Tube Lab
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- čas přidán 11. 05. 2023
- We take a first look at our new Kit Phono Preamp AND listen to it.
Woops the test track was actually "California Dreaming" not "Summertime" as stated in the video - both of course are wonderful tunes.
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Link to Mellow Tone Kits: valvesnmore.com/?page_id=13253 - Jak na to + styl
I would like to add and bring to your attention as well as to the future builders of your phono preamp kit a special dedicated comment to the nature of the creation of your phono preamp !
It is worthwile to mention that this phono preamp is something quite special in the way it performs and is build with tubes from before the microgroove era and Blumlein's 45/45 ° stereo recordings during the fifties ..............wonderfull to build it with tubes preceeding the noval tube era , this makes your creation even more asthonoishing and rewarding .
Good octal tubes sounds often more lush and open than their noval offspring ...........and richness of tone is also one of their many beautifull q.ualities
Yes absolutely what you said! From the very first prototype I had in mind 2 different designs. One with high gain and a very clean fast sound, that became the prototype 6n2p phono preamp and also one with a warm
ich sound and of course that became the Universal 6or12SL7 kit phono preamp and will be released to Test Builders soon.
Hey Frank. Thanks for that information! I could never quite put my finger on it, but always end up using octal tubes in my preamp. I did end up building a very rough version of skunkie’s color pre and ended up changing the 12au7’s to 12sn7’s for that bloom in the midrange and low-mid punch while still having beautiful highs. This 6SL7 phono pre is making me rethink my 12ax7 based phono stage. I wonder how a decent SUT would work with this one, but I’ve got a feeling it’d be fantastic.
Hi Jim and Charles , very nice project and it sounds very musicaleven on YT !
You can also use the military version .....6188
or the Philips/Mullard ECC35 ..............some are reinforced/high reliabilty /security tubes with glass tubing arround the internal wires .a practice seen also on some big nos triodes .
Some have blacked glass like the Kenrad 6SL7
and the 5691 red base is also a very nice and musical tube .
Succes with this project !
Voicing is the cream of the circuit indeed .......and as always that needs time, passion and knowhow.....
Thanks for the additional tubes, I'm sure between the three of us we still have missed a few. Really so long as the sub is a direct equivalent or higher mil/industrial spec the EQ should be stable and correct to my design/voicing. But be careful, if the impedance of the sub is different, even by a small difference, the EQ will shift.
@@tubelab194 Yes indeed , ....and synergy with the system, there's also the VT 229 to list another to the list .
The RCA Electron Tube Handbook #3 (1954) Receiving Tubes Part 2 states that 12SL7 => 6SL7 (pg 490) and Resistance Coupled Amplifier Chart #7 (part 1, pg 79)...
Does the chart #7 amp design incorporate a phono preamp circuit for the 6sl7?
12AX7 was extensively used for RIAA amplification,.............but it is not the most musical choice , the tube was primarly used for it's gain !
Besides as you mentionned good nos 12AX7's are now rare and expensive ..........low noise was the 7025A.............or the special german developped tube for low microphony and extreme low noise version.....................the ECC808 ( but with a different pin out than the ecc83 ) these tubes are also rare , they had a very symetrical pin lay-out and were used in professional recording gear .
@@ceylonmooney good resullts with nos ECC82....( selected ) ......nos ECC88 and real german E188CC are also good ( NOT the 6922/E88CC !!!! .
In the AX7 family .........5751 Sylvania Gold Brand , RCA command triple mica, ECC803S and TESLA E83CC ( same frame grid and identical to the
@@ceylonmooney One other note ...............when you waznt to use ECC83 for RIAA .........some vintage circuits do a great MUSICAL job nevertheless.........Look at the Marantz circuit and the AR preamp 3 circuit .........don't forget the secret of their musicality is also in the power supply for these circuits !!!
The Marantz has a bootstrap which gives the music an extra dynamic punch without disturbing the harmony of the melody .......Very clever engineers at that time ! engineers with EARS !
@@ceylonmooney Indeed .......some do an excellent job .
Quite looking forward to making one of these a winter project. Videos are great! Maybe I missed the point somewhere: Is there an advantage to using 6SL7 versus 12SL7, and visa vis? Thanks!
Same tube, just a different filament and voltage. But given the declining inventory of quality vintage tubes, this can be a huge advantage going forward, because you basically double your available tubes. And of course if you're using a pair of 12SL7's for the preamp stages you would also use a 12SN7 for the CF stage (cathode follower).
Real double mono does not need 2 rectifiers?
Correct you need two rectifiers for true dual mono, and if you look in the store www.valvesnmore.com under "Information" you'll be able to see the actual power supply schematic, which shows two bridge rectifier stages, one for the left channel and one for right. It's also possible to design a partial dual mono power supply that will work almost as well. I would note we are one of the only kit amplifier manufacturers that publish complete schematics.
For someone like myself who deal with arthritis and are unable to put kits like this together without the obvious obstacles, are alternatives to assemble this kit. Thanks in advance.
At some point we would like to offer a higher level of assembly, but that's a way off.
I’ll bet if you ask around on the Mellow Tone Kit forum one of the builders would be glad to build it for you. Many kit builders enjoy the process as much as the product.
Sure , some would be pleased to help him out... @@Brighamdoc
You keep bouncing around the issue: What's the gain? MM and/or MC?
Sorry it's a MM (moving magnet) preamp. We did the fun intro and listen first. In a future episode we'll go over the specs. Currently version 3.1v has a gain of 187.80, so if you put in a nominal 5mV you would get out 0.939vrms or just under line Voltage.
@@ceylonmooney at 1Khz 45db
The audio GODS will foo foo ir using a CF on tje output. I personally agred and also use CF on my phono preamps. Oh well the audio gurus are the ones that are full of crap lol
I designed many CF stages for early phono preamp designs and every one of them robbed the music of life and sounded awful. This one is just the opposite pushing lots of current (relatively small mA but lots for a typical 6SN7 design) and I think that's the difference.