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Old 25th November 2006, 11:59 PM   #1
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Default Newbie building d3A DRD 300B

Hi to you all! My first appearance on this forum.

Just decided to challange myself and go ahead and try to build a d3A DRD 300B just like ligascon and Kofi Annan. I have no prior experience and no technical education. I'm a lawyer and project manager who has been infected by the hifi-virus since 20 years. Used to play the violin when I was younger and love music of all kinds. Just bought a pair of Oris Reference Basic 200 hornspeakers with AER MD2 fullrange drivers so I think this is the way to go. I have a friend who is an electronics engineer who can help me when it's needed but he's not an audiophile so he will only be able to help me with practical (how to solder properly etc)and general electronics questions.

Like ligascon I will go for Lundahl transformers (as I live in Sweden)and TJ Fullmusic 300B meshplates. I have a few questions about component selection and I'm sure I will come back with a lot more questions along the way so please be patient.

1. Ligascon used ElectraPrint 1.5A filament chokes (I have no clue what it means but the point with this project is to learn the hard way) and I wonder if there is an alternative or is it worth the time and the money to go for these?

2. The "Common mode 2A", what shall I choose?

3. Other components? I want excellent match and quality without spending ridiculous amounts of money. Europen manufacturers are prefered because deliveryy time and shipping costs will be lower. If what you think is the best available components are resonable in price level please suggest these components.

4. I will not go for amorphous transformers (or should I???).

ligascon or Thorsten (or anybody else): If you have the time I would be forever thankful if you would write a list of what components I need and which manufacturers components to choose.

Thanks in advance and see you soon. I will try to keep you updated along the way.

Stefan
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Old 26th November 2006, 05:22 AM   #2
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Filament chokes are a waste of space and money. If you need clean DC then buy a $1 LM350 voltage regulator or modify a 5v switching supply.

Honestly you will get good results with standard parts instead of "audiophile" grade parts that cost 10x what they should. Stick with polypropylene for coupling caps and 1% metal film resistors and everything will turn out fine. You don't need silver wire or $1000 power cords either
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Old 30th November 2006, 03:22 PM   #3
garbage is offline garbage  Singapore
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Thumbs up Re: Newbie building d3A DRD 300B

seeing that it is your first post, and that there are not many replies... i'll just add my 2cents.

Quote:
Originally posted by stefanolo

1. Ligascon used ElectraPrint 1.5A filament chokes (I have no clue what it means but the point with this project is to learn the hard way) and I wonder if there is an alternative or is it worth the time and the money to go for these?
the filament choke is there to reduce ripple further. an alternative is to do without it or get a heater module from guido.

Quote:
Originally posted by stefanolo

2. The "Common mode 2A", what shall I choose?
common mode chokes are found in our computer supplies. if you have one lying around, you might want to rip it out to use. actually the 2A rating has a bottle neck of 1.5A caused by the filament chokes, thus a 1.5A common mode choke would be sufficient. but if you are using 300b variants that draw around 1.5A, you should not use both the filament chokes and the common mode chokes.

Quote:
Originally posted by stefanolo

3. Other components? I want excellent match and quality without spending ridiculous amounts of money. Europen manufacturers are prefered because deliveryy time and shipping costs will be lower. If what you think is the best available components are resonable in price level please suggest these components.

4. I will not go for amorphous transformers (or should I???).

ligascon or Thorsten (or anybody else): If you have the time I would be forever thankful if you would write a list of what components I need and which manufacturers components to choose.
component choices depends on individual builder and also ease of getting those parts. i suggest you use whatever is easy to source without paying a high price.

btw, i just rebuilt my drd as a d3a/vv302b, all using ac heating and LED bias for the d3a. hum at the speaker terminal with speakers connected is 13.1mV. with a 96db woofer attached for testing, i can barely hear it at a distance of one foot.

below is a night pic of the amp during testing.

Click the image to open in full size.

cheers
garbage
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Old 30th November 2006, 09:52 PM   #4
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astouffer and garbage:

Thanks a lot for your advice! I like your down to earth approach. It's obvious that you have a lot of experience and know what you're talking about.

I will start collecting components and gather info and as a part of that I've read the first 30 pages in "The RCA Radiotron Manual".

Very exiting and informative. Considering I'm a lawyer and not a technician I'm surprised I understand most of it. Every newbie should read it.

See ya,

Stefan
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Old 1st December 2006, 12:15 AM   #5
garbage is offline garbage  Singapore
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good to know that your interest is still running high.

if you intend to build according to the schematic, i think the most difficult parts to source would be the ultra-path capacitor and also the power supply capacitors.

ligascon used capacitors from ducati, which can be found at RS or Farnell. if you want to use vintage oil capacitors such as GEs, then you'll have to start sourcing from ebay or other means.

if you have problems with getting parts for the 300b heater supply, i suggest getting a module from guido tent. at least you will be sure that it'll work fine.

there's no need to match exactly to schematics. just tailor to whatever you can find and ask when in doubt. i'm sure the helpful people here will have an answer for you.

have fun and persevere! i'm sure it will be as much a rewarding project for you as it has been for me. do check out the links with guides for new builders at the sticky on top of this forum.

cheers
garbage
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Old 20th December 2006, 01:23 PM   #6
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Hi Stefan,

Just saw your message.

Firstly, Iīm no longer using the filament supply shown in the schematic but instead I went for Guido Tentīs filament supply. I like that solution better.

As for the transformers, I can just say that I have only tried Lundahl amorphous and I love them. Havenīt tried any others. BUT after buying a few items (transformer volume control and a few chokes) from Pieter at Tribute transformers, I think I will be ordering some output transformers from him in the future. The quality and sound is outstanding but be aware the the wait will be long for delivery.

Please feel free to ask, Iīm sorry I didnīt notice your post earlier.

Regards,

Luis
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Old 22nd December 2006, 02:16 PM   #7
garbage is offline garbage  Singapore
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updated pics of my completed amps if anyone's interested.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

merry xmas diyers!
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Old 3rd February 2007, 11:33 AM   #8
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Garbage and ligascon, very sorry for not responding to your posts. Have been burried in work lately so my first DIY project have been delayed a bit.

Bought a used Audion Silver Night Stereo MkII 2A3 power amp so that I can enjoy some music until the DIY project is finished.


Garbage: Are you satisfied with the sound from your amps?

Luis: Thanks for sharing your experiences of your developing project. I can imagine you never stop exploring what different components and tweaks can do for the sound. Thanks a lot for offering your help and assistance.

/stefan
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Old 3rd February 2007, 02:51 PM   #9
garbage is offline garbage  Singapore
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oh yes. very satisfied with the sound and the project itself.

i used them with a diatone pm610mb in a ported enclosure. around 94db.

currently doing up a 5687 preamp to go with the DRD. previously used passive pots, but gain was a little insufficient.
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