ZM - looking for advice.
I started measuring in REW at 1W, 5W, and 10W. I printed a sheet to write down distortions while ramping up from 30V-37V.
At first I thought my distortion figures were way out of whack compared to what you and BenMah were showing, but I think what I'm seeing is I need to turn up the voltages.
I noticed the trend that 2nd order distortion kept dropping as SIT drain voltage increased. And 3rd order moves up.
I got to 46V and wanted to check here before I try too high and let magic smoke out of something...
Now I'm wondering.
How high CAN the drain voltage go?
How high SHOULD it go?
Background facts: 2SK182ES, 2A3, 67.4V Rail Voltage
Both channels track in a similar fashion.
I started measuring in REW at 1W, 5W, and 10W. I printed a sheet to write down distortions while ramping up from 30V-37V.
At first I thought my distortion figures were way out of whack compared to what you and BenMah were showing, but I think what I'm seeing is I need to turn up the voltages.
I noticed the trend that 2nd order distortion kept dropping as SIT drain voltage increased. And 3rd order moves up.
I got to 46V and wanted to check here before I try too high and let magic smoke out of something...
Now I'm wondering.
How high CAN the drain voltage go?
How high SHOULD it go?
Background facts: 2SK182ES, 2A3, 67.4V Rail Voltage
Both channels track in a similar fashion.
Attachments
do not go more than 5V above Urail/2
in your case (67.4/2) + 5 = 38V7 so ....... 39V
more, and there is much hotter SIT than puck, and also you're cutting much from output voltage envelope , from upper side, resulting in lesser power
not a problem with efficient spks, but still a problem..... one of the reasons to make a Beast is to have power for funny peaks
in your case (67.4/2) + 5 = 38V7 so ....... 39V
more, and there is much hotter SIT than puck, and also you're cutting much from output voltage envelope , from upper side, resulting in lesser power
not a problem with efficient spks, but still a problem..... one of the reasons to make a Beast is to have power for funny peaks
Unfortunately there are differences between THF-51S and 2SK182ES. ZM's 2SK182ES had higher distortion also: The Singing Bush
Worth trying is taking the speaker out from between 0.3R and 0.3R. Or maybe not. My recollection is that H2 increased, but I did it so that my H2 was higher than H3.
Since the 2SK182ES is different, worth trying is different Iq. With 500VA transformer that is not a problem as long as the heat sink can take it.
Worth trying is taking the speaker out from between 0.3R and 0.3R. Or maybe not. My recollection is that H2 increased, but I did it so that my H2 was higher than H3.
Since the 2SK182ES is different, worth trying is different Iq. With 500VA transformer that is not a problem as long as the heat sink can take it.
Last edited:
Super - thank you!!!! Exactly what I needed to know. I'll set for 39v for now - then it goes into the horn rig.
Singing bush is sounding beautiful! I have to chase down some hum by playing with donuts and wire details. Any hum is showing up on my horns...
SissySIT gets to take a break. The amps are definitely related. It seems the SB is throwing a taller soundstage. I’m loving the transparency and all the detail. SITs & horns are magical.
Thank you ZM for the kit and all the support!! This design is world class!
SissySIT gets to take a break. The amps are definitely related. It seems the SB is throwing a taller soundstage. I’m loving the transparency and all the detail. SITs & horns are magical.
Thank you ZM for the kit and all the support!! This design is world class!
Attachments
My measurements. 2SK182ES. 500VA dual donuts. 67.4V Rails. 2A3 Iq. 39V @ SIT Drain. 8R
Attachments
Nice measurements rhthatcher. The more important question... Where did you get those JBL's?!? So nice!
Have you been able to get rid of all the hum yet?
Have you been able to get rid of all the hum yet?
I first heard the classic audio reproduction jbl’s at Midwest audio fest long ago. I was smitten. I found these reproductions on audiomart a few years ago and the price was right. They were located about a mile from my old office in south San Francisco. So I arranged a visit during a biz trip. They all checked out and I made a deal. This was a definite “beg for forgiveness, don’t ask for permission” scenario with my wife. I felt like I hit the jackpot on these. I have added the fostex super tweeters because the JBL compression drivers drop off hard at 10k. And later I hit another jackpot getting a Danley DTS-10 horn sub. It’s all run with an active xover in my DEQX preamp. Crown k2 on subs. Adcom 555 on 15”. SIT 500 hz and up.
I need to do some hum busting. Last night I lived with it and spent several hours enjoying a couple cocktails, LPs, and digital tracks.
I need to do some hum busting. Last night I lived with it and spent several hours enjoying a couple cocktails, LPs, and digital tracks.
Nice build! And nice speakers. I love these big, old JBL speakers.
I run a bi-amped JBL system with all SIT amps and have found that SITs on the lower frequencies make a noticeable difference as well. Reason to build another SIT amp.
I run a bi-amped JBL system with all SIT amps and have found that SITs on the lower frequencies make a noticeable difference as well. Reason to build another SIT amp.
Glad you can still enjoy even with a little hum rhthatcher.
I'm excited to get this build going. Ordering some Antek AS-4450's for monoblocks very soon.
I'm excited to get this build going. Ordering some Antek AS-4450's for monoblocks very soon.
I have 2 SissySITs (one at a friend's house now), and I'm building that friend Singing Bush Monoblocks after he orders some parts. I'll put his SB Mono's in place of the Adcom for a test! I was running an F5 in that position, but I wanted more power.
It will be much better without the hum, but after all that effort, I wanted to enjoy it a bit! I'm planning on telling my buddy to go for AS-3450's for his Monos. I'm also going to use 15kuF caps x 8 on spare DIYAudio boards I have on the shelf rather than the beer can sized caps I used. Live and learn. It looks like 4U Deluxe will fit everything nicely for a monoblock.
Also my buddy has THF-51S and 2SK182ES in his stash. I'm probably going to steer him towards the THF's. I'm tempted to get a set of used matched ones to try.
Last edited:
I haven't decided on caps for my mono's yet. Still researching the most economical/practical solution there.
4U Deluxe would be nice. I have a stash of server CPU coolers hanging out. I might go for a forced cooling, custom chassis, type deal.
I also have THF and 2SK182ES on hand. I'm leaning toward the THF's for Singing Bush and the 182's for a SIT-3X build.
4U Deluxe would be nice. I have a stash of server CPU coolers hanging out. I might go for a forced cooling, custom chassis, type deal.
I also have THF and 2SK182ES on hand. I'm leaning toward the THF's for Singing Bush and the 182's for a SIT-3X build.
It's a bit of a tricky one to get this voltage, decent uF rating, with good dimensions.
It looks like these might fit the bill. Voltage, lead spacing, 35mm. They'll fit the store universal board. And if you're talking 8 per channel, you get the volume price break.
United Chemi-Con ESMH800VNN123MA63T
https://www.mouser.com/ProductDetai...GEnT5q4ZgYtBqEM/XFM447Vexcyy1pUbixoK3CYlb/a9N
Botte designed the PCBs for me. He included my wish list: diode-incorporated ground lift, LED, bleeder, space for 50mm caps, 4 "pi resistors", and spacing at inputs and outputs for "Fast-On" connections. Mounting holes align with the ModuShop base plates.
I ordered them in 3oz copper from PCBWay.
Attached with Botte's blessing are the schematic, Gerber files, and a pic of an unpopulated board.
Thanks Botte!!!!!
I ordered them in 3oz copper from PCBWay.
Attached with Botte's blessing are the schematic, Gerber files, and a pic of an unpopulated board.
Thanks Botte!!!!!
Excellent idea! I just ordered 10 boards, 2 are spoken for to go into my buddy’s monos. I tacked it on to another pcb order currently being fabbed. I expect it will be a little while until they’re ready to ship with lunar new year holiday.
I added ability to put in a choke, added a 2nd LED (on for board, one to run a wire to the front panel). I tweaked the layout to put the same copper on both sides of boards. Connection to the board can be via quick disconnect spades or hardwired.
PM if interested.
I added ability to put in a choke, added a 2nd LED (on for board, one to run a wire to the front panel). I tweaked the layout to put the same copper on both sides of boards. Connection to the board can be via quick disconnect spades or hardwired.
PM if interested.
