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Old 14th March 2013, 02:24 PM   #1471
vgeorge is offline vgeorge  Greece
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Regarding gain structure, I think it depends on the maximum loudness you want to play sometimes. You have to adjust your system for that. If you want to rock hard sometimes, and your system can do that with no distortion, you want to adjust for that. Keep in mind also that some recordings are lower in level than others. With the TSSA I am using you can tune the gain to around 20 or 26 dB. I am using the higher gain now, but the 6V6 gives me the opportunity to use the lower gain, which I think has a tad better sound.
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Old 15th March 2013, 12:23 AM   #1472
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Buzz, I am using a combination of horn bass reflex from 80Hz to about 700Hz.
Regarding your 416, the thing is how well they are going to integrate with the horn and at what sensitivity, if you plan to use only one amplifier. With what horn are you planing to use your 288 with? For bass they are TD15X from Lambda, before they were taken over by AE. The box is big because I already had it and had the room for it. My plan is to integrate with the main speakers sometime in the future.
I plan to mate them to Iwata 290 to begin with. It will allow me to easily cross in the same range you have chosen. If i really like what i hear, i may try the azurahorn, since it is made specifically for the 288. I have my eye on the FD371 for top end, as most concede that the 288's need help up high. As stated earlier, the 416-8A will take bass duties in MLTQWT that is 25" wide by about 40"tall. The width will match the iwata width. I have considered making flange adapter that i can add to MLTQWT enclisure that will turn it into a horn. For the iwata, i will have custom mounting ring made to match throat angle of 288 and tie into Iwata.
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Old 15th March 2013, 05:32 PM   #1473
vgeorge is offline vgeorge  Greece
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Originally Posted by buzzforb View Post
I plan to mate them to Iwata 290 to begin with. It will allow me to easily cross in the same range you have chosen. If i really like what i hear, i may try the azurahorn, since it is made specifically for the 288. I have my eye on the FD371 for top end, as most concede that the 288's need help up high. As stated earlier, the 416-8A will take bass duties in MLTQWT that is 25" wide by about 40"tall. The width will match the iwata width. I have considered making flange adapter that i can add to MLTQWT enclisure that will turn it into a horn. For the iwata, i will have custom mounting ring made to match throat angle of 288 and tie into Iwata.
Buzz, looking forward for your results. Hope you like the outcome! The FD371 looks really nice.
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Old 15th March 2013, 05:34 PM   #1474
vgeorge is offline vgeorge  Greece
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Now playing!
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Old 15th March 2013, 05:37 PM   #1475
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Hey it has a window even and retro looks. Red and green LEDS for what? Heaters on and HT on?
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Old 15th March 2013, 05:45 PM   #1476
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Now playing!
...and... the ???
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Old 15th March 2013, 06:02 PM   #1477
vgeorge is offline vgeorge  Greece
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Hey it has a window even and retro looks. Red and green LEDS for what? Heaters on and HT on?
Yes, heaters and HT.
It was an old chassis and the holes existed already for the leds.
I painted the chassis for retro look, this was my intention. The mesh window helps ventilation for the valves. It already had it, though.

I had a small buzz in the beginning and had to rearrange the earthing on the phono, now it' s fairly quite. Very sensitive to microphonics, not a real problem now, but I will take more measures to isolate the tubes from vibration in the near future.
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Old 15th March 2013, 06:14 PM   #1478
Salas is offline Salas  Greece
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You got twice the gain than others now with the choke. Eat it out in the power amp and help the tubes isolation also will pay. When back on the bench to do something to it, if you will remember please set your pot half way and try get the -3dB bandwidth point (6 squares on the scope reducing to 4). Then run a square wave at about a 15 times lower frequency and take a pic, I wanna know how it behaves in real life with choke load VS LTspice. Bcs I have the resistive option I can only measure here. Thanks and have good listening.
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Old 15th March 2013, 06:40 PM   #1479
vgeorge is offline vgeorge  Greece
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I will, maybe tomorrow.
I will also reduce power amp gain and see.
Regarding sound quality, I must say I am thrilled!
Well worth the effort. Very detailed and holographic sound. Also bass is very tight and defined and at the same time very nice on voices with no trace of harshness.
P.S I am using obligato gold 1,5uF // ft-3 0.1uF at the output.
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Old 21st March 2013, 03:26 PM   #1480
vgeorge is offline vgeorge  Greece
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Finally took some measurements, as Salas requested.
First set is with the pot full on.
Gate stopper is 150R Shinkoh.
BW seems to be around 250kHz.
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File Type: jpg IMG_1753.JPG (808.8 KB, 48 views)
File Type: jpg IMG_1754.JPG (800.8 KB, 47 views)
File Type: jpg IMG_1759.JPG (769.8 KB, 48 views)
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