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Old 17th March 2007, 02:30 PM   #1
daly41k is offline daly41k  United States
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Default Pass 350.5 vs aleph

Friends and amigos, I have been trying to get heatsinks to begin my xa100 project when a local dealer near me offered a pass 350.5 at a very reasonable price (less than a house but more than some cars). It has made me pause for a moment. Are the 350.5's jfet approved! I built the Aleph 1.2's and they are going on 7 years old with absolutely no problems. But the Prime Minister of the house will not allow them in the living room. They have the standard mosfet input diff's.

With all the Aleph J's being built there must be a substantial improvement in the sound?

I think the 350.5 would make it to living room status but I am not sure what to expect from a sound difference pt of view. If anyone's heard them let me know. I would have to travel 300miles round trip to hear them.

I have heard the MARSH 400's which have a jfet input stage but they use transistors for outputs in class AB so I can't really tell what the affect of the jfets are. I have also built the borbley jfet phono stage with shunt regulators and it sounds terriffic! So i want to expeirment more with jfets.

I would buy the amp just because of all the effort NP puts in to help the diy community. dave
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Old 17th March 2007, 06:07 PM   #2
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It does depend on your taste, but the X350.5 is second only
to the X600.5 sonically in that series. There are very few that
prefer Alephs over it.

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Old 18th March 2007, 04:56 PM   #3
daly41k is offline daly41k  United States
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Default 350.5 vs aleph

Nelson, thanks for the response, my ultimate goal is to bi amp
my speakers. I could use the 350.5 now and then buy another later. I would use one channel for the tweeters and one for the mid bass for each speaker. For now I could use the Aleph 1.2's in the mix. Possibly for the tweeters. I have attached a picture of the speakers that I have built with the aleph's on the floor.

The tweeters do have impedance matching transformers and the array is about 7 ohms. The dc resistance of the fountek 5" tweeters is .2ohm. I will put a 40 uf or 20uf cap in series with the output of the amps for protection against dc offset per your owners manual warning. The dc offset of my aleph's is less than 40mv (one is actually only 20mv) after warmup.

I am also in the process of building an XA100 but my twist would be to use a power Jfett for the voltage gain stage.
To date I have blown up a few trying.

I am using an outboard passive crossover at 24db per octave at 2600hz but I want to try the digital crossover in my deqx speaker/room correction digital preamp at 96db/octave.
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Old 18th March 2007, 05:36 PM   #4
daly41k is offline daly41k  United States
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Default 350.5 vs aleph

Picture of the right speaker and Aleph 1.2. I never got the chasis chrome plated with black anodized heat sinks. Too much work to take it apart now. I did use hexfet diodes and an ac inline filter with a time delay relay to short the input thermistor after 15 seconds. Squeezes a few more volts out of the secondary.
I am using a c-i-c-i-c PS (96kuf per channel-1mh inductors)-2kva xformers. I have put the amps on dolleys so I can move them
around (that is why the prime minister will not let them in the living room).

I am in the process of squezzing the profit margin down at your dealer for the 350.5. He has the mistaken opinion that he can make huge quantities on money on a diy. The fact that I could come back for a second unit should motivate him to give me a huge quantity discount.

In this case, taking some fine wine to the dealers showroom and getting the dealer drunk while discussing the fact that we are related through dna evidence might be the perfect solution. have a good weekend. dave
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Old 18th March 2007, 08:19 PM   #5
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Dave,

nice basement, i take it that your Dali replicas are close to 8 feet high just like the original Mega ?
(keeping my fingers crossed for you obtaining a total black-out deal)
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Old 19th March 2007, 01:48 AM   #6
daly41k is offline daly41k  United States
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Default pass 350.5 vs aleph

Jacco, The problem I have is getting those monsters upstairs, yes they are 8 feet tall. I had the cabinets made at Meniscus audio in Grand Rapids, Michigan as I didn't have the wood working capabiltiy at my home. I put them downstairs to test them and tweak the crossovers. My wife won't let them upstairs with the huge Aleph 1.2's. The DEQX room correction and speaker correction pre amp (digital) allows me to compensate for the basement room. The speakers are 16 feet apart and the listening postion is 14 feet from there. My room is 30 feet by 60 feet. The subs are buggtussel transmission line with their own amp. I am retiring soon and will have to find a home where I can fitt all this into. I admire NP for all the help he gives to our small community and that is why I would buy his products (they also sound excellent) but I still plan to finish the xa100. By the way each speaker is approximately 250lbs or more. dave
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Old 19th March 2007, 02:06 AM   #7
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Quote:
but I still plan to finish the xa100
I have been seeing a lot of references like that lately....

"...half way done with my X1000" or " about to begin a xa350" etc. etc.


Yes, I am confused.

Did I miss something? When did Nelson release the schematics on these?
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Old 19th March 2007, 03:10 PM   #8
daly41k is offline daly41k  United States
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Default 350.5 vs aleph

Dear MPMarino, the schematic for the XA100 is published on the pass threads. Just search and you will find it. It is the 100 watt version. I haven't seen any schematics from NP for this amp. dave
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Old 19th March 2007, 03:19 PM   #9
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Thanks Daly,
I envy your basement. Nice plumbing (lots of clean-outs ) Your next DIY project needs to be to get that nice stuff into the living quarters, unless it's the basement you live in - like me

OK, it's what I thought, all the references towards building X amps consist of at least some conjecture. I'll wait - as long as it takes - I'll wait
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