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Old 22nd September 2008, 03:17 PM   #2641
lineup is offline lineup  Sweden
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Originally posted by Nelson Pass

Let's see....What is my position on Bandwidth?

Oh, I remember. Bandwidth is good unless it's not. By that I
mean that giving consumers a power amplifier with gain and a
very wide bandwith is an invitation to trouble because many
of them (consumers) can't put batteries in a flashlight, much less
do a proper job of grounding in their systems.

Also, bandwidth is good if I get it without having to make a
special effort. As a result my stuff usually gets up to 100 KHz
without any extra parts, so I don't monkey with it.

I have an abstract interest in the acceptance of the F4, but it's
bandwidth is not the part that will influence that - it is the total
lack of voltage gain. It's a surprisingly good sounding piece,
but very few consumers will find that out.

Lastly, since I switched over to FETs, I have not encountered an
instance of RF pickup except for the owner of an Aleph-Ono who
lived in the Empire State Building under the antennae.


1. ... is an inviatation to truble ...
yes, we can read issues/problems in topics all day if wish at diyaudio.com

2. ... 100 kHz without extra parts ...
yes, keeping amplifiers simple & good we often can end up
with an upper bandwidth 5-10 times higher than any man can hear

Your thinking on this is good & down to earth.
And this is one reason people build your amplifiers.
I know this is your philosophy when comes to Pass DIY designs.
Probably you have several exceptions in some of your experiments and commercial designs.

But a few exceptions to a rule, does not make the basic rule worse.
Exceptions does confirm that there is a General Rule.

Lineup regards
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Old 18th October 2008, 02:12 AM   #2642
Liliya is online now Liliya  Norway
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Default F4 and Aikido

CVILLER

I want to build a F4 NP amplifier according to the schema and the PCB layout that you brought in post #163. But as a first step I want to use Aikido. This will give me a kind of a “Moskido” amplifier, very much identical to what Marsupialx suggest in the Moskido thread.
Have I understod this right that with an Aikido as a first step, I have to leave out Q101/102. R101/102/103/104 and C103/104 from the PCB? The signal out from Aikido shall then go directly to the “meeting point” of C101/102.

The PCB you suggest, can I buy it from anyone?

Sincerely

Eivind Stillingen, Norway
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Old 18th October 2008, 02:33 AM   #2643
tms0425 is offline tms0425  United States
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I'm using an Aikido with a complete F4 with great results. I suppose it would be interesting to combine them this way but it sounds terrific as is. Tom
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Old 18th October 2008, 12:50 PM   #2644
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i too have used an aikido (12sx7) with a F4 and it sounded great--until i built the B1 and F5-much more detail
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Old 18th October 2008, 01:27 PM   #2645
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If you can manage to get some BG-NX Caps for the F4 plus a really good power supply, the F4 really comes alive and brings out the extraordinary detail and depth of a well set up Aikido, particularly the 6SN(L)7 version.
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Old 18th October 2008, 03:10 PM   #2646
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12sx7 and 6sn7 are variants of the same beast-imho the part count of a B1 and F5 is so much lower than an Aikido and F4 that they should have an advantage,and i think they do, on solo voices with one instrument it's a toss up but the more complex it gets the F5 just shows more detail and better placement---and on stuff that isn't "audiophile grade" the F5 shines a little more
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Old 19th October 2008, 11:20 AM   #2647
Liliya is online now Liliya  Norway
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Default F4/F5/Aikido

Thanks to Bubba 177, Jameshillj and tms for your answers. Your comments was interesting, even if they did not “hit” exact what I was asking for: What components in F4 do I have to drop out if I want Aikido to replace the first gain stage.

Bubba177, you have had the opportunity to compare F4 and F5. Your conclusion: the more complex it get-F5 give more details and better placement. Its a conclusion that, as far as can see, very much fits well to what NP said when he was asked the same question.

This thoughts have “given birth” to that I might reconsider F4 and go for F5 instead, but still with the Aikido as the first gain stage. Is it a good idea?? And again, what components shall I
“force out”, and where do I connect the signal from Aikido?

I have to mention that the signal to this mix of Aikido and F5 (or F4) will come from a Copland 306 pre, then into a very modded DCX 2496. My loudspeaker are Magnepan 1.6. From 28 to 60 I use NAD 208. From 60 to 600 I intend to use This F4/F5. The top range is taken care of with a modded Music Angel 845. My music taste is very wide, but very much into classics.

Any good advices from all the expert on this forum??

Sincerely

Eivind Stillingen, Norway
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Old 19th October 2008, 11:29 AM   #2648
Liliya is online now Liliya  Norway
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An important correction to my last post.

The signal from my CD (Copland 288) goes to DCX 2496 and then to the Copland 306 before it ends up into my amplifiers.

Eivind Stillingen
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Old 19th October 2008, 04:50 PM   #2649
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Default Voltage across source resistor

Hello! I just finished my F4 ( Finally ) But the bias voltage is slightly different at some of the source resistors +/- 15-20mV. Any ideas?

Thanks!

Dave
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Old 19th October 2008, 05:07 PM   #2650
lykkedk is offline lykkedk  Denmark
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Quote:
Hello! I just finished my F4 ( Finally ) But the bias voltage is slightly different at some of the source resistors +/- 15-20mV. Any ideas?
When i was building mine, i had the same issue with one source-resistor. It was because of improber-matching i think... I just swapped the IRF/IRFP, with another having the same Vgs, from my matching.

You say, that the difference is 15-20mV, which is not very much i guess. - I donno through.

Jesper.
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