Ono Parts Suggestions

[sbear]

Hello everybody. I hope you will all welcome me into the Pass Labs DIY community. And now: my story. . .

My roommate bought a JA Michell Focus One turntable and has been off and on looking for a better phono pre than the one on his receiver, but really can't afford to purchase a high class unit. And I, the amatuer electronics hobbyist, suggested that I could probably build a decent pre for a lot less money. So he told me to put my money where my mouth is; He said he would pay the cost of it, but ONLY if it worked. Anyway, after some research on the web I have decided on building the Aleph Ono.
I have studied the schematic and looked around on this forum for a while and have decided this project shouldn't be too hard. But, of course, I do have a few questions my searches failed to answer.

1. Anyone have a parts list that details brands and types of components? I just want to build! Not research every component. (I could also use suggestions on power transformers and supply caps)

2. I'm planning on building this point to point. (Hey, I got a lot of time, just not a lot of money). But, if anyone has a PCB they would like to unload, I might be interested.

3. Transistors- I understand the FETs in the MC stage need to be matched pretty closely. I wouldn't mind doing this myself, but I would mind spending a lot of money buying enough to get ones that match well enough. Can anyone provide these for an additional fee? Someone suggested in another thread that Pass Labs sells matched components, is this true? I might do that.

That's it for now. I would really appreciate any help anyone is willing to provide.

[sbear]

Ok, I guess I posted too quick. I have since found a parts list, but I do have some doubts regarding its accuracy. For starters, this parts list calls for 1/4 watt resistors throughout the entire amp, including the power supply. I figured that R2,44,and 71 (as per the service manual) would need higher power ratings. Is this correct, or is it safe to use the 1/4 watt resistors?
A few questions regarding the power supply- Some have suggested beefing up the power supply with more capacitance, How much higher would be good without going overboard? (related Question, I'm planning on using Panasonic FC series- are these a bad idea?
All the projects I have done before have run on batteries, (heaphone amp, guitar effects) and I have never made an AC power supply, so I could use a little guidance on this subject.

[mjounot]

sbear

I asked the same question on this forum when i built my ono.
I was told 1 watt resistors should do. I used 5 watt. I also used
Panasonic FC capacitors.

Mike

[Bakmeel]

sbear,

1W is a bit small, they tend to get hot. I used 2W metal film, and this works fine.

I have attached a List of Materials in pdf format, that I use with my PCB's. My power supply holds up to 60.000 uF caps per rail, so you can add quite some caps without going overboard. Using a lot smaller caps instead of 1 very big cap is preferred, as large capacitors tend to respond "slow" to load changes. paralelling caps improves this performance.

Building a simple but effective AC power supply is not too difficult. Only be sure to work safe with the parts that carry line voltage, and use a transformer with seperate primaries and secondaries. Most newly bought transfmers have this, so don't worry.

[sbear]

Bakmeel, thank you for the parts list. It's exactly what I needed. So far I have been able to source almost all the parts. I'm having the most trouble locating the LCR polystyrene caps. It seems LCR has no distributor is the USA. However, I have found some Xicon polystyrene caps rated at 50V (the LCR have a lowest rating of 63V) and I was wondering if anyone has an opinion on whether or not these will work okay.

Another PSU question- Are any of the supply caps more critical than the others? I would like to beef up mine, but should I just up the capacitance on all of them the same? or would it be benefical to just make some of them bigger and not worry so much about the other ones?

Thanks

[Bakmeel]

sbear,

If you take the original pass design, you can beef it up to twice of even triple the original capacitance. I suggest you use many smaller caps instead of a few large ones. Large capacitors have a large internal resistance, and a high parasitic impedance (due to the fact that they are actually rolled layers of film). You can overcome this problem by either using many small caps in parallel, or use so-called Low ESR caps. Another trick is to use one or two small caps parallel to a large one. Low-ESR capacitors are generally used in Switchmode PSU's, have a low resistance for high frequencies, and can therefore respond quicker to changes in power demand. These caps are also a bit more expensive than regular ones.

To save costs, you can apply slow and large caps right after the rectifier bridge, and the closer you get to the load, the faster you make them.

Don't oversize C22 and C29 (below the mosfets in the power supply) A large cap here will make your power supply "power up" too slow. 1000uF is the best choice here.

Bouke

[TheMyxin]

[QUOTE]Originally posted by sbear
[B]Ok, I guess I posted too quick. I have since found a parts list, but I do have some doubts regarding its accuracy. For starters, this parts list calls for 1/4 watt resistors throughout the entire amp, including the power supply. I figured that R2,44,and 71 (as per the service manual) would need higher power ratings. Is this correct,

Yes you need higher power rates for this resitors. I have used 2Watt resitors and this works.

, I'm planning on using Panasonic FC series- are these a bad idea?

I have used Panasonic Fcs and they work fine. I


You can send an E-Mail to TheMyxin@ngi.de if you need a Part-List
for the Ono.

[GaryB]

Originally posted by sbear
I have found some Xicon polystyrene caps rated at 50V (the LCR have a lowest rating of 63V) and I was wondering if anyone has an opinion on whether or not these will work okay.

The Xicon polystyrene caps will work fine, but I have found that the quality of the caps in the RIAA feedback network can make a big difference in sound. When I built my ONO, I first started with BC metallized polypro caps from Digikey. Then I upgraded these to polystyrene and foil caps from Michael Percy. I think I had to slightly tweak the RIAA components to match the available components. I can dig up the changes I made if there is interest. I also changed the RIAA resistors to TaN resistors at this point. There was a small but noticeable improvement in sound quality but not enough to get really excited about.
Next someone on this board let me have some 0.01uf Teflon caps and I upgraded the 0.01uf caps in the RIAA network. This was a huge improvement and I would recommend it in the strongest terms. Teflon caps are expensive but they are worth every penny at least in this one application. In a final experiment I replaced the rest of the RIAA caps with Teflon caps but didn't find as big an improvement. Not sure if the quality of these caps was different or if the application was less critical.


Good luck.
---Gary