ZV7-T (transformer)

[Magura]

Re: Just the man I want to see!

I'll explore air-core inductors. I can have them wound with a center tap.

Is there optimum size in wire gauge and in mH? My wire guy doesn't wind below 14 gauge. 16 is more cost effective...


Many thanks,

John Inlow

I made my inductors of 1.9mm wire. 1.9mm is the point where it turns too troublesome to work with VS. low resistance.

For 2*80mH you end up with a 20kg inductor, so you will need a couple of rolls of magnet wire

Magura

 

[carpenter]

20 kilograms!!!!!!!!!!!!!!!!




I think I'll stick with my nice little 1000V/A Plitrons. Good grief, I'd need a wheelbarrow and a handtruck just to move the thing around.

God, I love you crazy guys!

 

[carpenter]

ZV7-T coupled to a line array...

Can anyone tell me what it would take to coax this amplifier into handling a very low speaker impedance?

I'm considering the fabrication of a large line array--say 16 speakers per side. I'd like to keep these wired in parallel if possible.

Any thoughts?

John Inlow

 

[Zen Mod]

Re: ZV7-T coupled to a line array...

Can anyone tell me what it would take to coax this amplifier into handling a very low speaker impedance?

I'm considering the fabrication of a large line array--say 16 speakers per side. I'd like to keep these wired in parallel if possible.

Any thoughts?

John Inlow

just increase Iq to insane level
use several cascodes in parallel-'till xformer became too hot
then use bigger xformer

or buy bigger amplifier

or ,even better, buy bigger speakers with sane impedance


hehe-best of best - change hobby

 

[carpenter]

Choky, you put the smart in aleck...

I was thinking more along the lines of using those unused outputs of the current transformer as an impedance matching device.

I just wondered if the transformer can act as a step down transmission to drive insanely low speaker impedances.


John

 

[Zen Mod]

Re: Choky, you put the smart in aleck...

I was thinking more along the lines of using those unused outputs of the current transformer as an impedance matching device.

I just wondered if the transformer can act as a step down transmission to drive insanely low speaker impedances.


John

"Choky, you put the smart in aleck...."
I didn't get it....

anyway-you're right about "unused outputs"....in fact-old scheme known to me from one sort of push-pull tube amplifiers where output xformer was connected between cathodes......

I just didn't know that you have unused taps on xformer...

and ratios are (OK-voltages are?) ?

 

[carpenter]

don't know enough about transformers... bummer

The current supply transformer is Plitron's 1000V/A with 120/120 primaries with 50/50 volt secondaries. I'm guessing that this is a little more than a two to one step down.

wouldn't this double the current while halving the voltage?

John

 

[Zen Mod]

Re: don't know enough about transformers... bummer

The current supply transformer is Plitron's 1000V/A with 120/120 primaries with 50/50 volt secondaries. I'm guessing that this is a little more than a two to one step down.

wouldn't this double the current while halving the voltage?

John

from top of my head-if you use 120+120 for 8 ohms ,then 50+50 is for 1,83 ohms

 

[carpenter]

the schematic at the beginning of this thread...

It shows how the speakers are currently driven. What the schematic doesn't show is the unused 50/50 volt secondaries on the other side of the 120/120 volt coils. Does this change your feelings on the secondaries driving a 1.83 ohm load? Also, would the secondaries be series or parallel?

Thanks for taking the time to chat,

John Inlow

 

[Zen Mod]

Re: the schematic at the beginning of this thread...

It shows how the speakers are currently driven. What the schematic doesn't show is the unused 50/50 volt secondaries on the other side of the 120/120 volt coils. Does this change your feelings on the secondaries driving a 1.83 ohm load? Also, would the secondaries be series or parallel?

Thanks for taking the time to chat,

John Inlow

do not change or touch anything;
just connect these damn 2 ohm spks to 50-50 taps

 

[carpenter]

cool

But what if the load is 8 ohm times twenty speakers? Bwhahaha cough, chough, hahaha ouch...




John


Let's call it 16 speakers at 8 ohms. That is 0.5 ohms total, yes?

 

[carpenter]

speakers as inductance source?

Hi all,

I'm staring at the schematics and it occurs to me that the speakers are also inductors. If I ran a line array of many, many drivers in parallel, the overall impedance would probably match that of the Plitron. Could I remove the transformer and use the speakers as the inductor? I know it's kinda weird. But the spark of inspiration is there. Is that all it is?

If the center tap is necessary, I suppose one could use speakers with dual voice coils.

Kind regards to the brains out there...

John Inlow

I'll try this experiment with my next amp before placing it in the chassis with its brother. I'm sure I have a cheap dual-voice-coil pioneer speaker out there in the garage... if not, I could center tap two standard drivers run out of phase? To phase or not to phase, that is the

 

[carpenter]

mono...

I've been listening to the amp in mono while I fabricate the other channel. I've grown surprisingly fond of listening to mono.

Why?

I'm running two way with passive x-over. JBl 2446 w/paper mache 250hz horn on top, and twin 12" Eminence Pro Kappa's in a ported cement lined bass cabinet. It really is impressive to listen to.

So... here's my two-bit question: how do I sum the stereo inputs to create mono?

Sorry if this sounds dumb, but the sound is absolutely amazing, and I'd like to explore further. I'm listening to an old Patsy Cline/ Jim Reeves cd and it sounds like it was recorded with modern technology. They certainly used too much reverb back then. Other than that the voice is crystal clear.

Thanks guys,

John Inlow

 

[Zen Mod]

just install one switch between hots on your preamp pot
mono-stereo
stereo-mono


I bet that you already know that

 

[nobody special]

I don't think you can use the speakers as an inductor because you can't have the DC bias current flowing through them- think maximum excursion as in jumping the coil out of the gap.

 

[carpenter]

I tend to agree

I was considering a dual voice coil unit with current flowing in opposite directions, but that would probably just cancel out everything. Also, I forgot that the amp is drawing bias current.

Thanks for your input.

 

[flg]

The two winding idea only helps the transformer saturation. The oposite windings make a feild that opposes the other, for the bias current, so there for all intents and purposes, is no field. Except for the audio signal, which are opposite currents. But, as Nobody Special said, you can't have that 2 Amps bias current going through the light as possible voice coil
If one were to use this idea with a big xfmr, is the 1H Pri L the target? Is that obtainable from a manufactured, off the shelf, component? Do they give the Pri L specs on these big toriods we're using in the supply?? I suppose I will drag my 50V supply to work and measure the Pri L for starters... Actually, at work, I have some connections I had not thought about. I know people who wind inductors, Hmmm... JSOZ-T

 

[carpenter]

Ahhh flg!!

I kept focusing on the cancellation effects and forgot about the bias current and the bias transistor. If I were a pro, I'd be wearing egg on my face

Thanks for taking the time to post. Please keep us informed on you inductor quest. I just received an inductance meter from ebay. I just have to connect a nine volt battery and I can test the 1000v/a plitron for inductance.

later, my friend

John

 

[carpenter]

inductance

I performed an inductance test on my plitron 1000v/a. Results are 172.7mH and 172.4mH on the dual 110v inputs

That's really not so tough to transfer into air chokes. Is 4.66 ohms resistance per choke too much. I'm looking at 16 gauge wire. This yields a choke with the dimensions of 1" dia. core, 1" width, 6.89" outer dia. It will take two of these babies per mono-block. They could be placed side by side and connected like a center tapped plitron to cancel magnetics. Or is this totally unnecessary.

For those with curious minds, I guess that's most of us, aye?

John Inlow

 

[flg]

Well I like the idea. It appears a "Tube Like" sound approaching very good measured specs is very possible with the cascoded JFET. I'm thinking a SOZ style thing with the JFET. With the transformer I like the fact that the load efficiency and performance is better without the use of N.P.s I.P or monster resistors. A bridging or differential mode operation provides even more performance enhancement and power. Most tube power amps had a transformer and it must have contributed an inductor non linearity that was more plesent a sound than many of the modern designs. Otherwise, tubes would be gone from audio??? We would not be chasing simple, single ended, single stage amps that are the closest topologies to the tube designs. It will be interesting where all this JFET DIY goes... I think a cool preamp design will be available soon too from the sound of things.
Anyway, I'ld just like to get more of a handle how to design in this thing or select an optimum of the available??? If I want 8 ohms at 5Hz that's .25H right? And it goes up from there... I'm guessing that would be the largest inductor I could get anyway. I like to work this stuff out on Pspice before I buiild. Maybe after the current project I will try some of this coupled centertapped inductor loading stuff on the simulator...