[xtiva]

To be clear, I'm talking about wire only, without shielding and sleeves.

Wouldn't know what the actual conductor diameter is.. would guess about half the cable diameter? 0.9mm

 

[Isaacc7]

I mentioned it in the pentode thread but figured I should say something here too. Turns out that output tubes can indeed sound very different in different circuits and modes of operation. In my single ended pentode the Sylvania JAN 7c5 is a very balanced, slightly warm tube. In my Odyssey they are a very clear but forward sounding tube. Ultimately I found them fatiguing no matter which input tubes I used.

On the other hand the metal RCA 6f6 sounded dreadfully thin and brittle in my SEP amp. In Odyssey you could almost call them lush. If their curves are anything like the 6k6 I bet I’ve got them mashed up against the edge of their response curves and probably have’s a healthy dose of 2nd harmonic distortion.

Can’t tell if this is a good thing or a bad thing lol. It’ll be a bit annoying if some of the tubes I spent good money on turn out to not sound all that hot in the new amp. I guess experimenting was why I had the amp made so time to embrace the adventure!

 

[OctavianH]

I told you to wait.

 

[normie610]

So about 4x13awg that's ****in massive - I like it

Holy cow!!! That’s freakin’ thick! Me love thick cables my DHC C15 S-mod (I know it’s quite a mouthful) is already at 15.3 AWG and super thick, can’t imagine how thick this monster 13 AWG cable is.

 

[ThanatosVI]

Holy cow!!! That’s freakin’ thick! Me love thick cables my DHC C15 S-mod (I know it’s quite a mouthful) is already at 15.3 AWG and super thick, can’t imagine how thick this monster 13 AWG cable is.

It has been clarified since then, that this measurement was with shielding and sleeve.
The wire itself was estimated to ~19awg (half the diameter)

Actually I should have expected that. Anything bigger than 15-16awg per polarity doesn't physically fit into most connectors anymore

Edit:
I also checked the DHC C15 S-mod out, this looks like a cable to my taste.
I also bugged Trevor with something similar, let's see how that goes.

 

[DecentLevi]

Would anyone have an opinion on whether feedback switch would still do anything to the sound, even on an amp without TR/UL mode? I'm having Tomas convert my Finyssey to an Odyssey for several reasons, and he said feedback mode is only useful if you have TR/UL mode, though I'm wondering if it may still yield interesting results.

 

[UntilThen]

Would anyone have an opinion on whether feedback switch would still do anything to the sound, even on an amp without TR/UL mode? I'm having Tomas convert my Finyssey to an Odyssey for several reasons, and he said feedback mode is only useful if you have TR/UL mode, though I'm wondering if it may still yield interesting results.

How is the conversion done? With a new chassis and reusing whatever parts possible? Odyssey in my mind, is the most beautiful sounding tube amp I've ever heard.

 

[Isaacc7]

Would anyone have an opinion on whether feedback switch would still do anything to the sound, even on an amp without TR/UL mode? I'm having Tomas convert my Finyssey to an Odyssey for several reasons, and he said feedback mode is only useful if you have TR/UL mode, though I'm wondering if it may still yield interesting results.

Single ended or push pull? It depends on the kind of feedback I imagine. The speakers you have will be part of the equation too. I have only ever heard one amp with variable feedback. The Cary 805 lets you add up to 10db of global feedback. I found about 2-3db of feedback tightened up the bass and gave a more defined soundstage on the big Spendor monitors, SP100 I think. Zero feedback was certainly richer and rounder. Too much feedback made the sound progressively closed in. That amp uses either an 845 or 211 triode. Global feedback lowers harmonic distortion and increases the damping factor. Comparatively massive amounts of global negative feedback is what leads to vanishingly low distortion and super high damping factor of solid state amps. A lot of people say that too much global negative feedback makes a tube amp too solid state sounding. On the other hand some speakers require more damping factor to get good bass.

Triodes, including strapped triodes, are inherently pretty low in distortion so global negative feedback can be optional. It's pretty much essential if you are running pentode mode. I'm not sure it would be too easy to just add a variable global feedback to an existing circuit. Pretty sure the circuit needs to be made with feedback in mind otherwise it can lead to oscillations. Think I read that "higher quality" transformers allow you to use more feedback.

 

[UntilThen]

In my Odyssey, I use feedback only in UL mode and when using EL11 as drivers. That was advice by Tomas and it sounded great. It's quieter too with feedback applied. Strangely I didn't ask for feedback but Tomas just did it. It was a greenfield project and I didn't know what to expect until I got the amp.

 

[DecentLevi]

How is the conversion done? With a new chassis and reusing whatever parts possible? Odyssey in my mind, is the most beautiful sounding tube amp I've ever heard.

After having already converted the output section to auto-bias last year (this is when the Sowtwers came in and the name changed from Infinity to Finyssey), I basically just need the input tube section to be converted to auto-bias as well. As Tomas said this would be to:

"get rid of the input stage gyrators, the grid drivers and the B- power supply and all the adjustments.
Then replace that with resistor loads for the driver tube anodes and cathode bias for the input tubes."

Single ended or push pull? It depends on the kind of feedback I imagine. The speakers you have will be part of the equation too. I have only ever heard one amp with variable feedback. The Cary 805 lets you add up to 10db of global feedback. I found about 2-3db of feedback tightened up the bass and gave a more defined soundstage on the big Spendor monitors, SP100 I think. Zero feedback was certainly richer and rounder. Too much feedback made the sound progressively closed in. That amp uses either an 845 or 211 triode. Global feedback lowers harmonic distortion and increases the damping factor. Comparatively massive amounts of global negative feedback is what leads to vanishingly low distortion and super high damping factor of solid state amps. A lot of people say that too much global negative feedback makes a tube amp too solid state sounding. On the other hand some speakers require more damping factor to get good bass.

Triodes, including strapped triodes, are inherently pretty low in distortion so global negative feedback can be optional. It's pretty much essential if you are running pentode mode. I'm not sure it would be too easy to just add a variable global feedback to an existing circuit. Pretty sure the circuit needs to be made with feedback in mind otherwise it can lead to oscillations. Think I read that "higher quality" transformers allow you to use more feedback.

I'll leave this for Tomas to answer. I believe it's an SE amp. Stock output tubes are still KT66 pentodes, and input is 6SN7 triodes, and I would be using mainly with headphones. I now have the HEDD Audio HEDDphone. It sounds like feedback mode (hopefully variable gain not a switch) would be a nice option, but I'll wait for his feedback about any benefit of having this without TR/UL mode.

The manually adjustable input tube section of my amp developed unstable performance glitches after using apparently untested tubes a while back, so I sent it back to Sweden for another do-over. We may also find a way of further reducing the hum, and upgrading the initial audio input wire. The HEDDphone does completely reduce the hum to a barely noticeable amount, but lowering it would allow other headphones to play nice as well.

 

[baronbeehive]

If it's the Infinity it is a SET amp. The effect of getting rid of the gyrators would be to return the amp to old school design like the Odyssey. Which means more of the old style tube sound and less of the distortion free sound of the new school design with SS components such as FETs. The reason SS amps need massive amounts of feedback is they are usually very high powered whereas lower powered amps don't need so much and is the reason they have such a great sound as compared to a lot of SS amps.

I don't know if the Infinity is open loop design but if so that would be the reason for the huge open sounding soundstage, if it isn't then Sonic has used other wizardry to get such a great sound by all accounts. Open loop designs do not need feedback to sound great, by definition they are "open" ie. no feedback, if they did have feedback then the sound would be negatively affected in my view.

GNFB is normally built into the amp design not added on after. For example amps with high/low gain have this adjustment in feedback to either damp down the output response or allow it the full range of frequency response depending on what it needs for the optimal response. High gain, or low feedback will open up the sound whereas low gain, or high feedback, will control the sound more precisely at the expense of soundstage. Personally I prefer as little feedback as possible so long as it doesn't affect bass response negatively, or introduce other undesirable effects.

 

[Isaacc7]

After having already converted the output section to auto-bias last year (this is when the Sowtwers came in and the name changed from Infinity to Finyssey), I basically just need the input tube section to be converted to auto-bias as well. As Tomas said this would be to:

"get rid of the input stage gyrators, the grid drivers and the B- power supply and all the adjustments.
Then replace that with resistor loads for the driver tube anodes and cathode bias for the input tubes."

I'll leave this for Tomas to answer. I believe it's an SE amp. Stock output tubes are still KT66 pentodes, and input is 6SN7 triodes, and I would be using mainly with headphones. I now have the HEDD Audio HEDDphone. It sounds like feedback mode (hopefully variable gain not a switch) would be a nice option, but I'll wait for his feedback about any benefit of having this without TR/UL mode.

The manually adjustable input tube section of my amp developed unstable performance glitches after using apparently untested tubes a while back, so I sent it back to Sweden for another do-over. We may also find a way of further reducing the hum, and upgrading the initial audio input wire. The HEDDphone does completely reduce the hum to a barely noticeable amount, but lowering it would allow other headphones to play nice as well.

Right, I keep forgetting this is a headphone board lol. I don't think damping factor is important at all for headphones. Another thing global negative feedback does is reduce gain. I don't trust hifi amps that use 12ax7 input tubes. The only reason to use such a high gain tube is to apply lots of negative feedback. The only reason to use a ton of feedback is to use its distortion lowering capabilities like a sledgehammer. Measures well but... eh. Might as well use a solid state amp at that point.

 

[senseitedj]

Right, I keep forgetting this is a headphone board lol. I don't think damping factor is important at all for headphones. Another thing global negative feedback does is reduce gain. I don't trust hifi amps that use 12ax7 input tubes. The only reason to use such a high gain tube is to apply lots of negative feedback. The only reason to use a ton of feedback is to use its distortion lowering capabilities like a sledgehammer. Measures well but... eh. Might as well use a solid state amp at that point.

Based on my experience I think damping factor has the most influence with DD headphones, less so than its planar counterpart (though still important). Hence many people tend to praise DD driver HPs with high impedances, such as ZMFs, because their 300 ohm coil puts them in good stead with a wide range of tube amps.

 

[jonathan c]

Right, I keep forgetting this is a headphone board lol. I don't think damping factor is important at all for headphones. Another thing global negative feedback does is reduce gain. I don't trust hifi amps that use 12ax7 input tubes. The only reason to use such a high gain tube is to apply lots of negative feedback. The only reason to use a ton of feedback is to use its distortion lowering capabilities like a sledgehammer. Measures well but... eh. Might as well use a solid state amp at that point.

Interesting. The two h/p/a that I owned / own which ‘normally’ call for 12AX7 tubes - Quicksilver Audio, Icon Audio HP8 - sounded / sound better to me with 5751, 12AT7 tubes. More ‘dynamic headroom’, less ‘compression’.

 

[baronbeehive]

Interesting. The two h/p/a that I owned / own which ‘normally’ call for 12AX7 tubes - Quicksilver Audio, Icon Audio HP8 - sounded / sound better to me with 5751, 12AT7 tubes. More ‘dynamic headroom’, less ‘compression’.

Same here, I used TS5751's for ages until I found equally, or even better 12Ax7's, Philips, were fantastic. Now I replaced the Philips with a 12AT7, the Brimar. I do think that with the right 12Ax7 though they are at a very high level, I changed my mind after hearing the best there was.