rebuilding 6L6 amp ... suggestions? - Page 7

EC8010 · 16th April 2003, 10:37 PM

I think you are confusing power and voltage. You measured a voltage, so you should have used the 20log(V1/V2) equation, not the 10log one. A common mistake. (I used to teach this stuff.)

Knowing that the amplifier has a gain of 6 is nice, but not conclusive. What is really required is the input voltage required to make it clip at 1kHz. Since you have an oscilloscope, it is easiest for you to make the measurement in Vpk-pk.

What condition are your records in? Are they spotless, mint collectors items, or are they charity shop specials? You see, a better RIAA stage will allow you to extract the best from charity shop specials. I'd really like to convince you of the merits of buying an ECC88 and associated Noval valve base. Hell, I'll give you one if you really need it!

phonon · 16th April 2003, 11:24 PM

My records are definitely charity-shop specials

. Why is a good RIAA stage better for worse-condition records?

I did the previous meausurement with speaker attached for a realistic load; 1 Khz at full clipping power is painful to listen to, so the measurement was at a small signal level. Remeasuring with speakers detached, I get 5V rms output at clipping for a .73 V input. I am still using the wrong value cathode resistor (125 ohm), so the clipping point is probably not optimal.

I also gather that you think I should use an ECC88. My largest problem with this is that I cannot replace sockets without mechanical parts/tools that I don't have in my dorm room. However, at this point I can wait a few weeks until summer vacation when I will be at home and have access to the necessary tools. Where can i get an ECC88 and base at lowest cost?

EC8010 · 16th April 2003, 11:43 PM

Charity-shop specials tend to be scratched and mucky. When the stylus crashes into these obstacles, it produces lots of HF (it's a velocity transducer). If the pre-amplifier overloads at HF (and you'd be surprised how many do), the effect of the click or scratch is significantly exacerbated. Good RIAA stages are not overloaded...

I'll do you a swap. I'll send you an NOS Mullard ECC88 plus an NOS skirted PTFE socket if you send me five charity-shop LPs with music/performances that you think I ought to listen to.

fdegrove · 16th April 2003, 11:50 PM

Hi,

Quote:

I'll do you a swap. I'll send you an NOS Mullard ECC88 plus an NOS skirted PTFE socket if you send me five charity-shop LPs with music/performances that you think I ought to listen to.

You're one hell of a generous man EC8010.

Not only do you impress with your knowledge but more importantly, with your persona.

This gesture alone should grant you a 24 days anti-sinbin credit.

Cheers,

phonon · 17th April 2003, 12:15 AM

Thank you for your generous offer, but:
My tastes in music are for baroque/rennaissance/early; as a result, it is hard for me to find records to my taste. Over the about 4 years since I started listening to vinyl, I have only amassed a collection of ~100 records. I have little opportunity to travel, and the local used music store sold off its entire classical section bulk to some-one

. Although few of my records are "mint," and none are "collectible," as far as I know, they are mostly in reasonable condition (I don't buy the obviously heavily damaged kind); they are mainly cheap-used-vinyl-store grade, although I did clear out the local charity shops a few weekends ago. The music/performances that I own that I would recommend are all ones that I would want to keep to listen to, aside from one or two duplicate records. While your offer is very geneous money-wise, I value the records that I have far more than their purchase price because they are so hard for me to find. I would rather buy the tube/socket than part with any of my vinyl. If only I had more records...

If you want recommendations for recordings to listen to, I could give you those for free...

EC8010 · 17th April 2003, 12:15 AM

Now I'm all embarassed.

EC8010 · 17th April 2003, 12:20 AM

Quote:

Originally posted by phonon
Thank you for your generous offer, but...

I know what you mean about personal value versus financial value. Email me your postal address etc, and we'll sort something out.

phonon · 17th April 2003, 12:27 AM

Your profile is set to not give your e-mail address. Mine is michaelpmendenhall @ yahoo.com.

16th April 2003, 10:37 PM	#61
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	Power and voltage I think you are confusing power and voltage. You measured a voltage, so you should have used the 20log(V1/V2) equation, not the 10log one. A common mistake. (I used to teach this stuff.) Knowing that the amplifier has a gain of 6 is nice, but not conclusive. What is really required is the input voltage required to make it clip at 1kHz. Since you have an oscilloscope, it is easiest for you to make the measurement in Vpk-pk. What condition are your records in? Are they spotless, mint collectors items, or are they charity shop specials? You see, a better RIAA stage will allow you to extract the best from charity shop specials. I'd really like to convince you of the merits of buying an ECC88 and associated Noval valve base. Hell, I'll give you one if you really need it! __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

16th April 2003, 11:43 PM	#63
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	Bartertown Charity-shop specials tend to be scratched and mucky. When the stylus crashes into these obstacles, it produces lots of HF (it's a velocity transducer). If the pre-amplifier overloads at HF (and you'd be surprised how many do), the effect of the click or scratch is significantly exacerbated. Good RIAA stages are not overloaded... I'll do you a swap. I'll send you an NOS Mullard ECC88 plus an NOS skirted PTFE socket if you send me five charity-shop LPs with music/performances that you think I ought to listen to. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

17th April 2003, 12:15 AM	#66
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	Aw, shucks. Now I'm all embarassed. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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16th April 2003, 11:24 PM	#62
phonon diyAudio Member Join Date: Mar 2003 Location: St Louis, MO	My records are definitely charity-shop specials . Why is a good RIAA stage better for worse-condition records? I did the previous meausurement with speaker attached for a realistic load; 1 Khz at full clipping power is painful to listen to, so the measurement was at a small signal level. Remeasuring with speakers detached, I get 5V rms output at clipping for a .73 V input. I am still using the wrong value cathode resistor (125 ohm), so the clipping point is probably not optimal. I also gather that you think I should use an ECC88. My largest problem with this is that I cannot replace sockets without mechanical parts/tools that I don't have in my dorm room. However, at this point I can wait a few weeks until summer vacation when I will be at home and have access to the necessary tools. Where can i get an ECC88 and base at lowest cost?

17th April 2003, 12:27 AM	#68
phonon diyAudio Member Join Date: Mar 2003 Location: St Louis, MO	Your profile is set to not give your e-mail address. Mine is michaelpmendenhall @ yahoo.com.

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