Sakuma style Tango project

Vil · 27th March 2007, 11:23 AM

Hi ,

please criticize this idea . Sure its nothing new here , but maybe something can be done better . I will try AC and DC filament for both tubes .

kmtang · 27th March 2007, 01:03 PM

Surely this is a very interesting project. I believe it is better to use DC supply for the VT-25's filament to avoid excessive hum pickup at the first stage.

Also, the gain of this amp is very low and you need to drive it with a high gain line amp.

Johnny

Vil · 27th March 2007, 01:22 PM

yes I know about gain , I will need about 5-6 V RMS to drive that amp properly , but I got right preamp for that . Those gonna be mono amps . My main concern is about that beautiful Tango interstage transformer - it is 5K , but VT-25 sugested load is 10K . I don't wanna push vt25 to much .Anyway maybe not a big deal because thats not an output transformer stage .

Ashareth · 27th March 2007, 01:41 PM

Hi,
you could solve the gain problem and go a step further along the Sakuma path putting an input transformer in the circuit.
Unfortunately ISO-Tango doesn't make input xfmrs anymore, but you could still use a tamura one. Maybe a TN-351 just to have a 2x gain and not so low an input impedance.
If you have a preamp with an output xfmr with 600 ohm output impedance, you could use an input xfmr with 600 ohm primary and have much more gain.

Just my two cents,
Enrico

AndreasS · 27th March 2007, 05:01 PM

Quote:

Originally posted by Ashareth
...Unfortunately ISO-Tango doesn't make input xfmrs anymore...

You may use the ISO-Tango NP-126 as a 1:4 step-up transformer (last picture).

Andreas

Vil · 27th March 2007, 08:33 PM

gain isn't a problem here . I think 2 trafos more than enuogh for me

jlsem · 28th March 2007, 10:29 PM

Quote:

My main concern is about that beautiful Tango interstage transformer - it is 5K , but VT-25 sugested load is 10K .

The 250K ohms resistor acroos the secondary of the IT will present a load of 250K ohms to the VT-25.

John

Gluca · 28th March 2007, 10:38 PM

Quote:

The 250K ohms resistor acroos the secondary of the IT will present a load of 250K ohms to the VT-25.

mmm ... not at low freqs where the ITs primary inductance will be the limiting factor: the load seen by the VT25 will drop to a much-much lower value.

jlsem · 29th March 2007, 06:26 AM

Quote:

mmm ... not at low freqs where the ITs primary inductance will be the limiting factor: the load seen by the VT25 will drop to a much-much lower value.

It's a 1:1 transformer. A reflected load is a reflected load. Low end frequency response will be affected by primary inductance, but not the slope of the load line.

John

Gluca · 29th March 2007, 07:26 AM

The freq response will fall at low freqs because the gain of the tube falls because the load falls. The load line IS affected by primary inductance.

Ciao
Gianluca

27th March 2007, 01:41 PM	#4
Ashareth diyAudio Member Join Date: Aug 2004 Location: Rovigo	Sakuma style Tango project Hi, you could solve the gain problem and go a step further along the Sakuma path putting an input transformer in the circuit. Unfortunately ISO-Tango doesn't make input xfmrs anymore, but you could still use a tamura one. Maybe a TN-351 just to have a 2x gain and not so low an input impedance. If you have a preamp with an output xfmr with 600 ohm output impedance, you could use an input xfmr with 600 ohm primary and have much more gain. Just my two cents, Enrico

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27th March 2007, 01:03 PM	#2
kmtang diyAudio Member Join Date: Nov 2004 Location: Vancouver	Surely this is a very interesting project. I believe it is better to use DC supply for the VT-25's filament to avoid excessive hum pickup at the first stage. Also, the gain of this amp is very low and you need to drive it with a high gain line amp. Johnny

27th March 2007, 08:33 PM	#6
Vil diyAudio Member Join Date: Jan 2003 Location: Europe	gain isn't a problem here . I think 2 trafos more than enuogh for me

29th March 2007, 07:26 AM	#10
Gluca tarmac ripper diyAudio Member Join Date: Nov 2004 Location: Back to Italy	The freq response will fall at low freqs because the gain of the tube falls because the load falls. The load line IS affected by primary inductance. Ciao Gianluca

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