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Old 6th June 2011, 11:26 AM   #41
Gobble is offline Gobble  India
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Quote:
Originally Posted by mcgreg66 View Post
For drilling the topplate I took Scotts setchassislayout.pdf modified it to the real size, printed out a 1:1 template and fixed it on the topplate for drilling and cutting.....very recommendable!!!!!
Only if your transformers have the same cutouts and size!!!!

Where exactly is this pdf posted? Besides Transformer sizes, is everything else standard and re-usable for other projects?

Thanks
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Old 6th June 2011, 02:18 PM   #42
iNSuL is offline iNSuL  United States
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It was included with the manual Scott prepared for the kit.
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Old 20th June 2011, 04:32 PM   #43
Gobble is offline Gobble  India
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Any new feedback on the SQ of this kit over extended listening sessions?
Comparisons with other gear?
I am toying with the idea of importing the kit, so I would like somebody to tickle me a bit

Thanks
--G
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Old 20th June 2011, 05:49 PM   #44
Fjd is offline Fjd  United States
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Default KT88 SE Basic or Master Kit

I completed my amplifier kit by working on it a couple of hours at each sitting and it probably took about 14 Ė 16 hours total, which I didnít think was bad given I couldnít work on it for long periods each sitting. The instructions were easy to follow and I really didnít get stuck at any point during the build (just some refreshing my memory on previous pages covered given the time between my build sittings). Voltage measurements all came in really close to Scottís specifications.

I now have over 400 hours on the amplifier so far with no problems. Part of the 400 hours is because Iíve let it play during the night to break in the Cardas capacitors that a friend thought I would like, instead of the capacitors provided with the kit, given I run a pair of high sensitivity Klipschornís with mid-drivers that have beryllium mid-range diaphragms (very detailed and revealing).

My listening has really been only at low to moderate levels and the subjective reviews are not my specialty; however, as Iíve now done a lot of listening to this amplifier, it seems very detailed yet presents a nice level of smoothness. Another way to describe it would be tonally balanced with lots of resolution and great musicality (more modern sound and not the veiled and rolled-off sound of many of the vintage old tube amps).

It has been a great amp to roll the power tubes as Iíve used my Tung-sol solid plate 6550ís, GE 6550Aís, and new issue Genelex KT88s, in addition to the tubes provided in the kit. Given the simplicity of the circuit, I can hear the slightly different sound presentation of each type of tube. IMHO, the amplifier with the 6550ís have a slightly more ďtubierĒ (for lack of a better word) sound with what seems to be slightly more mid-range sweetness, while the KT88ís seem to have more presence in the frequency extremes.

If bass notes in the mid 30 Hz range (Klipschornís reasonable low end) are present in the music, the amplifier reproduces the notes with clarity. Most listening has been with blues, rock (60ís, 70ís & 80ís and some modern), jazz and some classical. While the bass listening to Zeppelin, Pink Floyd & Kid Rock has been sufficient for my listening levels, I havenít tried anything loud and I havenít tried any of the harder rock electronic deep bass music. However, I suspect I would not 'feel' the bass as with a strong SS amp.

The sound stage and imaging seem fine. Also, the amplifier is extremely quiet and there is really no discernable ďhum.Ē

Other equipment used has been the Klipschornís (tractrix flair mid horn/Beryllium mid-driver diaphragms) a Juicy Music Blueberry preamplifier, VPI scout turntable (Grado cartridge), and Rega Saturn CD player.
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File Type: jpg IMG_8485.JPG (185.4 KB, 1043 views)
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Old 22nd June 2011, 05:00 AM   #45
Gobble is offline Gobble  India
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Is this kit auto-biasing? Or is there a knob to adjust and tweak things? Can the be 6550 be a drop-in replacement?

The KT-88 amp I once heard sounded too smooth for my liking. I would be more interested in this kit if I could try rolling other tubes without having to open up the amp. I believe if voltages and bias is not tweaked, we can lose out on frequency extremes with different tubes (given their different requirements)? Is it possible to use beam tetrodes like 6L6 and Kt-66 with this amp after tweaking bias?

Lastly I am complete novice so pardon me if I have made any mistakes in my assumptions.


Thank you

Last edited by Gobble; 22nd June 2011 at 05:28 AM. Reason: Edit: Mixed up tube types and corrected my post.
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Old 22nd June 2011, 05:45 AM   #46
Gobble is offline Gobble  India
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Add KT-90 and KT-120 to the above list. I believe the 120 requires higher current?

Thanks
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Old 22nd June 2011, 07:41 AM   #47
Gobble is offline Gobble  India
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Quote:
Originally Posted by Gobble View Post
IIs it possible to use beam tetrodes like 6L6 and Kt-66 with this amp after tweaking bias?
After some googling i think not ...
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Old 22nd June 2011, 12:28 PM   #48
scott17 is offline scott17  United States
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Quote:
Originally Posted by Gobble View Post
After some googling i think not ...
The circuit is cathode bias. You can use KT88, 6550, EL34, 6CA7 with no modifications necessary. The B+ for this amp is a little high for the 6L6, and not enough current for the KT120. It is a variation of a design by Mikael Abdellah with subsequent modifications by Alex Gendrano, and DIYAudio & AudioKarma.org members. You can see the schematic for this version here: KT88 SE Complete Kit at post #126.
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Old 16th July 2011, 04:07 AM   #49
Dave R is offline Dave R  United States
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Default progress update

Thought I'd send a progress update on my tube amp project. This is my first time at an amp, so I'm not setting any speed records.

Here are a few shots of the chassis complete in its raw form. Still need to do the finishing work before mounting everything and doing the wiring.

Wooden base is oak and cherry construction to match my speakers. The top plate fits in the frame, with the supports set down 1/8", so that the plate is flush at the top.

Instead of mounting feet, I decided to cut a hand hold on each side. They are indeed centered -- near the center of gravity -- which is offset mainly by the transformers to be mounted along the back.

Going through all of the details (so far!) has been tedious and laborious, but now that it's all to this point, it's nice to step back, take a breath, and enjoy. Anxious to get it all together.

More pic's as progress is made.
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File Type: jpg ampchassis 006.jpg (121.9 KB, 917 views)
File Type: jpg ampchassis 007.jpg (106.5 KB, 869 views)
File Type: jpg ampchassis 008.jpg (105.3 KB, 845 views)
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Old 25th July 2011, 02:59 AM   #50
Dave R is offline Dave R  United States
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More progress . . .

The wood base is finished, and the top plate is finished with a clear acrylic coat. The oak and cherry base was finished with (natural) Danish oil, and coated with a furniture wax for a low gloss.

The volume control is mounted on a piece of sheet metal on the inside of the wooden frame. The through hole is cut with some clearance, and finished with a generous roundover for my fat fingers. Of course, the wood grain is more interesting around the flared opening as well.

Figured out how to make the rear mounting plates with a nice finished look. One is for the electrical power jack, and the other is for the RCA-type (L&R) input jacks.

The sheet metal was clamped in place between the 3/4" particle board blocks. I cut the blocks out on the table saw, then ran the corners through a roundover bit on the router. This technique provided a good way to cut the sheet metal with the band saw, as well as final filing down to the wood edges. It also made for a nice drill block for the 4 corner screws.

After priming and painting, I thought the plates came out pretty good. The topcoat is satin black.

more later . . .
Attached Images
File Type: jpg front_ready.JPG (86.6 KB, 343 views)
File Type: jpg rear_plates.JPG (103.5 KB, 316 views)
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