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Bijou All Tube Futterman Headphone Amplifier - Page 71

post #1051 of 3981
8/10/08 at 3:01pm
Pictures look great. I hope that you can finish the casing soon.

It appears that you have found a decent compromise with the power line resistors and the 6n6p.

I continue to be surprised at two things: 1) the conduction of the ECC99s and 2) the plate resistance of the EZ81.

But, when the current draw starts to creep into the 80mA range then we're out of the spec for the dropping resistors in the filter section. That is, they were originally designed to drop the right voltage for 50-65mA. At 84mA they drop too much voltage for the regulator.

You could try making R7 and R8 smaller, say 270R each. You probably won't increase the ripple noise, but you might be able to run with 84mA and the ECC99s.

Still, this seems to be good news.
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post #1052 of 3981
8/10/08 at 3:37pm
Quote:
Originally Posted by runeight View Post
Pictures look great. I hope that you can finish the casing soon.
Alex, thank you! The casing is finished, I just removed the top cover that also hold the back panel. I'm not sure if my casing is optimal. If I would start from the beginning I probably would go with externally mounted tubes and transformer.

Quote:
Originally Posted by runeight View Post
I continue to be surprised at two things: 1) the conduction of the ECC99s and 2) the plate resistance of the EZ81.
EZ81 seems to be pretty reasonable - with my ez80 I was getting lower voltage at C6. But from ECC99 I was expecting lower current draw than from 6n6p. Maybe I just need to give ECC99 more time? I remember 6n6p was drawing more current when it was younger :-) I have about 25 hrs on ECC99 right now (maybe less).

Quote:
Originally Posted by runeight View Post
But, when the current draw starts to creep into the 80mA range then we're out of the spec for the dropping resistors in the filter section. That is, they were originally designed to drop the right voltage for 50-65mA. At 84mA they drop too much voltage for the regulator.
I'm getting ~45 VDC on R7+R8 with 6n6p-s and ~50VDC with ECC99-s. So, it's about 68 mA and 76 mA respectively.

Quote:
Originally Posted by runeight View Post
You could try making R7 and R8 smaller, say 270R each. You probably won't increase the ripple noise, but you might be able to run with 84mA and the ECC99s.
Yes, I started thinking about that but wanted to take my chances with serial resistors to primary.

Quote:
Originally Posted by runeight View Post
Still, this seems to be good news.
Yep, and it sounds great also! Many thanks to you Alex! :-)

Maybe I'll try to redo the input wiring with the grounding method you mentioned a few days ago.

Alex, just wanted to mention that maybe we need larger holes for Plate and Cathode resistors. I had some hard time trying to fit 2W resistor for R3.
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post #1053 of 3981
8/10/08 at 7:38pm
I'm going to install a set of 47uF 500v Ruby Gold caps across my output caps to take the 410uF to 457uF. I just realized that I had those in my parts bin. Don't know if that will really extend the bass or increase low mids, or just reduce sound quality. Here goes. Edit: yeah thats good news Rfsam, happy to hear that you have built another great sounding amp! I'm really enjoying the sound too, but just another tweak to see if I can get even more.
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post #1054 of 3981
8/10/08 at 9:23pm
Did it make a positive change? Uh well yes, can I say Orpheus for the cash challenged? Wow! Nice and plump(like a fat grub from the Australian outback, juicy) signature, with plenty of detail. Fat bass and mids just right. Vocals golden, no distortion. I couldn't be happier with the sound now! Edit: I have to say that with the K701's, don't go any lower than 460uF for your total output capacitance. Edit: it cost about $400.00 to build the Bijou in my configuration, but sounds like ten times my investment! Built in an appropriate commercial grade chassis with WBT connectors, it wouldn't be out of place in the nearest high-end Hi-Fi stereo store.
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post #1055 of 3981
8/11/08 at 9:48am
Hey amphead, what cap are you using for your output cap (c5)? I am also trying to tweak my amp out for use with k701's
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post #1056 of 3981
8/11/08 at 3:01pm
Gents, I will build a bijou this year and am just putting in an order for a case (Buying from hifi2000, tagging it on to an order for a dac case.

I am looking at this: does it look a suitable size? modushop.biz
(330 x 280 mm).

It looks tight but doable. Or should i look for something bigger to give a bit more room for the transformer (is huma big problem? I will mount the tranny ontop, and all tubes will be poking through.
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post #1057 of 3981
8/11/08 at 3:33pm
Quote:
Originally Posted by amphead View Post
Did it make a positive change? Uh well yes, can I say Orpheus for the cash challenged? Wow! Nice and plump(like a fat grub from the Australian outback, juicy) signature, with plenty of detail. Fat bass and mids just right. Vocals golden, no distortion. I couldn't be happier with the sound now! Edit: I have to say that with the K701's, don't go any lower than 460uF for your total output capacitance. Edit: it cost about $400.00 to build the Bijou in my configuration, but sounds like ten times my investment! Built in an appropriate commercial grade chassis with WBT connectors, it wouldn't be out of place in the nearest high-end Hi-Fi stereo store.

Amphead, good to hear that! :-) I think in your case it's not the total value of the output cap that you increased but the total Q of those 3 caps (you have 3 of them in parallel, right?).
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post #1058 of 3981
8/11/08 at 3:41pm
sorry
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post #1059 of 3981
8/11/08 at 3:47pm
Quote:
Originally Posted by amphead View Post
Edit: yeah thats good news Rfsam, happy to hear that you have built another great sounding amp! I'm really enjoying the sound too, but just another tweak to see if I can get even more.
Amphead, thank you :-) I'll try to reduce the hum by using the grounded wiring scheme proposed by runeight. Maybe I'll just stop after that and just start listening more music :-) Could you post pictures of these caps?
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post #1060 of 3981
8/11/08 at 7:29pm
See next post.
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post #1061 of 3981
8/11/08 at 7:30pm
Here is a link to the 410uF photoflash caps that I used.

RUBYCON PHOTO FLASH / STROBE ELEC CAPACITOR 410UF 300SV - eBay (item 180242991066 end time Aug-12-08 08:48:03 PDT)

Here is a link to the 47uF Ruby Gold caps that I used.
http://cgi.ebay.com/Ruby-Gold-Caps-4...QQcmdZViewItem
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post #1062 of 3981
8/11/08 at 9:22pm
Quote:
Originally Posted by amphead View Post
Amphead, thank you! Why did you select this particular electrolytic cap? Is it good? I'm just trying to decide if I need these for myself :-) What could you recommend for polypropylene 1uF cap also? I remember there were some recommendations in this thread (from Ferrari?) but don't want to read all 100+ pages again :-) What do you have for 1uF cap right now?
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post #1063 of 3981
8/11/08 at 9:58pm
The photoflash was recommended by Mazuki, who was one of the first builders of the Bijou, and it turned out to be a smooth sounding capacitor with plenty of detail. The Ruby Gold was something that I had left over from another build and turned out to be very good.
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post #1064 of 3981
8/11/08 at 10:41pm
For 1uF bypass caps. I am using the somewhat pricey Mundorf silver/oil. It has a very detailed and smooth signature. Some others that I would recommend are the Obligato, Auricap and Vcap/teflon foil.
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post #1065 of 3981
8/11/08 at 11:26pm
getting my new transformers later.
will put them in tonight after i get back home from work.
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