Music Angel hard wired

[Audiophile]

Originally Posted by pre65

Hi Alan.

To a certain extent you can tell a resistor wattage by it's dimentions. To be honest I never use PCB's on my builds, and never use resistors less than 2W as they are too small and fiddly for me.

If in doubt go for the biggest wattage you can (size permitting).

If you ever progress to building your own amps then you will find find that electronics calculator invaluable (I do !). You don't have to learn the formulas, just a basic understanding of the relationships between voltage, current and resistance is enough to start with.

Cheers Philip, I dont like pcb's either, that was the reason for the original post, to hard wire the amp, as for using large R's as a precaution, another thing I wanted to do was to use some low power naked foils where possible, see here: http://www.ariaaudio.com/WVVishay.html
I can personally vouch for these having used them in my I/V conversion for 2 out of 5 cdp's I have tubed but thats another story. As for progressing to building my own amps I did that about 15 years ago, ok they werent mine they were JLH monoblocks but I built them using premium parts not on the spec sheet and I havnt heard anything since that sounds as good, including visiting all the shows. I am on a never ending journey and the JLH's are my ref. I have managed to do quite a bit without knowing the why and how, maybe some will say I am a neophyte but this hobby has kept me interested for over 20 years and I love it.

[Audiophile]

[quote=Richard;67615]Hi Alan,
So we have the component numbering to hand, here are the 3 circs we have so far.
Can you clarify which valves yours uses and any voltages you know.
Mostly it's easy to choose the rating of resistor but it can be better to use a larger one for reasons other than power rating.

Richard, where do you get the time! no wonder you are a mod! Thanks for keeping the thread going, my amp is engraved with 12AT7-12AU7, the second valve had joined heaters, I bought some equivelant valves but to be honest I havnt had any luck swapping them out, I am guessing that even though people quote valves as a straight swap its not always that straight forward, I tried mullard cv4024 for the first stage and some philips Jan 5963 for the second, both have ended in failure even though they are listed as equivalents. I thought I would get help before I burn anymore cash I dont have! As for the actual valves in my amp I can only tell you what I can read off the glass, I dont presume to believe they are anything but chinese copys though. The first one is the worst, its numbers are, 79(rusion emblem)3, bellow this looks like GN1, I guess it could be 6n1 for 6n1p? the second valve is clearer, its a usa 5963, funny how my JAN's failed in this possition, something to do with the joined heaters? Its been a while since I measured the voltages but I remember thinking the 315v caps were too small and the 400v caps were the same as the B+, one cap even has a bulge on top, I also remember checking the spec on the tubes and I thought the supply was over the max rating but 'Dr John' has had my amp and he said the voltage was fine, I think I just dont understand the thing with valve specs, isnt Va the diff between the supply voltage and the voltage on the anode or cathode? Ok dont quote me, thats where I fall down, I figure I have measured the B+ at 400v and for my own piece of mind I want higher voltage caps. Wether I should have higher value caps is another question?

Having decided to hardwire the amp, upgrade the R's for bulk foils were poss and do cap changes, I have also decided to configure the heater on the second valve to 4/5-9 instead of 4&5-9, I believe this opens the door for me to try more tubes? I guess this is where all those R's make a difference?
What tubes do I want to use? to be honest I dont have an answer for that, I want to be able to roll tubes without the thing dying or blowing valves. I have a pair of Siemens D3a that I was going to use in my CDP SRPP but I have been unable to get specs for them, I also have a good supply of 6n1p's. My aim is not to get bogged down with £200 a piece tubes. If its not to ambitious I also have a number of russian 6H8C's which I believe are equiv. to 6sn7gt and also some 1579's which I have heard are very speacial, I have the bases for these as they were bought for a project involving a hybrid amp so I could resurect my JLH's.
Sorry for the length of my post, I am eager to solder!!!

Alan

[Richard]

HI Alan,

Looks like your amp is another variation then. I asked as the anode Rs are different. If they are 6n1 (quite possible) you could drop in ECC88 equivs.

I'd be more inclined though to rewire the heaters to 4-joined-with-5 and 9 if a 6.3V supply, which will then be the same as your second valve I think, and change your 325R cathode R to 1k (you don't ned the 15R if no fb), so you could try any Ecc81/82/83 5751 12ay7 etc of which 5751 and 12ay7 would be good bets for the first valve and the 82 for the second.

The voltage looks ok. If the caps have not been blowing rate any replacements same or greater and you'll be fine. Anode voltage is the voltage the anode sees, the difference between the anode pin and the cathode pin, note that the HT supply may be much higher due to the drop over the anode R.

Typically the first stage will then be drawing around 1mA or so, so the anode load R will only need to be (0.1W) 0.5W rating. For stability and low noise a bigger one may be preferred. I think I'm being careful using 1W carbon films there in mine but by all means buy your nekked ones or try 0.6W or even 2W metal films from Maplin which are very low noise. The first stage is most important and the anode resistor of the first stage most of all. Most of them can be 0.5W but if you name any using Lampys numbers we can approximate a rating.

[Audiophile]

Originally Posted by Richard

HI Alan,

Looks like your amp is another variation then. I asked as the anode Rs are different. If they are 6n1 (quite possible) you could drop in ECC88 equivs.

I'd be more inclined though to rewire the heaters to 4-joined-with-5 and 9 if a 6.3V supply, which will then be the same as your second valve I think, and change your 325R cathode R to 1k (you don't ned the 15R if no fb), so you could try any Ecc81/82/83 5751 12ay7 etc of which 5751 and 12ay7 would be good bets for the first valve and the 82 for the second.

The voltage looks ok. If the caps have not been blowing rate any replacements same or greater and you'll be fine. Anode voltage is the voltage the anode sees, the difference between the anode pin and the cathode pin, note that the HT supply may be much higher due to the drop over the anode R.

Typically the first stage will then be drawing around 1mA or so, so the anode load R will only need to be (0.1W) 0.5W rating. For stability and low noise a bigger one may be preferred. I think I'm being careful using 1W carbon films there in mine but by all means buy your nekked ones or try 0.6W or even 2W metal films from Maplin which are very low noise. The first stage is most important and the anode resistor of the first stage most of all. Most of them can be 0.5W but if you name any using Lampys numbers we can approximate a rating.

Hi Richard, thats invaluble help thankyou very much. I will order those 2W metal films from maplins, no point buying the 'z' foils, too low power, you rate the anode at .5W, I dont fancy blowing them at this cost unless .1 isnt going to make any difference? http://www.hificollective.co.uk/comp...resistors.html shame really as they are probably the best r's in the world! Thanks for pointing out all the tube options aswell, I think I will try those 5751's, not because stevie likes em, I think I can afford some 2nd order distortion, it will probably put back some of the 'valve sound' i lost removing the R's making it so transparent.

All the best.

Alan

[Audiophile]

Richard, or anyone that feels like chipping in and giving the guy a break, I was just about to get some 5751 tubes, only everyone seems to recomend them to reduce the gain in an amp, to quieten it down, found what looks like a good supplier, its says particulary good as main driver. http://www.hotroxuk.com/electro-harm...ld-8836-0.html.
Dont know if I can afford much less, I am prob pushing it driving high capacitance cables and 6 drivers per chanell!



Alan

[Greg.]

Hi Alan,

Don't worry. There is a slight drop in gain if moving to 5751's but there is an opinion based bonus that you get a sweeter sound, which is why alot of us now use these. It's not much difference which equates to the volume pot being turned up just a tad more from what you're used to. After a couple of listens, you'll not think about the gain issue again but you probably will enjoy a better sound.

Regards,

Greg

[Audiophile]

Originally Posted by Greg.

Hi Alan,

Don't worry. There is a slight drop in gain if moving to 5751's but there is an opinion based bonus that you get a sweeter sound, which is why alot of us now use these. It's not much difference which equates to the volume pot being turned up just a tad more from what you're used to. After a couple of listens, you'll not think about the gain issue again but you probably will enjoy a better sound.

Regards,

Greg

Cool, many thanks Greg, I was wondering if that price is normal or maybe you have a secret supplier that is really cheap? Dont worry I wont tell anyone,

Alan

[Greg.]

Hi Alan,

Have a look at this thread and in particular post 33.

http://wduk.worldomain.net/forum/showthread.php?t=5404

I've read the EH 5751 you've selected are good. Historically, GE JAN 5751 are regarded as the benchmark choice. This is a nice price option on some well regarded NOS valves provided the offer is still going.

Regards,

Greg

[Audiophile]

Hi Greg, looks like I may get a chance to enjoy these valves before they become gold dust, thanks for pointing out the post and thanks to Richard for recomending them, I know its always risky, Ive seen forum frenzie push valve prices through the roof, lets hope theres plenty around to prevent it. Ive put in a quote request at Chelma, shame they dont have an online shop, sounds like they may be worth trying in my cdp valve output stage.

Alan

[jonas]

Hi, what must be changed in that schematic if i want to use 6N1P EV as a driver?

Many Thanks!