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Old 20th February 2014, 02:35 AM   #1581
RNMarsh is offline RNMarsh  United States
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The Hundred-Buck Amp Challenge
Looking for a bunch of EF86 tubes and 6CW4. ??

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Old 21st February 2014, 01:17 AM   #1582
AmpKiller66 is offline AmpKiller66  United States
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They're pretty readily available from most tube vendors. The EF86 in particular is a common tube in guitar amps and is currently produced by JJ and Electro-Harmonix, although opinions vary on their quality compared to NOS examples. The 6CW4 appears to be available from all the vendors I've checked for around $17
My band Waffle Stomp: http://www.facebook.com/wafflestompband
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Old 22nd February 2014, 08:59 AM   #1583
Gary Vee is offline Gary Vee  United States
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Location: I'm not here anymore !
Is that what those things are ? ! I have a lot of them but one is a shorty a 8B10 that I use as a paper weight on my table !
It has 4 sections that all test good ! . I always wondered what they were but I never remembered to ask anyone ! .

Last edited by Gary Vee; 22nd February 2014 at 09:04 AM.
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Old 14th June 2014, 06:03 PM   #1584
costis_n is offline costis_n  Greece
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Originally Posted by RNMarsh View Post
Looking for a bunch of EF86 tubes and 6CW4. ??

Go for 6J32P (Soviet equivalent). Cheap and plentiful on ebay or other sites.
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Old 22nd June 2014, 11:51 AM   #1585
scott17 is offline scott17
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Default 6AF11 revisited

About 2 years ago, I put together a 6AF11 amp based on the Squirrel Monkey idea. I was able to stabilize it with no oscillation, and it sounded good.

I wanted to see if I could easily replicate the stable circuit to make sure it was not just the original layout or some other fluke that made it not oscillate. The answer is yes. No oscillation at any volume or settings. At about half volume, it is clean and chimey. Full on it has pretty good drive and nice distortion. In pentode it is around 1 watt based on rough measurements, just hitting a power chord and measuring the RMS volts on the speaker terminals.

Sounds surprisingly good for a $3 TV tube. The only tone control is a bright switch. Enabling the feedback calms the bite down a little bit.

The speaker is the Eminence 8" 820H Patriot. Nice sounding speaker for an 8".

Attached Images
File Type: jpg 6af11a.jpg (337.2 KB, 331 views)
File Type: jpg 6af11b.jpg (282.3 KB, 292 views)
File Type: jpg 6af11c.jpg (289.4 KB, 279 views)
File Type: jpg 6af11d.jpg (280.7 KB, 279 views)
File Type: jpg 6af11e.jpg (363.6 KB, 274 views)
File Type: jpg 6AF11guitaramp.jpg (126.2 KB, 152 views)
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Old 22nd June 2014, 03:40 PM   #1586
scott17 is offline scott17
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Yes, I did leave the coupling cap after the second stage off of the drawing.


Here is the correction.
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Old 22nd June 2014, 08:56 PM   #1587
djgibson51 is offline djgibson51  New Zealand
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Nice circuit. Nice build. Did you use a star ground?
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Old 23rd June 2014, 12:44 AM   #1588
scott17 is offline scott17
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A hybrid star/buss ground. On the turret board there are 2 groups of ground points. I connected a solid copper bare 18AWG wire between the pentode & second stage cathode circuit grounds and the 1st stage cathode circuit ground. All other grounds: enclosure, power supply, volume control, input jack, OT secondary, and heater ground connect to this buss wire. The AC ground is a separate wire grounded to the enclosure right at the IEC power inlet.

Concerning the heater ground, I did not use the conventional artificial center tap method, I just grounded one side of the heater supply. It does make a difference in this case which side is grounded. One side gets rid of the hum, and the other side does not have as much of an effect.

Last edited by scott17; 23rd June 2014 at 12:47 AM.
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Old 23rd June 2014, 07:15 PM   #1589
scott17 is offline scott17
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Default Turret board layout

In case anyone is interested in putting one of these together, here is a layout for a 12 position turret or tag board.

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File Type: jpg 6AF11taglayout.jpg (128.0 KB, 155 views)
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Old 11th July 2014, 01:11 AM   #1590
multi-volti is offline multi-volti  United States
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Speco T-7010 trivia.

I got some of these years ago before they were redesigned. I recently had access to a fancy RLC analyzer and took a bunch of measurements on one.

This may be useless info since you can't buy the old design, but hopefully somebody else has some hoarded away.

I converted an XLSX spreadsheet to PDF because I don't have any spreadsheet s/w on this PC, and it's viewable.

I hope it's mostly self-explanatory...I measured inductances for various windings at 1 kHz 1 Vrms, then 10 Vrms and multiple frequencies, leakage inductance for various measured and shorted windings, and whatever else seemed interesting at the time, before I lost my opportunity...visiting someone with work access to a lab...

All inductance measurements were 'dry' (no DC).

I hope this of interesting if not useful to somebody. I found it interesting to see how much primary inductance it had under different measurement conditions. 10 V was the maximum available so that's as high as the data went.

The lamination stack approximate measurements were made by offsetting the stamped steel frame thickness or double that as appropriate with a digital caliper. The cryptic EI lamination dimensions refer to the E and I lamination shapes, and the 'E c w' is E lam center leg width. 'E t/b w' is the width of the other two legs of the E shape lamination.

I didn't figure out the core area, but that's probably easy to figure out, despite being of little use in this case ;O).
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File Type: pdf T7010.pdf (187.7 KB, 35 views)

Last edited by multi-volti; 11th July 2014 at 01:17 AM.
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