interesting to see a selfie, a shelfie is a glimpse into someone's home/environment to see what is of interest and what makes them who they are, so I spied the amp and here we have an interesting insight.
Regards
Lee
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Post by Deleted on Oct 22, 2019 0:50:12 GMT
Michael, others...yes the 6SN7 is now currently in production...since being declared obsolete in 1960. I recall as a kid in my uncles tv repair shop the 6SN7 being the vertical output tube of the old TV sets...if your set had only a white horizontal line or people were all looking like mister 5x5 you needed a new 6SN7...
There are some good tubes presently being culled from the lot manufactured, but quality control, materials, construction and process is the key. They say that creating tungsten of consistent purity typical in the 1950’s has not been since achieved.
Yes, certainly maintaining tube equipment from the 1960’s and prior becomes cumbersome...though amazed how some have stood the test of time.
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Post by Michael Messer on Oct 22, 2019 11:32:02 GMT
Thanks Michael, I knew it was not just me that has an appetite for this stuff. Of note I coined a term "shelfie" a few years back where as much as it is interesting to see a selfie, a shelfie is a glimpse into someone's home/environment to see what is of interest and what makes them who they are, so I spied the amp and here we have an interesting insight. Regards Lee Lee, in that case you didn't mention the Dali Katch bluetooth speaker, the Johnny Shines "Too Wet To Plough" CD, and the fact that my CD player was away being serviced! The two guitars on the wall are.... Conchord Mohan veena and Fine Resophonic. Shine On Michael |
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Post by creolian on Oct 22, 2019 15:58:53 GMT
Hello all,
Ive seen a couple muscians using Hi Fi tube amps... Papa John Creech, Jean luc Ponty both were using the iconic McIntosh mc300 600w tube amps with the aqua blue meters. Both were running two amps briged mono at once. Their sound was envelopingly loud and clean... unfortunately those amps weigh a ton... 98lbs each. Ive used a crown dc300 w a guitar pre and it worked really well for acoustics.
Wondering if youve ever used that beauty as a guitar amp ?
Green w Envy,😎
Jeff
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Post by Deleted on Oct 22, 2019 16:30:40 GMT
I guess a straight power amp can be used with a suitable pre-amp to amplify a guitar or other stringed instruments. Integrated HiFi ( MMs amp) and PA amplifiers are to some extent designed to reproduce recordings that basically are equalized in a non-linear manner. So usually they need to have their front ends modified when being used as guitar amplifiers. Maybe going thru something like an MXR Micro Amp bridged into the RCA aux input jack would sound good...
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Post by mitchfit on Oct 26, 2019 2:42:56 GMT
Fred,
re- "the 6SN7 is now currently in production...since being declared obsolete in 1960."
look for old JAN phillips metal can tubes. low cost red headed step child of the NOS world due to aesthetic appeal of glowing glass "light bulbs"*. it is overlooked that they have the advantage of an iron RF filtering capsule. have 2 of that same brand/military designation iron clad 6__7 scored about 10 years ago for <$20 to populate pre-amp circuit from early 1950's VALCO schemtic amp being built. even the 6SQ7, which was a known problem child design for microphonics and/or vibration sensitivity still works just fine.
have read where many recently mfgd tubes/valves won't make spec as per old RCA vacuum tube sheets. can't prove it due to big dollar/low bid entry fee to have an old TV7DU checked out and calibrated, even after me making a counter offer that i would supply the close spec NOS RCA 6L6 calibration replacement tube.
have also read that JAN designation only meant/proved that X amount of them randomly sampled from ~that~ production run made 100% (or more-not uncommon) spec. he said in a posting he had worked at RCA mfg plant, and managed to survive until i read his internet posting from early 2000's. i am throwing previous sentence info into the mix as the reason so few valve factories are extant is toxic material by-products in mfg process. searched long but couldn't find any documentation to dis/prove his statement for validity.
in a related story--when i asked him, a well known boo-teek Fenderesque amp builder in chicago told me by email that different designed/spec'd tubes will bear different alphanumeric designations. f'rinstance a special slow warm-up 6L6 designed for olde school computer use and the above mentioned RCA 6L6 calibration tube. also, the extinct hammer-n-sickle EL 84-M tubes that were specially designed for siesmic zone military vehicle use. IF you're lucky enough to find some of these still new, buy them! will shine for guit due to higher vibration resistnce strength or hi-fi due to close tolerance avionics out put requirements.
DISCLAIMER--if a low threshold breakup is desired such as an AC4 vox "bedroom level" type amp, walk on past...
back in the day, they were very tough units to begin with as proved by use in pre WWII in airplanes and automotive radios back when the roads were abundant with inverted speed bumps.
mitchfit
* you hadda be there--reference to by gone thread here at MM.com.
:^)
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Post by Deleted on Oct 26, 2019 12:56:56 GMT
Mitch. Yes agreed. The old metal can tubes are desirable.
I grew up a mile or so from the old GE, Westinghouse and TungSol factories in Bloomfield NJ. They are now highly toxic hazardous waste sites undergoing long term remediation. My dad, and several uncles worked there at varous times in their youger days. I suspect that coupled with smoking led to their relative early deaths in their late 60’s and early 70’s years of age...
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