How low can you go...?

[multi]

Davorin
My transformers provides ~600W with very low distortions at 20Hz (also at 16Hz!) with pair QB5/1750 tubes in push-pull AB1-class.
Great looking Transformers!!! You make them?
Phil

 

[davorin]

Yes, I wound up them last year for my next big project: 2 tubes QB5/1750 at output stage in each monoblock!

 

[nitrate]

Results

Ok, Here are the results of my weekend of testing.. All measurements made in volts peak on a scope, two EL34 run in ClassA pushPull, 70mA per tube, B+ a mere 300v hence the limited power all run into a resistive 8R load :-

Amplimo 3A524-UL Audio toroid Pentode mode :-

Max Pwr@1Khz, 8R = 18v ( 20W RMS )

50Hz = 18v,
40Hz = 18v,
30Hz = 15v,
20Hz = 9v,
10Hz = 3.6v

Amplitude flat @1W rms 15Hz -> 45KHz
-------------------------------------------

Amplimo 3A524-UL Audio toroid Ultra Linear mode:-

Max Pwr@1Khz, 8R = 15v (14W RMS )

50Hz = 15v,
40Hz = 15v,
30Hz = 15v,
20Hz = 10v,
10Hz = 4v

Amplitude flat @1W rms 10 -> 20Khz
-------------------------------------------

Vigortronix 12v 100VA mains toroid VTX-146-100-212 Pentode mode:-

Max Pwr@1Khz, 8R = 16v ( 16W RMS )

50Hz = 16v,
40Hz = 13V,
30Hz = 9v,
20Hz = 5v,
10Hz = 1v

Amplitude flat @1W rms 20 -> 100Khz
--------------------------------------------

2X Stacked Vigortronix 12v 100VA mains toroid VTX-146-100-212 triode mode:-

Max Pwr @1KHz, 8R = 11v ( 7.5W RMS )

50Hz = 11v,
40Hz = 11v,
30Hz = 11v,
20Hz = 11v,
10Hz = 7v

Amplitude flat @1W rms 10 -> 50Khz
--------------------------------------------

2x Stacked Vigortronix 12v 100VA mains toroid VTX-146-100-212 Pentode mode:-

Max Pwr @1Khz, 8R = 16.5v ( 16.5W RMS )

50Hz = 16.5v,
40Hz = 16.5v,
30Hz = 16.5v,
20Hz = 16v,
10Hz = 7v

Amplitude flat @1W rms 10 -> 50Khz
----------------------------------------------

I thought i might be able to use the nodes in the primary side connection between the two stacked torroids as 50% UL taps. Unfortunatly this was not possible as it resulted in a very smooth 80Khz oscillator LOL. I'll leave you all to draw your own conclusions about this data. Personally i think using stacked mains torriods is the way forward for me. This is not to suggest the Amplimo Transformer is in any way poor. On its own it kicks the mains torroids butt, but stacked, the mains toroids kick back. I have a 200VA mains toroid of the same type on its way. It will be very interesting to see how the single 200VA toroid stacks up against two 100VA units

Hope you enjoy my efforts and find the data of some use

 

[Shoog]

I always thought about series stacks but never got round to it.
Good work.

Shoog

 

[a.wayne]

Interesting stuff .....

 

[Tubelab_com]

I have experimented with 2 stacked, and 4 stacked power (mains) toroids for use as the OPT in a guitar amp. The reason for this was totally different than what is being done here because it was a guitar amp and I didn't need to go below 80 Hz, but I wanted big power and something that looked cool.

I wired the primary of each toroid to a pair of EL84's in the usual manner. The secondaries were connected in a series - parallel combination to yield maximum output power. The toroids were physically stacked on top of each other and 4 different colors of electro-luminescent wire are wound through the entire stack and fed with a LC bandpass filter from the output tube plates. The tubes are arranged circularly around the toroids. The amp is enclosed in a cabinet with reflective insides and a clear Lexan front.

This setup is called the "Tubelab sonic reactor" available in single core, dual core, and quad core versions. The EL wire pulses with music peaks and different notes result in different colors. There is a RGB LED under each tube, and a few inside the core, so the player can stage a "core meltdown" at the end of a gig for crowd pleasing effects. The whole thing isn't done yet, and is currently packed up for a 1200 mile move.

Not technically the same as what is talked about here, but the techniques can be used to combine many small output tubes for a lot of power. I get over 120 clean watts from the quad core reactor with 8 X JJ EL84. The OPT's were 50VA Antek toroids. Full power response is in the 45 Hz region. The high end is over 10 KHz. (don't remember the exact numbers).

That's $1000 for the OPT's.......Still cheaper than buying the Mac or a VTL ...

I got the transformers for USD $328 delivered. Yes, far cheaper.

 

[nitrate]

Lol, Tubelab, you certaintly know how to make an impact

The 200VA unit has just landed on my bench. When i get time i'll try it out. I'm curious to see if it performs roughly the same as the stacked 100VA's or if the process of stacking has great benifits ( or not ) as i suspect it does. Hmmm.. I'll post my results here soon...

 

[a.wayne]

I have experimented with 2 stacked, and 4 stacked power (mains) toroids for use as the OPT in a guitar amp. The reason for this was totally different than what is being done here because it was a guitar amp and I didn't need to go below 80 Hz, but I wanted big power and something that looked cool.

I wired the primary of each toroid to a pair of EL84's in the usual manner. The secondaries were connected in a series - parallel combination to yield maximum output power. The toroids were physically stacked on top of each other and 4 different colors of electro-luminescent wire are wound through the entire stack and fed with a LC bandpass filter from the output tube plates. The tubes are arranged circularly around the toroids. The amp is enclosed in a cabinet with reflective insides and a clear Lexan front.

This setup is called the "Tubelab sonic reactor" available in single core, dual core, and quad core versions. The EL wire pulses with music peaks and different notes result in different colors. There is a RGB LED under each tube, and a few inside the core, so the player can stage a "core meltdown" at the end of a gig for crowd pleasing effects. The whole thing isn't done yet, and is currently packed up for a 1200 mile move.

Not technically the same as what is talked about here, but the techniques can be used to combine many small output tubes for a lot of power. I get over 120 clean watts from the quad core reactor with 8 X JJ EL84. The OPT's were 50VA Antek toroids. Full power response is in the 45 Hz region. The high end is over 10 KHz. (don't remember the exact numbers).



I got the transformers for USD $328 delivered. Yes, far cheaper.

Cant you build one with a 1 ohm tap ..... ?

 

[Tubelab_com]

Cant you build one with a 1 ohm tap ..... ?

Not sure what you are asking, but if you are buying off the shelf power toroids, then you could choose the ratio (secondary voltage) to get the output impedance you want. A center tapped secondary will provide two different impedances, one is 4 times the other, IE 1 and 4 ohms, or 2 and 8 ohms.

I used some Antek power toroids I had from another project for the 8 X EL84 amp. I experimented with the secondary connections until the amp was happy driving a 4 ohm cabinet, since that's what I have.

I started working on a BIGGER version using 13GB5's, screen drive, and dumpster toroids. It needs to drive either one or three 4 ohm cabinets with the smaller cabinets in series for a 2.7 ohm total load. The right match here was a single secondary wound through all 4 cores using number 14 wire. Output power is in the 400 watt range with the 2.7 ohm load. The original secondaries (about 24 volts?) were wired in series with the primaries for a bit more inductance. The toroids were about 160 to 200 VA in size.

All of this fun stuff is packed away and 1200 miles from me now, so no progress for a while.

 

[a.wayne]

Why , you not in Sunrise anymore .... ?

 

[Tubelab_com]

I'm still here until the house sells, but most of my stuff is already in rural West Virginia. I am driving a 22 foot truck north with all of the furniture and more stuff next week. We will be in a temporary location with limited space until my new house is built. Not much tube time for the next year or so.

 

[a.wayne]

Wow , we were practically neighbors , anyway congrats on the butt Freeze ..

 

[Tubelab_com]

Wow , we were practically neighbors

Where are you at? I have been in south Florida for 61 years. I have worked at the Motorola plant for 41 of those years. They made it clear recently that they preferred for us old timers to go away, and even paid us to do so, so I'm outa here. My wife has always wanted to return to her home town, so that's where we are going.

 

[a.wayne]

Surprised you didn't rent , in case Butt freeze takes over and you want to return, make sure you have everything piped, saves on the shoveling and the icing..

One of the in-laws worked at that same Motorola office , he was offered out by XM radio and left some years ago and yep , I'm in sunrise too ....

 

[Tubelab_com]

We already have a house up there we inherited from my mother in law. I have been there every winter for the past 20 years. The cold doesn't bother me as much as it bothers her, so we will see whose butt freezes first.

 

[Tubelab_com]

One of the in-laws worked at that same Motorola office , he was offered out by XM radio

A lot of people left Motorola for XM when XM started up in Boca. Is the name a coincidence? eXMotorola = XM?

 

[nitrate]

More results

Hi all,

The results are in!
Bare in mind this is a 225VA toroid as it was as close to 200VA in the series i could get.
--------------------------------------------------------
Vigortronix 12v 225VA mains toroid VTX-146-225-212 Pentode mode:-

Max Pwr@1Khz, 8R = 17v ( 18W RMS )

50Hz = 17v,
40Hz = 13V,
30Hz = 9v,
20Hz = 5v,
10Hz = 2v

Amplitude flat @1W rms 20 -> 50Khz

As you can see this clearly demonstrates that this single toroid is inferior to to the stacked toroids adding up to the same amount of VA capacity. This lends to the conclusion that using multiple toroids in one output circuit has definate advantages. Possibly due to the potential being split accross the two or more windings lowering the possibility of saturation, the increase in core material and also the increase in inductance. Listing tests with real music reveal to myself that the audio seems improved too. A bit like a veil has been lifted off the music, more clarity and detail. Maybe down to less tonal coloring perhaps?? What are you thoughts??

Leigh

 

[nitrate]

Whilst i'm on the subject of transformers, is there anything wrong with winding antiphase windings on the filiment tap of a transformer. The idea is to have a filiment transformer running at 6.3V, then wind on some turns in order to reduce the voltage from 6.3 down to 5V for the rectifier tube ( Why they didnt just make them standard 6.3 or 12V i dont know ).

Will i be doing anything wrong here??

 

[Merlinb]

It would work, but if you have access to the windings then maybe you can just as easily unwind some of the turns? I think most people would just stick with 6.3V and use a dropping resistor for the 5V heater.

 

[Shoog]

I generally found that when winding on or off a toroidal 10-11 turns equaled about 1V (I think).
The advantage of winding your own heater or modifying an existing one is that it should supply 5V regardless of what rectifier you drop in, which cannot be said for a dropping resistor.

Shoog