Hi, I want to build a high quality single input line level valve pre to partner my quad 303 amps.
I've built elekit kits before which i really like, but they only offer a pre with included phono stage etc which i don't need.
If they built a cheaper single or double input pre without phono i would buy it.
Are there any tried and tested simple designs or kits that would cover what i am after?
Thanks for any suggestions.
I've built elekit kits before which i really like, but they only offer a pre with included phono stage etc which i don't need.
If they built a cheaper single or double input pre without phono i would buy it.
Are there any tried and tested simple designs or kits that would cover what i am after?
Thanks for any suggestions.
From what I see the 303s input impedance is 10K and sensitivity is 0.5V.
This points straight to a tube stage with a step-down output transformer. So I would start your journey by looking at a suitable and good sounding one. They're not cheap, so it would help to know your budget, and where you are from so we can give suggestions that meet your shipping requirements. There is always the Lundahl LL1660 which is quite popular but not cheap.
A possible alternative is a very low Rp tube, like around 1K. There are some directly heated ones like 4P1L and even 2a3/6B4G but they require filament regulators or a hum-pot for 2a3 with AC heating. They would be high quality, though. 4P1L is cheap but requires at least 30-35mA to sound good. Long thread here on that, and it's cheap and available. You don't need any added gain, which is why a step-down would be a good idea.
Another alternative is a mu stage like the gyrator Ale Moglia sells on his Bartola site. But you'd still have the gain to deal with.
This points straight to a tube stage with a step-down output transformer. So I would start your journey by looking at a suitable and good sounding one. They're not cheap, so it would help to know your budget, and where you are from so we can give suggestions that meet your shipping requirements. There is always the Lundahl LL1660 which is quite popular but not cheap.
A possible alternative is a very low Rp tube, like around 1K. There are some directly heated ones like 4P1L and even 2a3/6B4G but they require filament regulators or a hum-pot for 2a3 with AC heating. They would be high quality, though. 4P1L is cheap but requires at least 30-35mA to sound good. Long thread here on that, and it's cheap and available. You don't need any added gain, which is why a step-down would be a good idea.
Another alternative is a mu stage like the gyrator Ale Moglia sells on his Bartola site. But you'd still have the gain to deal with.
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Thanks for the detailed reply...I'll start investigating. Budget around £300 based in the UK
Preamplifers are a bit superfluous these days as sources are 2V and most amplifiers have 1V input sensitivity. Yours even 0.5V. So if there is no need for any gain why add it? Also most tube designs will be worse in drive capability than normal sources. So except generating some effect nothing will be improved with the majority of inserted devices. On the contrary.
A buffer (gain of 1x) with voltage divider at the inputs so attenuation in fact would seem more adequate for modern sources with 2V output level. So if there absolutely must be added something make sure it can drive 10 kOhm (it is always good to have standard drive capability as that 303s may be replaced one day), has no or very low gain and power on/off muting with a relay shorting outputs to GND.
There are a few chinese kits with both volume and source control with pretty good Omron bistable relays. Work quite good, have practically no negative influence on signal quality (contrary to TKD etc.) and therefor seem a good price/quality ratio solution as they are below 100 Euro. These are with remote control and can switch on the active circuitry too. Just add the buffet of your likings that has the right drive capability and required gain and put all in a metal casing and Bobs yer uncle.
It really is a good thing to look at boring stuff like impedances and signal levels before deciding anything. And eh 10 kOhm is not a tough load, today's sources drive 1 kOhm with 2 fingers in the nose.
A buffer (gain of 1x) with voltage divider at the inputs so attenuation in fact would seem more adequate for modern sources with 2V output level. So if there absolutely must be added something make sure it can drive 10 kOhm (it is always good to have standard drive capability as that 303s may be replaced one day), has no or very low gain and power on/off muting with a relay shorting outputs to GND.
There are a few chinese kits with both volume and source control with pretty good Omron bistable relays. Work quite good, have practically no negative influence on signal quality (contrary to TKD etc.) and therefor seem a good price/quality ratio solution as they are below 100 Euro. These are with remote control and can switch on the active circuitry too. Just add the buffet of your likings that has the right drive capability and required gain and put all in a metal casing and Bobs yer uncle.
It really is a good thing to look at boring stuff like impedances and signal levels before deciding anything. And eh 10 kOhm is not a tough load, today's sources drive 1 kOhm with 2 fingers in the nose.
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Thanks for this detailed explanation....could you link an example of a chinese kit with the functions you are talking about so that i can have an idea of what to to compare? Many thanks
Please have a look yourself and search for "relay volume". You should be able to know what you need and want.
An assembled balanced version just enough for you to search the right one. Part of the experience is to solder it yourself so a kit leaving options for mistakes 🙂 seems better.
https://www.aliexpress.us/item/32905973755.html?spm=a2g0o.productlist.main.9.5e8bO1pZO1pZzT&algo_pvid=1c18b183-08bd-4b20-92d0-660d547a1c64&algo_exp_id=1c18b183-08bd-4b20-92d0-660d547a1c64-4&pdp_npi=4@dis!EUR!118.11!100.39!!!121.20!103.02!@211b61d017339927614574952ead3b!65883981477!sea!DE!132128603!X&curPageLogUid=shFsQCxX1yTx&utparam-url=scene:search|query_from:
Please note the usual method based first on choice for tube type XXX does not work out well in practice (proof is checking threads on this ever returning subject). Certainly if no gain is needed, this narrows down choice severely. Most tubes are made for gain, gain you don't need. At all. You want a device that is no heavy load to the sources and that can drive any power amplifier with ease. 2V max. in, 2V max. (or even 1V max.) out similar to the sources driving that power amplifier directly. Imagine what the super duper gold pin Telefunken NOS/NIB ECC909 based preamp in a randomly chosen design with gain of 40x and maximum load of 30 kOhm will cause in your case.
An assembled balanced version just enough for you to search the right one. Part of the experience is to solder it yourself so a kit leaving options for mistakes 🙂 seems better.
https://www.aliexpress.us/item/32905973755.html?spm=a2g0o.productlist.main.9.5e8bO1pZO1pZzT&algo_pvid=1c18b183-08bd-4b20-92d0-660d547a1c64&algo_exp_id=1c18b183-08bd-4b20-92d0-660d547a1c64-4&pdp_npi=4@dis!EUR!118.11!100.39!!!121.20!103.02!@211b61d017339927614574952ead3b!65883981477!sea!DE!132128603!X&curPageLogUid=shFsQCxX1yTx&utparam-url=scene:search|query_from:
Please note the usual method based first on choice for tube type XXX does not work out well in practice (proof is checking threads on this ever returning subject). Certainly if no gain is needed, this narrows down choice severely. Most tubes are made for gain, gain you don't need. At all. You want a device that is no heavy load to the sources and that can drive any power amplifier with ease. 2V max. in, 2V max. (or even 1V max.) out similar to the sources driving that power amplifier directly. Imagine what the super duper gold pin Telefunken NOS/NIB ECC909 based preamp in a randomly chosen design with gain of 40x and maximum load of 30 kOhm will cause in your case.
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Yes i have tried this, but i have never liked the sound of my amps with a passive pre....
Try a simple 6SN7/12SN7 cathode follower line stage, like the original JE Labs. This gives you the gain of the first triode, and the low output impedance to drive the 10k load.
Here's a thread with basically the same circuit and the power supply: https://www.diyaudio.com/community/threads/vtv-octal-6sn7-line-stage-build-mod.307202/
jeff
Here's a thread with basically the same circuit and the power supply: https://www.diyaudio.com/community/threads/vtv-octal-6sn7-line-stage-build-mod.307202/
jeff
Aikido line stage. Yes you might get more gain then you need, but in my system it sounds bether than just a dac with volumcontroll.
I use a logarithmic volumcontroll.
I use a logarithmic volumcontroll.
Probably because no attention was paid to boring stuff like matching gain, signal levels and impedances. So effect generators versus a simple volume controller that also does not glow (can’t be right).
The best and most usable ones being 10 to 20 kOhm (logarithmic). DC coupled sources of the last decades have no trouble whatsoever to drive such a light load. Normal amplifiers have no trouble whatsoever with that either. So any inserted device must have the same drive capability unless it wishes to identify as a minority with special needs always requiring special care, consideration and a marriage with devices that respect that needs.
It occurs to me over and over again that some relatively simple things are not as known in the tube world as they should be. Calculating the right value coupling cap for instance. There is no way that 220 or 470 nF will cut the cake.
It occurs to me over and over again that some relatively simple things are not as known in the tube world as they should be. Calculating the right value coupling cap for instance. There is no way that 220 or 470 nF will cut the cake.