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Old 31st March 2013, 09:53 PM   #211
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Default SE KT88 Kit Headphone Mod

Here is the information for installing a headphone jack on your amp.

These are the resistors that I used:
Mills 5 Ohm 12W Non-Inductive Resistor 005-5
Mills 3 Ohm 12W Non-Inductive Resistor 005-3
CPF130R100FHB14 Vishay/Dale | Mouser

Here is the same toggle switch that was in the kit:
S6A NKK Switches | Mouser
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Old 11th April 2013, 09:09 AM   #212
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I'm going to build it and report, components are on it's way to home. Check out the sch, 30 Ohm resistor is shown as both 1W and 1/2W rated.

Thanks for that! Amusing to be able to use it as HP amp
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Old 11th April 2013, 09:51 AM   #213
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If anyone else is ordering from Mouser, that's the BOM I got. I propose two jack connectors, both from Neutrik, the pricier is a bit better and has a locking mechanism.

Switch
S6A NKK Switches | Mouser

5 Ohm 15W
MP915-5.00-1% Caddock | Mouser

3 Ohm 15W
MP915-3.00-1% Caddock | Mouser

30 Ohm 1W
CPF130R100FHB14 Vishay/Dale | Mouser

Jack
NMJ6HC-S REAN / Neutrik | Mouser
or
NJ3FP6C-BAG Neutrik | Mouser
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Old 11th April 2013, 12:32 PM   #214
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Quote:
Originally Posted by regiregi22 View Post
I'm going to build it and report, components are on it's way to home. Check out the sch, 30 Ohm resistor is shown as both 1W and 1/2W rated.

Thanks for that! Amusing to be able to use it as HP amp
Yeah, the 1/2W is incorrect. They are both the same 1W resistor. I think you'll be happy with the sound.
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Old 17th April 2013, 10:48 AM   #215
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Components have just arrived, but so many projects and so little time!! hum!
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Old 18th April 2013, 03:36 AM   #216
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I just finished mine 4 days ago. This was my 4th build, preceded by an AudioSector LM3875, Bottlehead Seduction and a Pass B1. I almost built an F5, but got discouraged searching for parts for it.

Here is my parts list:

I used all Edcor xfmrs
PTX: XPWR 222-120 (for the 320ma rating)
OPT: CXSE25-8-5K
Choke: CXC125-10H-200mA

I didn't want to venture too far into uncharted territory, so I mixed Scott's and Porkchop's schematics. I did use a basic PEC volume pot and JJ multi capacitors (32+32 & 50+50). Works fine for me. None of the "hum" that we've been warned about.

I am very pleased with and proud of this amp. I like Triode mode the best and 8 watts is PLENTY loud on my 89dB Fisher XP-10s. My room is 10x12 with paneled walls and thin carpet. I will definitely be building some full range mid-90's sensitivity speakers next.

Prior to this, I had never even heard a tube amp. So I don't have much of a frame of reference. I can only compare it with my dual mono LM3875 and a Marantz 2230. However, I have done a lot of research and decided on this one because of the reviews, the simple circuit and relatively reasonable cost. Not to mention Scott's outstanding documentation, R&D and continued support gave me a great comfort level. Thanks Scott. I really came to appreciate the amount of work you put in to this kit with a very modest profit.

Listening impressions. Great detail. Pretty "black". It is quiet, even considering that my wiring job probably isn't as tidy as it could be and I didn't use motor run caps. It is a little better in every way compared to the LM3875, but not as much as I expected. That isn't to say the KT88SE is average. It is definitely high quality, but I have a new appreciation for my LM3875 too (especially in bang for the buck). I'm curious what a speaker upgrade would do for both amps.

I can now say that after listening to the KT88SE, I realize what "sound stage" means! It has smooth and rich bass. More than my chip amp.
Nice smooth sound in all ranges. What amazes me is that without tone controls, it sounds perfectly balanced. If I run my Marantz with the controls flat, it sounds lifeless. It takes controls and a loudness button for the 2230 to sound nearly as good as the KT88SE.

Thanks to all the pioneers for their help and guidance.

Brian
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File Type: jpg P1040331.jpg (442.9 KB, 328 views)
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Old 18th April 2013, 10:09 PM   #217
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Glad that it worked out so well for you. It is a fine sounding amp. Great job.

The wiring photo must be before it was finished. I can't see the KT88 cathode resistors.

Did you get 4V bias with the two red LEDs? I had to use 2 green LEDs to get 4V.

Scott

Last edited by scott17; 18th April 2013 at 10:13 PM.
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Old 18th April 2013, 11:44 PM   #218
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Thanks Scott17. The cathode resistors are on the bottom side of the turret board, like Porkchop did. I will add the switch for EL34 operation later. My turret board was too large. That is one of the things I would have done differently. I like the way your kit divides the channels onto 2 separate boards. Live and learn.

In regards to the LEDs....I actually replaced them (after the photo) with the 1K & 100uF in your circuit. I'm not sure I understand, but I read where others are buying batches and "matching" them. That sounded kind of important, so I decided to leave LED's for later.

Another thing I would have done differently would be to orient the tube sockets 90 degrees from how I have mine (key of the tube oriented to 6/12 o'clock vs. 3/9 o'clock). Better view of the filaments that way. Otoh, the mounting screws look better set off to the sides.
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Old 9th May 2013, 11:45 PM   #219
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Quote:
Originally Posted by regiregi22 View Post
I'm going to build it and report, components are on it's way to home. Check out the sch, 30 Ohm resistor is shown as both 1W and 1/2W rated.

Thanks for that! Amusing to be able to use it as HP amp
I have already assembled the parts and it works pretty good! A very nice way to give this amplifier two different uses for the same cost.

The sound? Well, better to start by the headphones, they are not the best out there but for casual listening they do the job. I own a pair of Sennheiser HD595. I have only listened to about 10 songs, and while I like to give them some sessions to make an statement, all I can say is that is sounds fabulous. By the way, this is the first time I hear a pair of HP with a tube amp.
The sound is more or less the same as we expect with a pair of speakers. I am very bad at describing what I hear, but you can imagine, natural soundstage, pretty detailed with a black background and that kind of... well... pleasureness that tubes give to the sound.

If you have already assembled this amplifier, this mod is on your to-do list. With only a few resistors, a jack connector and a switch, you can turn it into a marvelous amp to pair with your headphones.
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Old 27th May 2013, 02:00 AM   #220
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I have not heard a single tube amp other than this one. Are they supposed to make a "jingling" noise when you turn them on? Mine sounds like a little like when you jiggle a burnt out light bulb. Filaments?

Is this normal?

My bottlehead seduction doesn't, but those are very tiny tubes by comparison.
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