[patrick jankowiak]

I have a case of 100 NOS 70L7's, and decided I could break it open and
use two of them. The input transformer is a 48 ohms to 5K 3 watt unit,
and the output transformer is a 120V to 6.3VCT 0.6A filament transformer.

I may have to go to a regular output transformer, because I have very
little low frequency response. The response seems severely tilted to the
highs, to the point of "hissy-ness" on music. The best size fil. xfmr to
use for this is a 1A or 1.5A and I don't have any. I found (late) a pair
of "50C5 output transformer" new in the packages.

I could use more gain as well, although the PC seems to be able to
overdrive the amp if pushed..
48:5000 is only 10:1 voltage step up. Bias is 7V, so I would need 14V
peak, meaning 1.4V peak from the PC - it should be able to do that.

The whole thing is transformerless for power like an All-American 5,
with the isolation being the input and output transformers. Right now I
am waiting to see if the heater dropping resistor is going to melt the
speaker cabinet, and have only put one together.

The rules for tube PC speakers is that only the tube can show.. my rules
anyway..

pictures are he
http://amfone.net/Amforum/index.php?topic=17284.0

[John Byrns]

In article ,
patrick jankowiak wrote:

I have a case of 100 NOS 70L7's, and decided I could break it open and
use two of them. The input transformer is a 48 ohms to 5K 3 watt unit,
and the output transformer is a 120V to 6.3VCT 0.6A filament transformer.

I may have to go to a regular output transformer, because I have very
little low frequency response. The response seems severely tilted to the
highs, to the point of "hissy-ness" on music. The best size fil. xfmr to
use for this is a 1A or 1.5A and I don't have any. I found (late) a pair
of "50C5 output transformer" new in the packages.

I could use more gain as well, although the PC seems to be able to
overdrive the amp if pushed..
48:5000 is only 10:1 voltage step up. Bias is 7V, so I would need 14V
peak, meaning 1.4V peak from the PC - it should be able to do that.

The whole thing is transformerless for power like an All-American 5,
with the isolation being the input and output transformers. Right now I
am waiting to see if the heater dropping resistor is going to melt the
speaker cabinet, and have only put one together.

The rules for tube PC speakers is that only the tube can show.. my rules
anyway..

pictures are he
http://amfone.net/Amforum/index.php?topic=17284.0

Why not replace the "heater dropping resistor" with a 4 uF film capacitor for
cooler running and to reduce the chances of melting the speaker cabinet?

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[patrick jankowiak]

John Byrns wrote:
In article ,
patrick jankowiak wrote:

I have a case of 100 NOS 70L7's, and decided I could break it open and
use two of them. The input transformer is a 48 ohms to 5K 3 watt unit,
and the output transformer is a 120V to 6.3VCT 0.6A filament transformer.

I may have to go to a regular output transformer, because I have very
little low frequency response. The response seems severely tilted to the
highs, to the point of "hissy-ness" on music. The best size fil. xfmr to
use for this is a 1A or 1.5A and I don't have any. I found (late) a pair
of "50C5 output transformer" new in the packages.

I could use more gain as well, although the PC seems to be able to
overdrive the amp if pushed..
48:5000 is only 10:1 voltage step up. Bias is 7V, so I would need 14V
peak, meaning 1.4V peak from the PC - it should be able to do that.

The whole thing is transformerless for power like an All-American 5,
with the isolation being the input and output transformers. Right now I
am waiting to see if the heater dropping resistor is going to melt the
speaker cabinet, and have only put one together.

The rules for tube PC speakers is that only the tube can show.. my rules
anyway..

pictures are he
http://amfone.net/Amforum/index.php?topic=17284.0

Why not replace the "heater dropping resistor" with a 4 uF film capacitor for
cooler running and to reduce the chances of melting the speaker cabinet?


That's a good idea. Thanks.
PJ

[Alex]

"patrick jankowiak" wrote in message
...
I have a case of 100 NOS 70L7's, and decided I could break it open and
use two of them. The input transformer is a 48 ohms to 5K 3 watt unit,
and the output transformer is a 120V to 6.3VCT 0.6A filament transformer.

I may have to go to a regular output transformer, because I have very
little low frequency response. The response seems severely tilted to the
highs, to the point of "hissy-ness" on music. The best size fil. xfmr to
use for this is a 1A or 1.5A and I don't have any. I found (late) a pair
of "50C5 output transformer" new in the packages.

Could it be that the high emphasis is due to the output transformer core
saturation (it is an AC transformer without non-magnetic gap) whereby its
inductance drops and the thing fails to deliver bass?

Regards,
Alex

I could use more gain as well, although the PC seems to be able to
overdrive the amp if pushed..
48:5000 is only 10:1 voltage step up. Bias is 7V, so I would need 14V
peak, meaning 1.4V peak from the PC - it should be able to do that.

The whole thing is transformerless for power like an All-American 5,
with the isolation being the input and output transformers. Right now I
am waiting to see if the heater dropping resistor is going to melt the
speaker cabinet, and have only put one together.

The rules for tube PC speakers is that only the tube can show.. my rules
anyway..

pictures are he
http://amfone.net/Amforum/index.php?topic=17284.0

[Alex]

"patrick jankowiak" wrote in message
...
I have a case of 100 NOS 70L7's, and decided I could break it open and
use two of them. The input transformer is a 48 ohms to 5K 3 watt unit,
and the output transformer is a 120V to 6.3VCT 0.6A filament transformer.

I may have to go to a regular output transformer, because I have very
little low frequency response. The response seems severely tilted to the
highs, to the point of "hissy-ness" on music. The best size fil. xfmr to
use for this is a 1A or 1.5A and I don't have any. I found (late) a pair
of "50C5 output transformer" new in the packages.

I could use more gain as well, although the PC seems to be able to
overdrive the amp if pushed..
48:5000 is only 10:1 voltage step up. Bias is 7V, so I would need 14V
peak, meaning 1.4V peak from the PC - it should be able to do that.

The whole thing is transformerless for power like an All-American 5,
with the isolation being the input and output transformers. Right now I
am waiting to see if the heater dropping resistor is going to melt the
speaker cabinet, and have only put one together.

The rules for tube PC speakers is that only the tube can show.. my rules
anyway..

pictures are he
http://amfone.net/Amforum/index.php?topic=17284.0

Also I think that your enormous electrolytics are not healthy for the
rectifier section of the tube on power-up. I guess you need to reduce them
to 33uF.

Regards,
Alex