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Old 27th February 2007, 02:30 AM   #1
Trout is offline Trout  United States
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Default 12AV7- 5965 Vs 12AY7

Hi, I have been looking for a bunch of 12AV7's to replace the 12AY7's in a couple guitar amps.

12AV7's appear to be very close to the 12AY7's but I might be missing the bottom line on compatability.

I have a couple sylvania branded tubes which seem like a near perfect match in the amp.

Does anyone have any experience with GE branded 5965? It is my understanding it might also be a viable replacement for the 12AV7.

Trout
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Old 27th February 2007, 03:18 AM   #2
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I'm interested in this topic too, but I'm on your side of the field, asking if:

Take a look at this site, and look at the description for the "classic" 5F6A.

http://www.thetubestore.com/earfenam...Bassman%205F6A

They say that "not" using a 12AY7 will change the sound, and they recommend, if not a 12AY7, to use a 6072A. (which is expensive)

They also say not to use a 5U4 or other than a GZ34. Why?
I've finally amassed several 5U4's since I have has the best of luck with them on my hi-fi amps.

The 5F6A has 4 input jacks, 2 for bright and 2 for normal.
On mods I've seen, they use a 12AX7 for the input stage, instead of the 12AY7, and then still 2 more 12AX7's for the second pre-amp stage (pre-tone block/phase inverter) and then the driver stage to the finals.

Only the first tube is different, it's used as a series gain, instead of a 4 channel parallel.

I found this mod a few months back, I couldn't find it today, as this gent rearranged his pages and it came up 404, but I did scan it from my paper copy:

Click on the link:

http://viewoftheblue.com/tubeworks/out.jpg

(I used a highlighter over all the pots switches & controls, so that's my work, and I hope you can see the gist of the circuit in spite of this marking)
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Old 27th February 2007, 03:44 AM   #3
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Now to go a few steps further. I would like to use a 5U4GB or GC in the power supply, any problem with that? I would eliminate the diodes and use tried & true capicitors 47uF / 100uF and a good min 7H choke.

As for questions on this circuit: I see they have 2 differing inputs, and 2 resistors stacked for them, which would be best for guitar and/or mic/other and why?

There's also an "early" volume control between stages of the first tube, then a master after the second tube and the tone stack. Any comments on this design?

The "smooth switch" circuit and it's 3 components (the 22M 10M and .047uf cap are entirely optional according to the author and can be omitted)

Then there's a bunch of stuff like the gain switch, deep switch, and half power switch.
Also a "presence" just before the last stage before the finals.
And also a fine-tune bias adj in the power supply area.

Aside from these mods, and looking at the original Bassman (which uses 5881's, and here using 6L6GC's), does this look like (in its entirety) that with the components shown here on the finals, (220k + 1500k to the triode grids from -48.7v)
and 438 B+ to 1k resistors for the tetrode grids
and 439 vdc through the OPT to the plates would work fine?

Just saying that because this guy has revised and moved his schematics quite a bit, and I'm hoping this would all look to be in the correct ballpark from a good observer, as I'd like to build one of these myself, and am ready to order the parts.
Thanks.
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Old 27th February 2007, 03:57 AM   #4
Trout is offline Trout  United States
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Both of The Models I tinker with call for 12AY7's in the v1 position.

Up until recently I had just used 12AX7's. In my 5E7 thats great, it had no adverse effects, But my 5E3's tend to be far to raw and gritty. Like a runaway frieght train.

I had a few 12AV7's laying around and figured eh, Try them, It cant hurt.
Well, in the 5E3 Deluxe it is a huge improvement. Smoother overdriven tones, and a much more linear volume control.


There are not many new prodution 12AY7's around, EH makes one, And Groove tubes sells some relabeled version.

So looking at NOS was an eye opener, 12AY7's average around 35.00 each on ebay?
OUCH!

12AV7's average $2.50? Thats pretty darn sensible.
I found a bulk lot of 5965 at a bargain, But Im confused on this one.

The Data sheet says computer tubes but this sheets says see 12AV7. http://www.nj7p.org/Tube4.php?tube=5965

Trout
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Old 27th February 2007, 05:10 AM   #5
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hi Trout,

U had perfect eye sight of tubes.

Since the sepc of 6072/12ay7 will close to 12ax7 but had different pins out.

If U like the 5965, pls considerate keep 7062/E180cc, this was HQ versions of 5965 & telefunken 5965 also a good choice.

I had bulk of this tube for future diy project use.

thx

thomas
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Old 27th February 2007, 01:25 PM   #6
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Wow, lots of things to clear up here, let me see if I can be of any help...

1. The 12AV7 has similar mu to a 12AY7/6072, but is tonally somewhat different. It does draw 50% more heater current than a 12AY7, but for most amps it's no problem if you are swapping one tube.

The GE clear top 5965 is a terrific tube in the 12AV7 family, but they can be a bit microphonic. Another 12AV7 family tube is the 7062/E180CC, it's quite nice but pricier. The 12AV7 is a steal!

2. The 5U4 family draws an amp more heater current than the 5AR4. Some amps can supply that, some can't. That's why it's recommended that you not use it.

3. There is no such thing as a 5U4GC (unless it's a relabel of some sort by a vendor). There was the 5U4G "coke" bottle, the 5U4GA, and the 5U4GB - and it's "twin", the 5AS4.

4. The fact that the data sheet says "computer tube" means NOTHING! Most tubes used in audio or music amps were originally designed for something else. A "computer tube" usually has a cathode that is specially constructed to resist "poisoning" (a lack of emissions) after being off for a long period as you might find in a logic gate in a computer. That's it.

5. You can replace the diodes with a tube rectifier, but it won't be easy. You need heater power and an appropriate secondary configuration for a tube. The SS diodes didn't have the same needs.

6. The 6072 and 12AY7 pinout is identical to the 12AX7.
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Old 27th February 2007, 02:04 PM   #7
Trout is offline Trout  United States
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Thanks
for the 12AV7 info Jim!


Quote:
The GE clear top 5965 is a terrific tube in the 12AV7 family, but they can be a bit microphonic. Another 12AV7 family tube is the 7062/E180CC, it's quite nice but pricier. The 12AV7 is a steal!
I have both RCA, and Sylvania 12AV7's here I have been testing in a 5E3 combo and have not run into any microphonic symptoms yet. At the current NOS price t looks to be a good viable replacement for the 12AY7.

The 5965 seems to be really plentiful also, In fact more so than the 12AV7.
My question is does anyone know what brand 5965 to avoid? I see loads of GE's out there.

Trout
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Old 27th February 2007, 02:24 PM   #8
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The GE 5965s are excellent. I know of no brand to avoid either.

As far as microphonics go, the 12AV7s seem pretty resistant, but the 5965 and 7062 have more microphonic tendencies.
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Old 27th February 2007, 02:30 PM   #9
Trout is offline Trout  United States
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Quote:
Originally posted by Jim McShane
The GE 5965s are excellent. I know of no brand to avoid either.

As far as microphonics go, the 12AV7s seem pretty resistant, but the 5965 and 7062 have more microphonic tendencies.
OK Cool,

Jim, Do you have a stockpile of these FS?

If So, PM me,

Trout
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Old 27th February 2007, 09:28 PM   #10
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Thanks for the replies, Jim especially, hopefully I'll be making a new 5F6A clone soon, and this thread has provided some vital info.

I see the pinouts for the 12AY7, 12AV7 and 12AX7 are identical, as are the heater amp ratings (.3a), but the 12AV7 uses .45a
Sounds great that the 12AV7's have given you (Trout) good luck as far as microphonics go, they may be a good route in that case, especially with the price of NOS being great.

There is a 5U4GC, I bought one and it's a Ruby (Russian, I believe), and has the old wavy "G" profile, I assume it's the same spec as a GB. Probably one brand's way to say it "newer".

As far as using a tube rectifier rather than a solid state, I'm trying to go with the original specs, and I'll be drilling the chassis, not converting a unit.

The power xfmr called for is this one:

http://www.tubesandmore.com/scripts/...item=P-TF22798

This does provide enough current (3amps) for a 5U4GB, but from what I've read, the time curves of a GZ34 (going from zero sound to some heavy playing) react well with this amp to provide the best response curves, so that should probably be the way to go.

So for me the original 5F6A plan seems the best, but there are a few mods I'm tempted to try (opinions please):

1) Using a 12AX7 as the input tube, cutting down the 4 input jacks to two, and having an extra gain stage, in conjunction with putting a "bright" switch in the cathode circuit of the very first tube element

2) A "deep switch" above the tone stack, and a "master" just after, would this keep the response and distortion fairly the same at a lower power level (cutting down the volume and keeping the same effects) , or is it not really worth adding?
The one mod also adds a half power switch.

3) A bias adjustment pot 10k, for 6L6GC's, or is the standard 48v in the original circuit OK, given the chance of some minor fluctuation?
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