Baby Huey EL84 Builds & Speakers Post Pictures

[eldarvanyar]

Hi all,

I am hoping to build a Baby Huey EL84 this year and am in the process of sourcing components.

I am thinking of using a Russian equivalents of the 12AX7 and EL84 vales / tubes as they are plentiful at good prices.

As the output is 10w I am wondering what speakers people are using to work with this design. What sensitivity etc works best with this?

Would people be willing to post pictures of their completed builds and speakers they are using?

Thanks

Lee

 

[Eli Duttman]

Paul Joppa has provided us with a rule for matching speakers to amps. Joppa's Rule states that for "typical" listening spaces, an amp/speaker combo should be capable of 102 dB. SPL peaks at a 1 M. distance. Applying the "formula" to 10 WPC yields a speaker sensitivity >= an honest 92 dB. Speaker manufacturers provide specifications that cast their wares in a favorable light. While not outright lies, the claims have to be consumed with copious amounts of salt. Look for things like large dips in the impedance curve, particularly in the deep bass region. Such dips may make a speaker unsuitable for mating to tubed power amplification. Another "gotcha" is a claim of a n dB. SPL, with 2.83 V. of drive. If the speaker's impedance is < 8 Ω, the provided number must be derated. 2.83 of drive is 1 W., only into 8 Ω. 2.83 V. into 4 Ω is 2 W. and the claimed sensitivity has to be reduced by 3 dB. CAVEAT EMPTOR!

 

[eldarvanyar]

Wow, thank Eli. I never knew that is very helpful.

Lee

 

[20to20]

Paul Joppa has provided us with a rule for matching speakers to amps. Joppa's Rule states that for "typical" listening spaces, an amp/speaker combo should be capable of 102 dB. SPL peaks at a 1 M. distance.

Eli, I think you should do your own CAVEAT EMPTORing when you put so much stock in someone's ...rule... based on what they define as typical. You push that over and over as if you think poster's listening spaces conform to some typicality. So what would I need for SPL in my combo system? Is MY combo producing insufficient power or too much? How would I adjust the computation to find the perfect match for my space? Did Joppa do a lot site surveys across what country to find what is typical? Does typical for Denmark equal typical for the US. I'd have to say that the "typical" listening space is not typical at all and the rule is bogus science for the sake of notoriety.

 

[Francois G]

20to20, you sounded a bit harsh. Let’s share information and behave nicely to our friends on this forum. I think Eli did the OP a favor by making him aware of this “rule”, and Eli’s “Caveat Emptor” already covered your objections to the atypical typical room.

 

[20to20]

20to20, you sounded a bit harsh.

Francois, don't apply your own emotional filter to my points. They are just as valid as any other's. You don't have to agree with them but other's might. Take a deep breath and read them one at a time and answer them for yourself and you might come in to the conversation with something others can also apply. Eli's CAVEAT is just a dig he has against published speaker specs and can't put any underlying firm science under his scary warning... that sounds so authoritative. So now on top of the "rule" we all have to do our own speaker analysis to get to final decision on how to pair our amps to speakers because you can't trust the numbers given for them. Leave your emotions out of your interpretations of posts that have no 4 letter words and let the chips fall where they may. Eli can handle it, I think.

 

[20to20]

Hi all,

I am hoping to build a Baby Huey EL84 this year and am in the process of sourcing components.

I am thinking of using a Russian equivalents of the 12AX7 and EL84 vales / tubes as they are plentiful at good prices.

Thanks

Lee

You must be able to get JJ's in Sussex, no? High quality, cheap and trustworthy. They have a better heritage.

 

[Eli Duttman]

Eli can handle it, I think.

It's not a personal attack. So, "If you can't take the heat, get out of the kitchen" applies.

Mr. Joppa himself cautioned about room size. It's a "Rule", not a "Law". V = IR is a Law.

I previously explained the 2.83 V. of drive "trap". Another instance of derating that's specific to tube amps lies in the area of impedance curve dips. Damping factor in tubed equipment is not gargantuan. If a speaker is nominally 8 Ω, but exhibits dips (especially in the bass region) down to 4 Ω, it should be connected to the 4 Ω tap and the 3 dB. "penalty" applied. The manufacturer did not do anything wrong, but an unfavorable intersection has occurred.

As long as outright false info. is not presented, speaker manufacturers "copy" is free to be favorable. Reasonable self promotion is part of business activity. The responsibility of separating grain from chaff lies with us, the potential purchasers.

 

[eldarvanyar]

You must be able to get JJ's in Sussex, no? High quality, cheap and trustworthy. They have a better heritage.

I am able to buy JJs easily. I thought the 6N14Ps are worth trying as there are plenty around.

I have matched JJ ECC803s from Karltone in my EAR834p Phono clone.

Are you saying that the modern production JJ84s are superior to the 6N14Ps that are available from the 1970s and 1980s.

I am really open to learning

Thanks

Lee