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PostPosted: 03 Feb 2014, 16:49 
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RossD: thanks for the nice comments. As you know I care as much about form as function. Fortunately in this case both excelled my wildest dreams. This schematic has been used elsewhere on this forum. The other build is very nice but totally different to mine.
Attachment:
image.jpg

Remember the PS is absolutely critical here. On HPs you will hear uVs of hum or noise so make it perfect not just good. Also half the output caps in the schematic. They do not have to be this big. I'm putting mine on the CRO today so hopefully can post some specs. later.


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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 03 Feb 2014, 23:02 
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here are some specs:

With 33ohm load:

-3db points -10Hz to 240KHz
max power with 2.03Vpp input = 1Vpp @ 1KHz
noise with input S/C = 0.45mV to 0.88mV RMS (that's really low) knob at 10:30 position my comfortable listening level
Xtalk - 1Khz at 2.03Vpp input in one channel = 1.6mV in the other channel (excellent)

With 180ohm load

-3db points -10Hz to 164KHz
max power with 2.03Vpp input = 6Vpp @ 1KHz
noise with input S/C = 0.45mV to 0.77mV RMS (that's really, really low)
Xtalk - 1Khz at 2.03Vpp input in one channel = 1.6mV in the other channel (same, excellent)

Channel matching was perfect 100%. Noise didn't change with attenuator fully open.

The SQR wave performance was excellent to 20kHz. I didn't bother going any higher. And excellent at 100Hz. Perfect at 1KHz of course. All in all exceptional good results. The two phones I have are the ATs - 33ohms and the Sennheisers - 150ohms.
Attachment:
1Khz SQRInto33ohmsJ.jpg
Attachment:
10Khz SQRInto33ohmsJ.jpg
Attachment:
20Khz SQRInto33ohmsJ.jpg


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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 09 Feb 2014, 19:48 
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Usually everyone who is into tube DIY has way too many tubes. Well I'm definitely in that class. But even being aware of my sickness hasn't stopped me ordering more. In the HP amp the 6AS7 "S" shape sits high. So I ordered some NOS NIB RCAs. $36 shipped is not to bad for a more squat tube and I like RCAs. When they show up i'll post an image. Lucky I'm about to make another 6AS7 power amp. I'll get to use up some of the six 6AS7s I already have.

I hope there is no cure.

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 09 Feb 2014, 20:21 
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I should have known, a two stage amp, preamp whatever is always inverting. I wonder how critical it is with HPs? I should have a look at the schematic and see what effect re-inverting the output would have. It doesn't worry power amps with the output floating via the OPT but this maybe different. I just swap over the speaker leads.

I understand no one is every really aware how the signal comes out of the recording studio. Is the studio signal inverted or is it right way up? And if it does come out of the studio inverted did they do that on purpose because it sounded better?

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 09 Feb 2014, 20:35 
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Here is an image of the tubes just ordered. Think they will look better in the HP amp.
Attachment:
image.jpg


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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 16 Feb 2014, 05:21 
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Sanguine is such an excellent, extremely quiet, HP amp I wonder does it make a very good preamp. The fact it will drive into 33ohms and has an extremely extended frequency range should make it a contenders. Any comments or better still tell me why not?

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 20 Feb 2014, 18:27 
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The U.S. RCA squat 6080 (6AS7) tubes arrives a few days back. I gave them 10 hours of play before comparing them with the Winded "C" original tubes. The RCAs have much greater weight and fuller bass than the winged "C"s. At this point the RCA are staying in.

Had a listened to a pair of Sennheiser 598. They sounded very good and possibly better than my pairs of AT ATH700 Airs. Should check the price. Result: a quick look on the 'net shows the HD598s go for $269. That makes them $100 dearer than the ATs. I would say for the $100 you are getting better phones and it probably worth the extra $100. The HD600 are $329. This could make the 598s a good deal.

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 21 Feb 2014, 23:33 
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I have been trying to build this 6as7 HP amp. Parts are slowly coming in. The tubes came in today but looks like the 6as7 is going back as the stem is broken off and nowhere to be found in either the tube box or shipping box. So much for testing before shipping. Grrrrrrrrr If i ever get it done i will let you know what the Sovtek 6as7 sounds like.


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PostPosted: 22 Feb 2014, 03:04 
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laurie54 wrote:
I have been trying to build this 6as7 HP amp. Parts are slowly coming in. The tubes came in today but looks like the 6as7 is going back as the stem is broken off and nowhere to be found in either the tube box or shipping box. So much for testing before shipping. Grrrrrrrrr If i ever get it done i will let you know what the Sovtek 6as7 sounds like.

I have a pair of Sovteks but they are well down on emissions. I could try them though.

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 22 Mar 2014, 00:50 
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I'm still waiting for the 6as7 to get my build out the gates. The trans came today and i am looking at a chain of RC's, load res, meters, and lots of wire. Just double checking the wiring before powering on. I have a variac so am using it to fine tune the B+ rail as the trans is a Hammond 270FX. Somewhat overkill i know but I like to have cooler running trans and may be put to use in other builds so good to see what it is made of. This means of coarse i have 550v not 450vac so i need to drop a bit more V's in the filter. Which is what i am spending the eve doing. Carefully! I salivate each time i see those RCA NIB's you picked up not to mention Sophia. A beautiful build mwhouston.


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