• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Amp refurbishing question.....

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Are there any advantages to using 40% screen taps with push-pull 6BQ5s versus staying with an original design that didn't use them?

I'm replacing OPTs in an old amp I'm refurbishing and the Edcors I'm using have this connection. If it has audible advantages, I want to use it, of course.

If this is advantageous, are any other changes needed, such as a resistor between the screen and OPT?

Thanks, Greg
 
I'm in Chillicothe.

Off and on for months, I've been restoring a 1959 Silvertone Model 29 integrated.

Yes, it is the UL connection. My Edcors say screen on the tap, so I just called it that. I'm wondering if the lower distortion is actually anything audible, and since the amp is only 10-15 watts to begin with, we're looking at very little power output, which isn't always a bad thing, I know. Maybe I'll install a switch and I can go back and forth.
 
69CamaroSS396 said:
I'm in Chillicothe.

Off and on for months, I've been restoring a 1959 Silvertone Model 29 integrated.

Yes, it is the UL connection. My Edcors say screen on the tap, so I just called it that. I'm wondering if the lower distortion is actually anything audible, and since the amp is only 10-15 watts to begin with, we're looking at very little power output, which isn't always a bad thing, I know. Maybe I'll install a switch and I can go back and forth.


switch is a good idea
15watts is plenty for efficient speaker
what speaker do you use?
 
69CamaroSS396 said:
Are there any advantages to using 40% screen taps with push-pull 6BQ5s versus staying with an original design that didn't use them?

I'm replacing OPTs in an old amp I'm refurbishing and the Edcors I'm using have this connection. If it has audible advantages, I want to use it, of course.

If this is advantageous, are any other changes needed, such as a resistor between the screen and OPT?

Thanks, Greg

"UL" is a form of feedback. You get a more linear amp but at the cost of some output power.

If all else is equal a UL amp will fall between an triode and pentode in terms of output power and gain. Many people think it's a perfect trade off.
 
, won't changing to UL require other circuit mods as well? [/B][/QUOTE]


no
compare these schem
pentode
 

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tim614 said:



switch is a good idea
15watts is plenty for efficient speaker
what speaker do you use?


The speakers I currently use are not particularly "tube friendly". 86dB sensitivity, but they sound fantastic. Signet bookshelf from about 1994. Bought them new at Progressive Audio on High Street in Cols. Actually got rave reviews as a budget buy. However, no low end to speak of.

I have parts and plans to build an open baffle based on suggestions I got from Martin King. Just don't have the time at the present to work on all the projects I'd like to. Unfortunately work gets in the way.
 
The speakers I currently use are not particularly "tube friendly". 86dB sensitivity, but they sound fantastic. Signet bookshelf from about 1994. Bought them new at Progressive Audio on High Street in Cols. Actually got rave reviews as a budget buy. However, no low end to speak of.

Add a subwoofer to the system and use the line level I/Ps. The idea is to keep power hungry low freq. info. out of the tube amp and those inefficient speakers.

Also, see if you can get impedance curve info. for the Signets. If they are nominally 8 Ohms, but have significant dips, treating them as 4 Ohms may be best.
 
69CamaroSS396 said:



The speakers I currently use are not particularly "tube friendly". 86dB sensitivity, but they sound fantastic. Signet bookshelf from about 1994. Bought them new at Progressive Audio on High Street in Cols. Actually got rave reviews as a budget buy. However, no low end to speak of.

I have parts and plans to build an open baffle based on suggestions I got from Martin King. Just don't have the time at the present to work on all the projects I'd like to. Unfortunately work gets in the way.


Greg i have a pair of fostex backloaded horn if you interested
 

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Thanks for the replies.

Eli,

I've always used a subwoofer when doing serious listening with any bookshelf speakers. But my system(s) are in disarray at the moment and I switch back and forth between a DIY KT88 SET and a vintage Sherwood S-5000 connected to the Signets. I have to say the Sherwood is one of my favorite pieces of gear ever for sheer listening pleasure.

Tim,

Thanks, but I'm not in the market for more speakers at this time. I may connect this little amp to my JBL Studio floorstanders just to see what it will do. They have a sensitivity of 91dB, IIRC.

And I think I'll just leave well enough alone and forget the UL connections. I'm planning to give the Silvertone amp to my Dad, and he wouldn't notice the difference anyway.

Cheers, Greg
 
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