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Does damping factor matter?


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The Grommes amp shows both negative voltage feedback and positive current feedback to increase damping factor.

 

The Bogen amp shows the same but instead of fixed positive feedback it shows a simple variable damping control.

 

I think it would be really cool for Klipsch to make a "heritage amplifier" specifically for their heritage speakers based on the Brook amp PWK himself said was the greatest amp for the K-Horns. Wink Wink to Vox to hire me for the design ;)

Grommes_215BA_sch.gif

bogen_do-30a_sch.pdf_1.png

Edited by captainbeefheart
grammar
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If you really want one,

there are builders who will make one for you

Custom wound transformers if needed

Would probably want to build a simulation in spice first

 

Also a lot of the current designs, are just updated old tube designs

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33 minutes ago, Bubo said:

If you really want one,

there are builders who will make one for you

Custom wound transformers if needed

Would probably want to build a simulation in spice first

 

Also a lot of the current designs, are just updated old tube designs

 

I personally prefer single ended amps. I built a Brook 12a a long time ago and it did sound great. I was just saying Klipsch should partner up with an amplifier manufacturer to re-make the Brook amp with some upgrades to the circuit because PWK himself was very fond of that amplifier pairing with his speakers. I can see it now, "heritage series amplifier" to be paired with Klipsch "heritage series" speakers.

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46 minutes ago, captainbeefheart said:

I can see it now, "heritage series amplifier" to be paired with Klipsch "heritage series" speakers.

 

I'm not sure what the Heritage Series sales are, but I don't think enough Heritage Series buyers would buy a tube amp to justify it's design, manufacture, tech support and warranty service. 

 

It's a great idea though. 

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1 hour ago, Bubo said:

Also a lot of the current designs, are just updated old tube designs

 

One of the most frequent mods for older tube designs, is to add a constant current source for the anode or cathode and DC to filament circuits (especially low-level circuits). There are a lot of things that can be done, you just have to be creative, but not all the mods are worth the trouble. Sometimes, a mod, is just a mod to show their technical prowess. 

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4 hours ago, Curious_George said:

 

One of the most frequent mods for older tube designs, is to add a constant current source for the anode or cathode and DC to filament circuits (especially low-level circuits). There are a lot of things that can be done, you just have to be creative, but not all the mods are worth the trouble. Sometimes, a mod, is just a mod to show their technical prowess. 

 

Some older circuits were using pentodes as constant current sources but today we have the means to get extremely cheap transistors to cascode them into a much higher AC impedance for plate loads. Using LM317's etc... for cathode bias I don't like, it creates more problems than helps. Long tailed pair phase inverters LOVE CCS as the tail load but requires a negative rail which is not hard to do.

 

For directly heated tubes like 300b, 2A3, 45 etc..... a current source is MUCH better than AC and DC voltage sources. The Current source on filaments avoids nasty in rush currents when filaments are cold. 90% of DHT failures I see are the filament burning out, using a current source they will last A LOT longer until their emissions run out.

 

I even used Mosfets as source followers for screen drive on sweep tubes, easily got 100 watts from just two tubes push pull :D

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4 hours ago, Curious_George said:

 

One of the most frequent mods for older tube designs, is to add a constant current source for the anode or cathode and DC to filament circuits (especially low-level circuits). There are a lot of things that can be done, you just have to be creative, but not all the mods are worth the trouble. Sometimes, a mod, is just a mod to show their technical prowess. 

 

Tube tech probably plateaued in the 1940s-50s

Analog plateaued in the 70-80s

Microprocessors are about to plateau, if they haven't already. Speed and spacing being the limiting factors.

 

Quantum processing....... we'll see

AI just a pipe dream ?

 

I'm still running with my flip phone and 1980s analog stereo, and I worked in high tech....

 

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4 minutes ago, captainbeefheart said:

 

Some older circuits were using pentodes as constant current sources but today we have the means to get extremely cheap transistors to cascode them into a much higher AC impedance for plate loads. Using LM317's etc... for cathode bias I don't like, it creates more problems than helps. Long tailed pair phase inverters LOVE CCS as the tail load but requires a negative rail which is not hard to do.

 

For directly heated tubes like 300b, 2A3, 45 etc..... a current source is MUCH better than AC and DC voltage sources. The Current source on filaments avoids nasty in rush currents when filaments are cold. 90% of DHT failures I see are the filament burning out, using a current source they will last A LOT longer until their emissions run out.

 

I even used Mosfets as source followers for screen drive on sweep tubes, easily got 100 watts from just two tubes push pull :D

 

To me the easy real estate in tube amps is the power supply, changing over to solid state.

As to output, simpler is better.

Especially if 2 Watts is ear splitting on your speakers.

Certainly tube designs can be hot rodded for more output, for direct radiators.

I understand there is some debate as to the best way to wire up the tubes, I'm guessing that there were dissertations written on them during the 40s-60s. Each likely produces it's own set of trade offs.

On a personal note, I wish I knew enough not to electrocute myself, set the unit on fire, or burn the house down.....but I require supervision.

 

 

 

 

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1 minute ago, Bubo said:

 

Tube tech probably plateaued in the 1940s-50s

Analog plateaued in the 70-80s

Microprocessors are about to plateau, if they haven't already. Speed and spacing being the limiting factors.

 

Quantum processing....... we'll see

AI just a pipe dream ?

 

I'm still running with my flip phone and 1980s analog stereo, and I worked in high tech....

 

 

I agree to a degree ;)   Yes tubes tech peaked a long time ago and almost everything has been done. But because we have access to better parts and all sorts of silicon to help we can improve on designs. Yes they used Pentodes for current sources as loads but now we can cascode two cheap transistors and drastically increase AC impedance that far out performs a pentode. We can build far better active regulators now with sand.

 

Although we are not reinventing the wheel we can continue to improve upon performance.

 

Actually one thing that was not done back in the 50's or 60's was active impedance bridges like the David Berning ZOTL amps. Yes they had OTL amps but that was paralleling ridiculous amounts of tubes and a total PITA. Now we can cutout the transformer and change impedance all with transistors.
 

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4 minutes ago, captainbeefheart said:

Actually one thing that was not done back in the 50's or 60's was active impedance bridges like the David Berning ZOTL amps. Yes they had OTL amps but that was paralleling ridiculous amounts of tubes and a total PITA. Now we can cutout the transformer and change impedance all with transistors.

 

Necessity is the mother of invention

My understanding is that the OTL was born by no copper available during WW2, it was all diverted to weapons manufacturing.

Lots of OTL radios produced.

Solid State power supplies and regulators make a lot of sense from both price and performance, anything else is gravy.

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On 10/28/2021 at 2:54 PM, Coytee said:

 

 

 

ewwwwww......  so what I'm hearing you say is you have hairy ears.  

 

TMI

 

:)

 

(yeah, I know this is 45 years after your post, I just saw the thread after it popped up  I guess that simply means your ear hair is now longer  EWWWWWW)

 

 

 

             I'm watching you! ;)

 

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There's too much to say and there's too little to say about DF.  Much finer minds than mine have already said everything twice.  I say pay attention to the acoustic design (speaker cab damping), pay attention to rooms & placement, and maybe what current FB costs is a sensible trade.  Oh, and pay attention to the PSU--big-time.  That's my 2c. 

 

Rooms always win--the reflections and standing waves wag our little transducers right around...arguably all the way back to the pole pig, by degree.  It's a resonant cacophony of mind-numbing combination--thank god for acoustic resistance and drywall stud walls (and maybe VC feedback) :)

 

Oh yeah, the older I get, ear-hair always wins, too.  When we are all gone, there will only remain ear hair and cockroaches (and the cockroaches will be arguing about DF). 

pwk_in_re_variable_damping__Radio-Electronics-1956-10..jpg

tomcik_damping_factor_paul_spelz_wayback_2k11_Missing_Link_in_Speaker_Operation.pdf

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