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Old 11th January 2009, 10:16 AM   #671
adamus is offline adamus  United Kingdom
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Update on this ....


Its had about 30hrs to settle in, but people do say blackgates need 100hrs+.

1sts few hours its sounded brilliant, deep bass, extended fluid treble and mids to die for.

10-25hrs..... not so good. muddied bass e.g. Ray lamontagne, till the sun turns black has a double bass throughout, some how the amp lost its definition and the pluck was gone, it was just too muddy).

30hrs+ now were talking! the bass is detailed and drops lower than my solid state. the treble is airy, creates a lovely sense of space. I still think the LF will tighten up some more.

Seems like the blackgate rumours are true, i'll be honest i didnt believe them until this experience.
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Old 11th January 2009, 12:42 PM   #672
Yvesm is offline Yvesm  France
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Quote:
Originally posted by adamus
Update on this ....


Its had about 30hrs to settle in, but people do say blackgates need 100hrs+.

1sts few hours its sounded brilliant, deep bass, extended fluid treble and mids to die for.

10-25hrs..... not so good. muddied bass e.g. Ray lamontagne, till the sun turns black has a double bass throughout, some how the amp lost its definition and the pluck was gone, it was just too muddy).

30hrs+ now were talking! the bass is detailed and drops lower than my solid state. the treble is airy, creates a lovely sense of space. I still think the LF will tighten up some more.

Seems like the blackgate rumours are true, i'll be honest i didnt believe them until this experience.


I probably never spend even a quarter for such caps
My religion forbids me to design power stages with by pass capacitors in their cathodes !

BTW, 1mA total current for the LTP is the right value.

Yves.
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Old 11th January 2009, 12:50 PM   #673
adamus is offline adamus  United Kingdom
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I know.... perhaps i could have rained the budget in on the caps. But i am very happy with the results. I only paid 10 for 4 X 470uf blackgates, and 4 for 4 x 1000uf silmics. I am going to have a play with removing the silmics, but i fear i may loose too much bass.

last question, should i increase the resistors between the UL taps and the screens. Currently they are as per the schematic, but i am running 340v b+.

Cheers

Adam.
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Old 11th January 2009, 05:02 PM   #674
Yvesm is offline Yvesm  France
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Quote:
Originally posted by adamus
I know.... perhaps i could have rained the budget in on the caps. But i am very happy with the results. I only paid 10 for 4 X 470uf blackgates, and 4 for 4 x 1000uf silmics. I am going to have a play with removing the silmics, but i fear i may loose too much bass.
No, you can't remove existing caps in this auto bias design, you must go to fixed bias to be allowed to do that.
Quote:

last question, should i increase the resistors between the UL taps and the screens. Currently they are as per the schematic, but i am running 340v b+.
Ahem, my religion also forbids UL

But it allows cult freedom

Yves.
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Old 11th January 2009, 05:07 PM   #675
adamus is offline adamus  United Kingdom
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I'm still an atheist, awaiting to be converted

I dont mean remove all caps, i mean just try blackgates on their own with no bypass.
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Old 12th January 2009, 03:07 AM   #676
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Hi Guys,
Back "on deck" after 3 weeks away on holidays.

On my latest Baby Huey monoblocks I have 350V rails and am using 150 Ohm resistors from the Ultralinear Taps to the EL84 screens.

I have resurrected the original Baby Huey with the CCS biased Output Tubes so that I can do A/B comparisons. On that amplifier I found that the 470uF Blackgate CCS Bypass Capacitors by themselves did impact bass a little and am now using 1000uF Blackgates.

Adamus - I would leave the Silmics in. Your experience with the Blackgate Capacitors is very typical - they sound quite good when first fitted, then they go "Squirrely" for a bit before eventually settling in. This typically takes about 40 hours.

Yvesm - would you care to elaborate on why you don't like Ultralinear. I've seen a number of respected designers (like yourself) say similar things yet I have never been unhappy with it myself - particularly with EL84.

Cheers,
Ian
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Old 12th January 2009, 08:14 AM   #677
Yvesm is offline Yvesm  France
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Quote:
Originally posted by gingertube

. . .
Yvesm - would you care to elaborate on why you don't like Ultralinear. I've seen a number of respected designers (like yourself) say similar things yet I have never been unhappy with it myself - particularly with EL84.

Cheers,
Ian
Mmmmh !

What I beleive in:

-UL reintroduces some Miller effect.
-UL asks for a better OPT.
-UL asks for better PSU regulation/smoothing, in other words, pentodes/tetrodes are less sensitive to plate voltage sag than to screen voltage one and it 'is easier to fix screen voltage than plate + screen one.

Probably, the importance of these points increases with the size of the tubes ? ?

Yves.
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Old 12th January 2009, 09:29 AM   #678
Skorpio is offline Skorpio  Denmark
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I have a pair of OPT used in a guitar KT88 amp. They are heavy (approx. 3kg each) and I guess used in 70-100W amp.

I wonder if they would be useable for hifi, when only needed to deliver 10-15W?

The are norminel 3500:8 Ohm with 40% UL tappings. But by using 4 Ohm secondary I can get 7000:8...will that be useable for Baby Huey or other EL84 amps?
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Old 12th January 2009, 10:37 PM   #679
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Skorpio,
For those output transformers there are 2 obvious options.
If you want to use EL84 then use parallel push pull, that is, 4 output tubes per channel.
Otherwise use a single pair of EL34.
Cheers,
Ian
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Old 13th January 2009, 10:07 AM   #680
Skorpio is offline Skorpio  Denmark
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Ok, do you think the Baby Huey concept will work with EL34 also?

As I understand the special feedback makes up for a good OPT?
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