Tube amp & preamp wives tales

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Wind Chaser

Re: Tube amp & preamp wives tales
« Reply #20 on: 26 Nov 2009, 02:46 pm »
What about current and tube amps vs. solid state?

Niteshade

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Re: Tube amp & preamp wives tales
« Reply #21 on: 27 Nov 2009, 08:53 pm »
Could you explain what you mean? Do you mean current tube amps vs. older tube amps vs. solid state?

What about current and tube amps vs. solid state?

CharleyW

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Re: Tube amp & preamp wives tales
« Reply #22 on: 28 Nov 2009, 04:17 am »
"Tube friendly" speakers are speakers that present a reasonably lnear load to the amplifier - no large swings in impedance and inductance.

I think (flame suit on) that a lot of the lack of bass perception of tube power amps comes from the fact that the power supplies tended to be a somewhat "soft" - tube rectifier (especially the ST-70 - it;s rectifier was designed to drive one pair of EL34's, not two).  And power supply capacitance was much more expensive in "those days" than it is now.

Just my $.02.

Niteshade

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Re: Tube amp & preamp wives tales
« Reply #23 on: 28 Nov 2009, 11:55 am »
You're right- current limitations can reduce a tube amp's performance.  The standard ST-70 isn't a bad amplifier. It's not a high performance amp, but does a good job on most things. Some make upgrades for them which I'm sure steps them up a few notches.

RooX

Re: Tube amp & preamp wives tales
« Reply #24 on: 28 Nov 2009, 02:43 pm »
Nightshade
Quote
I have not listened to an OTL but really want to. Would someone with an OTL like to talk about theirs?

have you ever thought about building one up to play with?

Niteshade

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Re: Tube amp & preamp wives tales
« Reply #25 on: 30 Nov 2009, 02:57 pm »
Yes and no. The reason why OTL's use so many tubes is because the tubes were not designed to be used to drive low impedance loads. I realize there are desirable outcomes from this topology but prefer using transformers because they are so efficient and reliable.

Nightshade
Quote
I have not listened to an OTL but really want to. Would someone with an OTL like to talk about theirs?

have you ever thought about building one up to play with?

Niteshade

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Re: Tube amp & preamp wives tales
« Reply #26 on: 13 Dec 2009, 03:42 pm »
Would you consider a pentode in triode mode to be better sounding than one in tetrode mode?

The common belief (wives tale) is yes. Some people do like the sound and I will not quarrel with that. But- to say tetrode mode is worse sounding isn't right. I prefer tetrode mode because it facilitates the tube's power handling capability efficiently. I see no reason to put a 'bottleneck' on a tube's abilities. Tetrode mode can provide exemplary performance and it does with the proper circuits.


Listens2tubes

Re: Tube amp & preamp wives tales
« Reply #27 on: 19 Dec 2009, 10:19 pm »
The afore meantioned Dynaco St-70 makes a superb case for tube amp reliability. So many still turn up at house sales and are seen at an uncles house to this day. They run in the backround in many peoples homes for countless hours. At 40+ years in some cases that an excellent record. :thumb:

Steve

Re: Tube amp & preamp wives tales
« Reply #28 on: 23 Dec 2009, 12:59 am »
If I may Blair, I would like to add a couple of more.

1) The component must be tube rectified. What can happen is that the rectifier tube can soften the sound too much.

2) The component must have choke(s) in the power supply. In this case, the power supply becomes more reactive when we want the power supply to be as linear as is possible.

As Blair mentions, the design is very important.

Cheers.

zybar

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Re: Tube amp & preamp wives tales
« Reply #29 on: 23 Dec 2009, 01:04 am »
Yes and no. The reason why OTL's use so many tubes is because the tubes were not designed to be used to drive low impedance loads. I realize there are desirable outcomes from this topology but prefer using transformers because they are so efficient and reliable.


My OTL amps have been the most reliable tube amps I have owned - I don't think you should paint such a broad picture when it comes to reliability and OTL amps.

I do agree with you about OTL amps having trouble driving low impedance loads...however, you can simply add something like the Speltz Zeros and you are in business.  Better yet, don't get speakers with very low impedance loads.   :wink:

George

Steve

Re: Tube amp & preamp wives tales
« Reply #30 on: 23 Dec 2009, 01:06 am »
Hi Zybar,

I have an old homebrew OTL amp and was wondering if anyone is manufacturing 32 ohm drivers these days?

Cheers.

zybar

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Re: Tube amp & preamp wives tales
« Reply #31 on: 23 Dec 2009, 01:22 am »
Hi Zybar,

I have an old homebrew OTL amp and was wondering if anyone is manufacturing 32 ohm drivers these days?

Cheers.

Actually, I think Zu will provide 32 ohm speakers. 

Of course you don't need to go to 32 ohm speakers to take advantage of an OTL amp.  My speakers (Vandy 5A's) go down to 4 ohms and are a great match with my Atma-Sphere OTL amps.

George

Jon L

Re: Tube amp & preamp wives tales
« Reply #32 on: 23 Dec 2009, 02:01 am »
Hi Zybar,

I have an old homebrew OTL amp and was wondering if anyone is manufacturing 32 ohm drivers these days?

Cheers.

My speakers (Vandy 5A's) go down to 4 ohms and are a great match with my Atma-Sphere OTL amps.

George

Bet your Atmas will also drive the Vandy 7's pretty decently  aa aa

Steve

Re: Tube amp & preamp wives tales
« Reply #33 on: 29 Dec 2009, 08:43 pm »
Hi Zybar,

I have an old homebrew OTL amp and was wondering if anyone is manufacturing 32 ohm drivers these days?

Cheers.

Actually, I think Zu will provide 32 ohm speakers. 

Of course you don't need to go to 32 ohm speakers to take advantage of an OTL amp.  My speakers (Vandy 5A's) go down to 4 ohms and are a great match with my Atma-Sphere OTL amps.

George

Hi George,

I guess I was getting at the high output tube impedance should control a higher impedance woofer better than a lower impedance woofer. That and a capacitively coupled output stage would require less capacitance. Are all the OTL amp manufacturers using dc coupled now?

Thanks George.
Steve

Niteshade

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Re: Tube amp & preamp wives tales
« Reply #34 on: 1 Jan 2010, 09:32 pm »
I am pretty sure most OTL manufacturers are using a system where no coupling device is necessary on the output due to using bi-polar power supplies.