Go Back   Home > Forums > Amplifiers > Tubes / Valves

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

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 14th April 2008, 06:22 AM   #11
nitrate is offline nitrate  United Kingdom
diyAudio Member
 
nitrate's Avatar
 
Join Date: Jun 2005
Location: England, Lancashire
Hmm, would a normal ecc88 work good and show good linearity at around 40V anode?? if not do they still manufacture ecc86 and if so were?

Leigh
__________________
The perfect amplifier is a piece of wire with gain....
  Reply With Quote
Old 14th April 2008, 08:00 AM   #12
diyAudio Member
 
Geek's Avatar
 
Join Date: Sep 2004
Quote:
Originally posted by nitrate
Hmm, would a normal ecc88 work good and show good linearity at around 40V anode?? if not do they still manufacture ecc86 and if so were?

Leigh
NOS floats around for cheap

http://thetubestore.com/nos-6gm8.html

More info:
http://tdsl.duncanamps.com/show.php?des=ECC86


Cheers!
  Reply With Quote
Old 15th April 2008, 03:30 AM   #13
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Default Re: I'm going in.....

Quote:
Originally posted by nitrate
How do valves REALLY sound? can i get clarity, transparency and detail from them as i've seen a few ppl spend ages building stunning amps spending loads of money and time on them just to say they sound 'not as good as i'd like', or 'i'll grow to love the sound'.
Hollow state sounds really good. You can easily get clarity, transparancy and detail. I certainly have managed this without too much trouble. Get the VTs with the best linearity (i.e. 6SN7, 6SL7, 6J5, 6FQ7, 6SF5) and develop a loadline with minimal estimated THD. Make sure to have adequate headroom, and go light on the gNFB.

Quote:
My master plan is to build a dual stage single ended classA input out of two ECC83 triodes ( one half for CC and the other for volt gain ) and simply run that into a heavily biased classA/B FET voltage follower for the output. This should get rid of the output transformer, and the supply transformer can be a simple 0-30-0-30 tordial. With this i can get a good +-40V for the fet output stage, and use a doubler across the 80v to give me 160v for the valve anode HT.6.3 heater voltage from a 7805 and a few diodes under its reference. If the amp sounds any good i'll refine the design and use it. If it sounds really bad from the start then i'll scrap it and go back to full solid state. Does any body see any unforseen trouble ahead with my idea on this hybrid amp?
Class AB MOSFETs aren't real good. The crossover behaviour is terrible, and "complementary" N-Channel / P-Channel devices are a good deal less complimentary than NPN / PNP complimentary pairs. If you're gonna go hollow state, then go hollow state all the way. No need to be afraid of OPTs, as there are some quite good ones out there, plus linear device + nonlinear OPT is still a good deal more linear than SS. Get a copy of the Radiotron Designers Handbook and take a good look at that before doing anything. Also, Pete Millet's Site has lots of freebies from the most basic to most advanced. Also, Steve Bench's Site is a must see.

Don't forget to go light on the gNFB.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 15th April 2008, 09:05 AM   #14
nitrate is offline nitrate  United Kingdom
diyAudio Member
 
nitrate's Avatar
 
Join Date: Jun 2005
Location: England, Lancashire
Thanx for that input Miles. With any look i'll use no global negative feedback. Just rely on a bit of local degeneration were design allows. I'm still gonnna go with a FET backside. I have some IRFP260N's lying idle, left over from a motor controller project. Not the fastest i know, but they wern't cheap so if i can make use of them i'll give them a whirl and see how they sound in SE classA.

Regards
Leigh
__________________
The perfect amplifier is a piece of wire with gain....
  Reply With Quote
Old 16th April 2008, 03:48 AM   #15
diyAudio Member
 
SpreadSpectrum's Avatar
 
Join Date: Nov 2007
Leigh,

I too am fairly new to tubes and audio amp design in general.

A few years ago, just after graduating from college, I was helping my mother-in-law clean out her attic and came across an old tube amplifier, a Fisher X-101-B. I tuned it up and plugged in some speakers and tested it out. I was amazed at how much better it sounded than my solid-state amp. My solid state amp has much lower distortion and much more power, but it does not sound as good. I don't know if the tube amp is coloring the sound in some way, but whatever it is it just sounds good.

Don't be afraid of high voltages, just be safe around them. I am afraid that you will try some weird low-voltage tube that doesn't sound that good and not be satisfied with the result.

On my current project, I have similar goals- minimal feedback and minimal coloration of the sound. I am looking at 6SN7s with active plate loads(transistor cascode). Pull up a 6SN7 data sheet and draw a horizontal load line at 8mA and you'll see why.

I've done some experiments with the ECC83 and I don't like it.

Morgan Jones' Valve Amplifiers is an excellent reference as is the Radiotron Design Handbook. However, start with the Jones book, since it is not 50 years old.

-Heath
  Reply With Quote
Old 17th April 2008, 06:32 AM   #16
nitrate is offline nitrate  United Kingdom
diyAudio Member
 
nitrate's Avatar
 
Join Date: Jun 2005
Location: England, Lancashire
.....Still waiting for my ecc83 from rapid. I took the opertunity whilst i wait to order some Electro Harmonix 6922 tubes from the net. The hope is they will be okay and quite linear being run at around 60V per triode. These will prob get here before the Rapid tubes. Anybody used the new Electro Harmonix tubes? Are they any good? Have i made the right choice for 60V operation or have i wasted money LOL??

Leigh
__________________
The perfect amplifier is a piece of wire with gain....
  Reply With Quote
Old 21st April 2008, 08:38 AM   #17
nitrate is offline nitrate  United Kingdom
diyAudio Member
 
nitrate's Avatar
 
Join Date: Jun 2005
Location: England, Lancashire
O.k,

My 6922's have arrived. I wasted no time in trying one out and playing at a very basic level until i feel comfortable with these strange objects. I first tried a very basic se classA gain stage, setting the idle current to 5mA. At the first power up all was well. I was supprised at how easy this seemed to be. I had 10X gain from a single stage with minimal noise and wide bandwidth. I was running at 70V supply, 6.8K anode resistor, 330R cathode resistor. Excellent i thought. Now to improve PSU rejection and boost gain i would replace the anode resistor with the other triode in the envelope set up as a constant current source. So i tried this and everythng seemed well except gain didnt change. It stayed at X10. Also, the CCS dosnt seem to be constant. Am i doing somthing wrong here?? The way i did the CCS is to connect its anode to the positive rail and then connect its cathode through a 330R resistor to the anode of the lower amplifiying triode. The upper triodes grid is also connected to the lower anode. When the suply voltage varies so does current. Whats wrong here?? It should work. Do you think i'm running the supply too low at 70V??

Anybody shed any light on this??
Regards
Leigh
__________________
The perfect amplifier is a piece of wire with gain....
  Reply With Quote
Old 21st April 2008, 09:24 AM   #18
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
I have had lots of fun with EC88s (6dj8/6922)in all kinds of things from buffers to headphone amps... The nicest was useing a small 2x24V PCB transformer and a greinacher doubler topology on the PCB, providing about 119VDC to use it as a buffer/preamp.
Capacitors for PSU was from a dead PC PSU.

Will look if I can find or draw from pcb my voltage doubler...you'd get a good voltage from that.... seeing what I got from just 2 24V secondaries in series, doubled..

Also headphone amps using 12 or 24V supplies with a 9V battery used for biasing... very versatile little beasties.. unfortunatly some time has pased since my tests and my memory fickle...
I do rember that the 119V one was most stable and reliable...and according to the datasheet, more linear...the little ones would change sound or drift bias in the course of listeing to a CD...


Ordering some tubes and a transformer today to build a guitar amp... so I have been brushing up a little over the weekend..Scored a 100VA 200VAC + 12V @2A tranny for just over $10...

Good luck

Here is one you could try... with the doubler...

Click the image to open in full size.

or maybe for some power...

Click the image to open in full size.
  Reply With Quote
Old 21st April 2008, 10:35 AM   #19
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
http://www.headphoneamp.co.kr/bbs/zb...sijosae&no=207

Some fun circuits ... in korean.. use google translate... but the schematics are universal
  Reply With Quote
Old 21st April 2008, 10:52 AM   #20
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
If you just want to get a taste for tube sound (and once you do,you're likely be hooked!!) don't worry TOO much about power output..
My first tube amp is a PP 6V6 dealie,and it makes ~8Wper chan. before any visible clipping/nasties on the scope. My speakers aren't very efficient either(old homebrews, I'd guess ~85db efficiency?),BUT,I'm in a fairly small room,so the 6V6 amp can get plenty loud in here.

So,I'd say (just my opinion),Go all tube,skip the SS part for now,and don't get too hung up on power(you can build a bigger amp later!) Just make sure you have enough power for your speakers.
On that note,I also have a pair of SE 6BQ5/EL84 mono blocks.They sound really nice,but there's just not enough power for my speakers.So,they've mostly been collecting dust for the last several years.

Something in the PP 6BQ5/EL84,6V6,EL36,etc. area should do you well for starting. If you are a SE purist and don't like PP,you're gonna need a fairly hefty tube to get a decent amount of power in SE. EL34,6550,KTxx might be a good start.
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 04:16 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2