One Power transformer to suppy two Eiclone channels?

[EWBrown]

You could probably get away with using one of the Dynaco ST70 type power trannies, providing that you keep the power levels down to around 35-45 WWPC, the PA-060 from Triode Electronics has higher current handling capacity than the original 1960s vintage power trannies.

For monoblock (and hgher power capacity) the P-782 (Triode's new replacement for the MKIII) would be a good choice for each channel.

I think you mentioned using Fostex full range drivers, they are quite efficient, so higher power levels isn't needed as it would be for typical modern speakers with efficiencies around 86 dB SPL (1 watt, 1 meter).

/ed B in NH

[Shannon Parks]

I was wondering if the eiclone amplifier can be powered by one power transformer rather than two? I have heard that splitting amplifiers into mono blocks is not as beneficial as some say. Any comments?

The one catch you want to look for, is filament rating for all the tubes. For example, the Hammond 278CX is the only 270-series tranny to handle the job yet the filament is rated at 6A. Just enough for four EL34s. The power tranny from Toroid of Maryland is a little ugly, but it runs cool and has plenty of power for this application. It's worked great thus far for the Ikezilla and zero noise from it even though it's not shielded. I'm a little hesitant about the PA060 (though the filament capacity is there), but the ST70 idled at not much over 200mA DC current (as Ed says you'd be making a 35-40W amp). I want to run them harder than that in the Ike.

Shannon

[mesherm]

dubwicht,
Normally one eiclone has a Hammond 274BX power tranny. This supplies 375-0-375 volts HV secondary @ 175 milliamps, 3 amps @ 5 vac , 6 amps @ 6.3vac. This is plenty for 2 EL34s (1.5 amps @ 6.3 vac each = 3 amps), the 6SN7 (0.6 amps @ 6.3 vac) and the 12AX7 (0.3 amps @ 6.3 vac).
To run 2 eiclones from one transformer you will have to feed 4 EL34s, 2 6SN7s and 2 12AX7s. This adds up to 7.8 amps @ 6.3 vac. You also need I would guess a minimum of 300 milliamps at 375-0-375 (750 vac) for the HV. The Hammond 278CX has plenty of HV at 400-0-400 @ 465 milliamps but is amost 2 amps short in the 6.3 vac department.
So the task now is to find a power tranny that has both the HV and current for two eiclones AND can supply the extra 6.3 vac for the tube filaments.
The toroid tranny Shannon mentioned is from www.toroid.com , part number 236.5072. It has 360-0-360 vac @ 0.75 amps HV, two 6.3 vac @ 5 amp plus a 5 vac @6 amp filament taps in case you wanted dual tube rectifiers. It also has bias taps.
There is also the possibility of using the 278CX to feed just the EL34s and a separate small filament transformer under the chassis for the 6SN7s and 12AX7s. One could also feed the smaller tube filaments with a DC supply of some kind.

[TerrySmith]

Maybe old color tv transformers could work? Late 60's Zenith and RCA, and other quality brand tv trans. were rated at around 300 to 340v @ + - 500ma, 6.3v @ 8 to 10a.

These mostly used FWB rectifiers, some had doublers.

[Shannon Parks]

It looks like the cost savings I could find using one transformer rather than two would be eaten up by the cost of the single transformer.

Hi dubwicht,

Even looking at some of the classis stereo tube amps, the criticism of the power transformer stands out (eg the ST70's 'undersized' PA060). Heat and weight distribution are other factors. Weight concentration in a stereo unit means you need a very high quality chassis that won't bow or flex. For example, the Eico HF89 is a back breaker to carry around, and the steel chassis is just barely stout enough to keep from buckling. A DIYer would need to fork out some coin for the proper chassis, whereas a monoblock can be fitted into a Hammond aluminum box.

Shannon

[EWBrown]

I've worked on a couple of VTL MB450 amps, the custom made power and output trannies in those are very massive, and undoubtedly very expensive.

These powerful amps have 8 6550s (or KT88s) plus the two driver tubes (6201/12AT7 and 6350) which have a separate small power trannie, mounted on the PC board. The circuitry isn't very much different from the basic "Ike" oe Mullard curciut, just different tubes, a lot more power ahd monster iron, and huge HVDC filter capacitors.


/ed B in NH

[Andrea80]

Hallo all,

I have a power transformer with this data:
360+360V 360mA
6.3V 5.5A
6.3V 5.5A
5V 4A.

Is this able enough to supply a stereo version of Eiclone?
The output power is reduced?

Thanks,
Andrea

[Shannon Parks]

I have a power transformer with this data:
360+360V 360mA
6.3V 5.5A
6.3V 5.5A
5V 4A.

This will be perfect for a stereo unit. But don't be tempted to use tube rectification. Best to use UF5408s for this project and get the maximum B+.

BTW, there's an Antek toroid being produced for $60 that is similar to this, so that is a new option for us.

[Andrea80]

Thanks for yor fast reply Shannon!!!

I have power transformer, all tubes and some components.

I need only O/T...in the U.S. Hammond products cost less than Europe...and not little bit.

[sorenj07]

I don't know what the desired voltage is, but the Antek does provide 360-0 360-0 500mA, and 6.3-0 6.3-0 5A. Another option is to go choke-input with the Hevi-Duty E550, which I am. It essentially quadruples line voltage when run backwards, putting out 120 --> 480V at around ~1140mA (550VA). Total secondary resistance is around 5 ohms 0_0. Less than $30 shipped on eBay. It weighs like 15 pounds though.

[Andrea80]

...But don't be tempted to use tube rectification. Best to use UF5408s for this project and get the maximum B+.

If I would try tube rectification with GZ34...the voltage drop of this tube is 17V...the secondary winding must be about 390-400V...I'm right?

I'm thinking in dual mono assembly Yellow_Light_Colorz_PDT_08 !!

[erichayes]

Hi All,

Andrea, with a 720 VCT power transformer, a 5AR4 rectifier, and a capacitor-input filter network with a primary capacitance of 40 µF, your DC voltage will be in the low 400s--probably between 415 and 425 when you're pulling 225 mA. That 17 volt figure is an instantaneous, one shot value that doesn't take any other parameters (plate dissipation, cathode emissivity, line frequency) into consideration.

If you do decide to go with tube rectification, you'll need to use two 5AR4s even if you use a common power transformer. A single 5AR4 will go vesuvius the first time a kick drum gets hit.