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Old 16th May 2011, 03:59 AM   #1
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Smile Pete Millett has another Red Board for sale

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
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Old 16th May 2011, 05:48 PM   #2
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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.
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Old 16th May 2011, 06:15 PM   #3
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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.
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Old 16th May 2011, 07:24 PM   #4
hihopes is offline hihopes  South Africa
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Looks like they have RCA's both sides - but do note that they are rated for a max 5v input signal.
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Old 16th May 2011, 07:46 PM   #5
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5vrms, not 5vpp. Also they have like 5 to choose from, so you can do rca/rca, rca/screw tabs, etc.
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Old 17th May 2011, 04:18 AM   #6
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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
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Old 23rd June 2011, 05:50 PM   #7
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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
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Old 2nd July 2011, 08:29 PM   #8
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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
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Old 22nd March 2012, 12:23 PM   #9
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Hi all
someone has made some progress in the construction of this amplifier?.
I'm thinking of build it and could use the experience of other.

Br

AL
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Old 22nd March 2012, 12:34 PM   #10
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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!

Mono push-pull driver PCB
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