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Old 5th January 2006, 03:18 AM   #1
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Default Pls recommend a power amp to build?

Hi all,

Currently, I am hooking up my simple single stage common cathode 6h30 preamp to a SS power amp (yamaha MX-2), and enjoying it (I suppose the coupling caps are being broken in gradually)

I am looking to go another step now in building a tube power amp. I have been reading up on some of the common types and configurations but still cannot decide. I am leaning on a simple EL84 PP, but some warned me that it will not sound as good on vocals as SETs. Unfortunately, I have Infinity primus 360s, which are speced at 93db but Stereophile measured them at 91+db only. With my SS power amp, I do have the punch that I like, and I was warned that with SETs, I will lose significant portion of the punch.

I hope to get some advice, comments, feedback form you guys to come to a good compromise that is still relatively simple and safe to build.

thanks!
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Old 5th January 2006, 03:25 AM   #2
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What sort of budget do you have?

It is possible to make SETs with plenty of punch and simple layouts, though it would involve lots of high voltage and heat. Iron will cost.

You might also like a PP amp, possibly with the tubes triode strapped.
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Old 5th January 2006, 04:17 AM   #3
navin is online now navin  India
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I would suggest an EL34 PP UL that will give you about 30W and plenty of punch. There are atleast 3 or 4 good ckts out there (read the EL34 schematic confusion thread).

As far as kits go the ELLA Consonance is nice as it can take 6550 and KT88 as well.

My brother in law who lives in Singapore has built this kit and i have heard it with the 6550 and EL34 (different driver tube) and prefered the 6550.

Lastly at 91db even an EL84 PP UL can give you enough. Tube watts sound louder than SS watts. dont know why.
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Old 5th January 2006, 04:22 AM   #4
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Tube amps are often much better behaved about clipping than SS.
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Old 5th January 2006, 04:49 AM   #5
navin is online now navin  India
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Tue but why should a 100W SS amp clip at all. I have found a 30W tube amp sounding more forceful than a 100W SS amp. Cant put a finger on it.
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Old 5th January 2006, 05:55 AM   #6
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"Tube watts sound much louder than SS watts" - for sure.

Putting clipping aside, I don't know if it is related to high-ish 2nd (and higher even) order distortion(s). Tube amps sound much smoother, rounder, fatter, and thicker than SS amps, the later usually measure substantially better THD figures even though the odd order distortion may be higher.

I have this recent experience with my 12B4A line stage preamp. When I initially used a pair of low quality fake Philips as filter caps the sound stage was very big but very muddy. The bass was very heavy. I guess some ringing in the lower frequencies in the PSU might have caused that. Replacing the fake Philips with genuine Panasonic ED and Vishay the sound was substantially cleaner but less thick. I noticed that I had to turn the volume control up 20% more to get the same sound level. In the latest event I changed all filter caps to Panasonic TSHA (with a 20uF ICW Clarity Caps in parallel with the last TSHA cap) and installed a snubber on the secondary winding to damp the resonance caused by the leakage inductance (measured by the transformer manufacturer) and the capacitance of the diode bypass caps, again the sound is slightly cleaner possibly due to reduced ringing and I need to turn the volume control up another 5-10% to get the same sound level. In those cases, it was distortion (undamped resonances) that cause the louder sound.

Is it because additional even order harmonics on top of the signals causing the louder sound in tube amps? Obviously tube amps usually sound quite thick and warm. While adding presence, "realism" to the music it is sometimes bigger than life. My tube friends love playing female voices or pianos with Audio Note preamps, 300B and Rogers LS3/5A and said the voices and pianos were real. I would say the sound was sweet and very nice but in no way real.

I certainly don't mind having a little bit of 2nd order distortions and indeed, I much prefer tube preamps to SS or IC preamps. Tube preamps are much nicer to the ears and can create an illusion of realism. It is like cooking dishes with a bit of spices - the original tastes are still there but now with added flavours. It is nice. Without spices the food could be fairly tasteless, but if too much are added they will destroy the original tastes. This leads me to believe that there is no such a thing as the ultimate HiFi and it is really subject to personal tastes like our preference for food. I
'd be open minded.

Regards,
Bill
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Old 5th January 2006, 06:14 AM   #7
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Quote:
Originally posted by navin
Tue but why should a 100W SS amp clip at all. I have found a 30W tube amp sounding more forceful than a 100W SS amp. Cant put a finger on it.
It's the nature of SS devices to clip viciously. (This is part of the reason why they make such good digital devices.) Add the necessary NFB to linearize them for audio, and that exaggerates the clipping behaviour. This, in turn, generates lots of disagreeable high order harmonics. VTs, when overdriven, don't hit the rail like that. Instead, they sort of "sneak up" on the rail, and have to be overdriven considerably to generate those horrible-sounding harmonics. Audio signals tend to spend a lot of time at some low average value with transients that can be up to ten times higher than that average.

So you have to run that 100W SS amp considerably below 100W in order to have enough head room to accommodate the fast rising transient without clipping. Due to how VTs clip, a transient can cause clipping without your even noticing it. (unless it's built like a SS amp: lots of NFB). Therefore, the 30W VT amp can run at a higher average that makes it sound louder than a more powerful SS amp.
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Old 5th January 2006, 07:45 AM   #8
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How about something like this?http://www.diyparadise.com/simpleel84.html

Should be quite simple since I already have a 6h30 preamp right? Will this work?
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Old 5th January 2006, 09:57 AM   #9
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Originally posted by pengboon
How about something like this?http://www.diyparadise.com/simpleel84.html

Should be quite simple since I already have a 6h30 preamp right? Will this work?

With your Infinity speakers, the match is POOR. As I said over on AA, there are significant damping factor considerations.

If a SIMPLE tubed circuit, with a typically modest damping factor, is to be employed, you will need to acquire a different pair of speakers.
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Old 6th January 2006, 07:59 AM   #10
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Originally posted by Eli Duttman



With your Infinity speakers, the match is POOR. As I said over on AA, there are significant damping factor considerations.

If a SIMPLE tubed circuit, with a typically modest damping factor, is to be employed, you will need to acquire a different pair of speakers.
Eli, I am willing to spend more and go slightly more complicated in terms of circuitry, pls advice.

thanks again!
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