Hello,
Pete Millett has another Red Board for sale, I just bought a pair. Has anyone built it?
The Red Board is a "universal" driver PCB for a “Push-Pull KT88 / 6L6GC / EL34 / 300B / 2A3 amp”. See the link. Push-pull KT88 class A amp with "universal" driver PCB
Looks pretty cool to me.
The most expensive piece of the PCB build is the iron “Lundahl LL1690 input transformer”. For playing with on the bench what do you think of using this Edcor matching transformer EDCOR Electronics Corporation. WSM10K/10K
It can be breadboarded without PCB mounting and costs less than 1/10 of the LL1690.
Two parts to this:
The “Push-Pull KT88 / 6L6GC / EL34 / 300B / 2A3 amp looks pretty cool. What do you think?
Is the Edcor matching transformer worth the effort?
DT
All just for fun!
Pete Millett has another Red Board for sale, I just bought a pair. Has anyone built it?
The Red Board is a "universal" driver PCB for a “Push-Pull KT88 / 6L6GC / EL34 / 300B / 2A3 amp”. See the link. Push-pull KT88 class A amp with "universal" driver PCB
Looks pretty cool to me.
The most expensive piece of the PCB build is the iron “Lundahl LL1690 input transformer”. For playing with on the bench what do you think of using this Edcor matching transformer EDCOR Electronics Corporation. WSM10K/10K
It can be breadboarded without PCB mounting and costs less than 1/10 of the LL1690.
Two parts to this:
The “Push-Pull KT88 / 6L6GC / EL34 / 300B / 2A3 amp looks pretty cool. What do you think?
Is the Edcor matching transformer worth the effort?
DT
All just for fun!
I'm building a pair of "Uniamps" now (waiting on Edcor for power and opt. xfmrs). They will be running KT88's. The boards Pete is selling now are the 2nd (improved) version. I'm not using the spec'd Lundall input xfmr, but sourced a much less expensive one from Altronic in Australia (M0706). I don't know if the Edcor will work properly in this design as it's not shielded. If the Uniamps sound and work as good as my Millett DCPP, I will be very satisfied.
I havent heard anything but good news from edcors matching transformers. Ify u want sheilded, for the extra 5 bucks you can get them in stereo pairs in a metal box with rcas on one end.
EDCOR Electronics Corporation. S2S Series
All of these have the same transformers inside. I guess you just use your edcor decoder ring to find the leads you want.
Nice thing about transformers is they have there own built in sub and ultra sonic filters.
EDCOR Electronics Corporation. S2S Series
All of these have the same transformers inside. I guess you just use your edcor decoder ring to find the leads you want.
Nice thing about transformers is they have there own built in sub and ultra sonic filters.
I built the original ones , I had quite problem with a low frequency oscillation Pete was quite patient and helped me work my way through it. I have also have some ringing I have been meaning to look at but have not had time. As of recent I have been giving thought of thinking the herd but this amp will be one of the keepers. I was using it with a pair of Austin 166 back loaded horns and they have a phenomenal sound stage.
Bill
Bill
Hello,
Several weeks later this is moving along slowly. I have received a pair of the red Uniamp II red PCB’s from Pete. They are very nice high quality boards. I have a pair of output transformers ready to go. Today I ordered a pair of Hammond 272HX power supply transformers. Then came the realization that these are not going to be cheap amplifiers.
Thanks for the feedback regarding the input transformers I like the idea of optional balanced input using the Lundahl input transformers. I will order the LL1690 input transformers.
I will post progress here. It will be slow as this project is the fill in distraction between work and life. (You make plans and then life gets in the way!)
To other builders, are you using a line stage with gain for this amplifier or is a passive or buffer line stage going to work?
DT
All just for fun!
Several weeks later this is moving along slowly. I have received a pair of the red Uniamp II red PCB’s from Pete. They are very nice high quality boards. I have a pair of output transformers ready to go. Today I ordered a pair of Hammond 272HX power supply transformers. Then came the realization that these are not going to be cheap amplifiers.
Thanks for the feedback regarding the input transformers I like the idea of optional balanced input using the Lundahl input transformers. I will order the LL1690 input transformers.
I will post progress here. It will be slow as this project is the fill in distraction between work and life. (You make plans and then life gets in the way!)
To other builders, are you using a line stage with gain for this amplifier or is a passive or buffer line stage going to work?
DT
All just for fun!
Today I received two 272HX Hammond power transformers from Gerber Electronics. Never heard of them before, they had the best price. Good service.
Gerber Electronics - Browse Parts - Our Greatest Component is Your Satisfaction
These transformers are labeled 600 V ct at 230 ma 191 VA. The output voltage tends to be higher than name plate at less than maximum ma.
Hammond has added a tap to the primary they now have 115 V and 125 V taps.
Any other builders?
neonthecat, any progress?
DT
All just for fun!
Gerber Electronics - Browse Parts - Our Greatest Component is Your Satisfaction
These transformers are labeled 600 V ct at 230 ma 191 VA. The output voltage tends to be higher than name plate at less than maximum ma.
Hammond has added a tap to the primary they now have 115 V and 125 V taps.
Any other builders?
neonthecat, any progress?
DT
All just for fun!
Pete also recently came out with another red P-P universal driver board. It does not use an input transformer. He made a KT88 amp with it, which is on his web site. I have a pair and will be "testing" tubes with it shortly. I also wired it up in a manner Pete never dreamed of and got over 8 watts out of the board without any output tubes!
http://www.diyaudio.com/forums/tube...push-pull-driver-pcb.html?highlight=6j4+12by7
http://www.diyaudio.com/forums/tube...push-pull-driver-pcb.html?highlight=6j4+12by7
I really like my Millett Uniamps. They have several hundred hours of flawless operation on them now, impressing everyone who has listened. They run cool and are as quiet as a graveyard. I'm so pleased with the performance, I haven't had the yen to build anything else since the day I first turned them on.
Attachments
Thanks for the replies.
I'ma rookie and I think something that fits uniamp my knowledge. The other pcb P. Millet is for more advanced users.
It looks great neonthecat that amp! , Have you encountered many difficulties to mount?,
Can you compare with a commercial amplifier to get an idea of quality?, How much did it cost you your total construction?
Forgive the questions, I'm in study phase of the project
Br
Al
I'ma rookie and I think something that fits uniamp my knowledge. The other pcb P. Millet is for more advanced users.
It looks great neonthecat that amp! , Have you encountered many difficulties to mount?,
Can you compare with a commercial amplifier to get an idea of quality?, How much did it cost you your total construction?
Forgive the questions, I'm in study phase of the project
Br
Al
Hi,
i used unshielded line input transformers (like Edcor) many times and never had problems. Circuits were pro audio, but as hi-fi has similar levels at line level i'm pretty sure unshielded is OK for this amp.
Btw, i'm very surprised that you guys seem to not have much love for Cinemag; they have very good products at good prices and their CMLI-15/15 can probably be used instead Lundahl 1690. It has shielding can (single or dual) and shields between windings. See the datasheet, note that max. level is quoted at 20Hz (30Hz for LL):
http://cinemag.biz/line_input/CMLI-15-15PCA.pdfhttp://cinemag.biz/line_input/CMLI-15-15B.pdf
IIRC, this is a version of highly regarded Jensen JT-11-P and Cinemag holds it's patents...
It would be interesting to know how amorphous cores sound compared to ones with ordinary steel or nickel. I like Cinemag's cores with 50%Ni50%Steel for cases where i want a bit of coloration, and nickel cores for cleanest sound. You guys might be interested in reading this paper about transformer laminations:
http://cinemag.biz/application_notes/AN-104.pdf
Since i heard Ni and 50%Ni/50%Steel i almost stopped using transformers with steel cores like Edcor because first two tend to sound better.
Thank you for the compliments. I'm very proud of this project, especially how good it sounds. I currently have some PrimaLuna tube gear that I use as a reference. The PL products are very good performers. The Millett Uniamps compare favorably except when it comes to imaging and soundstage; things the PL gear are superb at. But the comparison is not really fair considering the respective costs. I have also compared the Uniamps to a Dynaco kit built by a friend. The Uniamps sounded better in all respects.
I don't really have a tally on the cost. I didn't keep track and never do
. Of course, monobloc construction adds to the cost. I used Edcor xfmrs; nothing exotic. Decent parts on the PCB but no "boutique" caps or resistors. Tubes are SED KT88 and E-H. The chassis is a standard 19" rack case which I always use for my projects. Plenty of room for the xfmrs, PCB and tubes.I wanted more room in my layout as opposed to Pete's prototype as shown on his website. My amps run cool and very, very quiet.
Pete's boards are top-shelf. I also built his "Engineers Amp" and it also worked well right off the start. However, the Uniamps are a big leap ahead in performance; far more than I expected actually.
Taking the usual care in construction, and using Pete's excellent documentation, you should have no trouble building a pair of fine-sounding amps. Like I said, I haven't felt like building anything else, feeling these would be very hard to top. Good luck with your build!
layout and wiring
Neonthecat,
I'm collecting my parts to build these amp. This will be my first amp build and I too thought the design was easier. I was wondering if you had a picture of the bottom of your amps? I would like to see how you ran the wires. As you mentioned you didn't have any noise problems.
I've seen several different builds including Pete's layout. Gio's uniamp build in another forum looked nice. lI already have the James output transformers and have contacted them for a quote on the PT and chokes. I will order them when I go back on holiday to the U.S. Wire transfers from China can be a bit problematic.
Your right this is not a budget build. If I go with the LL1690 inputs it will run the cost up even more.
Neonthecat,
I'm collecting my parts to build these amp. This will be my first amp build and I too thought the design was easier. I was wondering if you had a picture of the bottom of your amps? I would like to see how you ran the wires. As you mentioned you didn't have any noise problems.
I've seen several different builds including Pete's layout. Gio's uniamp build in another forum looked nice. lI already have the James output transformers and have contacted them for a quote on the PT and chokes. I will order them when I go back on holiday to the U.S. Wire transfers from China can be a bit problematic.
Your right this is not a budget build. If I go with the LL1690 inputs it will run the cost up even more.
Sure. Nothing fancy here. Lot's of room in the chassis.
Attachments
Thanks, I was just curious about the heater wiring between the KT88 and overall wiring layout. I understand the transformer orientation and heater wiring from MJ books.
Just curious why you split the power tubes up? Did you do it because you like the look better? I'm just trying to learn. I only want to cut my chassis holes once.
Just curious why you split the power tubes up? Did you do it because you like the look better? I'm just trying to learn. I only want to cut my chassis holes once.
I just wanted it to look symmetrical. And there is lots of space around the KT 88's for cooling.
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