vintage hifi

[cybot]

Well done Fran as usual. Reminds me of a more sophisticated Series 5 Croft...

[barry robin]

very nice mod there fran. with the updated three-banger board and those coke bottle valves, it must pack quite a punch. i'm envious.
i myself only went with the wimpy EL84s because paula and i wanted that liquid midrange more than we wanted the extention.
paula just looked at the pics of yours and started to warble something that sounded like "honey....wouldn't some more slam be nice..."
since you know her, you know that she actually says things like that.

-b

[Fran]

Well, you're in the right part of the world to be able to pick one up. from reading around on the net, there's a thriving valve community around SF.

I switched to the 8ohm taps last night, and things definitely sounded better. The highs seemed cleaner and the whole sound was a bit more neutral. I have ye tto try the 4 ohm ones. What might be of interest is the triode switches - that may just give back the bit of midrange warmth that the EL84s give you.

Ivor also kindly lent me a set of EL34s to try out. I want to get a better handle on the sound of it as it stands and then compare the kt66 with the EL34.


More listening to follow!

Fran

[Fran]

Another little update..... I had to do a few tweaks to drop the gain a bit on the amp - it was sky high and I couldn't get the volume control on the pre past the first notch or two. Also, I was hearing hum from the pre that I never knew existed!!!

Anyway, thats largely sorted now, and the sonics are unaffected. Now that the amp has had a little time to settle in I can comment a bit more about the sound. I have found that the preamp can make a large difference to this amp - not that great with the pass DCB1 (which is very good with other amps I have tried), a very wide open refined soundstage with one version of an aikido valve pre and a much more exciting, upfront sound with another version of the aikido. I find this pretty interesting given that the last 2 in particular are the same circuit with different valves. I wouldn't have thought it would be the case.

The sound does sit on the slightly warm side, but still with plenty of dynamic slam and clarity. Its hard to say it works better with some music compared to others - with one aikido, the sound is refined, big wide open resolved soundstage, good for detailed recordings. The other aikido puts voices out in front of the speakers, and with its greater dynamics, it does rock very well.

Overall I'm surprised at how good it sounds - given that this thing dates from 1964! OK, essentially I have gutted it and replaced it with all new components, still I think it does very well. Knowing what I know now, I could easily recommend some of the kits that are on sale. For about USD700 you can buy a complete kit to build one of these - chassis, valves, the lot.Its a good bit of money, and of course you have to build it, but I still think its great value. I think it would be much smarter money to buy one of these compared to a chinese one from ebay. The other thing is the support available. Lots of people have these, and mention ST-70 on any of the DIY fora and lots of people are familiar with it.

In short, I'm delighted I sprung for it now - even though I felt I had paid over the odds at the time.


Fran

[tony]

Its great that it worked out for you Fran. Always nice when a risk turns out to be the right decision. Lucky for you that you can do so much work as some others including myself would have given up and felt we had got a bad deal. I didnt comment before on this as the other lads have said it all but it looks a lovely amp. I think the fact you had to rebuild to make it all come together makes it an even more enjoyable purchase for you while for me it would be nerve wracking and I would be waiting for the electric shock to finish me off.

[Fran]

Well, to be honest I'm kinda paranoid about getting a shock from it! That kind of DC can kill easily, so I'm always very careful. And its not the dramatic shock that will throw you across the room - its the kind that stops your heart and you just slump down. Not what you want!!!

One of the rules I read early on in one of the valve bibles was not to do anything with power late at night when you're tired. Its a rule I follow, no matter how excited you might be to get it done. So I will go as far as wiring some of the audio side, or fitting new RCA jacks etc etc etc. But the power switch stays off. The other thing is that it allows some space for you to think about it all - when you come back the next day I often find that you have resolved some issue you had earlier.

I'm working on a DAC at the moment and the voltages are refreshingly low..... 3.3V ain't going to harm you too much!!

Fran

[cybot]

[quote="Fran"]Well, to be honest I'm kinda paranoid about getting a shock from it! That kind of DC can kill easily, so I'm always very careful. And its not the dramatic shock that will throw you across the room - its the kind that stops your heart and you just slump down. Not what you want!!!

One of the rules I read early on in one of the valve bibles was not to do anything with power late at night when you're tired. Its a rule I follow, no matter how excited you might be to get it done. So I will go as far as wiring some of the audio side, or fitting new RCA jacks etc etc etc. But the power switch stays off. The other thing is that it allows some space for you to think about it all - when you come back the next day I often find that you have resolved some issue you had earlier.

I'm working on a DAC at the moment and the voltages are refreshingly low..... 3.3V ain't going to harm you too much!! Fran [quote]

Another refreshingly honest appraisal of the dangers of diy electronics and some sensible tips too. I remember Glenn (Croft) warning me always to have one hand free when testing/working with dangerous voltages.Your comment about allowing some space strikes a chord with me; It's a long running joke with myself and my little wife! Anytime something goes wrong in the house, panic ensues and I'm watched like a hawk while I try to fix it (sound familiar!). More times than not we end up having a nark and nothing gets fixed! But as soon as she leaves the building it's fixed in no time at all :-)

[JAW]

Well, to be honest I'm kinda paranoid about getting a shock from it! That kind of DC can kill easily, so I'm always very careful. And its not the dramatic shock that will throw you across the room - its the kind that stops your heart and you just slump down. Not what you want!!!

One of the rules I read early on in one of the valve bibles was not to do anything with power late at night when you're tired. Its a rule I follow, no matter how excited you might be to get it done. So I will go as far as wiring some of the audio side, or fitting new RCA jacks etc etc etc. But the power switch stays off. The other thing is that it allows some space for you to think about it all - when you come back the next day I often find that you have resolved some issue you had earlier.

I'm working on a DAC at the moment and the voltages are refreshingly low..... 3.3V ain't going to harm you too much!! Fran

Another refreshingly honest appraisal of the dangers of diy electronics and some sensible tips too. I remember Glenn (Croft) warning me always to have one hand free when testing/working with dangerous voltages.Your comment about allowing some space strikes a chord with me; It's a long running joke with myself and my little wife! Anytime something goes wrong in the house, panic ensues and I'm watched like a hawk while I try to fix it (sound familiar!). More times than not we end up having a nark and nothing gets fixed! But as soon as she leaves the building it's fixed in no time at all :-)

I remember studying for the Radio Officer exam in the long gone Atlantic College in Leeson Park where it was drillede into us to have one hand in a pocket when working on valves. Must have made sense - I'm still here despite my best efforts!

[Fran]

Yup - good move to make. I usually clip the ground on and then poke with the positive probe. I remember reading a thread ages back where old boys related tales of accidents etc and there were quite the number of deaths from people sticking fingers where they shouldn't. As the voltage rises so do the risks. I wouldn't like to be working on an 845 set amp with 1200 + volts!


Fran

[tony]

Fran the last few posts have cured me of any desire to poke around inside an amp. I will leave it to the professionals. Don't mind soldering copper pipe with nothing in it and connect only to the water supply but wiring sockets and some lights are as far as I would be prepared to venture. Water leak never hurt anyone. Maybe the abuse from she who must be obeyed but its normally a non lethal assault.