Captn Dave said:
And it's a much better performing and sounding design than the one described earlier in this thread.
Twenty five years ago I was experimenting with this exact topology and even ultimately added the CF mentioned elsewhere to drive both tube and solid state amplifiers. Measurements were excellent, but the sound unfortunately wasn't even on par with my Yamaha C-2 which IMO is not a very good sounding pre-amp despite the wonderful build quality. All of that feedback is the kiss of death in a tube circuit, squashes all of the life out of the music whilst giving very good static measurements. The sound was at best uninvolving, and in some respects relatively unpleasant - enough so that I almost abandoned tube audio right as I was beginning to explore its possibilities.
Hi,
Guys thank you all very much for the inputs !!
Well I have infact checked the Tubecad blog regularly in my quest to learn and start a tube project !
What perhaps I have not mentioned or took it for granted that you guys know !
First off, I cannot order anything from Abroad
! the shipping cost and the duty will kill me 
!! have tried all this and decided against ordering even a single resistor from outside of India !
There are tonnes and tonnes of problems, to begin with our Govt considers Us Audio Lovers as crazy rich folks and have levied a heavy customs duty on these imported items ! and to top that the shipping (sometimes as much as the item being ordered or more ) !
So I cannot afford !! Am not that rich to do this
!
So that leaves me with only domestic options (which is next to none ) ! the Tube availability itself a major issue here ! but somehow I can manage only 12AU7 and 12AX7 for a reasonable price !
So only have stuck with the designs based on these !!
Anyways coming back to my last question, Please Please give me a feedback on the trafo ASAP ! I need to order it today !!
Regards.
Guys thank you all very much for the inputs !!
Well I have infact checked the Tubecad blog regularly in my quest to learn and start a tube project !
What perhaps I have not mentioned or took it for granted that you guys know !
First off, I cannot order anything from Abroad
! the shipping cost and the duty will kill me !! have tried all this and decided against ordering even a single resistor from outside of India !There are tonnes and tonnes of problems, to begin with our Govt considers Us Audio Lovers as crazy rich folks and have levied a heavy customs duty on these imported items ! and to top that the shipping (sometimes as much as the item being ordered or more ) !
So I cannot afford !! Am not that rich to do this
!So that leaves me with only domestic options (which is next to none ) ! the Tube availability itself a major issue here ! but somehow I can manage only 12AU7 and 12AX7 for a reasonable price !
So only have stuck with the designs based on these !!
Anyways coming back to my last question, Please Please give me a feedback on the trafo ASAP ! I need to order it today !!
Regards.
Filament winding is okay (for regulated duty or use dropping resistor to get 6V); HT secondary voltage is okay, current rating ditto BUT overkill: you won't draw much more than 10mA for the stereo amp... Unless you're enjoying a very special offer, a 100mA transformer is much more expensive than a 10mA counterpart.
Simon
Hi,
Simon thanks a lot for the reply
!!
Yes I am using a regulated supply with LM317 ! so that 9V will be.......
As with the HT supply, at first I had set it to 50MA,but later when I put the figures in other forum folks said its not enough ! so had to change it to 100MA !!
So should I change it back to 50MA ??
As with the special offer, Am getting a CRGO Split Core E&I Trafo for about 8$ or so,that's why I said what the hell !!
Regards.
Simon thanks a lot for the reply
!!Yes I am using a regulated supply with LM317 ! so that 9V will be.......
As with the HT supply, at first I had set it to 50MA,but later when I put the figures in other forum folks said its not enough ! so had to change it to 100MA !!
So should I change it back to 50MA ??
As with the special offer, Am getting a CRGO Split Core E&I Trafo for about 8$ or so,that's why I said what the hell
!! Regards.
Are you certain that these are your only valve options. Have you talked to a TV repair man and seen the huge range of pentode valves which can be pressed into service. Do not discount the possibility of using valves with different heater ratings (ie the P and U series ones). This simplifies heater requirements a great deal and makes cheap transformers usable. At these currents you can consider using back to back transformers for you HT - they will work very well and it allows you to use just about any readily available transformers.
I feel certain you haven't explored all of the options and a bit more digging will be more than worth it.
Shoog
Hi,
Shoog I greatly appreciate your inputs and the suggestions !!
But Sir, I have thoroughly checked all the places in my city and also in couple of others !No luck so far !
As with me talking to repair men,yes even that option was explored to the fullest ! No one here has them or even most of the new guys are not even aware of them
!!
In the entire country there's only one major source for tubes, I did talk to him aswell and he says any odd numbers that I wish to have will cost premium,but he doesn't guarantee that he will be able to source but only will try if I say the asked high sum for the tubes are ok !!
So I have asked him to check 6H30 as I found them to be better then the said ones ! so far no reply from him (almost 4months up)
!!
So with all above handicaps I choose to do a Pre with the easily available one's !!
I just don't know how to react to this
!! will think over and let you know (Am only concerned bout the shipping) ! I really don't want to burden you or trouble you !
Please send your address and such,will check with the locak postal service and get an estimate and then will take a call !!
Regards.
Shoog I greatly appreciate your inputs and the suggestions !!
But Sir, I have thoroughly checked all the places in my city and also in couple of others !No luck so far !
As with me talking to repair men,yes even that option was explored to the fullest ! No one here has them or even most of the new guys are not even aware of them
!!In the entire country there's only one major source for tubes, I did talk to him aswell and he says any odd numbers that I wish to have will cost premium,but he doesn't guarantee that he will be able to source but only will try if I say the asked high sum for the tubes are ok !!
So I have asked him to check 6H30 as I found them to be better then the said ones ! so far no reply from him (almost 4months up)
!!So with all above handicaps I choose to do a Pre with the easily available one's !!
I just don't know how to react to this
!! will think over and let you know (Am only concerned bout the shipping) ! I really don't want to burden you or trouble you !Please send your address and such,will check with the locak postal service and get an estimate and then will take a call !!
Regards.
It will probably cost less than €10.00 to send to you and thats nothing to me.
Do a search for a datasheet and see what you think, it is a slightly unusual tube as it has a common cathode. I haven't got them yet so it might come to nothing.
I know the Indian attitude to business (I visited many years ago), its very similar to how it is here in Ireland - its called "Putting you on the long finger".
Shoog
Do a search for a datasheet and see what you think, it is a slightly unusual tube as it has a common cathode. I haven't got them yet so it might come to nothing.
I know the Indian attitude to business (I visited many years ago), its very similar to how it is here in Ireland - its called "Putting you on the long finger".
Shoog
So I cannot afford !! Am not that rich to do this
So that leaves me with only domestic options (which is next to none ) ! the Tube availability itself a major issue here ! but somehow I can manage only 12AU7 and 12AX7 for a reasonable price !
If you really are on a tight budget, here is an idea that can be adapted. the cost is about zero for a small HT supply. The design below uses two transformers and other parts selvage from 12VDC "wall wort" power cubes. You open them by cracking them in a bench vice. His plans below create a 140V HT supply but by using other kinds of wall wort supplies, say for example a 9VDC and a 12VDC you can get a 200V supply and so on.. This works because you only need a few milliamp. This lets you experiment with one tube (two triodes) for almost zero cost.
http://www.dogstar.dantimax.dk/tubestuf/mchowit.htm
Thats what i meant by back to back.
However you cannot get more than the line voltage by this method - by feeding more AC into the second transformer than it is rated for - it will saturate and stop working (it will also heat up). I have tried this.
If you really need more than the 140V DC then a voltage doubler would be needed.
Shoog
However you cannot get more than the line voltage by this method - by feeding more AC into the second transformer than it is rated for - it will saturate and stop working (it will also heat up). I have tried this.
If you really need more than the 140V DC then a voltage doubler would be needed.
Shoog
I would suggest using the circuit discussed by Broskie found here http://www.tubecad.com/2009/03/blog0161.htm If you plan on using back to back transformers for supplies then the regulation will not be great (voltage sag for varying current draw). A constant current draw circuit would help. 12ax7 and 12au7 can both be used in this circuit easily.
Hi,
Thanks Chris and others for trying to help !! Am really really glad to read all the replies !!
Chris Am sorry if I have given wrong picture or idea ! But Am not tight budget so much so that I cannot afford to get a proper transformer !!
I have already posted the quote for the Trafo,
So getting a trans for a decent price is not an issue,I've even got a quote for toroid which 2$ or so more then E&I ! I go with any of them,no probs at all !!
What I meant was,Importing stuff from abroad is not an option !! this has been the problem for many years and will continue to be ! So cannot choose that option thats all !
Even for PSU Am going with a regulated one ! so its not a Shoe String budgeted one but at the same time not in $$$ also !!
Regards.
Thanks Chris and others for trying to help !! Am really really glad to read all the replies !!
Chris Am sorry if I have given wrong picture or idea ! But Am not tight budget so much so that I cannot afford to get a proper transformer !!
I have already posted the quote for the Trafo,
So getting a trans for a decent price is not an issue,I've even got a quote for toroid which 2$ or so more then E&I ! I go with any of them,no probs at all !!
What I meant was,Importing stuff from abroad is not an option !! this has been the problem for many years and will continue to be ! So cannot choose that option thats all !
Even for PSU Am going with a regulated one ! so its not a Shoe String budgeted one but at the same time not in $$$ also !!
Regards.
If I wanted a nice tube amp I'd simply buy one already built at the store. I have a job and can afford a high and amp. But that's not the point. I actually prefer to keep my eye out for used, broken and surplus equipment. To me it is more fun to build a (say) guitar amp from a 50 year old broken Hammon organ then to buy one.
In fact I was at the store and the salesman offered his demo amp at discount. It had a nice sound that I liked. Was a good price too. I could not buy the parts to build it at his offering price. Would cost me at least $100 more to build it with new parts. I had to resist. I don't learn anything from buying amps.
I'm going to build something from a pair of these "free" transformers just to see what happens. I think I have every required part all salvaged.
Hi,
Hello All Am back with another query !!
I've built the said circuit and Am very happy with the sound ! So now I thought to take it to the next step incorporating the Additions that Rich mentioned (the Inclusion of CSS ) !!
I've searched long and hard and finally found this which seems to be the best !
I have the following quires on this.
1)how to calculate the values which is missing ??
2) for both source and sink can the given B+ work as shown in the schematic ? (although the NPN and PNP trannies are used for the said purpose but still coz some of them suggest a separate negative supply)
3) can this be implemented on a SRPP design or only suitable for Cathode follower ??
Please do help me on this !!
And finally I was also thinking of adding a Volume Buffer to the input of the Circuit,so can I use the B1 from Passlabs for said purpose ??
Hello All Am back with another query
!!I've built the said circuit and Am very happy with the sound
! So now I thought to take it to the next step incorporating the Additions that Rich mentioned (the Inclusion of CSS ) !!I've searched long and hard and finally found this which seems to be the best !
I have the following quires on this.
1)how to calculate the values which is missing ??
2) for both source and sink can the given B+ work as shown in the schematic ? (although the NPN and PNP trannies are used for the said purpose but still coz some of them suggest a separate negative supply)
3) can this be implemented on a SRPP design or only suitable for Cathode follower ??
Please do help me on this
!!And finally I was also thinking of adding a Volume Buffer to the input of the Circuit,so can I use the B1 from Passlabs for said purpose ??
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