811a SET amp.
- Paul Barker
- Social Sevices have been notified
- Posts: 8980
- Joined: Mon May 21, 2007 9:42 pm
#241 Re: 811a SET amp.
Hope so, it is going really well.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#242 Re: 811a SET amp.
I'm having an 811a session.
All the parts of the amp were retrieved from their various hiding places, and vast quantities of accumulated dust have been removed.
Everything was connected up (once I had found the wires) and on power up everything seemed OK, although the hum is still there.
Playing now is Solid Air, and it seems more "dynamic" with 811a than it was with GK-71.
So, shall I bring it to Owston ?
All the parts of the amp were retrieved from their various hiding places, and vast quantities of accumulated dust have been removed.
Everything was connected up (once I had found the wires) and on power up everything seemed OK, although the hum is still there.
Playing now is Solid Air, and it seems more "dynamic" with 811a than it was with GK-71.
So, shall I bring it to Owston ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- IslandPink
- Amstrad Tower of Power
- Posts: 10041
- Joined: Tue May 29, 2007 7:01 pm
- Location: Denbigh, N.Wales
#243 Re: 811a SET amp.
Wow ! - yes if you have space !
"Once you find out ... the Circumstances ; then you can go out"
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#244 Re: 811a SET amp.
It (the 811a amp) has been to Owston before.
But, as I'm bringing the van there should be room for it.
Should also be room for a good selection of music to annoy DTB.
But, as I'm bringing the van there should be room for it.
Should also be room for a good selection of music to annoy DTB.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10579
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#245 Re: 811a SET amp.
My 3 will be Val Doonican, James Last, and Richard Clayderman.pre65 wrote:
Should also be room for a good selection of music to annoy DTB.
Hope your 3 are as good.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#246 Re: 811a SET amp.
Mantovani, Des O'Connor and Mozart.
I thought I'd try and do something about the hum.
First thing was to make a pseudo centre tap for the 6.3v windings on both the mains transformers.
I really wanted 100R, or 220R, but none were found, so matched (as near as poss) 470R 3W were used. Each pair of 6.3v windings (per transformer) is paralleled, and supplies one pair of 6D22s damper diodes and one 6CG7 driver/cathode follower.
Back in action now, and there is deffo a bit less hum, more a touch of hiss now.
I thought I'd try and do something about the hum.
First thing was to make a pseudo centre tap for the 6.3v windings on both the mains transformers.
I really wanted 100R, or 220R, but none were found, so matched (as near as poss) 470R 3W were used. Each pair of 6.3v windings (per transformer) is paralleled, and supplies one pair of 6D22s damper diodes and one 6CG7 driver/cathode follower.
Back in action now, and there is deffo a bit less hum, more a touch of hiss now.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#247 Re: 811a SET amp.
I was looking for Arabian Nicks capacitor list on the old computer, when I came across a circuit for 811a in A2.
Now, I never really got my version working as I would like so I studied this circuit with interest. It uses a 56 and a "powerdrive" mosfet to drive the 811a.
56 seem quite rare, but it seems 76 is the same but 6.3v filaments, and I do have a pair of 76 in the valve drawer. So, another project waiting in the wings.
I'll add a picture of the circuit soon. Can't seem to log into Photobucket at the moment.
Now, I never really got my version working as I would like so I studied this circuit with interest. It uses a 56 and a "powerdrive" mosfet to drive the 811a.
56 seem quite rare, but it seems 76 is the same but 6.3v filaments, and I do have a pair of 76 in the valve drawer. So, another project waiting in the wings.
I'll add a picture of the circuit soon. Can't seem to log into Photobucket at the moment.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#248 Re: 811a SET amp.
pre65 wrote:Mantovani, Des O'Connor and Mozart.
Now there's a combo you don't see every day.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#249 Re: 811a SET amp.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#250 Re: 811a SET amp.
Pondering...
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#251 Re: 811a SET amp.
In the article the author states that feedback from the OPT to 811a cathode might be beneficial.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- jack
- Thermionic Monk Status
- Posts: 5502
- Joined: Wed Dec 29, 2010 8:58 pm
- Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
- Contact:
#252 Re: 811a SET amp.
Pah. Today is Martyrs' Day, so is a national holiday; tomorrow is Friday so it's really Saturday, but on Saturday (the real one) we're all off to the Dubai 7s. Even though Friday is a weekend day, this Friday is special - it's UAE National Day, so there are flags everywhere (they are very proud of their country).pre65 wrote:...Arabian Nicks capacitor list...
I even saw some hummus in the supermarket decorated with coloured herbs to make the national flag. There was also a sheep's head in there attached to a fake tinfoil body.... I thought that the parsley/grass was a nice, if somewhat surreal, touch...
Anyway, back on topic, I'll be in Blighty over "the holiday season", if anyone wants some caps...
Vivitur ingenio, caetera mortis erunt
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#253 Re: 811a SET amp.
In the 811a A2 amp circuit there is a cascaded CCS in the driver valve anode.
Is there likely any performance preference in using either
A) 10M45s
or
B)DN2540
Is there likely any performance preference in using either
A) 10M45s
or
B)DN2540
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- IslandPink
- Amstrad Tower of Power
- Posts: 10041
- Joined: Tue May 29, 2007 7:01 pm
- Location: Denbigh, N.Wales
#254 Re: 811a SET amp.
What's a cascaded CCS ? Is there a circuit diagram somewhere ?
"Once you find out ... the Circumstances ; then you can go out"
- pre65
- Amstrad Tower of Power
- Posts: 21399
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#255 Re: 811a SET amp.
IslandPink wrote: ↑Mon Nov 13, 2017 10:56 am What's a cascaded CCS ? Is there a circuit diagram somewhere ?
http://usr.audioasylum.com/images/2/22845/CCS1.jpg
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)