Exotic component choice for a GC

carlosfm · 2004-01-19 5:07 pm

Peter, you should have the 22k resistor IF you don't use the cap from Ri to ground.
I think that the input cap doesn't change anything here.
And you're right, you should have a resistor at around the same value as the feedback resistor, so 22k is correct.
Higher value resistor and DC jumps to a higher value.

In my case, I use a 33uf bypassed with 150nf cap from Ri to ground.
I have a 50k log pot.
Initially I had a 22k shunt resistor.
I removed it.
No difference in DC and better sound.
This is my experience.
BTW, the electrolythic cap is not such a bad thing IF you bypass it.
Otherwise you'll notice some lack of clarity, detail.
The sound, as it is, is amazing, AND no DC.

It's up to you guys to experiment and decide what's best.

amo · 2004-01-19 8:21 pm

Nuuk said:
I second the suggestion to use a stepped attenuator instead of a pot. IMHO the attenuator is clearly superior.

For the IGC, use the one shown on my Gainclone FAQ page on Decibel Dungeon.

I like a pair of Welwyn RC55 resistors for the feedback and matched carbon films elsewhere.

The Blackgate caps are unlikely to sound that much different to the Panasonic FC's given the huge different in price.

I use the MUR860's for the rectifier bridges and have no inclination to try anything else given the sound of any of my Gainclones.

Do use a transformer for each channel with either one or two bridges.

Use a heavy heatsink, not only for keeping the chip cool but for resonance reasons too.

For an input cap, a polypropylene is ideal.

But do remember that this is all personal taste - there is no ideal recipe other than the one you achieve by trial and error!

Hi-

Why does your GC on the Dungeon Site have such a high value for the Feedback resistor, compared to National's documentation, and other designs as well? How did you arive at that value and what are the effects? Thanks!

Nuuk · 2004-01-19 9:50 pm

Why does your GC on the Dungeon Site have such a high value for the Feedback resistor, compared to National's documentation, and other designs as well? How did you arive at that value and what are the effects? Thanks!

All the GC circuits that I have built have been based on circuits that I have seen on this and the Chip Amp forum.

Also, I am not sure which one of the four Gainclones that I have built you refer to.

The VBIGC feedback resistor is 1 meg as recommended by Joe Rasmussen who came up with the original idea. You can read more on his circuit HERE.

Peter Daniel · 2004-01-19 9:56 pm

amo said:
Hi-

Why does your GC on the Dungeon Site have such a high value for the Feedback resistor, compared to National's documentation?

National's documentation shows the amp in NI version. If you build an inverting circuit, the feedback resistor is usually 10 times bigger (200k, up to 1meg, depending who's behind the circuit)

jean-paul · 2004-01-19 11:27 pm

I'm not interested in BG NX caps. I was using N type for a while, but I don't think they are worth the price.

2 Euro per piece and not worth the money !?!?

static · 2004-01-19 11:30 pm

Peter probably meant the higher valued ones (and much more expensive) for PS filtering

Alex

Peter Daniel · 2004-01-19 11:33 pm

jean-paul said:
2 Euro per piece and not worth the money !?!?

If you can get 1000/50 for 2 Euro/pc, I'll take any amount

I still regard 4.7 BG N as one of the best choices for coupling applications, but in PS filtering they are not that appealing comparing to STD grade.

jean-paul · 2004-01-19 11:35 pm

Since you were talking about NX I assumed you meant the input cap ( 4.7 uF ) because there does not exist a NX 1000 uF 50 V....

IIRC 1000 uF 50 V N series is 15.65 Euro/piece here.

Peter Daniel · 2004-01-19 11:37 pm

Do you know how sonically NX compares to N?

Peter Daniel · 2004-01-19 11:38 pm

jean-paul said:
IIRC 1000 uF 50 V N series is 15.65 Euro/piece here.

It's about $70 here, so check your info again. If you are correct, you might have a good product to offer here (in a Trading Post section)

Peter Daniel · 2004-01-19 11:43 pm

Actually it was $70 last year. It seems like prices on BG go down. First it was partsconnexion and now I see that percy reduced his prices on that caps as well. Currently it's $54/pc. Much cheaper but still expensive. I don't think you can get it for 15 Euro.

static · 2004-01-20 4:42 am

Peter, how come you had never tried the Blackgate FK type?
I heard from several sources that they are significantly better as PS caps than standard type.

Here is one link:
http://www.musicalconcepts.com/what's_new.htm

Personally i think you should give them a try (and let us know about it after

I was a bit surprised when you decided to use N/NX on PS. I never heard of anyone using nonpolars on PS. But I appreciate an open mind.

Alex

Peter Daniel · 2004-01-20 4:55 am

You ever heard about people using film caps in PS? Well, some do. Even Sonic Frontieers tried that at one time.

What blows me away is when I'm playing two identical amps to people, one with STD version of BG, the other with type N, and they prefer STD caps

Pretty interesting, isn't it?

I bought some F series BG recently and they are not that much different from STD version.

static · 2004-01-20 5:10 am

By F, do you mean the FK type?

That is good that you actually tried both. I contacted John Hillig, the owner of Musical Concepts, the website i posted a link to in my prev post.
He only tried the FK, and was happy with it.
FK's are like 4 times more $$$ than STD.

Maybe you (or me when i get them, or someone else) should try the N/NX in super-E configuration.
Some claim improvement and the BG website also recommends the super-E for the least possible distortion.

Also I heard that Blackgates take forever to break in properly.

Cheers
Alex

Peter Daniel · 2004-01-20 5:59 am

If you check http://www.percyaudio.com/Catalog.pdf you'll notice that FK are not even twice as expensive as STD. I tried N type in super-E configuration (2 x 1000/50) and didn't like the effect at all. A single cap in PS filtering sounded much better. It is also said (in some circles) that BG work best if not paralleled.

Mad_K · 2004-01-20 6:36 am

Audio Note UK has BG STD 50V/1000uF listed at £ 9.99 ...

Steve Eddy · 2004-01-20 6:41 am

static said:
By F, do you mean the FK type?

Hehehe. That reminds me of an old advertising slogan by outdoor advertising (i.e. billboards) giant Foster & Kleiser.

The slogan was "When you see F, you see K."

Think about it.

se

tbla · 2004-01-20 7:19 am

.....did someone mention the ELNA SILMIC 1000/50V....

JOE DIRT® · 2004-01-20 7:29 am

elna caps are quite good ...but I have no recordable evidence

secanbj · 2004-01-20 7:38 am

Reasonably Priced Black Gate Capacitors

I just found this site
http://www.kyoto-electro.com/index.html were they claim to sell Black Gate standard 50v/1000uF for 15$

/Anders

Exotic component choice for a GC

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