Alternative Tubes

Chappy · Post by **Chappy** » Mon 12/12/05 9:12 pm

Has anyone here tried building amps with "other than mainstream tubes"?

I've got a whole bunch of used 2C51's and 6AQ5's all of which are military grade. I understand that the Western Electric 2C51's are dead quiet preamp tubes and that the 6AQ5's are similar to the 6BQ5/EL84's in tone. Anyone tried these in a homebrew guitar amp?

Chappy

Easto · Post by **Easto** » Thu 12/15/05 12:00 pm

^bump^

Just to keep the thread alive.

I'm a relative newcomer to the whole tube amp thing myself and have wondered the same. I understand what everyone is using now (12a*7, EL84 etc) have probably been determined to be the best choice through much testing... but when I see other preamp/amp tubes being sold for next to nothing i.e. not the tube dejour, I wonder if there may be a new configuration waiting to be found.

Easto

Andrew4566 · Post by **Andrew4566** » Thu 12/15/05 12:08 pm

The 6aq5 is actually a 7pin version of the 6v6 and has been used in the micro champ here:

http://www.firebottle.com/ampage/homebr ... 832pEJcGc1

I think in push-pull they put out like 10 watts.

There is also a princeton with one here:

http://www.diycustomamps.com/diy_amps.html

And the Fender musicmaster bass

http://www.ampwares.com/ffg/

-Andy

brownnote · Post by **brownnote** » Thu 12/15/05 1:01 pm

I can tell you from experience that the 6AQ5 tube rocks!
Really nice compression and tone. I recommend trying a single ended design like the princeton, etc.

Chappy · Post by **Chappy** » Thu 12/15/05 1:15 pm

brownnote wrote:I can tell you from experience that the 6AQ5 tube rocks!
Really nice compression and tone. I recommend trying a single ended design like the princeton, etc.

Thats what I wanted to hear. These things are only 5 bucks a piece for mil spec 6005 versions, or RCA NOS. I don't need a screaming loud amp anyway, its just for home use.

Andrew thanks for the links.

stratwrassler · Post by **stratwrassler** » Fri 06/30/06 1:28 pm

I just got it in the mail and fired it up yesterday. I need to tame the eq and the gain of that 6au6 preamp a bit, but man it screams through my 4x10.

Tone wise it definately reminds me of the 18watt circuits I've heard with el84's, so I'm a bit surprised it's considered a lil' 6v6.

Peace,
Rico

P.S. Anyone got shematics for a K10 or anything else using a 6au6 and 6aq5's?

Bluesmechanic · Post by **Bluesmechanic** » Fri 06/30/06 6:31 pm

Here is one I like.

Post by **zaphod_phil** » Sat 07/01/06 8:47 am

stratwrassler wrote:I just got it in the mail and fired it up yesterday.

You just got what in the mail...

novemberrain · Post by **novemberrain** » Sun 07/02/06 1:32 pm

There's a couple great things about 6AQ5s...

Great Thing One is that in North America they were used in a million applications so they're quite common. Just about every old black and white television set used one for the audio output as did numerous tape decks, phonographs, CB radios and the like. The industrial 6005 version shows up in vintage oscilloscopes as does the plain vanilla 6AQ5. If you can't round up a shoe box full of used 6AQ5s in a year in the U.S. you are certainly not eligible for your Ultimate Parts Scrounger merit badge!

Great Thing Two is that a 6AQ5 within its ratings acts a whole lot like a 6V6. I have a bushel of small power transformers that have 240-275 volts on the high voltage, yes a 6BQ5 will work with that but the point is to get your 6AQ5s for FREE! It's great fun and entertainment to build small amps for minimal monetary outlay but y'all know that already!

BTW you'll find the proper output transformer to work with your 6AQ5 in most audio applications where you'll find the 6AQ5 itself. If you're parting a phonograph or a tape deck the power tranny will usually be aplicable to a small guitar amp as well.

stratwrassler · Post by **stratwrassler** » Sun 07/02/06 3:15 pm

zaphod_phil wrote:
stratwrassler wrote:I just got it in the mail and fired it up yesterday.
You just got what in the mail...

Heh, a Bogen K10 which uses a 6au6 preamp and 6aq5 finals.

Peace,

Rico

Post by **zaphod_phil** » Sun 07/02/06 3:59 pm

Another alternative 6V6-like tube is the 6EZ5 which was also used in a lot of TVs. Its characteristics are very close to the 6V6, except it has a max dissipation of 12W, rather than 14W like a regular 6V6G. They're pretty cheap and I've just bought a couple off eBay to try out. Supposedly a 6EZ5 sounds very much like a small EL34. If so, that's going to be way cool.

engels · Post by **engels** » Wed 07/05/06 6:49 am

I would suggest buying 7C5's which are loctal 6V6 equivalent and they're cheap. The only problem is getting loktal sockets, but I've found them as cheap as $15 for ten units on ebay new - if someone needs a link to the ebay store I will post it. 7C5 is superb and you will find only NOS stuff which sounds awesome. I love them.
Now I'm ordering a pair of 6Y6's which falls somewhere between 6V6 and 6L6 but require low voltage - 200V plates and 135V screens.
As for preamp tubes - the choises are endless... check out 6C8G, 7F7, 6F8, ...

www.tubesandmore.com have discounts on many cool tubes untill 17 of july

jimincfalls · Post by **jimincfalls** » Fri 02/09/24 12:31 pm

I realize this is an older thread, but wouldn't mind knowing if there are options for building a fender style tube amp using "alternative" tubes in 2024. for example, a quick check of tube sets, for a Princeton Reverb, cost between $125 - $150 using the traditional set.

Post by **Bieworm** » Fri 02/09/24 1:42 pm

jimincfalls wrote: ↑
Fri 02/09/24 12:31 pm
I realize this is an older thread, but wouldn't mind knowing if there are options for building a fender style tube amp using "alternative" tubes in 2024. for example, a quick check of tube sets, for a Princeton Reverb, cost between $125 - $150 using the traditional set.

I use NOS Russian Voskhod 6N2P-EV instead of 12AX7, which cost 4€ a piece and are extremely reliable + sound great. The 6V6 I substitute with EL90, which are 9 pin 6AQ5 or 6V6. But for the EL90 you need to drop the plate voltage to max 275VDC. No tube rectifier either. It saves €€€ but doesn’t compromise the sound.

jimincfalls · Post by **jimincfalls** » Fri 02/09/24 7:36 pm

Thx for the heads-up on the russian tubes. From the quick search I did on the web, it looks like they can be had much cheaper than the "traditional" tubes.

I'm still learning with amplifier electronics and had a couple questions:
1. Dropping plate voltage: is this done through setting the bias?
2. Rectifier: why is there no need for a rectifier tube?

Post by **Bieworm** » Sat 02/10/24 3:10 am

You can get equivalent tone characteristics with a solid state rectifier. It’s way more reliable too. The only thing it doesn’t is provide sag. But you can get some sag by adding a higher powered 100 ohm resistor after the rectifier.
Dropping B+ will happen when you adjust the bias to a hotter level, but that’s not the proper way. It all starts with choosing a matching PT (power transformer). For the Princeton Reverb with EL90 I use a PT with a 200-0-200V secondary, or even a 0-200V without center tap. This would yield a B+ of 283V approximately. This is fine.
The reverb driver tube is preferably still a 12AT7, which would be the most expensive tube in the amp at about 20€.
Here is the layout. Schematic is pretty much Princeton reverb, except some cathode bypass caps, which I changed the value of. Also the NFB on/off switch is added, as is the dwell control. The MV is easily omitted and totally obsolete IMHO

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