Ho costruito il pre 6j1 facendo alcune modifiche che si trovano sul web: Sostituito Condensatore C13 con 2200uF 16v su alimentazione filamenti, ho cambiato tutti i condensatori da 35v con 50v più un condensatore da 470uF 50v con negativo alla giunzione delle resistenze R8-R9 e positivo a GND. Ho tagliato le tracce che portano all'interruttore di accenzione ed ho ponticellato per spostare l'interruttore a monte. Ho aggiunto un diodo alla resistenza da 2.2ohm per abbassare la tensione dei filamenti da 13.15v a 12.45v. Ho messo due resistenze da 47K tra ingresso uscita e massa per togliere il potenziometro del volume. Dopo aver collegato un lettore mp3 all'ingresso del pre e collegato l'uscita all'ingresso di un t-amp, già prima di dare il segnale si sente ad intervalli regolari un "Bump" che fa muovere i woofer delle casse e cosi' anche con la musica, anche se si sente bene. Non ho alzato troppo il volume per non danneggiare i woofer. Non riesco a spiegarmi da che dipende, qualcuno ha idea da che può dipendere, dove ho sbagliato? Grazie a chi riesce a darmi una spiegazione.
I'm sorry, here is the translation.
I built the pre 6j1 making some changes found on the web: I replaced C13 Capacitor with 2200uF 16v on filament power supply, I changed all 35v capacitors with 50v plus a 470uF 50v capacitor with negative at the junction of the R8-R9 resistances and positive to GND. I cut the tracks that lead to the switch and I jumped to move the switch upstream. I added a 2.2ohm resistor diode to lower the filament voltage from 13.15v to 12.45v. I put two 47K resistors between input, output and the ground, in order to remove the volume potentiometer. After connecting an mp3 player to the input of the pre and connecting the output to the input of a t-amp, even before giving the signal, one can hear a "Bump" at regular intervals that makes the speakers woofer move and so even with music, therefore the sound is good. I didn't turn up the volume too much to avoid damaging the woofers. I don't understand what the "Bump" depends on, where did I go wrong? Does someone have any idea? Thanks to those who can help or give me an explanation.
379/5000
Maybe I solved it, I realized looking at the other card to mount that the 4 fet are not equal but they are two pairs, I went to check the card that is not good and I realized that I reversed 2 fet. B647 was to be set on TR3 and I placed D667. D667 had to be set on TR1 and I put B647, tomorrow with great care I will reverse them and I think the pre will sound good. Greetings
Everything okay! I reversed the two fets with great difficulty and great patience, it sounds great. Between one song and another there is a very slight background noise, it may be the old recording, I will try more recent recordings (in fact with a recent recording no noise, no breath) that's okay. Greetings
I built the pre 6j1 making some changes found on the web: I replaced C13 Capacitor with 2200uF 16v on filament power supply, I changed all 35v capacitors with 50v plus a 470uF 50v capacitor with negative at the junction of the R8-R9 resistances and positive to GND. I cut the tracks that lead to the switch and I jumped to move the switch upstream. I added a 2.2ohm resistor diode to lower the filament voltage from 13.15v to 12.45v. I put two 47K resistors between input, output and the ground, in order to remove the volume potentiometer. After connecting an mp3 player to the input of the pre and connecting the output to the input of a t-amp, even before giving the signal, one can hear a "Bump" at regular intervals that makes the speakers woofer move and so even with music, therefore the sound is good. I didn't turn up the volume too much to avoid damaging the woofers. I don't understand what the "Bump" depends on, where did I go wrong? Does someone have any idea? Thanks to those who can help or give me an explanation.
379/5000
Maybe I solved it, I realized looking at the other card to mount that the 4 fet are not equal but they are two pairs, I went to check the card that is not good and I realized that I reversed 2 fet. B647 was to be set on TR3 and I placed D667. D667 had to be set on TR1 and I put B647, tomorrow with great care I will reverse them and I think the pre will sound good. Greetings
Everything okay! I reversed the two fets with great difficulty and great patience, it sounds great. Between one song and another there is a very slight background noise, it may be the old recording, I will try more recent recordings (in fact with a recent recording no noise, no breath) that's okay. Greetings
I was looking for a first tube preamp project, as well as a first pcb-kit project. After reading all of this I must say I am pretty excited. It seems like a great low cost project.
I think I will get this kit from Aiyima. I've had modules from this brand before and even though they are the same as the many unbranded ones, I have little to complain about their products. AIYIMA Tube Amplifiers Audio board Amplificador Pre Amp Audio Mixer 6J1 Valve Preamp Bile Buffer Diy Kits -in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
The acryllic case saves a lot of hassle with fabricating an enclosure, and for the price I will definetly pick one up too. Acrylic Box Shell Case 6J1 Valve Preamp Pre amp Tube PreAmplifier Board Headphone Amplifier Buffer Transparent-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
I plan on making the modifications shown in this thread before.
My only question remains the power supply. There is a 12v AC power adapter with EU plug available on Aliexpress, link below. AC 12V 1A power supply EU plug for 6J1 tube preamp amplifier board Pre amp Headphone amp 6J1 valve preamp-in Chargers from Consumer Electronics on Aliexpress.com | Alibaba Group
I also stubled across this 30VA 15v toroidal transformer. 1pc 115V/230V 30W Audio R Core Transformer high quality 12V+12V for preamp -in Transformers from Home Improvement on Aliexpress.com | Alibaba Group
Logically I would assume this transformer will be the better option for a preamp. But I do not know what is inside of the plug-in power adapter. And it would require my to make a bigger case for it.
I would really like to hear opinions on the power supply options.
EDIT: Even cheaper transformer: 30W double 15V power transformer Input:220V 50Hz / output:double15V-in Transformers from Home Improvement on Aliexpress.com | Alibaba Group
I think I will get this kit from Aiyima. I've had modules from this brand before and even though they are the same as the many unbranded ones, I have little to complain about their products. AIYIMA Tube Amplifiers Audio board Amplificador Pre Amp Audio Mixer 6J1 Valve Preamp Bile Buffer Diy Kits -in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
The acryllic case saves a lot of hassle with fabricating an enclosure, and for the price I will definetly pick one up too. Acrylic Box Shell Case 6J1 Valve Preamp Pre amp Tube PreAmplifier Board Headphone Amplifier Buffer Transparent-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
I plan on making the modifications shown in this thread before.
My only question remains the power supply. There is a 12v AC power adapter with EU plug available on Aliexpress, link below. AC 12V 1A power supply EU plug for 6J1 tube preamp amplifier board Pre amp Headphone amp 6J1 valve preamp-in Chargers from Consumer Electronics on Aliexpress.com | Alibaba Group
I also stubled across this 30VA 15v toroidal transformer. 1pc 115V/230V 30W Audio R Core Transformer high quality 12V+12V for preamp -in Transformers from Home Improvement on Aliexpress.com | Alibaba Group
Logically I would assume this transformer will be the better option for a preamp. But I do not know what is inside of the plug-in power adapter. And it would require my to make a bigger case for it.
I would really like to hear opinions on the power supply options.
EDIT: Even cheaper transformer: 30W double 15V power transformer Input:220V 50Hz / output:double15V-in Transformers from Home Improvement on Aliexpress.com | Alibaba Group
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I upgraded the caps to 63v and ran the power supply part of the circuit with no other changes. I got the following DC voltages at the +/- 28V pins:
IN__OUT
12__73
14__77
16__88
18__99
20__110
22__122
So to keep away from the 63v cap limit, I'll probably choose an 18v power supply for this project. 100v for the tubes should be better then 56v..??
This brings me to the next hurdle: 6.3v heater supply.
The original circuit deals with this by putting the 12VAC through a nasty half wave rectifier then heaters in series.
Any suggestions how to make this better - I'm thinking either a dummy load in series with the other 2 heaters or a regulator such as the LM7812 to drop the ~18v down?
IN__OUT
12__73
14__77
16__88
18__99
20__110
22__122
So to keep away from the 63v cap limit, I'll probably choose an 18v power supply for this project. 100v for the tubes should be better then 56v..??
This brings me to the next hurdle: 6.3v heater supply.
The original circuit deals with this by putting the 12VAC through a nasty half wave rectifier then heaters in series.
Any suggestions how to make this better - I'm thinking either a dummy load in series with the other 2 heaters or a regulator such as the LM7812 to drop the ~18v down?
A 2 dollar buck converter would do the trick.
2X LM2596 DC-DC Adjustable Buck Converter Step Down Power Supply Module 1.23-30V | eBay
2X LM2596 DC-DC Adjustable Buck Converter Step Down Power Supply Module 1.23-30V | eBay
I would keep the half wave filament rectifier to keep things simple. 6J1 filament draw about 170mA, if you put a 35 ohms resistor in series (18V AC) that should drop 35 * 0.17 = 6V and get to the 12V that you need. You will need a 3W resistor for that (3X of 6V * 170mA).
I tried to add the resistance into the heater circuit by changing out the R1 (2.2 ohm) with first a 39 then 33 ohm, 5 watt but it seems the current isn't dividing as nicely as I'd hoped.
With the 39 ohm, I did not get the V2 heater to operate.
With 33 ohm, I got V1 looking normal and a faint glow out of V2.
So I think I'm going to need to drop in a regulator (got some buck converters on the way).
Do I still need to have a higher value at R1 then R1->regulator->V2;
or revert to the 2.2 ohm;
or remove R1 altogether?
With the 39 ohm, I did not get the V2 heater to operate.
With 33 ohm, I got V1 looking normal and a faint glow out of V2.
So I think I'm going to need to drop in a regulator (got some buck converters on the way).
Do I still need to have a higher value at R1 then R1->regulator->V2;
or revert to the 2.2 ohm;
or remove R1 altogether?
Have anyone tried this preamp?
AIYIMA 6J1 Tube Amplifier Bile Preamplifier HIFI Preamp Treble Bass Adjustment Audio Preamplifier DC12V For Amplifier Speaker-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Amazon.com: AIYIMA 6J1 Tube Preamp with Treble & Bass Control HiFi Audio Tube Preamplifier DC12V Amplifier Preamp NE5532P Chips for Home Theater System(Tube-A3,Black): Home Audio & Theater
Is this worth for the money? How about the sound quality? It seems the reviews are great.
AIYIMA 6J1 Tube Amplifier Bile Preamplifier HIFI Preamp Treble Bass Adjustment Audio Preamplifier DC12V For Amplifier Speaker-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Amazon.com: AIYIMA 6J1 Tube Preamp with Treble & Bass Control HiFi Audio Tube Preamplifier DC12V Amplifier Preamp NE5532P Chips for Home Theater System(Tube-A3,Black): Home Audio & Theater
Is this worth for the money? How about the sound quality? It seems the reviews are great.
That resistor is dropping around 1.8W in my build so I changed it out to a 3W resistor to increase the longevity and decrease the temperature load.
It was running a little too close to limit for my liking.
If you are uncomfortable with how hot it gets, try increasing the power rating of the resistor to 3 or 5W.
It was running a little too close to limit for my liking.
If you are uncomfortable with how hot it gets, try increasing the power rating of the resistor to 3 or 5W.
Hi guys, I recently bought one of these pre-amplified kits, and my idea is to convert into a buffer without volume, for this I know that I must remove the potentiometer with ignition of 50kohms and bypass the entrance terminal with the central but what I am in doubt is that if I only have to bridge or if I have to do the bridge with a resistance of the same value of the potentiometer or maybe a little lower, what I intend is that the same signal enters and leaves those terminals and achieve unit gain and only colloquial a power switch. I come to you because I was investigating but I am still in that problem and maybe you who know much more know how to help me, sorry for my lousy English but I attached an image to understand what I consult
Thanks friend for answering !!! In a comment that I had seen here they said that it had been designed with gain, if so, then I will have to place resistances instead of bridges, will you know what is the gain with which it was built in order to place the appropriate resistances? Or better perhaps, what else should I change to achieve my goal of only being a buffer without any volume alteration in input and output?
very thanks
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Good thread
Hi Guys,
Ive been following this thread while waiting for one of these preamps from Amazon. Of course I had to breadboard something while waiting
I noticed some comments about clicking or booming sound in one channel.
My circuit is not exactly the same but had a similar problem with interference from my smartphone while data is running. Phone was being used as audio source. Shut off data and just played an audio file and click sound was gone.
Maybe the tube was working as a detector somehow picking up the radio frequency of the data network?
Anyway, just an observation.
Hi Guys,
Ive been following this thread while waiting for one of these preamps from Amazon. Of course I had to breadboard something while waiting
I noticed some comments about clicking or booming sound in one channel.
My circuit is not exactly the same but had a similar problem with interference from my smartphone while data is running. Phone was being used as audio source. Shut off data and just played an audio file and click sound was gone.
Maybe the tube was working as a detector somehow picking up the radio frequency of the data network?
Anyway, just an observation.
I had one of these too. It was like the dime bag that got me addicted to tubes. These may not the most refined items out there, but for the price they're hard to resist. If you're tube-curious and/or want to get your ear around the relationship between gain and volume, these little gadgets are a really accessible place to start.