my CELLINI triode amp

[keantoken]

Thanks Keantoken for the good words on the amp. I'd be interested to hear more about your receiver (PM me) as I have one too !

The question about the source is a bang on the money. I don't plan to look at making a better amp than Cellini without considering the whole audio chain because the source maybe the weak link. But broadly speaking, what I gather from reading so far, there are key points in the chain where tube amps are believed to offer a benefit - and these points are where the electronics interface with the real world - transducers (the microphone/pick-up/speaker). It's a topic I'm not very knowledgeable of and probably deserves a separate thread to cover it properly.

In terms of there being a specific flaw in SS amps - I'd suggest this is not the way to think about it. I'd suggest that different amplifiers with their respective topologies, types of active devices, construction details and operating points each have their own pro's and con's and the skill of the designer shines through in how he/she makes all the relevant choices.

I'd be honoured to try out your headphone amp ! - but I don't have any high quality headphones. I may be able to borrow a pair, I'd have to ask around.

Very helpful insights, thank you. If your speakers are sensitive, you don't need headphones. The amp is rugged enough and as it's class A can be scaled up a little without major modifications. I'm running mine on my BetsyK's which get to 5.4ohms at 250Hz and have never had problems with clipping whatsoever. Even so, I'm using a pair of Koss portapros, bought for $32, and I'm happy!

- keantoken

 

[keantoken]

For safety (= protection in fault regime), the diodes should be rather beefy, right? 1N5409?

K

If you think you need to make the diodes beefy, why not instead put a fuse in series with the input ground?

- keantoken

 

[kavermei]

If you think you need to make the diodes beefy, why not instead put a fuse in series with the input ground?

- keantoken

Dangerous voltages could then appear on the input jacks under fault conditions... Beefy diodes give the GFI a chance to trip before something bad happens.

 

[Bigun]

I'm using 8A TO-220 packaged diodes. Should be beefy enough.

 

[AKSA]

Gudonya, Gareth,

Nice circuit, conventional, simple, zero feedback.

The ZFB may well be the reason you like this amp so much...

An output tube worth considering is the KT90, quite decent power, too.

Hugh

PS: Pete Millett did a very nice 813 SET using a 12HG7 IIRC, inexpensive, excellent power, very low low order distortion, worth a look.

 

[Bigun]

Hugh, thanks for the kind words - it does seem that the traditional SET has a good reputation for a good reason !

You might be right, it may be the zero feedback, I know that the harmonic profile wasn't sufficient to meet my listening needs judging from testing of my SS amps. I think I'm gonna have to try a zero feedback SS amp to round out the testing.

 

[Bigun]

based on some mumbo jumbo.... http://www.diyaudio.com/forums/tubes-valves/178505-mumbo-jumbo-power-supply-caps-5.html

I added some bypass caps across the last B+ electrolytic caps and across the power tube cathode bypass caps. I used high voltage 1uF MKP.

I don't detect a noticeable change in sound, but will keep monitoring it. Which reminds me, I have a number of 6H8C tubes to try out (1957, 1980 etc.).

 

[Bigun]

Now I'm in big trouble !

My benefactor decided to loan me a turntable and a Cambridge phono-pre to connect up to Cellini, playing through my MARTELLO speakers. It sounds wonderful....

Included was a gift of a vinyl disc, so I guess the journey has started.

 

[Bigun]

Wait until he hears the 2A3/45,

I've recently been trying out a mono-amp from a friend based on 6C4C, close enough to a 2A3. It sounds pretty good

 

[Bigun]

Well it's nearly two years for Cellini and time to review it and perhaps make some adjustments.

I have a pair of Hammond 835 transformers that can be wired to give me a 1:2 voltage ratio. This will give me a bit more gain - the amp has a gain of 1.8 at the present time.

I wired up a transformer this evening (photo on left) to try it out. And it seems to work quite well. The family said the sound was clearly more 'lively' - it is louder and there didn't appear to be much lost in sound quality. The freq. response of the transformer does imply some loss in the extremes.

The other photo (on the right) was from a new amp a friend of mine just built and it reminds me why I like tubes

 

[Bigun]

update: the input trafo has been removed. I now have a more sensitive speaker (Audio Nirvana super 15) and Cellini makes for some nice music