I finished an Aleph-J amp which had a pretty comprehensive build guide and didn't expect too much from the assembler in terms of in-depth calculations or even too many choices which allowed me and I suspect lots of others to build this amazing amp and many other amps.
I run it using a cheap Monoprice integrated amp which happens to have a line out from the valve preamp and I am pretty happy with the sound. However I would really like to make a good quality valve preamp[line stage] and even a phono one as well as mine is a tiny solid state Rega.
OK here's the thing. I have spent day after day reading through various preamp threads but I have not found one that documents the build completely in a way that makes it possible to just buy the parts and build it. Even the Aikido has so many choices that I was left confused and would need advice to choose the various components and still more advice to choose the specific transformers.
Every single thread goes into interminable arguments about all kinds of variants many of which are only measurable with pro equipment and the knowledge required exceeds my very newly acquired interest in this field. I could probably build from a schematic but then I get crossed wires about how many transformers are needed and all the talk of valve substitution and it goes on and on and on and the more I read in a thread the less inclined I am to get halfway into one of these projects only to find I can't get through it or fix too much hum or something.
So I'm actually begging for someone to do a full build guide for a 12B4 or something sweet and simple, including the whole process, power supply, BOM and layout whether or not there are circuit boards available, but using components that are easily purchased.
I believe something like this may be in the pipeline in the DIY shop which will then no doubt have an excellent build thread by 6L6 and we'll be able to join the ranks of the experts at least in being able to have this stuff to listen to.
But I'm putting this thread up here in the hope that some alternatives are already about that apply to this beginner level.
Cheers.
I run it using a cheap Monoprice integrated amp which happens to have a line out from the valve preamp and I am pretty happy with the sound. However I would really like to make a good quality valve preamp[line stage] and even a phono one as well as mine is a tiny solid state Rega.
OK here's the thing. I have spent day after day reading through various preamp threads but I have not found one that documents the build completely in a way that makes it possible to just buy the parts and build it. Even the Aikido has so many choices that I was left confused and would need advice to choose the various components and still more advice to choose the specific transformers.
Every single thread goes into interminable arguments about all kinds of variants many of which are only measurable with pro equipment and the knowledge required exceeds my very newly acquired interest in this field. I could probably build from a schematic but then I get crossed wires about how many transformers are needed and all the talk of valve substitution and it goes on and on and on and the more I read in a thread the less inclined I am to get halfway into one of these projects only to find I can't get through it or fix too much hum or something.
So I'm actually begging for someone to do a full build guide for a 12B4 or something sweet and simple, including the whole process, power supply, BOM and layout whether or not there are circuit boards available, but using components that are easily purchased.
I believe something like this may be in the pipeline in the DIY shop which will then no doubt have an excellent build thread by 6L6 and we'll be able to join the ranks of the experts at least in being able to have this stuff to listen to.
But I'm putting this thread up here in the hope that some alternatives are already about that apply to this beginner level.
Cheers.
You might start with your own gain and output impedance needs. Sometimes you need gain and sometimes you don't. You might want to run more than one amp from this, put in a volume control and other things that might need a certain amount of drive or buffering.
Other things you can work toward are a clean ground point to start, along with input RCAs into a chassis. Source switching, balance control, amp level matching and whatever else.
Other things you can work toward are a clean ground point to start, along with input RCAs into a chassis. Source switching, balance control, amp level matching and whatever else.
I wouldn't mind some gain but it isn't really needed with the AlephJ for room listening. It would be nice to run different amps later no doubt but that's unknown. It would need a volume, tone and possibly balance. Aikido attenuation units look to be good there except I wasn't convinced by the tone solution that equally increases bass as it decreases treble and vice versa.
I am more inclined towards them being independent. I have an external source switch but I don't understand what is meant by amp level matching. So I see the predicament you are illustrating, that it probably can't be a one size fits all scenario. That's why Aikido seems the best option with a wide choice but it gets complicated by high voltage versus low voltage, old and new variants etc. It's also unclear which transformer is need for what etc. I get confused there. Maybe I should write them a letter explaining my requirements and they can advise. Unless there's a simpler option.?
I am more inclined towards them being independent. I have an external source switch but I don't understand what is meant by amp level matching. So I see the predicament you are illustrating, that it probably can't be a one size fits all scenario. That's why Aikido seems the best option with a wide choice but it gets complicated by high voltage versus low voltage, old and new variants etc. It's also unclear which transformer is need for what etc. I get confused there. Maybe I should write them a letter explaining my requirements and they can advise. Unless there's a simpler option.?
Really good tone controls are complex. The provided Max Robinson design requires (sic) 2X 12AX7/ECC83s per channel. Also, few recordings benefit from the use of tone controls. Most of the time, tone controls should be completely out of the signal path. The provided setup is "unity" gain, which greatly assists the defeat feature.
FWIW, I suggest you forget tone controls, this time around. You said a small amount of gain would be good. There are quite a few 12B4 based designs in the archives, which should meet the need. Don't worry about a PCB, as these are simple circuits. "Monkey see, monkey do", will get you to a satisfactory end point.
FWIW, I suggest you forget tone controls, this time around. You said a small amount of gain would be good. There are quite a few 12B4 based designs in the archives, which should meet the need. Don't worry about a PCB, as these are simple circuits. "Monkey see, monkey do", will get you to a satisfactory end point.
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I was looking at the manual for the Aleph J. It says the input impedance is 242k ohms (very high) and the input capacitance is "vanishing" low. It requires 1.5V signal input to reach full power (25W). That's about 14V rms into 8 ohms, so if that 1.5V input signal is rms, then the gain is a bit less than 10X, or almost 20dB. So I don't know what good an active preamp would do going into this amp.
I think the best way to go about this is to define the benefits you want from this project.
- How much gain, if any?
- What input impedance, and what output impedance?
- Do you want to add some 'tube sound'? Or do you want this to be as low distortion as possible?
- Tone controls? Or no tone controls?
- Do you want to isolate the amp's inputs using signal transformers?
- What input switching capabilities do you need?
- What kind of attenuator do you want to use?
If all you need is input switching and a volume control, you might want to try an inductive attenuator like those from Intact Audio or similar. They do sound really good. Put one of those in a nice chassis with a good input selector switch and good RCA jacks, and that might be the solution.
It all depends on what you want this thingie to do for you.
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I think the best way to go about this is to define the benefits you want from this project.
- How much gain, if any?
- What input impedance, and what output impedance?
- Do you want to add some 'tube sound'? Or do you want this to be as low distortion as possible?
- Tone controls? Or no tone controls?
- Do you want to isolate the amp's inputs using signal transformers?
- What input switching capabilities do you need?
- What kind of attenuator do you want to use?
If all you need is input switching and a volume control, you might want to try an inductive attenuator like those from Intact Audio or similar. They do sound really good. Put one of those in a nice chassis with a good input selector switch and good RCA jacks, and that might be the solution.
It all depends on what you want this thingie to do for you.
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Tube Buffer Preamp Design
If you don't need any gain. This is a good thread for options.
I am a noob so I built the Muchedumbre buffer preamp since I have a Tubelab SSE and did not need any gain,
Muchedumbre Buffer Preamp – wauwatosa tube factory has a BOM, plenty of details and pictures to build the amp for noobs. The only thing I needed to look up was the tube details on wiring it up which the documentation mentions.
If you don't need any gain. This is a good thread for options.
I am a noob so I built the Muchedumbre buffer preamp since I have a Tubelab SSE and did not need any gain,
Muchedumbre Buffer Preamp – wauwatosa tube factory has a BOM, plenty of details and pictures to build the amp for noobs. The only thing I needed to look up was the tube details on wiring it up which the documentation mentions.
Tube Buffer Preamp Design
If you don't need any gain. This is a good thread for options.
I am a noob so I built the Muchedumbre buffer preamp since I have a Tubelab SSE and did not need any gain,
Muchedumbre Buffer Preamp – wauwatosa tube factory has a BOM, plenty of details and pictures to build the amp for noobs. The only thing I needed to look up was the tube details on wiring it up which the documentation mentions.
If you don't need any gain. This is a good thread for options.
I am a noob so I built the Muchedumbre buffer preamp since I have a Tubelab SSE and did not need any gain,
Muchedumbre Buffer Preamp – wauwatosa tube factory has a BOM, plenty of details and pictures to build the amp for noobs. The only thing I needed to look up was the tube details on wiring it up which the documentation mentions.
Thanks guys, That's a very good start and has given me something to go on with. Kerux, I like the look of this Muchedumbre unit, it's only one channel right so I'd need a pair, maybe fitted in the same box. I only ask because I am muchedumbre. I'd probably add a volume attenuator instead of the pot but otherwise yes I think it can suit me for a start. Eli Duttman, thanks for your comments, you've convinced me about tone controls. Is your schematic there somewhere else with a build thread ? You say the power supply is so simple, but for me there are too many unknowns about transformer types, and the various voltages required. Or are you saying there could be a universal valve power supply? I thought some valves take 6.3volt heaters and others are 12v. And the main power seems to vary from 250 volts to 500vDC. That's where I get confused and worried.
The signal circuitry is simple, in my version of a 12B4 preamp. The PSU in the schematic I'm providing is somewhat involved, but using it is not essential. I worked up that design to accommodate what "Buzz" had on his parts "pile". Well filtered "150" VDC and 10M45S plate loads will be fine into the "friendly" I/P impedance of the "Aleph".
BTW, you don't need pricey Mundorf O/P coupling caps. too. "Buzz" likes "boutique" parts.
Given the high I/P impedance of your "Aleph", 0.22 μF. Soviet surplus K40 paper in oil (PIO) parts will be FINE.
BTW, you don't need pricey Mundorf O/P coupling caps. too. "Buzz" likes "boutique" parts.
Given the high I/P impedance of your "Aleph", 0.22 μF. Soviet surplus K40 paper in oil (PIO) parts will be FINE.Attachments
Triad magnetics offers inexpensive stuff with dual primaries that work in both "120" & "240" VAC zones.
A Triad N-68X isolation trafo will be fine for bridge rectified B+. A Triad VPL24-400 will take care of heater power. Use 1 of the paired secondaries in each channel.Maybe the provided upload will help. Also, install IrfanView on your PC. That freeware is great for manipulating all sorts of graphic files.
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Triad magnetics offers inexpensive stuff with dual primaries that work in both "120" & "240" VAC zones.
So I only need one of each transformer to make stereo? And the white lead of the isolation trano is earth? In your schematic what are components 9H and 5H please? Chokes?
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A separate heater transformer can bring benefits but with a little care, a combined B+ and heater transformer can be used with the same level of success.
The laminations should be connected to protective earth via the chassis, as should the mounting hardware and any external shielding. Often this is achieved through the mounting bolts. The white wire connects to an internal electrostatic shield that works against noise coupled through interwinding capacitance, and this can also be grounded.
The laminations should be connected to protective earth via the chassis, as should the mounting hardware and any external shielding. Often this is achieved through the mounting bolts. The white wire connects to an internal electrostatic shield that works against noise coupled through interwinding capacitance, and this can also be grounded.
Yes, those are chokes and they can be costly. The unit of inductance is the henry. "Buzz" already had them and that's what I designed around. The schematic shows a pseudo choke I/P filter and pseudo dual mono. That = $$. You can get away with a "simple" CLC, AKA Π section, filter. Once again, Triad offers a suitable, inexpensive, part for the L. It's the C-7X. Constant current source (CCS) loading of the 12B4s will give you a pretty good power supply rejection ratio (PSRR).
For tubes you should assemble the SP9 preamp. Or one of the dynaco preamps by Bob Latino. From your questions you should not do without support and detailed instructions. For a non tube option with some of the most immaculately detailed instructions imaginable I’d highly recommend the AMB a10 preamplifier.
At this point I am attracted to Eli's design, I have the good schematic for the preamp and I have the correct transformers however I am not at my stage able to design or source a nice little well filtered power supply that fits.
I feel that if such a schematic or kit were available this could be a reasonable project and I would be prepared to order the bits and have a go. I have come to a stalemate every time I look hard at any of these projects for my lack of downhome knowledge that you guys take for granted. Fair enough,I know how dull it can be teaching people how to repair their musical instruments as well. Aikido may come up with answers for me when they get my email.
Spaceistheplace, I would be going full circle to end up with Dynaco but I did have a look again on your suggestion and could not find the place where I once saw those preamps of which you speak. Do you have the link? Edit , found it thanks.
Also I would like a link to that other preamp you mentioned[ AMBa10] as a matter of interest.
I feel that if such a schematic or kit were available this could be a reasonable project and I would be prepared to order the bits and have a go. I have come to a stalemate every time I look hard at any of these projects for my lack of downhome knowledge that you guys take for granted. Fair enough,I know how dull it can be teaching people how to repair their musical instruments as well. Aikido may come up with answers for me when they get my email.
Spaceistheplace, I would be going full circle to end up with Dynaco but I did have a look again on your suggestion and could not find the place where I once saw those preamps of which you speak. Do you have the link? Edit , found it thanks.
Also I would like a link to that other preamp you mentioned[ AMBa10] as a matter of interest.
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