M Gregg.....
If you are THAT desparate to hear what its gonna be like, and you have them, You could make up some adaptors and use a couple of ECC82 or any of its variants--12AU7 / 5814 / 5963 etc...
At least then electrically the voltages/gains etc will be pretty darned close, (If not the same...) to what it should be with the 6SN7....
If you are THAT desparate to hear what its gonna be like, and you have them, You could make up some adaptors and use a couple of ECC82 or any of its variants--12AU7 / 5814 / 5963 etc...
At least then electrically the voltages/gains etc will be pretty darned close, (If not the same...) to what it should be with the 6SN7....
LOL,
They have been on order for 2 weeks so I guess they won't be long.
Just having a laugh.....I just want to know if I need to adjust the bias level... Then again that would be impatient wouldn't it..octal relay bases ....b9a base...wires....solder. Rather pin the tail on the donkey!
Restless twitch!...fidget
Regards
M. Gregg
They have been on order for 2 weeks so I guess they won't be long.
Just having a laugh.....I just want to know if I need to adjust the bias level... Then again that would be impatient wouldn't it..octal relay bases ....b9a base...wires....solder. Rather pin the tail on the donkey!
Restless twitch!...fidget
Regards
M. Gregg
Alastair,
Is the 180mA with one heater or both?
So you are sinking about 20W in the valves. (40V...180ma... 220 Ohm)
With 300 ohm I'm sinking about 15W. (36V...120mA...300 Ohm)
I could change to 220 Ohm I guess..Its that cold soldering iron..
I have a box full of 12AU7....you have me thinking..
DC power rails;
Across both +/-……………………………..…334.3V DC
Minus rail…………………………………….-165V DC
Plus rail………………………………………+168.8V DC
I was looking at the thread re: 6C41C
Just for fun a comparison re heaters:
6C41C........6.3V...2.8A=17.6W
Full 6c33c.....12.6....3.3A=41.6W/2=20.79W=half 6c33c.
Only 3W difference?
Regards
M. Gregg
Last edited:
Thats with both heaters running, = 220 ohm cathode-resistors, 180mA at 150V plus/minus, 300V across the rails.
My rails are within half a volt of 150V--both the plus and the minus, Wonder why yours are a couple of volts apart...?
The 6C41C does work quite happily in this circuit, and has an O/P around the same as one half of 6C33C
--For some reason though--the 6C41C sounds utterly horrible for a couple of hours, then comes alive--NO idea why there is such a huge change after burn in though....
You're gonna do it aint ya!--Youre gonna bung some 12AU7 in adaptors in there till you get your SN7 aint ya!
--Go on,--You might as well.....Boring Sunday night, nothing else to do!
My rails are within half a volt of 150V--both the plus and the minus, Wonder why yours are a couple of volts apart...?
The 6C41C does work quite happily in this circuit, and has an O/P around the same as one half of 6C33C
--For some reason though--the 6C41C sounds utterly horrible for a couple of hours, then comes alive--NO idea why there is such a huge change after burn in though....
You're gonna do it aint ya!--Youre gonna bung some 12AU7 in adaptors in there till you get your SN7 aint ya!
--Go on,--You might as well.....Boring Sunday night, nothing else to do!
Well here is a story to tell:
I made these:
As I finished the last joint and cleaned the base up, These arrived (6H8C). I thought I can't believe it chaos theory reigns supreme. Honest I had not taken my hand off the base of adapter last one in the socket!!!!!
So I put the 6H8C's in ......a strange buzzzzz from one channel. I thought it must be one of my earths are not correct, however I put the music on WOW.....then my DC heater protection cut in...
Thoughts are that it did not cut in with the SL's so I put in the adapters and WOW.....no cut out!....The tubes are stuffed....so the adaptors are in at the moment the Mullards sound nice! So me thinks, I have had some more on order for 2 weeks should be matched.....I think A couple of Tung sol are on the cards....I still haven't changed the bias...running 300 Ohm. Yes it is running my Alpair 7's...sounds very nice. I will let it warm up and have a play let you know more....
Regards
M. Gregg
I made these:
As I finished the last joint and cleaned the base up, These arrived (6H8C). I thought I can't believe it chaos theory reigns supreme. Honest I had not taken my hand off the base of adapter last one in the socket!!!!!
So I put the 6H8C's in ......a strange buzzzzz from one channel. I thought it must be one of my earths are not correct, however I put the music on WOW.....then my DC heater protection cut in...
Thoughts are that it did not cut in with the SL's so I put in the adapters and WOW.....no cut out!....The tubes are stuffed....so the adaptors are in at the moment the Mullards sound nice! So me thinks, I have had some more on order for 2 weeks should be matched.....I think A couple of Tung sol are on the cards....I still haven't changed the bias...running 300 Ohm. Yes it is running my Alpair 7's...sounds very nice. I will let it warm up and have a play let you know more....
Regards
M. Gregg
Attachments
Last edited:
Hmm--What a shame the 6H8C is causing probs...
-Nothing worse than waiting for something and finding when it arrives its broken, or not as expected!
One thing I have noticed with the 6H8C, the heater-current is quoted as 600+-50mA but always appears to be higher--although Ive never measured it. Sounds like you have a H-C leak or short in one of the 6H8C....
--Whats your protection scheme for the DC heaters...?
Have you 'biassed' up the heaters 30-50V Positive with respect cathodes? Ive found this helps with hum injection from heaters with various amps Ive made in the past....
Knew you would end up making some adaptors, The ECC82 is basically the B9A equiv of 6SN7 anyway, so at least you'll run right with those (Its Just a personal thing, I'm not too keen on the B9a twin-triodes, but that doesn't mean they are bad!)....
Glad its working and sounding good so far for you...
--Let us know how it sounds, You may find it better with the higher bias on the O/P stage though....
-Nothing worse than waiting for something and finding when it arrives its broken, or not as expected!
One thing I have noticed with the 6H8C, the heater-current is quoted as 600+-50mA but always appears to be higher--although Ive never measured it. Sounds like you have a H-C leak or short in one of the 6H8C....
--Whats your protection scheme for the DC heaters...?
Have you 'biassed' up the heaters 30-50V Positive with respect cathodes? Ive found this helps with hum injection from heaters with various amps Ive made in the past....
Knew you would end up making some adaptors, The ECC82 is basically the B9A equiv of 6SN7 anyway, so at least you'll run right with those (Its Just a personal thing, I'm not too keen on the B9a twin-triodes, but that doesn't mean they are bad!)....
Glad its working and sounding good so far for you...
--Let us know how it sounds, You may find it better with the higher bias on the O/P stage though....
Alastair,
Yes its a bit of a pain, the SN7's seemed to have more gain and bass response than the ECC82.
The protection on the heaters is a regulator with usual protection + electronic fuse on primary and DC out.
I have increased the bias using 220 ohm resistors. Average current is 182mA.
Sill playing with different things at the moment..So still trying different things. I guess I will have to wait for the same sound I got with the short time run of SN7's
Only just done the bias change so not listened yet!
Sorry about the delay answering taking measurements...
Regards
M. Gregg
Yes its a bit of a pain, the SN7's seemed to have more gain and bass response than the ECC82.
The protection on the heaters is a regulator with usual protection + electronic fuse on primary and DC out.
I have increased the bias using 220 ohm resistors. Average current is 182mA.
Sill playing with different things at the moment..So still trying different things. I guess I will have to wait for the same sound I got with the short time run of SN7's
Only just done the bias change so not listened yet!
Sorry about the delay answering taking measurements...
Regards
M. Gregg
Last edited:
Alastair,
You stopped me in my tracks...current! Thats why the ECC82 worked same current as......
REVENGE OF THE SL7.....yep you guessed it I polyfused for the SL7's what a git I am!...
I have replaced with correct rating. No tripping just a noisy valve they have agreed to replace it! I am just listening to Shakespeare's Sister as I type this! Sounds realy good....waiting for the trip again.... nothing yet!
So at 180mA Bias and SN7's albeit a noisy one for now.....sounds Great!
I might need to bring the gain up a bit for the Ipod....I will see....Let you know how it goes...burn in time
Regards
M. Gregg
You stopped me in my tracks...current! Thats why the ECC82 worked same current as......
REVENGE OF THE SL7.....yep you guessed it I polyfused for the SL7's what a git I am!...
I have replaced with correct rating. No tripping just a noisy valve they have agreed to replace it! I am just listening to Shakespeare's Sister as I type this! Sounds realy good....waiting for the trip again.... nothing yet!
So at 180mA Bias and SN7's albeit a noisy one for now.....sounds Great!
I might need to bring the gain up a bit for the Ipod....I will see....Let you know how it goes...burn in time
Regards
M. Gregg
Alastair,
The gain is OK,
Just listened to loreena mckennitt the book of secrets.
I can hear things on CD's that I was not aware of before, its not in your face its just their... Strange.
The noise on the tube has stopped, I will change it as soon as possible.
http://www.youtube.com/watch?v=OG7La2pYAUU&feature=related
Regards
M. Gregg
The gain is OK,
Just listened to loreena mckennitt the book of secrets.
I can hear things on CD's that I was not aware of before, its not in your face its just their... Strange.
The noise on the tube has stopped, I will change it as soon as possible.
http://www.youtube.com/watch?v=OG7La2pYAUU&feature=related
Regards
M. Gregg
Last edited:
Still no transformers and lot of promisses from supplier
Good to see you´re almost there M Gregg.
Looking forward to your impressions when it´s up and running full throttle.
flatheadmurre,
Are you going to fit grid-cathode protection on the driver tube?
Regards
M. Gregg
Of to work hopefully a couple of toroids has arrived when back.
Size inside has now forced the KISS aproach if it´s not essential forget it.
PSU will be bridge C-R-C and no more if i haven´t learned some new magic spells until tonight.
Small signal PSU with heater heater reg.
Size says 4 small processor fans sucking air thruu heat shield sitting under each 6c33c.
I even put the fuses inside to cut down on wiring.
I think i have 9 fuses right now.
Size inside has now forced the KISS aproach if it´s not essential forget it.
PSU will be bridge C-R-C and no more if i haven´t learned some new magic spells until tonight.
Small signal PSU with heater heater reg.
Size says 4 small processor fans sucking air thruu heat shield sitting under each 6c33c.
I even put the fuses inside to cut down on wiring.
I think i have 9 fuses right now.
About such situations I'd like always ask: what do you think will happen to sound signal, when we move strong little magnet close to vacuum tube? Will it improve or what..?
flatheadmurre,
To protect the driver/phase splitter tube just put a neon across the grid to cathode of the phase splitter. No resistor just a neon, I think it is important. It does work on this amp and stops high grid-cathode voltages. Just solder them onto the valve base.
Also I find the ability to switch between one and two heaters per 6C33C very important. I can put my speakers quite close to the amp, this gives a big power and heat reduction. (volume is still very good).
I have no fans only ducted air.
(OK you have to take care and plan it well).
My chassis internal size is 360mm x 320mm.
Listening to Fleetwood Mac...very nice...
Regards
M. Gregg
Last edited:
Sorry missed the height,
Its about 140-145mm, the angled cuts make the face profile look less.
If it helps anyone,
I put all my components on a piece of cardboard and moved them arround until I was happy then cut the cardboard to size and checked the plan again. Then cut the aluminium to suite.
Alastair,
I never heard a tube amp that sounds like this, Warm and detailed, natural sound<<hard to describe. As you say its defiantly not weak sounding. Still waiting, its changing as its running <<getting better.
Regards
M. Gregg
Its about 140-145mm, the angled cuts make the face profile look less.
If it helps anyone,
I put all my components on a piece of cardboard and moved them arround until I was happy then cut the cardboard to size and checked the plan again. Then cut the aluminium to suite.
Alastair,
I never heard a tube amp that sounds like this, Warm and detailed, natural sound<<hard to describe. As you say its defiantly not weak sounding. Still waiting, its changing as its running <<getting better.
Regards
M. Gregg
Last edited:
M-Gregg....
Well, I am really happy that you like the amp and its performing well for you.
One of my requirements when I was designing modding and generally playing round with it was that it was to perform well with regards to its 'weakness/strength'
OTL's appear to have a reputation for 'weak' sound, personally I think thats unfounded, but that was always in the back of my mind...
Are you still using your difficult to drive Alpair 7 speakers...?
I'm rather surprised its driving those so well for you! 4 ohm is a hard load for any OTL....
You'll find that the sound will alter as the 6C33C etc burn in. It may take several days of say, 3 hours each to fully 'develop'--for want of a better word....
(This efefct is MUCH more pronounced with the 6C41C!--Those sound literally Horrible when first used, but tame-down after around 6 hours or so...)
How was that gain issue you were thinking of? Was there sufficient for your ipad?
Well, I am really happy that you like the amp and its performing well for you.
One of my requirements when I was designing modding and generally playing round with it was that it was to perform well with regards to its 'weakness/strength'
OTL's appear to have a reputation for 'weak' sound, personally I think thats unfounded, but that was always in the back of my mind...
Are you still using your difficult to drive Alpair 7 speakers...?
I'm rather surprised its driving those so well for you! 4 ohm is a hard load for any OTL....
You'll find that the sound will alter as the 6C33C etc burn in. It may take several days of say, 3 hours each to fully 'develop'--for want of a better word....
(This efefct is MUCH more pronounced with the 6C41C!--Those sound literally Horrible when first used, but tame-down after around 6 hours or so...)
How was that gain issue you were thinking of? Was there sufficient for your ipad?
Still using the Alpair 7's they sound great!
Yes the sound is changing..getting better, its been on for about 3 Hrs so far today.
The bass is very deep, I tried some 6 Ohm speakers that I have the Alpairs sound better! I have some 8 Ohm I will try later.
It is definatly better with the 220 Ohm resistors. Running at 180mA app.
The gain is fine, I think it was an album with low recording level.
I can put it very close to my other equipment ect with heat being OK on one heater. I will look at any small mods over the next few days...
If I had to compare it, it would be top end SS with tube sound if that makes sense.
The bass can be very very deep!
Regards
M. Gregg
Last edited:
Yup--That makes pretty good sense...
The usual drawback of the Valve-Amp, (Unless you spend mega-bux on one...) Is the actual O/P Transformer....
Being a Transformer its an 'AC' device with limitations, The 'Lower' you go, the more attenuation...
We don't 'Do' O/P Transformers round here!
So, you have the possibility of very deep bass but with the magic of Valve amplification.
Just arrived,
Matched pair CH8C.
So I have the replacements.
Regards
M. Gregg
Get 'em in there--How do they sound?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.