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300B SET Design Project
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=2699
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Author:  mwhouston [ 16 Oct 2010, 17:25 ]
Post subject:  Re: 300B SET Design Project

Matt has managed to give us some values of the passive components. The cathode by-pass caps I can get from work and I used low ESR electros.

The all important inter-stage caps I have had to order from parts connexion. Qian, the customer, has requested Audio Note Silver caps. I, in obedience to his command, ordered the Audio Note Silver and Mylar caps (0.1uf) last night. Only $US404.00 for the pair. I can build a whole amp for that!

https://www.partsconnexion.com/capacito ... ilver.html

Anyone had any experience with these caps? Any comments? Should we have gone for Tin?

Author:  rock4016 [ 16 Oct 2010, 19:09 ]
Post subject:  Re: 300B SET Design Project

http://www.v-cap.com/reviews.php

Some of these folks above prefer V-Caps, I've also heard from several of my friends who can afford audio note silver caps, that the V-caps (TFTF) sound better. I'm more than please with my set, but have no direct comparison experience.

Author:  mwhouston [ 16 Oct 2010, 21:34 ]
Post subject:  Re: 300B SET Design Project

rock4016 wrote:
http://www.v-cap.com/reviews.php

Some of these folks above prefer V-Caps, I've also heard from several of my friends who can afford audio note silver caps, that the V-caps (TFTF) sound better. I'm more than please with my set, but have no direct comparison experience.

So you do have the Audio Notes - Silver?

Author:  Bennybuis [ 17 Oct 2010, 00:16 ]
Post subject:  Re: 300B SET Design Project

Hi Mark,

I do! But I don't like 'em any better than my Russian KI40's, btw. Difference in sound, almost inaudible, difference in price, huge, hahaha.

All the best.

Author:  Geek [ 17 Oct 2010, 05:15 ]
Post subject:  Re: 300B SET Design Project

Bennybuis wrote:
....Russian KI40's, btw. Difference in sound, almost inaudible, difference in price, huge....

I was about to say that when I saw your post.

What about plain ol' MKP polypropylene from WIMA, Vishay/BC Compnents or Epcos?

Panasonic also has great sounding ones... their ECW-F(L) is available through Digikey. Example:
http://search.digikey.com/scripts/DkSea ... ND&x=0&y=0

Cheers!

Author:  tombethe [ 17 Oct 2010, 08:47 ]
Post subject:  Re: 300B SET Design Project

Hi all,

like Gregg mentioned before, I would also vote for the good and cheaper MKP caps.
Since i bought them the first time, I stick with my Mundorf, Audyn or Solen caps. They are really good - for a resonable price.
Even the Orange Drops work fine (they are a bit like the Panasonics and sound really sweet to me).

All this caps are a bit different in sound, but who can really hear and feel that difference? "Normal" listeners or customers imo not.
Someone must have very good ears to hear the sonic quality and the special sound of a very special capacitor..
If there exists any very special sound for xxx dollars... I hope they are also made by japanese virgins at full moon.
That would explain the price ;-).

A pretty much better way to get a good sounding amplifier is a damn good design (IMO), not an $$$ component.

A few months ago i found an interesting article from Gabi (Gabriel Bucataru from Sound GarageTales)
about capacitors and the noise if they are not connected right. Might be a better improvement instead of spending much $$$:
http://www.soundgaragetales.com/amp-building/outside-foil-capacitor

Have fun ;-).

Author:  mwhouston [ 17 Oct 2010, 09:31 ]
Post subject:  Re: 300B SET Design Project

Thanks for your comments. I have a customer who wants these caps and I get to listen to them with no money leaving my pocket. Who am I to argue?

I'm a Jensen copper.paper and oil fan. Not just that I bought a $1K's worth so I have to love them for a long time yet.

Author:  Suncalc [ 17 Oct 2010, 11:53 ]
Post subject:  Re: 300B SET Design Project

Quote:
A few months ago i found an interesting article from Gabi (Gabriel Bucataru from Sound GarageTales)
about capacitors and the noise if they are not connected right. Might be a better improvement instead of spending much $$$:
http://www.soundgaragetales.com/amp-bui ... -capacitor


Be careful what you take away from this article. He is correct in the effects for his test setup, but his conclusions are dependant on the capicator having one side at AC ground. When installed in this position, if you grip the cap and induce a hum signal in the outer layer there is a normal capicative reactance to the inner layer (i.e. the no-outer foil part of the cap). For an 0.1 µf cap this is about 26.5kΩ (1/(2*pi*60*0.1e-6)). If the outer foil end is at ac ground, then the induced signal will be greatly attenuated, if not it gets pumped directly into the amp.

However, if the capacitor is installed in a position where one end is NOT at AC ground, say as a coupling capicator, then the effective noise path impedance is dependant on the components around the cap as well. In this configuration, any noise attenuation seen from signal induced in the outer shell is only attenuated the same as any other 60Hz part of the signal.

The only place I see where this might be an issue is in a very low signal input stage where a capacitor is being used as part of an equalization network and has one side tied to ground. In the coupling role I just can't see this making any real difference.

Just one Engineer's opinion. :)

Author:  tombethe [ 17 Oct 2010, 17:36 ]
Post subject:  Re: 300B SET Design Project

Hi Matt,

thanks for the kind reply and for the comment. This was a great explaination!
I also must say that your thread is great. All the work and all the calculations you have done
are great stuff for learning and also great to improve the tube builders knowledge of basic designing.
The basics are explained very well and i think that advanced builders also can learn a lot here.

I must admit that i didn't follow the thread from the beginning, but the more i read the more i keep in mind!
Man - you must be an old school professional engineer ;-).

Let me thank you for all the work and knowledge you have submitted and shared in this thread.
I wish we had more people who share their knowledge on the DIY-Forums.
There are many people out there who want to know howto. Just my :2c:.

Have fun ;-).

Author:  Suncalc [ 18 Oct 2010, 23:22 ]
Post subject:  Re: 300B SET Design Project

An interesting issue has arisen with the power supply.

The combination of the high DC voltage (454v) and the moderately high current (196mA), giving rise to an equivalent load of only 2.31kΩ, while using a vacuum tube rectifier (5U4) means that the effective Edc/Em is only about 0.74. This means that I need a transformer secondary voltage of 1226VCT. I can get a 700 series Hammond transformer with a 1250VCT, 200mA secondary (it's an 8 pound beast) but it has no filament windings. This means that I'm thinking about a dual secondary Hammond u-bracket transformer for the 300B DC heaters (to remain hidden inside the chassis) and an Edcor dedicated filament transformer (XPWR28) for the 5U4 and 6SN7 filaments.

It looks like the power supply itself is going to be more complicated then the rest of the amp. I'll get the details of the design decisions and the resultant schematics posted as soon as possible.

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