re the transformer.
that 50ma may well be for AC only.
if it is not gapped anything other than a tiny DC current can saturate its core and greatly affect bass response.
One way to help it is to have counter DC running through the secondary. If you could arrange close to the same current it might do it.
But probably not possible on this design as you may have to cap couple the secondary and so lose the whole point of the transformer ;-)
cheers
that 50ma may well be for AC only.
if it is not gapped anything other than a tiny DC current can saturate its core and greatly affect bass response.
One way to help it is to have counter DC running through the secondary. If you could arrange close to the same current it might do it.
But probably not possible on this design as you may have to cap couple the secondary and so lose the whole point of the transformer ;-)
cheers
cap coupling
the SEWA has cap coupling on input as is. I was assuming the whole point of an IT was to avoid such cap coupling.
If you were to then put DC through its secondary this would affect the SEWA bias. This being the Gate to Source voltage.
If you leave this cap there what is the point of the 1:1 IT???
the SEWA has cap coupling on input as is. I was assuming the whole point of an IT was to avoid such cap coupling.
If you were to then put DC through its secondary this would affect the SEWA bias. This being the Gate to Source voltage.
If you leave this cap there what is the point of the 1:1 IT???
Ryssen,
If you are not sure about the transformer being gapped just use a cap and get on with it. The purpose of the transformer is to have an impedence change, iand isolation of the two circuits. A capacitor will work fine see my post:
http://www.diyaudio.com/forums/showthread.php?postid=984638#post984638
If you are not sure about the transformer being gapped just use a cap and get on with it. The purpose of the transformer is to have an impedence change, iand isolation of the two circuits. A capacitor will work fine see my post:
http://www.diyaudio.com/forums/showthread.php?postid=984638#post984638
Uncharted Territory
Ryssen 6C45PI has been sucessufully used at 24V, 15.5V is probably pushing it a bit, but you could try it and let us know, that would reduce the plate resistor to under 1K. Good Luck, after all if you don't venture into the unknown you won't know what is there. Here is a link to a similar effort.
http://digilander.libero.it/paeng/6c45_pe_low_power.htm
Ryssen 6C45PI has been sucessufully used at 24V, 15.5V is probably pushing it a bit, but you could try it and let us know, that would reduce the plate resistor to under 1K. Good Luck, after all if you don't venture into the unknown you won't know what is there. Here is a link to a similar effort.
http://digilander.libero.it/paeng/6c45_pe_low_power.htm
Tyimo said:
Hey Tyimo, as the most experienced (AFAIK) SEWA tester I know, it's time you started auditioning different MOSFET's! (Unless you are too busy with the Choke loaded OTA idea)
I am in the process right now, and I can tell you; IT'S A LOT OF FUN! You can do whatever you want with the passive components, but the main difference in sound is produced by the actual mosfet used. As Circlotron mentioned in the OTA thread, he recommended smaller, logic level mosfets. So I am experimenting now. Another big improvement (also what actually makes most of the "sound" from this amp) was the change in preamp from the X2 Rev.1 to BOZ. Sometimes one step backwards is two steps forward 
So far I have only tested the IRFP140 (sounds like you described above), but now I put in IRF540; sounds smoother (I don't know why, they are nearly identical, except the case). I can't wait to try the RFP12N10L from Fairchild I just ordered (next week).
Another change I found to be a nice improvement was to lower the gate impedance to 100K. 1u coupling and 100K bleeder, for a 50K input Z. I have also added a 1nF CB comp cap across Q3 because the sim showed better HF stability. Like Nelson did with the later Zen rev.
As a practical matter I am using my very latest Rev.D proto layout ( like Rev.C, only with HMT components and layed out for the smaller TO220 mosfets. Here I have inserted wires from the mosfet mounting holes and have the mosfet free on the heatsink so I can just swap them in a few minutes (I have a extra 100R locally at the gate)
--- LIVE THE MUSIC ---
As I think about it more
Ryssen, with 24VDC supply the 6C45PI can get 11V P-P clean output. Since SEWA is a gain of 1 you will need about 48VDC for the 6C45PI to provide enough volate swing to drive the SEWA properly.
Ryssen said:
Yes I kow..might as well usa a cap then.
If you don´t get a tube that uses 15,5v at the anode and do dc coupling.Can 6c45 work at 15,5v?
Ryssen, with 24VDC supply the 6C45PI can get 11V P-P clean output. Since SEWA is a gain of 1 you will need about 48VDC for the 6C45PI to provide enough volate swing to drive the SEWA properly.
Hi Mads!
Thanks for the infos!
Yes it is true, mostly by such a simple but splendid design like yours with just 1 active device!
I am interested very much about different devices too!
I am looking for this RFP12N10L, but mostly I would like to try the BOZ with different MosFet, for example the Hitachi 2SK216!
What do you think???
Please looking for a better mosfet for the BOZ too! Maybe the RFP12N10L could be excellent here?
You know, I am using IRFP044N. I think it is the best from the IRFP series....
Yes, I thought on the same and if we use the BOZ for preamp we needn't anymore the high 100-200K input Z.
Now I don't have many time to make experiments, but hopefully I will be ready in September with my new BOZ and the CL-OTA.
Greets:
Tyimo
Thanks for the infos!
Yes it is true, mostly by such a simple but splendid design like yours with just 1 active device!
I am interested very much about different devices too!
I am looking for this RFP12N10L, but mostly I would like to try the BOZ with different MosFet, for example the Hitachi 2SK216!
What do you think???
Please looking for a better mosfet for the BOZ too! Maybe the RFP12N10L could be excellent here?
You know, I am using IRFP044N. I think it is the best from the IRFP series....
Yes, I thought on the same and if we use the BOZ for preamp we needn't anymore the high 100-200K input Z.
Now I don't have many time to make experiments, but hopefully I will be ready in September with my new BOZ and the CL-OTA.
Greets:
Tyimo
That 2SK216 looks like a very interesting part for the BOZ! Go ahead and plug it in!
The IRFP044N is a even higher power device than the IRFP140, I think that's the source of the "roughness" you are experiencing
I think the IRFP040 would be one of the best TO3/TO247 types..
You're right, we don't even need the 100K Zin, but it let's us get away with the 1u coupling cap. If you've got space, I'd suggest 10K/10u
The IRFP044N is a even higher power device than the IRFP140, I think that's the source of the "roughness" you are experiencing
I think the IRFP040 would be one of the best TO3/TO247 types..
You're right, we don't even need the 100K Zin, but it let's us get away with the 1u coupling cap. If you've got space, I'd suggest 10K/10u
As I think about it more
Ryssen, with 24VDC supply the 6C45PI can get 11V P-P clean output. Since SEWA is a gain of 1 you will need about 48VDC for the 6C45PI to provide enough volate swing to drive the SEWA properly.
Ryssen said:
Yes I kow..might as well usa a cap then.
If you don´t get a tube that uses 15,5v at the anode and do dc coupling.Can 6c45 work at 15,5v?
Ryssen, with 24VDC supply the 6C45PI can get 11V P-P clean output. Since SEWA is a gain of 1 you will need about 48VDC for the 6C45PI to provide enough volate swing to drive the SEWA properly.
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