• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

10/10/ preamp

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etalon90

etalon90

Member
Joined 2004
The 10/10Y are great

But I prefer the #26 over the 10 in preamp. (I swing 1.6V output for clipping my amp)
I also try the 801,417A,c3m,6j5gt,6922(not a joke) and the #26 beat them all.

Don`t forget to battery bias!

I have to specify that my amplifier contain 10, 801 and 845,
I using all DHT exept in my DAC and my RIAA preamp (I may change that some day)

Regards
 
etalon90

etalon90

Member
Joined 2004
Kmtang,

The #26 heater is usualy hard to deal, You must have perfect DC.

I use a switching power supply designed for computer computer use. At my local surplut, I pay $4.99 CAD each!
It deliver 12V@1.75A.
This psu feed an LCRC circuit to provide a 100% clean 1.5V.
(even without filter circuit, on my scope, the voltage is very clean, I guest that an RC only will do as good)

And I use an isolation transformer on the main because I don`t want the switching psu to put some noise on the main.

It sound very good. I didn`t compare to battery but I didn`t find much difference between Current regulation. (even my heater psu is a bit better and less expensive)
 
B

bone43

Member
Joined 2004
etalon90 said:
Kmtang,

The #26 heater is usualy hard to deal, You must have perfect DC.

I use a switching power supply designed for computer computer use. At my local surplut, I pay $4.99 CAD each!
It deliver 12V@1.75A.
This psu feed an LCRC circuit to provide a 100% clean 1.5V.
(even without filter circuit, on my scope, the voltage is very clean, I guest that an RC only will do as good)

And I use an isolation transformer on the main because I don`t want the switching psu to put some noise on the main.

It sound very good. I didn`t compare to battery but I didn`t find much difference between Current regulation. (even my heater psu is a bit better and less expensive)
Click to expand...

etalon90,

Very good idea as i have had this noise problem with the 27 also, mostly the old mesh plate glodes maybe with this supply i can get better than 1 in 5 is usable in a line stage.

Thanks Tony
 
D

day

Member
Joined 2004
i build 10y preamp with intersatge but hummmmm how can i do
my circuit is
b+350v
r cathod 1.2k
tango its 10k
thak you
DAY
 

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kmtang

kmtang

Member
Joined 2004
The 10 tube's filament supply is 7.5V 1.25A. You probably need two 12V car batteries and DC regulator to get it down to 7.5V.

I think it is just impractical having two big batteries next to the line amp. Also, you need to recharge them everytime after use.

If you use regulated DC supply for the filament, it should not cause too much of hum. The hum probably from either B+ or induced from the magnetic leakage of the power transformer and choke. It's much better to have a separate power supply for the line amp.

Johnny
 
kmtang

kmtang

Member
Joined 2004
Hi Day,

Are you using IC regulator for the filament circuit? If not, you need to be very careful on the filament voltage. Probably you need to put an RC filter for the filament for limit the voltage to the correct value and it will provide better filtering for the filament.


Johnny
 
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