211 amp test. Square wave measures

[enzoastro]

How do you find the ef180 compared to the 6e5p? I found the 6e5p difficult to better with Idh tubes, as long as the gain is sufficient.

 

[Celsius]

You can't expect good results with little or no interleaving. OK for wireless receivers and guitar amps. For hi-fi you need significant (=expensive) interleaving; I believe some use 16 way interleaving.

The new winding frame will have at less 3 primary and 2 secondary, but the factory affirm that will be flat 20 to 20khz. I will try and if the measures follow at before will buy a hammond or SAC under 500usd pair.

The coupling cap that use now is 0,22uf PIO KBG with good result maybe a little less resolution that the silver mica SSG that used before.

 

[artosalo]

The pics you have provided are quite typical for non-feedback amplifiers with an average quality OPT.
With propely applied GNFB would essentially improve the amplifier.
The effect of the speaker's varying impedance will be reduced.

 

[Celsius]

Now have the NFB from e180f cathode to speaker + with a 6k resistor, the sound is more gentle, I am waiting the new OPT winding to measure again, I hope that the new winding improve the measures, the 5,5kg OPT have Z11 silicon steel 0,35mm E I core

 

[artosalo]

I think that you should make the measurements now to see what the effect of the GNFB is.

 

[Celsius]

I have received the OPT new coil design and new core Z11 0.35mm oriented grain audio grade, the measures are better than before but the with the speaker load have some estrange measures. See the 100hz and 500hz with speaker load, now at 30khz and 40khz have better measures that at 20khz .

I would like to know why there are a big different between the measures with resistor or speaker, with three different speaker has the same measures. If I buy a 500usd new OPT would like to be sure. Why at 30khz or 40khz has better measures. ??
Airgap 0.4mm give 40H impedance

The airgag can influence in this measures?

0db NFB

100hz with speaker load. ------------100hz with 8ohm resitor load

500hz speaker load

1khz speaker load -----------------------1khz resitor load

20khz speaker load

33khz speakeer load

40khz speaker load

 

[enzoastro]

Presumably speakers have far higher capacitance and inductance than a load resistor so you'd expect worse measurements

 

[deafbykhorns]

What he said ^
As far as I know, these measurements are usually published (commercial high-fi) with a resistive load.
What does it look like at the Grid of the 211?

 

[kmtang]

I have tried the Lundahl LL1688 which driven by 300B SE. The OPT is designed for use with 845 tube. The 10KHz square waveform is about the same as shown.
Even though the high frequency isn't that great when compare with the lower impedance ones, it sounds so good.
If you are looking for best frequency response, you shall consider Plitron OPT which has great square wave reproduction and extended frequency range.

 

[Celsius]

How do you find the ef180 compared to the 6e5p? I found the 6e5p difficult to better with Idh tubes, as long as the gain is sufficient.

Sorry Enzo I don't see your post. I think that the 6e5p is maybe one of the best preamp tubes, Ri low, THD low, price low maybe a SE EL34 drive by them can give a big surprise.

today I put g2 and g3 together to plate, I can test my stock of preamp tubes
e180f philip
e280f sylvania
ef184 philip
6j51p ?

 

[Celsius]

I have tried the Lundahl LL1688 which driven by 300B SE. The OPT is designed for use with 845 tube. The 10KHz square waveform is about the same as shown.
Even though the high frequency isn't that great when compare with the lower impedance ones, it sounds so good.
If you are looking for best frequency response, you shall consider Plitron OPT which has great square wave reproduction and extended frequency range.

Kmtang, I have a friend with 845 amp with hammond 1638SEA and the measures are clearly better, both with resitor and speaker.

Your measures at 10khz were with resistor or speaker load .

 

[bwaslo]

You might consider adding a network to your speakers' (or amps') terminals to flatten the impedance of the speaker and make it more resistive. You'd need to know the impedance curve of the speaker first, using something like a WooferTester WT2, WT3, or DATS device. I did that when trying a high-output impedance SET amplifier and the difference was very much to the better. High impedance amplifiers don't like non-flat impedance speakers (i.e., most of them!).