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Hi,
I need abit of advice about component placement on an el84 monobloc valve amp i'm building.
Here is a computerized image i've created which shows the way i think would be ok.
http://i514.photobucket.com/albums/t...impression.jpg
not sure about this flux leakage i've heard about.
I've already built the cases to match the valve dac/pre so can't change the base.
http://i514.photobucket.com/albums/t...00/dac-pre.jpg
tia
Duncan
Hi Duncan, that looks great! and a bit like the Decware EL84 amp I have at the moment, but with a difference of course being that the decware is stereo. Can I ask, I presume this is your own circuit design? do you have any expected specs? Thanks.
Oh, and what s/ware did you use to make the image????
Hi,
Spec:
Class A 15W per amp into an 8ohm load.
Frequency response 17Hz to 30KHz
Input sensitivity 380mV, might change this depending on the preamp.
Simulated in Multisim 9
Description:
This configuation has been used very successfully in other designs, one I built but which had a shared power supply was good but limited its channel separation capability somewhat.
The power supply was designed using PSU Designer II, which is a great piece of software.
Power supply uses a EZ81 rectified with capacitor input then choke.
First stage is the pentode section of a ECF80. This is used for voltage gain.
Second stage, the triode section of the ECF80, is used as a phase splitter in Concertina format.
Then onto the output stage which is the classic push pull using EL84Ms
Parts:
VVT mains transformers
VVT choke
EZ81 rectifier tube JJ
Input capacitors Obbligato PSU Film 47uF 500V
further smoothing Obbligato PSU Film 47uF 500V
then rc voltage drop Obbligato PSU Film 100uF 500V though I might regulate here.
ECF80 Mullard tube
Welwyn 1% resistors throughout
Ampohm paper in oil DC blocking/coupling capacitors
Blackgate electrolytic cathode bypass capacitors
EL84M Russian military output tubes
Custom wound Sowter output transformers with 20% taps
The image was created using PTC ProDesktop2000i, I find this software very easy to use and you can have a design finished very quickly. It also dimensions everything automatically so you have a template to use for cutting the cases.
Duncan
Thanks Duncan. You so obviously know what you are talking about, and haing heard one or two items you have produced can honestly say they sound boody brilliant, no brainers really.
Finally got the transformers.:)
Why is there such a long wait for things in this country?
http://i514.photobucket.com/albums/t...0/IMG_4385.jpg
All I've got to do is cut the case and wire it up!
Looks very naughty, Dunc!
Are you sure you couldn't have over-spec'd it even more? :eyebrows:
Looking forward to hearing the results when you bring it round to Ian's :cool:
Marco.
WELL GET CRACKIN THEN :lol::lol::lol::lol:
....can i light the fireworks?......
Looking well smart Duncan!
I remember having to wait what seemed forever for a pair of Sowter output transformers for my KIT88
Looking really good Duncan if itas good as the DAC/PRE you will have something very special
Wow respect is due. That looks amazing.Quote:
Originally Posted by tubehunter
When Steve(aquapiranha) visited me recently he was telling me all about the amazing Dac-Pre you made and which Ian Walker got as a replacement for a certain well like Japanese Dac S---;). All I can say not having heard one of your designs is double WOW. That is testament indeed to how good you must be at building and designing. I look forward to your write up of this amp when finished.
Regards D S D L
Very silly question (perhaps not?)
Regarding input sensitivity, might it be better to keep this fairly low and try to push more signal down the interconnects as long as impedances aren't screwed up in the process?
I only ask as a mate in the recording industry couldn't understand all the audiophool foo regarding wires, although he did admit that the facility he worked at used 5V signal levels I understand (ok, balanced..) and this sort of level may help with cable type immunity.
Apologies if this is a silly question, but I'd genuinely like to know if anyone has experimented with this sort of thing...
P.S. Amp looks great so far. How much for the bits?
I also have this Dac Pre and its stunning Totally destroys my old PS Audio Digital link 3Quote:
Originally Posted by Dalek Supreme D L
Well four hours later and I now have the two copper cases prepared.
Do I complete them tomorrow?:)
http://i514.photobucket.com/albums/t...0/IMG_4387.jpg
As regards input sensitivity, I think I'll leave as simulated as I plan on feeding it with a Dac via passive pot. But yes you're right, if the amps were placed next to the speakers and long interconnects used I would re-evaluate.
As for the cost, I haven't totaled the reciepts yet but I didn't want to scrimp on this amp.
Nae laddy the night is young,if you keep going they'll be done by 3.30 on the moro....i'll set me alarm for 3.15:)Quote:
Do I complete them tomorrow?:)
Neil,
Ahem... Funnily enough, he's still got his Sony! ;) ;)Quote:
When Steve(aquapiranha) visited me recently he was telling me all about the amazing Dac-Pre you made and which Ian Walker got as a replacement for a certain well like Japanese Dac S---;)
No harm though I suppose in having two superb DACs at your disposal :eyebrows:
Dunc, I have a feeling that this amp could be special!
Marco.
Lovely job of folding and cutting!... what do you use for that sort of thing? :)
Cheers...
I think you have something very special; nice workQuote:
Originally Posted by tubehunter
well all the hardware mounted ok.
http://i514.photobucket.com/albums/t...0/IMG_4393.jpg
I use a homemade bending machine made out of heavy angle to fold the material and good quality holesaws, coping saw and files to cut the holes.
Fairly hardwork but if your marking out's correct everything should fit.
I can't wait to finish them off but I've got to get out on the bike.:)
Dunc, excuse me if I've missed this already, but are the valves you're going to use EL84s? :)
I think Ian made a mistake when he mentioned 'KT84s' to me (I'm not sure there's such a valve), and certainly the valves bases on your amps would not fit a large 'KT'-type valve ;)
Marco.
Yep EL84 PP Marco-see the first post of the thread.Should be a nice musical amp.I like the EL84.
No he didnt ya big daftee he said EL84s:mental:Quote:
Originally Posted by Marco
Mmmm......................................... Ok!
;)
Marco.
Looking good Duncan as usual, let me know how much.... I will need two pairs! (I wish...)
WOW
http://i514.photobucket.com/albums/t...0/IMG_4403.jpg
Finally finished them, no major problems.
They sound amazing much better than expected, I'm very pleased with them.
It hasn't blown up then? ;)
Marco.
The last and only project that I had blow-up big time was an old valve tv in 1975, threw me across the smoke filled room.:)
After that experience I'm very carefull.
Valve TVs? They were mental things - some serious voltages in there!
So when are your babies making their way over to Ian's? I must attend :cool:
Marco.
Just had a dem of the amps in my system...all i can say is GET IN THE QUEUE BEHIND ME:)
Hehehe... And why was I not informed of this monumental event taking place? ;)
Marco.
cos i knew youd be tryin to jocky jump the queue:ner:
Duncan
Great job they must sound pretty special
Nayyyyy.... Ah gots me a copper doo-dah :eyebrows:Quote:
cos i knew youd be tryin to jocky jump the queue:ner:
Marco.
Worry not Dunc was sayin he'd like to hear them with your reds so give him a bell to arrange..
Shounds good. Will do :)
Marco.
Nice one Ian. I think maybe Duncan needs to get himself a proper workshop and a marketing strategy!
If I start saving now I may be able to afford some in say, 9? maybe 10 years!!
:lolsign:
Hey, beautiful looking amplifiers. You should be very proud of your achievement.
Are those obbligato psu film oil caps you used ?Quote:
Originally Posted by tubehunter
I know Brian at diyhs has used these in his amp kits for sometime now favouring them over elects even BG's.
Yes they are, as stated earlier, only I went for the 100uf 400v spec throughout.
I have found that I can listen all day with no fatigue what so ever and still can't turn off late into the evening.
My music has become real again, since starting out forty years ago listening using a Farranti portable which funnily enough utilized the EL84 tube also
I think its to do with the good old days in domestic environments. Tuners and tape could only put out low signals. I think this was more to do with lack of foresight than anything else. Hifi amps had a sensitivity to match and then CD came out with its 2.2V output which was A LOT LOUDER!!.Quote:
Originally Posted by DSJR
You're right (I think) it would be much better for sources to put out 5V or even more with plenty of current so long cables can be driven easily.
Nice amps by the way:)