Hi. I am interested in building a line level preamp circuit and based on my research, i have found these: nelson pass' b1 , rod elliott tone control preamp. Which one of these is better and why
? Also, is it possible to control volume and eq settings with rotary encoder and digital pots? Thank you for your time.
? Also, is it possible to control volume and eq settings with rotary encoder and digital pots? Thank you for your time.
Please specify your source max AC voltages and types.
In general cell phones, CD players, MP3 players, radio earphone jacks, TV earphone jacks, tuner audio outputs, don't need amplification for amps with a LTP input. In that case your "preamp" is just a switch, set of stereo volume balancing pots, and a master volume control. Plus input and output jacks. If you don't need tone controls. Tone controls require gain. Many purists don't like tone controls, and those that use them often prefer the more modern graphic equalizer, which gives more frequency bands to adjust than 3. I've picked up 3 graphic equalizers at charity resale shops & off the curb on garbage day. They are often discarded because the pots & electrolytic capacitors wear out. Perhaps you should get out more early in the morning. A little repair saves all the power supply input filtering and enclosure work.
Digital pots may require a special power supply, which you must supply.
I don't know why any of these circuits would be "better" than any other. All are usually reliable sources. Your construction practices at first will badly affect hiss & hum over any defects in the base circuit design.
I use commercial mixers as my entertainment hubs that have picked up for $15 to $70 and repaired for $20 to $40. Much less machine work on the cabinets. You go straight to the worn out e-caps & or pots, and the bad solder joints that caused them to be discarded. The RA-88a $15 was a hummy hissy package design disaster with classy unused pots, upgraded by taking out the mains power transformer for a wall one and upgrading the op amps to low noise ones with suitable anti-oscillation improvements. The Peavey MMR-875t had unused pots, 2 bad solder joints and was apparently unused for 25 years, although the mains e-caps were high ESR & I replaced them.
If you have golden ears and use headphones only, you may be able to hear the .02% HD or so that commercial products put out. If you're using a honey badger, probably your speaker distortion will cover up any HD in the after decimal point range. Quiescent (no source) hiss & hum is one's major challenge with diy line level IMHO.
In general cell phones, CD players, MP3 players, radio earphone jacks, TV earphone jacks, tuner audio outputs, don't need amplification for amps with a LTP input. In that case your "preamp" is just a switch, set of stereo volume balancing pots, and a master volume control. Plus input and output jacks. If you don't need tone controls. Tone controls require gain. Many purists don't like tone controls, and those that use them often prefer the more modern graphic equalizer, which gives more frequency bands to adjust than 3. I've picked up 3 graphic equalizers at charity resale shops & off the curb on garbage day. They are often discarded because the pots & electrolytic capacitors wear out. Perhaps you should get out more early in the morning. A little repair saves all the power supply input filtering and enclosure work.
Digital pots may require a special power supply, which you must supply.
I don't know why any of these circuits would be "better" than any other. All are usually reliable sources. Your construction practices at first will badly affect hiss & hum over any defects in the base circuit design.
I use commercial mixers as my entertainment hubs that have picked up for $15 to $70 and repaired for $20 to $40. Much less machine work on the cabinets. You go straight to the worn out e-caps & or pots, and the bad solder joints that caused them to be discarded. The RA-88a $15 was a hummy hissy package design disaster with classy unused pots, upgraded by taking out the mains power transformer for a wall one and upgrading the op amps to low noise ones with suitable anti-oscillation improvements. The Peavey MMR-875t had unused pots, 2 bad solder joints and was apparently unused for 25 years, although the mains e-caps were high ESR & I replaced them.
If you have golden ears and use headphones only, you may be able to hear the .02% HD or so that commercial products put out. If you're using a honey badger, probably your speaker distortion will cover up any HD in the after decimal point range. Quiescent (no source) hiss & hum is one's major challenge with diy line level IMHO.
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Thanks very much for your reply. Ok, my inputs are going to be the following:
1) Phono 2) CD 3) Tape 4) Tuner 5) DAC 6) Auxialiary
Note that the first input, the phono, requires an external phono preamp. I don't want to have the phono preamp in the same box with the line. So you could say that I want 6 inputs that are all line level which means ~2V RMS (i guess). A passive "preamp" could do the job but I have read an article from Nelson Pass that stated that passive preamps sound dull and that active preamps - even buffers are better. So I'd like to have one of those. Now about the tone controls; I don't know whether I need them or not, they obviously add some gain because they boost frequencies. For someone that builds line levels for the first time what would you recommend?
1) Phono 2) CD 3) Tape 4) Tuner 5) DAC 6) Auxialiary
Note that the first input, the phono, requires an external phono preamp. I don't want to have the phono preamp in the same box with the line. So you could say that I want 6 inputs that are all line level which means ~2V RMS (i guess). A passive "preamp" could do the job but I have read an article from Nelson Pass that stated that passive preamps sound dull and that active preamps - even buffers are better. So I'd like to have one of those. Now about the tone controls; I don't know whether I need them or not, they obviously add some gain because they boost frequencies. For someone that builds line levels for the first time what would you recommend?
Check out Salas excellent DCG3 pre/headphone amp. Can be set from 2 to 4 times gain if I remember correctly.
His DCB1 buffer pre is also an excellent performer especially when taken to hot rod mode.
Boards available from Teabag.
Salas DCG3 preamp (line & headphone)
His DCB1 buffer pre is also an excellent performer especially when taken to hot rod mode.
Boards available from Teabag.
Salas DCG3 preamp (line & headphone)
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Sounds as if you can build a "passive preamp" to listen to music from differenct sources while you are building something more elaborate. Yes your amp would clip and blast you out of the room if you fed it with 3 vac.
One doesn't "need" tone controls. One wants them, or one doesn't. If you want to try them out to see if you like them, build the elliot tone control version preamp. Bass boosted was popular in the 60's when everybody had 8" woofers in their speaker. If you can find a used graphic equalizer, you might like that better after you repair it. Some people use the tone controls to compensate for speaker deficiencies, some people use the graphic equalizers to "warm up" vocal tracks for example.
I've got the RIAA input in the same box as the 3 line levels, in the Ra-88a "mixer". The difference between the op amp circuits is the value of the feedback resistor and a couple of ceramic filter caps. The 4558 op amps hissed like a boiler at 50 x gain (for mm cartridge) so I changed it to ST33078, which is nicely quiet. No tone controls but a sub-bass cut on that model though. Note a lot of changers sold today have the RIAA preamp built in.
Actually enclosures are a lot of dirty machine work requiring a vise & a electric drill and paint. Slots for linear pots require a saw or vertical head mill. Rotary pots can be installed with an electric drill. The enclosure has to be metal to keep the RF interference out. You ought to be able to find some used mixers on ebay or gumtree in greece, if there are no charity resale shops that have them. Look or preamps or mixers "for parts or repair". You'll probably find used preamps are thousands of euro's, used mixers are E20 plus the cost of shipping. 80's-90's mixers like Peavey or Ampeg or Allen & Heath have nice discrete components to work on. Watch out and don't buy monoaural guitar amp heads, if your honey badger is stereo. Later mixers like Numark and Behringer are all surface mount parts & short life ribbon cable, don't bother with those. Too hard to work on IMHO.
High end mixers have 8 or 11 band graphic equalizer built in, slightly lower market point like my Peavey unity 12 have an "effects loop" set of connectors & op amps where you can plug in the graphic equalizer or a reverb or effects digital box.
If you have a PC, you can experiment with tone controls with recorded tracks and the audacity program. Download audacity and record a song into it. It has internal tone controls and also bandwidth boost & cut. Listen to the PC output with headphones. Some people use a laptop PC as the effect in the effects loop of a mixer.
One doesn't "need" tone controls. One wants them, or one doesn't. If you want to try them out to see if you like them, build the elliot tone control version preamp. Bass boosted was popular in the 60's when everybody had 8" woofers in their speaker. If you can find a used graphic equalizer, you might like that better after you repair it. Some people use the tone controls to compensate for speaker deficiencies, some people use the graphic equalizers to "warm up" vocal tracks for example.
I've got the RIAA input in the same box as the 3 line levels, in the Ra-88a "mixer". The difference between the op amp circuits is the value of the feedback resistor and a couple of ceramic filter caps. The 4558 op amps hissed like a boiler at 50 x gain (for mm cartridge) so I changed it to ST33078, which is nicely quiet. No tone controls but a sub-bass cut on that model though. Note a lot of changers sold today have the RIAA preamp built in.
Actually enclosures are a lot of dirty machine work requiring a vise & a electric drill and paint. Slots for linear pots require a saw or vertical head mill. Rotary pots can be installed with an electric drill. The enclosure has to be metal to keep the RF interference out. You ought to be able to find some used mixers on ebay or gumtree in greece, if there are no charity resale shops that have them. Look or preamps or mixers "for parts or repair". You'll probably find used preamps are thousands of euro's, used mixers are E20 plus the cost of shipping. 80's-90's mixers like Peavey or Ampeg or Allen & Heath have nice discrete components to work on. Watch out and don't buy monoaural guitar amp heads, if your honey badger is stereo. Later mixers like Numark and Behringer are all surface mount parts & short life ribbon cable, don't bother with those. Too hard to work on IMHO.
High end mixers have 8 or 11 band graphic equalizer built in, slightly lower market point like my Peavey unity 12 have an "effects loop" set of connectors & op amps where you can plug in the graphic equalizer or a reverb or effects digital box.
If you have a PC, you can experiment with tone controls with recorded tracks and the audacity program. Download audacity and record a song into it. It has internal tone controls and also bandwidth boost & cut. Listen to the PC output with headphones. Some people use a laptop PC as the effect in the effects loop of a mixer.
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Thank you for your quick answer. I have decided that I don't need tone controls, because the point of buying and building expensive high end stuff is to color the sound from the vinyl record to the speaker as less as possible. The chassis part is my favorite! The cases from modushop.biz are cheap and I would like to "dress" them with lacquered wood planks on the sides and on the top. Also, the front panel will be from plexiglass that has been printed black and there are transparent parts only for an LCD and vu meters. But because I'm getting off topic here, I will contact Salas who is by the way from the same country as me, in order to get some information about his line/headphone pre amp. Maybe I could just connect a headphone jack in parallel with the output jack and have a headphone amp too.
I was thinking of mentioning Salas has a shop in Piraes where he might be willing to sell you a "not economic to repair" mixer for not too much. Heavy discrete part mixers are out for bar bands that tear down & set up every night. I've found old hand soldered Peavey dogs have good looking solder joints that don't actually conduct electricity. Takes some hours tracing the music (1.5 vac) through the circuit to find the bad point, but costs nothing but time to fix those. The good part is Peavey will give you the schematics & parts layout diagrams. Behringer won't.
Have fun packaging. You still haven't fought the battles to keep AM radio or police/fire band out of your appliance, not to mention keeping the transformer hum or switcher supply howl over in the dirty corner of the box away from the RIAA.
Have fun packaging. You still haven't fought the battles to keep AM radio or police/fire band out of your appliance, not to mention keeping the transformer hum or switcher supply howl over in the dirty corner of the box away from the RIAA.
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I could have 2 rca jacks: one input and one output on the back of the pre that will work as an effects loop; that way, if I ever stumble upon a mixer that has good eq, I could throw it in the effects loop and call it a day. After all, having as many components in separate boxes as possible is the best according to true audiophiles, ain't it?
Do I have to worry about AM interference with the line level preamp? How am I gonna keep 'em out? Also, in every "good" riaa amp, the power supply is in a separate enclosure, and I guess that unlike having separate psu for power amp, in this particular occasion it actually makes sense to separate the two modules (the riaa and the psu).
Taking equipment apart & repairing it is very instructive.
My dynaco PAS2 preamp has a separate steel box inside the outer box, for the sensitive high gain wiring. The transformer has a steel jacket. The preamp separate from the power amp was common in 1960 because tube power amps were so hot and powerful electric fields swirl around in them from the high currents & voltages. Also the $100 price point for each made for good sales, that was > a week's pay for most 20 somethings back then. You could play a radio into the power amp until you could afford a preamp for a turntable.
The Peavey MMA-875t mixer/amp has a steel wrapper around the transformer, and a separate steel band over it. The high level tone controls are near the transformer & rectifier, the high gain input circuits are on the back in a separate steel box. In 1990 a mixer & amp could co-exist in the same box, but only up to about 100 w/ch. (this one is mono for my voice over top of an acoustic piano, and will fit in my bicycle bags for performance, don't buy one for stereo). Mixer amps are bargains on the used market, usually have blown amp part from the usual 1/4" phone plug shorts to the speaker.
My RA-88a mixer benefited from separating the grounds of the RCA jacks from the case ground with o-rings, plus 33 pf disk caps to analog ground on each input to trap RF. A 22 turn choke was put on the DC power supply entry to keep RF out, after the transformer was moved out of the box. Triple pi filter was required to make the hum go away. I use this all the time for my phono/CD/Fm radio hub since I don't have to walk around the organ to switch the inputs, just put the media in the device. Also the RA-88a uses 1/20 the electricity of the PAS2 and produces less heat, too.
I think separating riaa & line level is silly, but purists love their complications. Finding a "disco mixer" with Riaa was difficult, except for the ubiquitous and vile Radio Shack model. I gave up on Radio Shack in the seventies, when I read the "flat +- 3 db 20-20000 cyc/sec" was modified by a "+- 20 db production tolerance". Some proofreader missed deleting that spec on a headphone. No wonder their products sounded so bad in the store. My ears were trained by 8 years piano & band training by age 16, I'm hard to fool with *****y sound.
My dynaco PAS2 preamp has a separate steel box inside the outer box, for the sensitive high gain wiring. The transformer has a steel jacket. The preamp separate from the power amp was common in 1960 because tube power amps were so hot and powerful electric fields swirl around in them from the high currents & voltages. Also the $100 price point for each made for good sales, that was > a week's pay for most 20 somethings back then. You could play a radio into the power amp until you could afford a preamp for a turntable.
The Peavey MMA-875t mixer/amp has a steel wrapper around the transformer, and a separate steel band over it. The high level tone controls are near the transformer & rectifier, the high gain input circuits are on the back in a separate steel box. In 1990 a mixer & amp could co-exist in the same box, but only up to about 100 w/ch. (this one is mono for my voice over top of an acoustic piano, and will fit in my bicycle bags for performance, don't buy one for stereo). Mixer amps are bargains on the used market, usually have blown amp part from the usual 1/4" phone plug shorts to the speaker.
My RA-88a mixer benefited from separating the grounds of the RCA jacks from the case ground with o-rings, plus 33 pf disk caps to analog ground on each input to trap RF. A 22 turn choke was put on the DC power supply entry to keep RF out, after the transformer was moved out of the box. Triple pi filter was required to make the hum go away. I use this all the time for my phono/CD/Fm radio hub since I don't have to walk around the organ to switch the inputs, just put the media in the device. Also the RA-88a uses 1/20 the electricity of the PAS2 and produces less heat, too.
I think separating riaa & line level is silly, but purists love their complications. Finding a "disco mixer" with Riaa was difficult, except for the ubiquitous and vile Radio Shack model. I gave up on Radio Shack in the seventies, when I read the "flat +- 3 db 20-20000 cyc/sec" was modified by a "+- 20 db production tolerance". Some proofreader missed deleting that spec on a headphone. No wonder their products sounded so bad in the store. My ears were trained by 8 years piano & band training by age 16, I'm hard to fool with *****y sound.
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Well, if you want to build something like the Pearl 2, which might be one of the best riaa preamps available**, it'd be hard to fit everything into the same chassis. But it would be cool to have all the rf-sensetive stuff (riaa pre, line pre etc) into the same chassis and then have a separate power supply to power them all.
I would really like to know whether it makes sense to have a separate power supply for your power amplifier or not.
**DIY preamps
triad makes nice 16 vac 24vac 1.5 amp wall transformers that can power op amps. Farnell sells them. These can be rectified filtered and two 78/79xx regulators can make an analog ground. The PV8 mixer I bought uses one of those.
I power the RI-88a with a 16 vdc race car wall transformer that I use two 5 watt 7.5 v zener diodes to regulate and drive the analog ground.
You can't as an individual buy steel wrapped copper band center tap EI transformers as the PAS2 & MMA-875T have. You have to buy junk equipment. You can get toroids, I've not seen a mixer that uses one. Toroids are up into the surface mount era that I do not attempt to repair. The PV8 is that, was shocked, oh well, $38 down the drain. Has a bad solder joint preventing one channel from working.
As I said above, if the transformer or switcher supply is inside the power amp or preamp, having a separate steel box inside the outer steel box for the sensitive stuff is a best practice. The RA-88a didn't have one, had the transformer & AC switch 2.5 cm from the 50 x gain RIAA op amp, hummed about 50 db down. Not good enough.
I power the RI-88a with a 16 vdc race car wall transformer that I use two 5 watt 7.5 v zener diodes to regulate and drive the analog ground.
You can't as an individual buy steel wrapped copper band center tap EI transformers as the PAS2 & MMA-875T have. You have to buy junk equipment. You can get toroids, I've not seen a mixer that uses one. Toroids are up into the surface mount era that I do not attempt to repair. The PV8 is that, was shocked, oh well, $38 down the drain. Has a bad solder joint preventing one channel from working.
As I said above, if the transformer or switcher supply is inside the power amp or preamp, having a separate steel box inside the outer steel box for the sensitive stuff is a best practice. The RA-88a didn't have one, had the transformer & AC switch 2.5 cm from the 50 x gain RIAA op amp, hummed about 50 db down. Not good enough.
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Some preamps provide all the gain for an amp as they are 0dB gain output stages. Like F4 etc. for those amps, a preamp with 40Vpp is needed to reach 25w output power.
Aksa Lender is a preamp that can do this and also can be run with reduced gain like 9dB. This is a nice level that allows most sources to drive 22dB gain amps to full clip with typical line level signals.
In general, I can’t get the dynamics I need with 0dB (or passive preamps).
Aksa Lender is a preamp that can do this and also can be run with reduced gain like 9dB. This is a nice level that allows most sources to drive 22dB gain amps to full clip with typical line level signals.
In general, I can’t get the dynamics I need with 0dB (or passive preamps).
Why would one build a preamp with dual mono PSU? I thought that the reason we do this is because power amps draw a lot of current and when both channels get power from the same psu board, the one influences the other and they are not completely separated. In preamps, this is not the case cause they draw very little current, especially phono preamps. Does it make sense to do it or you spend your money without a reason.
b1 is more like a purist buffer preamp. ba3 will do more as a linestage. I like the vocal best on that. Dcg3 is single ended but haven, t started mine.usspa is great for me good designs. All is very nice preamp anything with jfet in them is worth diy in my opinion cause its difficult to buy them now. Rest is matter of taste
But what makes interesting for me is coupling free preamplifier. They sounds the most dynamic. Focus and transparent. Its as pure as you can get. Solid state is not so expensive compared to tubes so its not so bad to make a few and play around.
Eq and such.. Better use a preamp dsp. Minidsp. Or dac with dsp. Digital volume control on dsp or dac works great.its very bad experiences for me diy those. Its very fine to double preamp.
Dual mono psu.. Channel separation? Slightly better depth and focus. It can be a pain to do both channel the same to get the benefits,
But what makes interesting for me is coupling free preamplifier. They sounds the most dynamic. Focus and transparent. Its as pure as you can get. Solid state is not so expensive compared to tubes so its not so bad to make a few and play around.
Eq and such.. Better use a preamp dsp. Minidsp. Or dac with dsp. Digital volume control on dsp or dac works great.its very bad experiences for me diy those. Its very fine to double preamp.
Dual mono psu.. Channel separation? Slightly better depth and focus. It can be a pain to do both channel the same to get the benefits,
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Check out the review of this box at Audio Science Review:Hi. I am interested in building a line level preamp circuit and based on my research, i have found these: nelson pass' b1 , rod elliott tone control preamp. Which one of these is better and why
Review & Measurements of Talema Relay Pre-amp | Audio Science Review (ASR) Forum
I prefer the version with a larger enclosure.
Finished HIFI Remote volume Controller 128 steps /4 way input + display | eBay
After I received the item, I used remote controlled selector and volume control alone for several week, essentially as a passive preamp. It is one of the best e/bay value that I got in recent years. It is completely quiet and perfectly neutral as it should. No switch noise that I can hear. I have 3 inputs connected. The Harman Kardon AP2500 used as a phono stage only, a Marantz ST7001 tuner and a modified ES9038Q2M DAC for cable TV box and Blu Ray player (also for streaming). The aluminum cased remote is heavy and the shape is awkward, but the control bottoms are responsive. The preamp output is routed to a rack housing the 3-way Linkwitz-Riley Crossover and the 3 stereo power amplifiers.
I added an output buffer and removed the AC switch at the back.
After adding the JC-2 board, the sound remains neutral and musical. After 6 months, I have one complaint against this JC-2 board. It is very good 90% of the time. But if I listen to music with exceptional dynamic range and want to turn up the volume more, I can hear a faint noise in the background. The board is not extra noise, Just the combined result of a simple JC-2 with a simple power supply. The noise may not be noticed by most users. I do not have enough skill and experience to improve the noise performance of this box. I used an shielded twisted wire from the buffer board to output RCA, but I did not change the input wires thinking that they are short and away from the main. Hopefully, some one may see it as a good DIY project to improve the noise, then, I can copy.
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