I'm in for one!
Scot, what do you think about this "standby" power switch?
Carling DPST Toggle Switch, OFF-STBY-ON
Scot, what do you think about this "standby" power switch?
Carling DPST Toggle Switch, OFF-STBY-ON
Good luck with this Scott. I'm absolutely loving my SE Master Kit with my 100db speakers. Anyone thinking of doing this build, for the money, it really is a brilliant amp.
It will eventually fail if used to switch the HT. Here is a link to info about standby switches: The Valve Wizard
This design does not need a standby switch if the power supply capacitors as specified are used or series connect the equivalent uF value, 450V, electrolytics with balancing resistors.
Thanks very much. I really glad that you are enjoying the amp.
The tricky part here is getting 25 individuals to collectively send me $19,375 and then wait 3 months for a product.
Might be a slight issue.
TerryO is referring to a couple of diy speakers that I put together, dubbed "DR1" and "DR2". The DR1 sounds somewhat better, and it makes a great combination with this KT88 SE tube amp.
They are bookshelf speakers, both using the same 4.5" Vifa/JBL midwoofer in a 5 liter vented box. The original DR1 uses a 3/4" Audax tweeter, while the DR2 uses a 1" Peerless tweeter. All of these drivers were obtained on a discontinued buyout, and are no longer available.
Both designs use a series crossover (different). Above the vent tuning frequencies, the impedance of both designs is relatively constant at around 4 or 5 ohms. They are both approx. 89 dB. Attached is a shot of a pair of DR2's that I made for a friend. I can't find a shot of the DR1's now.
Attachments
Hi Tim,
Dave's the designer of the DR1 & 2. I built a pair for the Planet10 DIY Fest near Victoria, BC. Actually, I built them "at" the meet, which is a bad habit I picked up many years ago. As it was nearly an all tube meet, I decided to leave out an optional resister in the series crossover. Then someone wrote from the Meet, that I had left out the optional resister because I didn't need the extra bass boost when running them with tubes. As I said, this was published during the meet and I believe that Dave was a little put out with me for changing his design. After getting home from the meet, he maintained that the resister was there to tame the tweeter a couple of dB if desired. Anyway, I explained that I had thought it was optional in case somone used a SS amplifier and wanted to restore the lost bass. Anyway, Dave did some simulations and found that the optional resister actually did give some boost to the bass as well as extending it a bit as well.
One thing about the woofers that Dave used is the smooth frequency response and smooth roll-off even in a ported enclosure. I've maintained for years that a smooth frequency response at the lower end with minimal resistive increases (spikes) around the tuning frequency will allow excellent bass with tube amps.
I hope that Dave will correct any errors that I may have made in my recounting the situation and the confusion!
Best Regards,
TerryO
Dave's the designer of the DR1 & 2. I built a pair for the Planet10 DIY Fest near Victoria, BC. Actually, I built them "at" the meet, which is a bad habit I picked up many years ago. As it was nearly an all tube meet, I decided to leave out an optional resister in the series crossover. Then someone wrote from the Meet, that I had left out the optional resister because I didn't need the extra bass boost when running them with tubes. As I said, this was published during the meet and I believe that Dave was a little put out with me for changing his design. After getting home from the meet, he maintained that the resister was there to tame the tweeter a couple of dB if desired. Anyway, I explained that I had thought it was optional in case somone used a SS amplifier and wanted to restore the lost bass. Anyway, Dave did some simulations and found that the optional resister actually did give some boost to the bass as well as extending it a bit as well.
One thing about the woofers that Dave used is the smooth frequency response and smooth roll-off even in a ported enclosure. I've maintained for years that a smooth frequency response at the lower end with minimal resistive increases (spikes) around the tuning frequency will allow excellent bass with tube amps.
I hope that Dave will correct any errors that I may have made in my recounting the situation and the confusion!
Best Regards,
TerryO
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
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
Attachments
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
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
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.
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
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
Attachments
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.
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.
Attachments
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.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
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.
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.
Is this normal?
My bottlehead seduction doesn't, but those are very tiny tubes by comparison.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.