Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

The point of an 845, 211, 805 amp?
The point of an 845, 211, 805 amp?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 25th June 2019, 02:52 PM   #1
samsdad is offline samsdad
diyAudio Member
 
Join Date: Jan 2017
Default The point of an 845, 211, 805 amp?

Hello,

Iím trying to understand the point of an 845, 211, 805, etc. amplifier. Let me explain:

From what I understand, all things being equal, and assuming competent circuit design, parts quality, etc. the more gain stages an amplifier has, the less likely it is to be linear. And, from what I understand, generally speaking, the more transformers involved in a circuit, the more it will suffer from transformer-based distortion.

Iíve never heard such an amp, mind you, so maybe the proof is in the pudding. But as a general observation, all of the amps that Iíve seen that use these tubes in their power section are all preceded by something like an input tube such as a 6922 or 12ax7, followed by a 300b or 6L6 section (described as the driver section), then followed by an 845, etc. Or, it omits the input section and requires a separate preamp. In any event, all of such amps seem to have a veritable village of transformers stacked around these tubes, or because of weight and space limitations, stacked in a separate case.

Are these amplifiers really more linear than say, a El34 ultra linear amp running in class A designed with, again, a quality circuit, parts, etc.? Is there something super special that Iím missing in an 845 SET amp (line magnetic, for example) that canít be achieved in a 6p15 SET (Decware zen Torii, for example) plus a quality subwoofer?
  Reply With Quote
Old 25th June 2019, 04:42 PM   #2
analog_sa is offline analog_sa  Europe
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Cascais
The point of an 845, 211, 805 amp?
Quote:
Originally Posted by samsdad View Post
generally speaking, the more transformers involved in a circuit, the more it will suffer from transformer-based distortion.

This may hold some academic merit bit is completely irrelevant in real life. Good transformers have negligibly low harmonic distortion and subjectively sound more transparent than capacitors. At least to some listeners.

Not sure why would you compare any of the big transmission valves to an EL34, at the very least they offer a much higher power compared to a triode strapped EL34.

As for the linearity, some very highly regarded amps are far from linear. Perhaps we should not overstate its importance.

As with everything else it all boils down to implementation. It is very easy to end up with a poor sound amp full of transformers, chokes and transmission valves.
  Reply With Quote
Old 25th June 2019, 05:02 PM   #3
FullRangeMan is offline FullRangeMan  Brazil
diyAudio Member
 
FullRangeMan's Avatar
 
Join Date: Aug 2009
Location: Brazil
Its beyond me why they use these expensive 845, 211, 805 tubes, when a GM70 or GK71 price is only $17
''GSTube.com''. Tubes, sockets etc. Search result for <u>gm70</u>
They use 12AX7 why is a ready available tube in China and have lots of gain 100x
__________________
>Never go to a psychiatrist, adopt a cat or dog from the streets. On the streets pets live only two years average.

Last edited by FullRangeMan; 25th June 2019 at 05:04 PM.
  Reply With Quote
Old 25th June 2019, 05:29 PM   #4
Lingwendil is offline Lingwendil  United States
diyAudio Member
 
Lingwendil's Avatar
 
Join Date: Apr 2008
Location: Oakley California
The "super special" that can't be acheived with a Decware or similar amplifier should be quite obvious- it isn't a big, huge, hot "statement" of an amplifier the same way the impractically heavy and large amps are. For some folks they have a biting desire to simply make something that way, so they do.

While the car they drive is different than yours, and the road they drive is different, they still aim to take the same journey to audio enjoyment. It's fun, it's ridiculous, and it's expensive. It's all valid to an extent.
__________________
Check out My 6SN7 Push-pull Flea Amplifier project! PCB COMING SOON!
  Reply With Quote
Old 25th June 2019, 06:26 PM   #5
multi is offline multi  Australia
diyAudio Member
 
Join Date: Jan 2011
I think the price of $17 is for sockets not the tubes
  Reply With Quote
Old 25th June 2019, 06:32 PM   #6
schiirrn is offline schiirrn  Germany
diyAudio Member
 
Join Date: Nov 2018
Quote:
Originally Posted by samsdad View Post
Are these amplifiers really more linear than say, a El34 ultra linear amp running in class A designed with, again, a quality circuit, parts, etc.?

Quite on the contrary, winding an output transformer for such tubes is a nightmare if you aim at full range operation and just want +-3dB from say 25Hz to 40kHz.
But then again, for some people there might be more aspects to an amplifier than linearity.
__________________
Preferred BSC? Just using a wide enough baffle.
  Reply With Quote
Old 25th June 2019, 06:36 PM   #7
GoatGuy is online now GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
This may be both anecdotal and mathematically possible to formalize, but in my experience, one shouldn't ask each voltage gain stage to maximize its gain. Doing so seems to 'accentuate the triode/pentode distortion' of the stage.

For instance … whether one uses 6SN7s — hugely reputed to be marvelously linear — or 12AX7's or any of its socket substitutes of equally legendary quality, since the incoming signal to a main amp is relatively low (typically 700 mVRMS, allowing for Ī3000 mVPK) … having the first stage being “only” a 10◊ to 15◊ gain merit is a good balance between minimizing noise and stage distortion at the same time.

Now the signal is (say) 15 ◊ 700 mVRMS = 10 VRMS.

Great! As KodaBMX has posted in other fora, the next stage is optimally the symmetric signal inverter (supposing feed to a push-pull output section).

Higher current valves such as the 6SN7 seem to do well, tho' there's not a thing in the world wrong with low power pentodes. Not-exquisitely-matched anode and cathode resistors … plus a trimmer to dial in symmetry … then gives a nice pair of complementary VRMS ≈ 10 V signals.

THEN … each phase is voltage-amplified again.

Not much, maybe only 3◊ or 4◊ at the next stage. A single 6SN7 or other dual triode (or dual pentode) manages this well without a capacitor bypassed cathode resistor. Now with VRMS at about 35 V, there is a good strong drive for some powerful output valves in PP configuration.

Just saying,
GoatGuy ✓
__________________
Burnished unicorn horn circuit design only go so far. When the unicorn's magic fails, its best to rely on maths. JustSayingô
  Reply With Quote
Old 25th June 2019, 07:14 PM   #8
samsdad is offline samsdad
diyAudio Member
 
Join Date: Jan 2017
So, what Iím gathering so far is that Iím not missing anything other than perhaps a physical behemoth of an amp when compared to, say, your typical PP integrated El34-sized fare, all other things being equal.

I own both a Decware SE84 CKC (SET EL84, 2 watts) and Torii Junior (PP EL34 UL, 20 watts) and, imho, the Jr. outclasses the CKC in terms of soundstage depth (which apparently is an artifact of negative phase 2nd harmonicóhere somewhat adjustable, apparently, via the VR tubes in the circuitóat least thatís what my ears tell me) and power.

Iím thoroughly chuffed with the sound of the Jr. running it into Klipsch RB 81 mkii speakers (97 dB efficient supposedly), but, not having heard an 845, etc., was just making sure that there wasnít another nearly universally accepted higher level of enjoyment that Iím missing out on comparatively speaking, by moving to transmission-line-tube level amps.
  Reply With Quote
Old 25th June 2019, 08:27 PM   #9
FullRangeMan is offline FullRangeMan  Brazil
diyAudio Member
 
FullRangeMan's Avatar
 
Join Date: Aug 2009
Location: Brazil
Quote:
Originally Posted by multi View Post
I think the price of $17 is for sockets not the tubes
I confirm the GM70 tube price is $17.50 each graphite plate version its a impressive tube.
The socket for this tube has no price why its out of stock.
I had bough various GM70 and 6C33 tubes from Andrey.
__________________
>Never go to a psychiatrist, adopt a cat or dog from the streets. On the streets pets live only two years average.

Last edited by FullRangeMan; 25th June 2019 at 08:30 PM.
  Reply With Quote
Old 25th June 2019, 08:30 PM   #10
Lingwendil is offline Lingwendil  United States
diyAudio Member
 
Lingwendil's Avatar
 
Join Date: Apr 2008
Location: Oakley California
You've got to wade through a lot of ad-copy type of speak, even among the DIY side of tube and "audiophile" hobbyists. Everyone has a special idea that they swear by, and there are a lot of "spiritual" reasons behind design decisions, regardless of whether or not they're good engineering or financially sound.

If you like what you have, cool. Don't let it stop you from building/buying different amplifiers or speakers. Try different stuff, even wildly different. Step outside of your comfort zone and build something crazy, everyone should build a boat-anchor of an amplifier at least once.
__________________
Check out My 6SN7 Push-pull Flea Amplifier project! PCB COMING SOON!
  Reply With Quote

Reply


The point of an 845, 211, 805 amp?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
HQ Ceramic insulated turret terminals, chassis mount, for point to point amp/pre-amp cathodes Swap Meet 2 20th February 2017 10:12 AM
HQ Insulated turret terminals, chassis mount, for point to point amp/pre-amp etc cathodes Swap Meet 8 11th April 2016 03:44 PM
Lots of craziness (weird noises and osc) happening in point to point 5W EL84 Amp 777funk Instruments and Amps 17 2nd March 2014 06:20 PM
Anyone use magnet wire for point to point wiring projects? Hybrid fourdoor Parts 10 2nd February 2004 08:11 AM


New To Site? Need Help?

All times are GMT. The time now is 04:44 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki