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Old 4th March 2013, 12:48 PM   #21
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Quote:
Originally Posted by Vinylsavor View Post
Hi Erik,

I did not really start to work on it yet. I will rebuild a fully differential phono stage design which I had years ago first. I will probably apply some aspects from that design. Fully differential from in to out, choke in the cathode, common to both tubes. IT coupled.

But its too early really...

Best regards

Thomas
Thanks Thomas. I am indeed seeing more and more fully differential PP amps popping up, probably also due to availability of nice depletion mosfets. I am always reading your site, and when the PP comes I am sure you will post it over there as well.

Best regards, Erik
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Old 4th March 2013, 02:41 PM   #22
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Hi!

Quote:
Originally Posted by jcmusic View Post
Ok brother thanks for the info and tips, I am not hearing anything that tells me I need more power. My backup amp is a PP using 6L6 tubes at 25 wpc and it just seems to have so much authority that I thought if my 45 just had a little more power, well you get it...
Did you measure the actual power, you are pumping into your speakers? Hook up a scope to the output terminal of the amp, while connected to the speaker and watch the voltage peaks to get an idea which kind of power you are actually using

Thomas
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Old 4th March 2013, 02:52 PM   #23
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Hi!

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Originally Posted by Vincent77 View Post
Can you please tell me what kind of speakers you drive with your 45 SE amps? What would be the minimum sensitivity you recommend?
One is an active speaker set up in which the 45 drives the horn section, a 110dB field coil.

The other set up uses the 'Rho' from Haigner. It has a mere 91dB. This seems unusable with a 45, but since I rarely listen at loud levels, it works nicely. If I need more power I have plenty of amps to swap.

What is the minimum for you depends largely on your listening habits, your room and how honest the sensitivity measurement of the speaker manufacturer is.

Unfortunately many speaker manufacturers use the loudest spot in the frequency response of their speakers to measure the sensitivity.

I have seen speakers which had been claimed as being 98dB sensitive, which actually after measurement where more like 89dB!

Also the sensitivity is often given as dB per 2.8V in 1m rather than 1W. For 8 Ohm that translates to 1W, but if the speaker has 4 Ohms impedance that translates to 2W, which means the sensitivity is 3dB less for 1W!

Best is to try. Difficult to give any advice from the distance if speaker and amp are not known.

As a rough guideline I would say with honest 98dB and up most listeners will be happy with a 45 amp. With lower sensitivities, test it out

Best regards

Thomas
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Old 4th March 2013, 03:38 PM   #24
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Originally Posted by Vinylsavor View Post
Hi!



Did you measure the actual power, you are pumping into your speakers? Hook up a scope to the output terminal of the amp, while connected to the speaker and watch the voltage peaks to get an idea which kind of power you are actually using

Thomas
Hi Thomas,
I am getting right at 2 wpc to my speakers...
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Old 4th March 2013, 04:48 PM   #25
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Hi!

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Originally Posted by jcmusic View Post
I am getting right at 2 wpc to my speakers...
Then more power would be helpful to also cover some headroom for transients.
Are you sure your speakers are 106dB? That would mean you are listening at very loud levels

Thomas
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Old 4th March 2013, 07:42 PM   #26
Gluca is offline Gluca  Italy
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The last amp I built, actually just one channel running as I am missing a few minor parts, is a 6CG7 differential stage direct coupled to a VT52 differential stage. So far this is the best (maybe the second best after my EIMAC 75TL) amp I built. Filaments are AC heated and output noise is 0.8mVRMS. D1 is a string of 12V zeners for a total 252V but 6CG7 is feed from the 216V tap

Gianluca
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Old 4th March 2013, 07:52 PM   #27
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Originally Posted by Vinylsavor View Post
Hi!



Then more power would be helpful to also cover some headroom for transients.
Are you sure your speakers are 106dB? That would mean you are listening at very loud levels

Thomas
Hi Thomas,
Yes I am sure I listen between 85-95db most of the time, just kinda depends on what it is and my mood. My speakers started life as Klipsch Corner Horns the only thing original are the 15" woofers and the cabinets. I have upgrade all other componets. The mid driver is a 2" BMS rated at 118db so I have them padded down to match the other drivers so 106db is about where they are...
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Old 5th March 2013, 12:45 AM   #28
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If you want a cheap experiment, use 4P1L in triode instead of 45s. Similar power and plate impedance. I use these in PSE as my output stage, rather than PP, and I'm very happy. One good reason for this is that I can run the output 4P1Ls in filament bias, eliminating the cathode bypass or the requirement to make a fixed bias supply. Sound is very clean. It's possible that this in itself makes up for any intrinsic sound advantage of a 45 with a cathode bypass capacitor. I have a large box of 4P1L so I laugh at the prices of 45s.
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Old 5th March 2013, 03:11 PM   #29
SET12 is offline SET12  United States
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Originally Posted by jcmusic View Post
45 Type Push/Pull
How many here use or have heard one of these type amps? What are the important factors here in this being able to produce quality sound of this tube with out the noise???
Can this amp achieve the sound quality of an SET amp?
Thomas really said it all, but really the real issue from my stand point is most people don't go far enough IMO in their vision or imagination of what it takes to get extraordinary sound. My philosophy is "if you want extraordinary sound you mush do extraordinary things."

Quote:
Originally Posted by Vinylsavor View Post

If you want the SE sound character that stay SE IMHO

Best regards

Thomas
Quote:
Originally Posted by jcmusic View Post
Hi Thomas,
Yes I am sure I listen between 85-95db most of the time, just kinda depends on what it is and my mood. My speakers started life as Klipsch Corner Horns the only thing original are the 15" woofers and the cabinets. I have upgrade all other componets. The mid driver is a 2" BMS rated at 118db so I have them padded down to match the other drivers so 106db is about where they are...
This is where you grabbed my attention. I own Klipsch as well (Fortes 98db/watt) of course highly modified. I have been DIYing for nearly the last 25yrs, I have 40yrs experience in the hobby. It was only when I began DIYing that I finally had some satisfaction.

When I said not far enough here is a typical George Wright 2A3 Monoblock contrasting a 45 Monoblock that I designed the circuit for my very good friend John. John did the layout with some assistance from me which is very unconventional but the amp is dead quite on his highly modified LaScala's.

Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.

Further I would like to thank Thomas for his work with tube full wave bridge rectifiers which was eventually added to the project using 4 6D22S's/mono along with an additional paralleled mains power transformer.

John has said that he has not heard the amp clip or sense any form of compression. I designed this thing to be ultra fast both in impact and recovery. He lives 450mi away from me but I did get a chance to hear it and he was right as all I heard was effortlessness. As to playing to 100db, I ran some SPL #'s on his system efficiency vs mine and our system max SPL levels match. His amps incorporate many of the same principles that I have in my amplifiers. And I can easily obtain 100db in my system from SET Mono's, 10 watts from a 811-10 running Class A2 with no sense of compression.

I hope you enjoy the photo's. I don't get here to often so please e-mail me if you'd like to know more on John's system and the design of John's BOS45 amplifiers.

SET12
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Old 5th March 2013, 06:55 PM   #30
jdg123 is offline jdg123  United States
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Default 1W and 86dB

Hi jcmusic, I am the guy SET12 was talking about with the 45SET. I run La scalas with stock drivers. I have a better midrange horn and a Universal crossover made of premium parts and that helps some but really we can't be that far apart...unless...

Is your room huge? How close do you sit? What is in the room that might absorb sound energy? Have you ever done work to your crossovers?

I get by with way less than a Watt but then again I have a separate sub woofer with it's own amp. There are lots of factors I guess, it is just funny that we like about the same SPL = 86-89dB for listening. One Watt should do you just fine IF you have everything else going right.

SET12 is a super smart guy. He is not conventional unless conventional makes sense. He has been ALL OVER the process of stereo's making music and I'd trust what he tell you.

What folks don't like and understand it completely is that what he is saying is not well corroborated by a crowd of engineers. His very well worked out numbers indicate that low DCR is an extremely good way to keep the music signal flowing freely, uncorrupted and whole all the way through the chain of events. When I heard his system I knew I had to try it. It was the most dynamic stereo I have ever heard and I have listened to quite a few systems that cost like houses cost.

Good sound comes through a commitment to physics not hyperbole. I don't know if you are going to believe me but my experience tells me you need to find what is choking off your 1 or 2 Watts because that is all you should need with even 104dB/Watt speakers. That's physics.

I have some ideas but SET12 could tell you better.

Don't give up on the 45 SET as a possible answer because mine rocks the house! If you don't have the heart to go "deep in" or "whole hog" to make the 45 work, try a 2A3 SET (a 2A3 is just a pair of 45s in one bottle )but don't go PP. Even the very best efforts of the very best designers can't seem to put the music back together again once you split it up. PP is a step in the wrong direction once you have committed the space, money and time to good efficient speakers. Don't break up the music if you can help it!
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