Search found 26 matches

by dominique
Sun Aug 23, 2009 4:18 pm
Forum: Inductors
Topic: small 49% nickel chokes
Replies: 3
Views: 7388

high cdr plate choke

hi dave, thanks for the 1:2 autoformers i got on last monday ;-) i am already working on a 2-stage amplifier design and i would like to implement a high dcr plate choke for biasing and direct coupling reasons. Do you think a plate choke of 35H at 15 mADC could be wound in order to have a DCR of 4000...
by dominique
Sun Jul 19, 2009 10:30 am
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hi dave, just to give you news about that pair of opt's done for 6e5p. amp is using only one 6e5p per channel with unusual biasing method, gives 1W+ in triode and almost 2.5W in pentode. sound gorgeous either pentode or triode connected (selected by switch) ! extremely live sound with plenty of micr...
by dominique
Sat May 16, 2009 2:03 pm
Forum: Transformers
Topic: power output se transformer as input transformer
Replies: 1
Views: 3904

power output se transformer as input transformer

hi all, i had some weeks ago the idea to use tube amplifier output s.e. transformers as step up input transformers connected in reverse, to get real input voltage swing and no bandwidth limitation. you need to correctly load the output winding to reflect an acceptable load to the source. that way on...
by dominique
Mon Apr 13, 2009 4:36 pm
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hi dave,

you can put the red shim. by the way i have some remaining plastic foils you sent me with the bifilar chokes to adjust the gap, i can use them also.

regards,
dominique
by dominique
Mon Apr 13, 2009 8:55 am
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hi dave,

thanks for your reply. when do you you think you could ship one pair of those transformers ?

dominique
by dominique
Sun Apr 12, 2009 11:47 am
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hi dave, thank you for all those explanations. you are absolutely correct regarding lenz's law, thanks for reminding me :oops: the 6e5p will be used at 220V Vpk, -2.4 Vgk, 150V Vg2 and 30mA dc Ip in order to almost get 2.5W out. your tests and figures at 20mA dc Ip clearly show that i should go with...
by dominique
Fri Apr 10, 2009 5:34 pm
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hi dave,

i have one more question regarding the frequency response of the transformer. What about level vs. frequency in the region of 80 Hz ?

best regards,
dominique
by dominique
Tue Apr 07, 2009 7:57 pm
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hi dave,

the green and blue curves are more than acceptable :) they look very good to me. just go ahead with one pair ;)

best regards,
dominique
by dominique
Sat Apr 04, 2009 11:11 am
Forum: Transformers
Topic: 8K:8R 49% nickel outputs for a pentode.
Replies: 13
Views: 10598

hello dave, thanks for those information. so you wound a 1K:1R transformer that you connected to an 8 ohm load, didn't you ? it sounds perfect to me regarding the primary inductance for the "80Hz up" purpose. By the way the anode current swing won't be higher than +/- 20mA around the 30mA ...
by dominique
Wed Feb 04, 2009 7:35 am
Forum: Transformers
Topic: tapped grid choke as input step-up autoformer
Replies: 6
Views: 6937

hi dave,

thanks a lot for those measurements.

they clearly show the peak at high frequency, peak that is growing as long as the step up ratio increases. let me do some listening tests first before i place an order for a real step up transformer.

best regards,
dominique
by dominique
Sun Feb 01, 2009 4:17 pm
Forum: Transformers
Topic: tapped grid choke as input step-up autoformer
Replies: 6
Views: 6937

hi dave, thanks for the explanation, sounds clear to me now. further to your explanations, i have a question regarding the avc connection. do you think that an avc like yours (i do like them as they sound extremely good on my system) could be used reverse connected ? i mean does it make sense to use...
by dominique
Mon Jan 05, 2009 11:59 pm
Forum: Transformers
Topic: tapped grid choke as input step-up autoformer
Replies: 6
Views: 6937

hi dave, thanks for your reply, and happy new year 2009 ! would the troubles come from the grid choke itself or from the fact it would be tapped ? i can understand that such high inductance values could give some headaches to sources ... what would you suggest as an input autoformer with 1:2 step-up...
by dominique
Mon Dec 29, 2008 3:06 am
Forum: Transformers
Topic: tapped grid choke as input step-up autoformer
Replies: 6
Views: 6937

tapped grid choke as input step-up autoformer

hi dave, i have been thinking in using a grid choke instead of the usual grid resistor as an input load in my new single tube se amp. the tube would need to be biased at -6v between grid and cathode so i was wondering whether a grid choke could be tapped in order to give some gain to the stage like ...
by dominique
Wed Nov 26, 2008 11:55 am
Forum: Transformers
Topic: differential parafeed PP amp with 1:1 bifilar plate chokes
Replies: 2
Views: 6282

hi dave, i hope you are fine since we met in denver, it was a great pleasure. the amp with bifilar plate chokes is now working, and i find it to sound extremely good ! compared to the other 5902 parafeed amp i have i.e. source current loading, the one with bpc and 0.006" gap, connected to feast...
by dominique
Mon Sep 08, 2008 8:53 am
Forum: Transformers
Topic: differential parafeed PP amp with 1:1 bifilar plate chokes
Replies: 2
Views: 6282

differential parafeed PP amp with 1:1 bifilar plate chokes

good morning, i have been in touch with dave about 1:1 bifilar plate choke (bpc) and parafeed output stage without coupling capacitor to opt. i am about to make some tests with the very nice bpc's i purchased and received from dave, with a simple circuit using only one tube for one watt. however it ...
by dominique
Tue Sep 02, 2008 6:16 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi steve and dave, it appears that if we closely look at a parafeed output stage using a 1:1 bifilar plate choke direct feeding an opt, the last psu cap still remains in the audio signal path. if we admit the opt connected to the choke reflects a constant impedance across its primary winding, the lo...
by dominique
Wed Aug 27, 2008 7:11 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi dave, thank you for your comments. i sent a private e-mail to you regarding purchase of a pair of chokes. regarding the 5902 specs, there must be a printing error with the rp value. i have several data sheets of 5902 tube and all state 15,000 ohms. but it is not a problem according to your measur...
by dominique
Wed Aug 27, 2008 6:21 am
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi dave, thank you for the new measurements. i have to say that the behaviour of the 1:1 bifilar plate choke is pretty impressive all over the audio range whatever the DCR and the load impedance. i am curious to see what happens with a 100 / 150 DCR choke as the L seems to change a bit around the 30...
by dominique
Tue Aug 26, 2008 5:24 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi dave, thank you for all those measurements. as far as i have understood, it appears that the frequency response vs. load remains quite constant up to 100kHz and easily goes down to 40Hz whatever the opt primary reflected impedance connected to the 1:1 bifilar plate choke. is it correct ? one ques...
by dominique
Mon Aug 25, 2008 4:56 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi dave,

thanks for your reply. as soon as you have some numbers, we will discuss and make a decision.

cheers,
by dominique
Sun Aug 24, 2008 5:14 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi dave, thank you for your post and your e-mail. the options described in your post will be discussed with my friends, all sound very good to me. by the way the idea of 49% nickel output autoformer for bass amp is highly appealing, we will talk about that later on. regarding full range 1:1 bifilar,...
by dominique
Fri Aug 22, 2008 4:16 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi dave, thank you for your post. i sent a private e-mail to you, feel free to reply to my private address. there are some changes regarding the 1W amplifier project and you will like it :D we have decided to separate bass and mid-high for bi-amping therefore i will work on two amplifiers using 1:1 ...
by dominique
Thu Aug 21, 2008 4:15 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

Hi Dave, Thank you for your quick and extremely detailed reply. The idea i would like to go further with is not that far from the one tried and enjoyed by the Colorado guys. The current amplifier is using a Sowter 50% mumetal 50% M6 grade core gapless opt with a 3K primary coupled to a high quality ...
by dominique
Thu Aug 21, 2008 11:53 am
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi, i think i have understood how to insert a bifilar plate choke in a parafeed output stage. is the schematics correct ?
your comments highly appreciated.
cheers,
by dominique
Wed Aug 20, 2008 6:08 am
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

hi, sorry to disturb again but i would appreciate if somebody could draw a simple parafeed tube stage using bifilar plate choke and post it on the forum for everybody use. thanks a lot. i have been using a tiny parafeed single stage pentode amplifier as full range amp with duelund coupling cap (extr...
by dominique
Tue Aug 19, 2008 5:13 pm
Forum: Transformers
Topic: 1:1 bifilar output to remove the parafeed coupling cap.
Replies: 31
Views: 37037

1:1 bifilar output to remove the parafeed coupling cap

hi, this my first post to the forum, extremely interesting, thanks to dave and to the all of you. i have been reading and reading again about the 1:1 bifilar plate choke as 1:1 output transformer without need of parafeed coupling cap but i can't understand how it works. sorry not to understand but i...