Forums - SE84C-S Schematic Help

roguemonk

Ex Member

SE84C-S Schematic Help
03/01/06 at 06:27:11

Hey Folks

I am obsessed with the tube amp thing and am working on teaching myself how it all works...

I'm working on learning to read schematics as part of the process ... using the Zen Amp SE84C-S as a "case study." So far, so good, except for...

1) I am not seeing the front bias adjustment switch on the schematic

2) nor am I seeing the front input jacks ...

Please let me know what I'm missing.

Just to show how nuts I really am ... I've read through the Zen Triode Support Forum and the Tube Lovers Forum. What an amazing collection of information and ideas!

Thanks for all the effort that goes into this community!

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crazy bill the eel killer

Ex Member

Re: SE84C-S Schematic Help
Reply #1 - 03/01/06 at 12:26:57

Hello Roguemonk,

First, welcome to the forum
:)

If you go to the spec page here on the Decware site for the SE84CS, you'll see there are two links for the schematic. One is part of the owners manual ( I'm at work now, and this computer won't open PDF files or I'd give you the direct link). One shows the front inputs, one doesn't. the one that doesn't is probably the older version, as that also shows a bypass cap on the cathode bias resistor on the SV83.

Both schematics do show the adjustable bias feature. Look at the input tube, and you'll see that there are two cathode bias resistors for each side(I'm doing this by memory, but I think they were 1.5k and 2.7k). In the laid back position, only the 1.5k is biasing the tube, and in the forward position the 2.7k is paralleled with the 1.5 to give an effective resistance just under 1k(again, I don't have the schematic in front of me, so if my memory is betraying me, my apologies and someone please correct me).

Have fun Bill :D

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roguemonk

Ex Member

Re: SE84C-S Schematic Help
Reply #2 - 03/01/06 at 13:38:47

Hey Bill

Thanks a whole bunch ... I have it now.

On the front inputs,
I have those spotted clearly now.

On bias adjustment switch (oh man!)
I hate to tell you this, but I will, just to show how far I have to go in this thing...
I saw those all along but thought that was the POWER switch!!
(Which really confused me, because it made no sense...)

I'll keep studying!!

Thanks again for the help

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crazy bill the eel killer Ex Member	Re: SE84C-S Schematic Help Reply #3 - 03/01/06 at 14:14:33 Hello again, http://www.audioxpress.com/bksprods/books/bkaa42.htm Buy this book. It's a great place to start. Bill
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roguemonk

Ex Member

Re: SE84C-S Schematic Help
Reply #4 - 03/01/06 at 15:00:50

Hey Bill

Yet again, thanks!

I have seen Mr. Rozenblit's work recomended a number of places and that title will be my next purchase.

I already have a couple good books on basic electricity and electronics and the two Morgan Jones books. Morgan Jones's Valve Amplifiers is a tad over my head, but, strangely, now that I am getting the schematic deal to make sense, some of his stuff is coming together for me too.

Truth is .. I am having a delightful time!

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DirtDawg

Ex Member

Re: SE84C-S Schematic Help
Reply #5 - 03/01/06 at 15:13:22

Good memory, Bill.

I have an unrelated question, but rather than start a new Zen thread, I thought I'd throw it at the current open thread and see if it draws a response.

In this pic it shows the speaker cables crossing at about a 90 degree angle. I'm wondering if this is an important concern and if it makes a real audible difference. The line cables seem to be arranged similarly.

Another question: The line cables appear to be twisted pairs of unshielded cable, but I could easily be mistaken. I have read about many not using shielding on ICs and this seems absolutely impossible in my area, because of extreme RFI where I live. Are the Decware Silver Reference Interconnects shielded or not? Is the proper twisting of the individual cables enough to reject interference in most cases?

Any advice will be helpful. Thanks.

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Rap_in_Belgium Ex Member	Re: SE84C-S Schematic Help Reply #6 - 03/01/06 at 16:16:34 Has youre Zen arived DD? how does it´s power handling mesure up to the Mac´s ? I mean how does it sound
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DirtDawg

Ex Member

Re: SE84C-S Schematic Help
Reply #7 - 03/01/06 at 16:31:50

I don't have a Zen, yet. There are some concerns starting to enter my mind, today. Not about the seller, but poor mail service as a whole.
Trust me the very first thing I will do is compare it (fairly) with the "high water mark amp" in my experience, that I've come to love. That Mac also has a phenominal "first watt" and clear, warm presence, but it has a very deep bench in case the first watt is injured in play. Grin

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crazy bill the eel killer

Ex Member

Re: SE84C-S Schematic Help
Reply #8 - 03/01/06 at 17:53:43

Thanks Dirtdawg,

First question is I don't know if it makes an audible difference or not. The reasoning is that any fields produced by the cables will influence each other the least if they cross at right angles. Or so I've read.

As for the interconnects, according to Steve's blurb on the Reference Silver, they are not shielded.

Cable configuration can have a lot to do with extraneous field rejection. Twisted pair helps, true Litz configuration is even better.

http://www.chimeralabs.com/diy_braid.html

Shielded cable, of course, can be very effective at rejecting said fields, but other interactions occur between the conductors and shield(which I don't remember off the top of my head. I'll try to find a link or two tonight), that are detrimental to the audio signal. If you must use shielded cable, roll your own. Connect the shield at one end only(the source end), and float it at the other connector.

http://www.alphacore.com/

I use Goertz cabling exclusively. They are absolutely immune to RFI/EMI interference. The webpage makes a great read.
I have two ten foot pair, one balanced, one single ended.(silver Micro-purl). I use neither. If you are willing to pay shipping both ways, you are welcome to borrow either or both to give 'em a listen.

Hello Roguemonk,

I also have the morgon Jones book, and it can be a little overwhelming at first. Doing Rozenblit first will definately help
make Jones an easier read.

Here's a hint.

As you go through both books, FORGET THE MATH, and concentrate on the CONCEPT first. Once you understand the concept, working the numbers makes a lot more sense.

Let me know, Bill :D

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roguemonk

Ex Member

Re: SE84C-S Schematic Help
Reply #9 - 03/01/06 at 19:02:19

[quote author=crazy bill the eel killer link=1141198031/0#8 date=1141235623]
Here's a hint.

As you go through both books, FORGET THE MATH, and concentrate on the CONCEPT first. Once you understand the concept, working the numbers makes a lot more sense.

Let me know, Bill :D [/quote]

Hi Bill

That's really what I am trying to do now ... get the concepts down. I'll admit that I am itching to start soldering the snott out of stuff. But I actually do have kind of an agenda ... basic concepts being #1.

Thanks for the support
John

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