Hi
I am completely new to valve and would like to build a good quality pre-amp (or integrated amp if affordable) to replace both my Rotel preamp and Passive preamp that I alternate between.
System used is CD & Tuner with Quad 306 and floorstanding reflex speaker with ribbons.
I can carry out basic electronic, however, I do not wish to experiment, I would like a tried and tested quality design that uses components that are easily sourced, idealy below UK£200.
I can understand schematics and make things when hardwired, PCB's are beyond me. Also I would appreciate advise on where to get suitable power supplies for any amp I make.
Ian
I am completely new to valve and would like to build a good quality pre-amp (or integrated amp if affordable) to replace both my Rotel preamp and Passive preamp that I alternate between.
System used is CD & Tuner with Quad 306 and floorstanding reflex speaker with ribbons.
I can carry out basic electronic, however, I do not wish to experiment, I would like a tried and tested quality design that uses components that are easily sourced, idealy below UK£200.
I can understand schematics and make things when hardwired, PCB's are beyond me. Also I would appreciate advise on where to get suitable power supplies for any amp I make.
Ian
Power Supply
I am able to source all of the components from www.rswww.com in the UK.
But where can I get a power supply and what would the spec be for say Joel's Preamp.
Ian
I am able to source all of the components from www.rswww.com in the UK.
But where can I get a power supply and what would the spec be for say Joel's Preamp.
Ian
Aha !
There are a few small problems with this pre-amp idea . Firstly the B+ (unless choke loaded) will need to be a lot higher than 24V . 6080 is a bit of a beast to heat up (2.8A @ 6.3V) and finding one with closely matched sections may be difficult . May be an idea as a newby would be to build a proven design (I do not know this 6080 design) such as the Bottlehead Foreplay (put a posting on the Bottlehead forum of www.audioasylum.com to request where a schematic is held on the web) . Maplin sell cheap transformers with 240V and 6.3V secondaries for about a tenner which may be a good starting point . Good luck !
316a
There are a few small problems with this pre-amp idea . Firstly the B+ (unless choke loaded) will need to be a lot higher than 24V . 6080 is a bit of a beast to heat up (2.8A @ 6.3V) and finding one with closely matched sections may be difficult . May be an idea as a newby would be to build a proven design (I do not know this 6080 design) such as the Bottlehead Foreplay (put a posting on the Bottlehead forum of www.audioasylum.com to request where a schematic is held on the web) . Maplin sell cheap transformers with 240V and 6.3V secondaries for about a tenner which may be a good starting point . Good luck !
316a
Re: Aha !
The chaps was Christian Rintelen (it's on www.rintelen.ch) - he has them in PP with an OPT.
I was thinking more of using the 6080 SE.
What about a 40-50V supply, and a 4.7mA CCS diode in the anode circuit - no need for a choke. Hell, you could lash together 4 or 5 PP3 batteries for the HT supply and still have loads of headroom. For a real quick lash up, you could use a 6V battery to heat the thing as well - or use a mains adaptor for about £5.
Super cheap, utterly safe.
Cheers
316a said:
The chaps was Christian Rintelen (it's on www.rintelen.ch) - he has them in PP with an OPT.
I was thinking more of using the 6080 SE.
What about a 40-50V supply, and a 4.7mA CCS diode in the anode circuit - no need for a choke. Hell, you could lash together 4 or 5 PP3 batteries for the HT supply and still have loads of headroom. For a real quick lash up, you could use a 6V battery to heat the thing as well - or use a mains adaptor for about £5.
Super cheap, utterly safe.
Cheers
Why not use the tube at the voltage it was designed to operate at? The cost for a high voltage power supply will be a little higher but not much, 20 to 50% maybe.
Will the tube work at those low voltages? Well, yes, but not up to it's best potential, (which is a higher voltage, HAHA).
Later
BZ
Will the tube work at those low voltages? Well, yes, but not up to it's best potential, (which is a higher voltage, HAHA).
Later
BZ
Re: Re: Aha !
CV, I think you need to readjust your calculations. A single 6080 will draw 200mA of plate current. That is not in the good range for battery use.
It's heater draws 2.5 amps! I'd like to see the battery that can deliver that much current for an extended amount of time.
And an isolation transformer with a VA of 10-15 will cost a lot more than £5, unless you have an "in" somewhere?
CV said:
CV, I think you need to readjust your calculations. A single 6080 will draw 200mA of plate current. That is not in the good range for battery use.
It's heater draws 2.5 amps! I'd like to see the battery that can deliver that much current for an extended amount of time.
And an isolation transformer with a VA of 10-15 will cost a lot more than £5, unless you have an "in" somewhere?
6h30 on the paeng site
I was looking at the Paeng site that Frank linked to. I vote for the 6h30 preamp. This unit will be a great performer relative to the complexity of construction.
http://digilander.libero.it/paeng/projects_frame.htm
Robert Morin
I was looking at the Paeng site that Frank linked to. I vote for the 6h30 preamp. This unit will be a great performer relative to the complexity of construction.
http://digilander.libero.it/paeng/projects_frame.htm
Robert Morin
Re: Re: Re: Aha !
Hi Joel,
I wasn't suggesting that he run 200mA through it, especially at 25V ! Have a look at:
http://www.rintelen.ch/pdf/Line_6080_1.pdf
Christian's running it at a few mA - that's why I suggested a 4.7mA current source diode, they're readily available and would present a nice high load to the valve without the expense of inductors. He reported that (his version) sounded exceptionally clear and extended, and was very low in distortion (0.03%).
let's look at the cost
£10 6080+socket
£2 CCS diodes
£10 heater transformer or a bit more for a dc supply
£5 alkaline PP3 batteries
I'm assuming he has resistors etc handy
Now the rest of the budget could be spent on a pair of Sowter volume control transformers...the whole setup would be dead quiet too.
Who says you have to use valves in their intended application/at the textbook op-points? The 6C33, which features in the most highly praised commercial amps (Lamm ML2 & Tenor OTLs) was meant to be found in the radar supply in Mig29s...
Cheers
Chris
Joel said:
CV, I think you need to readjust your calculations. A single 6080 will draw 200mA of plate current. That is not in the good range for battery use.
It's heater draws 2.5 amps! I'd like to see the battery that can deliver that much current for an extended amount of time.
And an isolation transformer with a VA of 10-15 will cost a lot more than £5, unless you have an "in" somewhere?
Hi Joel,
I wasn't suggesting that he run 200mA through it, especially at 25V ! Have a look at:
http://www.rintelen.ch/pdf/Line_6080_1.pdf
Christian's running it at a few mA - that's why I suggested a 4.7mA current source diode, they're readily available and would present a nice high load to the valve without the expense of inductors. He reported that (his version) sounded exceptionally clear and extended, and was very low in distortion (0.03%).
let's look at the cost
£10 6080+socket
£2 CCS diodes
£10 heater transformer or a bit more for a dc supply
£5 alkaline PP3 batteries
I'm assuming he has resistors etc handy
Now the rest of the budget could be spent on a pair of Sowter volume control transformers...the whole setup would be dead quiet too.
Who says you have to use valves in their intended application/at the textbook op-points? The 6C33, which features in the most highly praised commercial amps (Lamm ML2 & Tenor OTLs) was meant to be found in the radar supply in Mig29s...
Cheers
Chris
Low voltage pre-amp
If you want to keep HT voltages low one valve which will perform well at low volts is the PL82 - originally designed as a line output valve for 1950s TVs it will produce a useful output on just 17 volts HT. I have seen it used as a driver for a power transistor in this way with just one transformer providing the heater and HT from the same winding. Another alternative is to search eBay for old hybrid car radios, which used special low voltage valves for the RF/IF stages - valves such as the EF98 and ECH83 will run quite happily on 12 volts HT.
If you want to keep HT voltages low one valve which will perform well at low volts is the PL82 - originally designed as a line output valve for 1950s TVs it will produce a useful output on just 17 volts HT. I have seen it used as a driver for a power transistor in this way with just one transformer providing the heater and HT from the same winding. Another alternative is to search eBay for old hybrid car radios, which used special low voltage valves for the RF/IF stages - valves such as the EF98 and ECH83 will run quite happily on 12 volts HT.
Like Ian, I am also keen to make my first venture into the world of valve audio with a preamp.
The trouble is, ask for advice and you get absolutely swamped with it to the point of being even more confused than before you asked!
I've found one circuit that looks good to me. You can see it Here
What I would like to ask is if I can reduce the amount of gain and if so how? Also what current does this circuit draw?
Lastly, the 5687 is said to need a lot of current for its heater so would I be OK using a transformer with secondary heater ratings of 0-6.3V @ 1.5A? I was thinking of using a seperate power supply for each channel.
Then of course, there's the question of the PSU....
The trouble is, ask for advice and you get absolutely swamped with it to the point of being even more confused than before you asked!
I've found one circuit that looks good to me. You can see it Here
What I would like to ask is if I can reduce the amount of gain and if so how? Also what current does this circuit draw?
Lastly, the 5687 is said to need a lot of current for its heater so would I be OK using a transformer with secondary heater ratings of 0-6.3V @ 1.5A? I was thinking of using a seperate power supply for each channel.
Then of course, there's the question of the PSU....
Bottlehead
I built the Bottlehead Foreplay for my first tube kit. Very easy to build, inexpensive, great support, and great sound.
http://www.bottlehead.com/et/adobespc/foreplay/foreplay_line_stage_kit.htm
I built the Bottlehead Foreplay for my first tube kit. Very easy to build, inexpensive, great support, and great sound.
http://www.bottlehead.com/et/adobespc/foreplay/foreplay_line_stage_kit.htm
Hi Nuuk,
You don't say how much gain you need or what you're driving. No point stepping the signal up only to attenuate it all the way back down. Likewise, the source impedance of your amp (and possibly cable type/length) will dictate how low an o/p impedance you need from your preamp - if the load is low, you need large coupling caps and vice-versa.
Without knowing about the rest of the system, you may end up with something that sounds turdlike - and your opinion of valves might forever be sullied :-(
Ian implicitly didn't need much gain (he mentioned a passive preamp) hence part of my reasoning behind the 6080. It also has a low o/p resistance, even allowing for the low current suggested, so as not to get too fazed by Ian's SS amps.
The 5687 does take a fair bit of heater current for its size, but don't let that put you off; people have built preamps around 125W transmitting tubes with 50W heaters. I can send you a 5687 for next to nowt if you decide to go for it.
cheers
You don't say how much gain you need or what you're driving. No point stepping the signal up only to attenuate it all the way back down. Likewise, the source impedance of your amp (and possibly cable type/length) will dictate how low an o/p impedance you need from your preamp - if the load is low, you need large coupling caps and vice-versa.
Without knowing about the rest of the system, you may end up with something that sounds turdlike - and your opinion of valves might forever be sullied :-(
Ian implicitly didn't need much gain (he mentioned a passive preamp) hence part of my reasoning behind the 6080. It also has a low o/p resistance, even allowing for the low current suggested, so as not to get too fazed by Ian's SS amps.
The 5687 does take a fair bit of heater current for its size, but don't let that put you off; people have built preamps around 125W transmitting tubes with 50W heaters. I can send you a 5687 for next to nowt if you decide to go for it.
cheers
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