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Super simple single stage tube preamp
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=3266
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Author:  eldarvanyar [ 15 Jan 2019, 14:28 ]
Post subject:  Re: Super simple single stage tube preamp

If I were to build the S4 inside a case, rather than on top, would this be suitable

External dimensions: width 222MM * depth 308MM * height 91MM

Internal dimensions: width 210MM * depth 296MM * height 85MM

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F273080552510

As I am in the U.K. I would be looking to use a Hammond 369EX transformer (if that is the correct one to use 240v)

AC High Voltage Secondary R.M.S 380V C.T. @ 75ma.
Bias Tap: 50 VAC tap from high voltage secondary C.T
Filament 1 VAC 6.3V C.T. @ 2.5A


However there is the 369BX with AC High Voltage Secondary R.M.S 300V C.T. @ 86ma.
50
6.3V C.T. @ 2A

Length: 69.85 mm
Width:63.5 mm
Height: 77.72 mm

https://www.mouser.co.uk/datasheet/2/177/300-951115.pdf

If not what would the minimum suggested size be

Thanks

Author:  mwhouston [ 15 Jan 2019, 16:54 ]
Post subject:  Re: Super simple single stage tube preamp

Small tubes like a 12AX7 run quite cool. I have built a few devices where the tubes are enclosed. I think if there is some venting holes or grill at the top and some holes in the bottom, near the tube, you should have no problems. The power tranni may get hotter than the tube.

Author:  Suncalc [ 15 Jan 2019, 19:26 ]
Post subject:  Re: Super simple single stage tube preamp

This may work with everything inside. Just remember that the transformer will have to be mounted a little off the metal so you can route the wires out from under the bell. Just a couple of washers under each foot should do. You only have about 7mm margin in transformer height so it will be tight. Unless, of course, you mount the transformer to the side of the case instead of the bottom plate.

Author:  mwhouston [ 16 Jan 2019, 01:42 ]
Post subject:  Re: Super simple single stage tube preamp

Suncalc wrote:
This may work with everything inside. Just remember that the transformer will have to be mounted a little off the metal so you can route the wires out from under the bell. Just a couple of washers under each foot should do. You only have about 7mm margin in transformer height so it will be tight. Unless, of course, you mount the transformer to the side of the case instead of the bottom plate.

With all my tranni mounting, OPT mounting and on ocassions Choke mounting I mount them on split rubber grommets. This provides vibration isolation for tubes etc. easy and cheap to do.

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