F6 Amplifier

[Zen Mod]

Here the Teaser-6 in stereo, installed on a heatsink and chassis previously used for an F5 built using Cviller boards.

It sounds very good. With ear 1 inch from speaker cone, no hiss and hum is barely detectable. Bass is strong and high roll-off not really noticeable. My initial impression is that something in the midrange is a bit "muddy". I need to do a lot more listening and wire up some switches so I can to A/B comparisons.

My amplifier of choice for the past year has been a balanced F5, similar to EUVL's F5X. It will be hard to beat soundwise.

nice looking , from every perspective

I would not expect same sort of quality as from balanced or even SUSY F5 ;

 

[Rush]

Look what came in the mail !

Thanks lhquam,
That was fast shipping.

The boards look great!

Rush

 

[lhquam]

I suspect the "boomy" sound on the bass is due to a low damping factor of about 4.6. I estimate the output impedance is around 1.7 ohms. The closed-loop gain is 4.7.

 

[buzzforb]

I would not expect same sort of quality ;

Read carefully the chosen words.

 

[buzzforb]

I suspect the "boomy" sound on the bass is due to a low damping factor of about 4.6. I estimate the output impedance is around 1.7 ohms. The closed-loop gain is 4.7.

F5 more versatile but must consider more than just amp with this amp.

 

[buzzforb]

Transformers shipped on Friday and should be there by Friday.

When faced with fine wire, a fragile pin connection and silver solder ROHS idiocy, we make the first hot pot dip in 60/40 offensive metallurgy and then over dip in 3.4% silver, 94% tin, 2.6% unknown iron pot eating materials. Not detectable.

Bud

Not too worried as i believe i will be the only limitation with this amp.

Woohoo,triple post!

 

[lhquam]

Huh? 🙄 What are you really trying to say?

F5 more versatile but must consider more than just amp with this amp.

 

[lhquam]

It is impressive that the Teaser-6 sounds this good considering that with 0R47 source resistors Rs, the open-loop gain is only 20 or so. With a closed-loop gain of around 5, that doesn't leave much for feedback. One could decrease Rs, increasing open-loop gain and damping factor at the cost of changing the balance between local and global negative feedback. I haven't listened to the difference between Rs=0R47 and R2=0R12. It might be worth experimenting with.

nice looking , from every perspective

I would not expect same sort of quality as from balanced or even SUSY F5 ;

 

[buzzforb]

Is the F2 comparable to the F5? Is the F3 comparable to F4? Not necessarily intended to be comparable.

 

[lhquam]

I have listened long enough to know that the Teaser-6 will NOT replace either my F5 or F5-balanced. I am starting to have listener fatigue with this amp. Perhaps my implementation isn't up to Papa's standards, but the overall limitations imposed by the "F6 Conceptual Schematic" prevail. Bottom line: Too little open-loop gain.

Sorry to be a wet blanket. 🙁

 

[Zen Mod]

I expect one or few more tricks from Pa , but it's not mine to reveal them

 

[lhquam]

I expect one or few more tricks from Pa , but it's not mine to reveal them

I am eagerly waiting for them and trying to figure out what they might be. Perhaps I should tweak the circuit and its parameters some more.

 

[lhquam]

How does this relate to the F6?

just for your amusement

pics of next (semi public) Bfish Ikebana



(we must keep this silly thread alive , or Pa will forget to publish bloody article , to stop this agony )

 

[Zen Mod]

we were talking about Ikebana style prototyping

 

[Melon Head]

I expect one or few more tricks from Pa , but it's not mine to reveal them

All will be revealed on April 1st, 2013

 

[Antoinel]

I suspect the "boomy" sound on the bass is due to a low damping factor of about 4.6. I estimate the output impedance is around 1.7 ohms. The closed-loop gain is 4.7.

Your loudspeakers were optimized by its manufacturer to work with an ideal voltage source amp [Zo <0.1 Ohms]. Now you drive the same loudspeakers with TEASER 6 of higher Zo = 1.7 Ohms. TEASER 6 gave you [and us] the correct and expected answers. Your build is A+. Its got power, low %THD, is stable with no hum and buzz. Unfortunately, its loudspeaker mate is suboptimal. What is Zo for your F5 build?

• Do know the impedance versus frequency curve of your loudspeaker especially in the midrange; to explain the mud and listener fatigue?
• The classic designs used a voltage gain stage on the primary side of the transformer. kasey197 used a step up transformer to harness more open loopl gain than available as depicted by Conceptual F6. You also have indicated other options to lower Zo!

 

[buzzforb]

That was the point i was mqking earlier.

 

[lhquam]

Here is Stereophile Mag's impedance measurement of my B&W CDM1 speakers. Yup, my next tweak will be to lower the output JFET source resistors to somewhere near ZERO ohms, which will increase open-loop gain to around 100 or so. I could also reduce the closed-loop gain below 4.7, requiring an input source capable of higher voltage drive.

Your loudspeakers were optimized by its manufacturer to work with an ideal voltage source amp [Zo <0.1 Ohms]. Now you drive the same loudspeakers with TEASER 6 of higher Zo = 1.7 Ohms. TEASER 6 gave you [and us] the correct and expected answers. Your build is A+. Its got power, low %THD, is stable with no hum and buzz. Unfortunately, its loudspeaker mate is suboptimal. What is Zo for your F5 build?

• Do know the impedance versus frequency curve of your loudspeaker especially in the midrange; to explain the mud and listener fatigue?
• The classic designs used a voltage gain stage on the primary side of the transformer. kasey197 used a step up transformer to harness more open loopl gain than available as depicted by Conceptual F6. You also have indicated other options to lower Zo!

 

[buzzforb]

Listener fatigue does not fit what i would expect. I would expect smooth and transparent.

 

[Antoinel]

That was the point i was mqking earlier.

buzzforb. I second you opinion and first point you made earlier. You also build and know loudspeakers very well.