A midbass transformers with fast core
-
- Posts: 22
- Joined: Fri Feb 13, 2009 1:52 am
A midbass transformers with fast core
Hey, David, long time no see…
I think I will have a project for you. I am contemplating to have a single-ended transformer made foe my new midbass channel (not lower bass). I would need it to be bass-transformer only. Not too crazy on inductance as my current bass transformer. I would say 10Hz clipping at full power would go. It shall be 20W. The upper knee roll off might be anywhere above 1.000Hz. I would need to load a full 6C33C (100-120R on plate) with 1500R-1700R, driving 15R driver. I would prefer to keep DCR of primary as low as possible, in teens of the Ohm is preferable. The transformer has to be made from relatively fast core, faster than M3 steel. It has to be able to handle 350-400mA of plate current. So, will you have such a large chunk of core?
Rgs, Romy the Cat
I think I will have a project for you. I am contemplating to have a single-ended transformer made foe my new midbass channel (not lower bass). I would need it to be bass-transformer only. Not too crazy on inductance as my current bass transformer. I would say 10Hz clipping at full power would go. It shall be 20W. The upper knee roll off might be anywhere above 1.000Hz. I would need to load a full 6C33C (100-120R on plate) with 1500R-1700R, driving 15R driver. I would prefer to keep DCR of primary as low as possible, in teens of the Ohm is preferable. The transformer has to be made from relatively fast core, faster than M3 steel. It has to be able to handle 350-400mA of plate current. So, will you have such a large chunk of core?
Rgs, Romy the Cat
-
- Posts: 2092
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
Hello Roman,
I'm not clear what you mean by a fast core but CV has approached me with this question several times before. Of course he was thinking SE 212's but the end result, I suspect is the same. We usually ended up looking at the amorphous materials and everything you propose seems doable.
dave
I'm not clear what you mean by a fast core but CV has approached me with this question several times before. Of course he was thinking SE 212's but the end result, I suspect is the same. We usually ended up looking at the amorphous materials and everything you propose seems doable.
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 22
- Joined: Fri Feb 13, 2009 1:52 am
-
- Posts: 2092
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
what frequency range are you considering for this specific situation?
dave
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
Yo shines here,
CV pointed me in the direction of this thread... I think Romy meant 1kHz, not 1.000 Hz, so 2 decades...
Romy - your actual Idc is 200-220mA, right? If you quote 350-400mA to Dave, I'd guess (only slightly kidding) you might end up with an airgap good for 1A... Similarly, are you really going to get 20W out of that loading on the 6C33?
With other manufacturers, I would spec exactly as you have done, but with intact I'd tell them what the actual Idc and power output is, and discuss optimising air gap and headroom afterwards...
cheers
shines
CV pointed me in the direction of this thread... I think Romy meant 1kHz, not 1.000 Hz, so 2 decades...
Romy - your actual Idc is 200-220mA, right? If you quote 350-400mA to Dave, I'd guess (only slightly kidding) you might end up with an airgap good for 1A... Similarly, are you really going to get 20W out of that loading on the 6C33?
With other manufacturers, I would spec exactly as you have done, but with intact I'd tell them what the actual Idc and power output is, and discuss optimising air gap and headroom afterwards...
cheers
shines
-
- Posts: 22
- Joined: Fri Feb 13, 2009 1:52 am
Shinebox, and what in your view difference between 1000 Hz and 1kHz?shinebox wrote:Yo shines here,
CV pointed me in the direction of this thread... I think Romy meant 1kHz, not 1.000 Hz, so 2 decades...
I usually specify current that I would like to have and it is up to manufactures to figure out how it gets converted in air gaps. I would like to have my midbass channel to be loaded to 1500R, this will make, if I am correct, 1:5.3 transformer driving 15R driver. The tube is driver at 220-270 mA, with a perspective to do 300mA, so 350-400mA transformer will not hurt. This transformer shall not be as crazy as my current one that goes to 7.5Hz at 22W. I think 15Hz at full power will do with a lot of reserve. The channel is high-passed at 20H and it also will never see a full power (109dB horn)shinebox wrote: Romy - your actual Idc is 200-220mA, right? If you quote 350-400mA to Dave, I'd guess (only slightly kidding) you might end up with an airgap good for 1A... Similarly, are you really going to get 20W out of that loading on the 6C33?
I do not know yet what will be the optimum current. For this channel I idea the 6C33C very heavy, burning power and harmonics and gaining damping. With a faster transformer (higher permeability core) , I might load a tube a bit heavier or use less current (higher plate impedance). I do not know yet. It is not a DSET transformer, se there is not objective in HF. Why do not take a larger chuck of code and to have some reserve?shinebox wrote:With other manufacturers, I would spec exactly as you have done, but with intact I'd tell them what the actual Idc and power output is, and discuss optimising air gap and headroom afterwards...
-
- Posts: 2092
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
Hey,
Sorry for the late reply. Things were busy for be getting ready for RMAF.
I generally shoot for equal extension on either side of the frequencies in question so until we nail that down along with the other basics I cannot select a core size.
Big Amorphous would be my choice for this application.
dave
Sorry for the late reply. Things were busy for be getting ready for RMAF.
I generally shoot for equal extension on either side of the frequencies in question so until we nail that down along with the other basics I cannot select a core size.
Big Amorphous would be my choice for this application.
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 22
- Joined: Fri Feb 13, 2009 1:52 am
Dave it looks like I have finally found what I need. The transformer need to be amorphous core, 9:1, be gaped for 370mA and to have inductance good for 12-15Hz at 20W. It shall have sub 15R primary (lover is better) and no sections on secondary – just a single coil. The upper roll of this thing I would like to be no higher then 1000Hz (lover is better). I do not care about size and appearance of the transformer, sure I care about price (lover is better :-). So, what will you say? Wonna try?
-
- Posts: 2092
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
This meand your expected 6C33Rp will be around 180 ohms?
What is the driver impedance it will be seeing?
dave
What is the driver impedance it will be seeing?
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 22
- Joined: Fri Feb 13, 2009 1:52 am
-
- Posts: 2092
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
I think I have everything I need to do some calculations / experiments to see what needs to be done in this case.
dave
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 22
- Joined: Fri Feb 13, 2009 1:52 am
Dave, hold for now with calculations / experiments. I have put in there a 9.35:1 transformer with a regular M6 core that roll at 800Hz and I eliminated my power limitation but because of more tube load I got too long harmonic tail. I was forced to roll of this tail with shaper filter but I got some time alignment delay with 3rd order. My concern is that in this configuration if I introduce a faster core transformer then it will be wide open to 20K and would force me to go for even sharper filters – the option the I do not think I have. Let me to put the faster core transformer ide on hold for now and I need to think a bit how I would accommodate it.
-
- Posts: 1
- Joined: Mon Oct 20, 2014 6:40 pm
@Romy the Cat, You can hold it off for now but I think you’ll have to go with this idea sooner or later. A faster core, one having greater permeability will certainly make you change some of the parameters in your circuit and you’ll have to tune a few values of resistors but in the end you’ll have a much better circuit than you have currently and will be according your requirements of a midbass transformer.