Hi Marek - thanks again. I meant a 5v supply, which is floating. Filament bias isn't possible/practical with the 300b like it is with the 4P1L.
Are you thinking the 4P1L is a double valve?
Are you thinking the 4P1L is a double valve?
Hello Marek,
Thank you for helping my old friend Andy hope he didnt switch his latest adventure on.
Talking about errors just discovered i wired up the heating of my e80cc input tube wrong. I have a 6,3 volt transformer, i have a humdigger. SO 4+5 in parallel. 6,3 volts to 4+5 and 9 .Humdigger between those 2 and centertap of the digger to the chassis. That is the right way, isnt it?
My line pre amplifier uses the Telefunken ob2 but you only see the glow in a dim light. But all the other tubes glow.
Here some people like Andy rave about choke input. Recently i replaced the input choke in my dddac with a bigger one. My dac needs 1A so that's why it is big.
I am using vt25a tube in my power amp. Later on there will be a passive 12 db filter at the input. Did try to make the signal part compact.
My favourite resistor is the Mills when they get hot, grid stopper and grid leak A.B , cathode resistor e80cc audio note tantal.
Greetings, Eduard
Thank you for helping my old friend Andy hope he didnt switch his latest adventure on.
Talking about errors just discovered i wired up the heating of my e80cc input tube wrong. I have a 6,3 volt transformer, i have a humdigger. SO 4+5 in parallel. 6,3 volts to 4+5 and 9 .Humdigger between those 2 and centertap of the digger to the chassis. That is the right way, isnt it?
My line pre amplifier uses the Telefunken ob2 but you only see the glow in a dim light. But all the other tubes glow.
Here some people like Andy rave about choke input. Recently i replaced the input choke in my dddac with a bigger one. My dac needs 1A so that's why it is big.
I am using vt25a tube in my power amp. Later on there will be a passive 12 db filter at the input. Did try to make the signal part compact.
My favourite resistor is the Mills when they get hot, grid stopper and grid leak A.B , cathode resistor e80cc audio note tantal.
Greetings, Eduard
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Yes I was. Excuse my not checking.
It's still a good idea even if it isn't.
I also assumed you wanted 80v of bias. Adjust the numbers accordingly if not.
kind regards
Marek
The pentode project is temporarily on ice, but I may come back to it. I restored my 4P1L input stage to triode and the sound immediately went up several levels. In fact the 4P1L in triode with a NP Acoustics amorphous plate choke, 40mA, 180H, is so good that I can't think of anything better out of all my experiments over the years. Maybe a 10Y but I'm not in a hurry to try it again, and I need more drive than an 01A. So that stays.
With the 300b I have background listening levels at very high quality. At some point I'll try a solid state stage and a better input step-up transformer. If I want more volume all I need to do is switch back to my usual PSE 4P1L output stage which is just sitting there ready to connect up.
I have two options right now at different volume levels, but both give me the sound I've worked so hard to achieve over a period of around 12 years building only with DHTs. And also the goal has always been 2 stages out of a DAC which up to now has outputted 2v.
With the 300b I have background listening levels at very high quality. At some point I'll try a solid state stage and a better input step-up transformer. If I want more volume all I need to do is switch back to my usual PSE 4P1L output stage which is just sitting there ready to connect up.
I have two options right now at different volume levels, but both give me the sound I've worked so hard to achieve over a period of around 12 years building only with DHTs. And also the goal has always been 2 stages out of a DAC which up to now has outputted 2v.
Thanks djn. What's the whole circuit? Is it SE or PP - can't really see. Just a 26 into 300b would require a preamp to bring the gain up unless you have super sensitive speakers or there's something else in the circuit like a step-up transformer.
I tried out the PSE 4p1L output stage versus the 300b stage. The 300b is better. Better instrumental tone and details. Better treble and bass. More musical. The 4P1L PSE is still good - that's not an issue and it is still the easy solution. But I like the 300b enough to continue trying to reach a 1:2 step-up, which would probably do me in my smallish listening room.
If you compromise to the lower power (and a little limited HF bandwidth), the LL1540, 4P1L, LL1160, 300B is the acceptable compromise.
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euro21: Yes, I'm beginning to see my step-up options.
- I can use my LL1660/18mA in 2:4.5 or 2.25:4.
- I can use a 1:2 SUT on the input. The LL1540 sounded quite bad, but I have a pair of LL1544 which is amorphous and should sound better. Lots of others available from Sowter, Cinemag, Jensen etc.
Fortunately I don't need too much step-up since I already have OK background listening level. Those I've tried so far compromise the sound too much, but there must be something that is fairly transparent. There's a NE5532 on the end of my DAC and that's obviously working well since I'm already getting good sound out of it. Who knows - may be a DAC output solution in the end.
I suspect that 2 stages of DHT is a solution many of us would think of as close to ideal.
- I can use my LL1660/18mA in 2:4.5 or 2.25:4.
- I can use a 1:2 SUT on the input. The LL1540 sounded quite bad, but I have a pair of LL1544 which is amorphous and should sound better. Lots of others available from Sowter, Cinemag, Jensen etc.
Fortunately I don't need too much step-up since I already have OK background listening level. Those I've tried so far compromise the sound too much, but there must be something that is fairly transparent. There's a NE5532 on the end of my DAC and that's obviously working well since I'm already getting good sound out of it. Who knows - may be a DAC output solution in the end.
I suspect that 2 stages of DHT is a solution many of us would think of as close to ideal.
UPDATE: I hooked up a cheap Chinese PCB with a single NE5532 on it. Just a single 12v AC/DC input. It also has too much gain - much more than I need. But simple as it is, it actually sounds pretty good - close to transparent.
This is the first real progress I've seen. I'll leave it in for a while, but at first hearing I'd say I might be able to live with a solid state solution like this if it were optimised. Beginning to see light at the end of the tunnel.
This is the first real progress I've seen. I'll leave it in for a while, but at first hearing I'd say I might be able to live with a solid state solution like this if it were optimised. Beginning to see light at the end of the tunnel.
It is a simple 2 stage 300B on the bottom of the rack. On top is a 6SN7 line stage to give the 300B more gain.
After much thought I've come to a provisional position on how I want to construct my audio system. In simple terms I can start with the assumption that I want a gain of x100 after the 2v output of my typical DAC. This fits my room and my Alpair 10 single unit speakers. For almost 10 years my method was to start with an output stage with a gain of x10, which I got from two 4P1L in PSE. All that was required then was a driver with a gain of as near to 10 as possible. So again the 4P1L but I also got results with 10Y, 2P29L and 26. This satisfied me for years until I threw the 300b back into the mix and realised it was a better output tube than 4P1L in PSE, good as that was. No surprise to find the 300b was a bit special.
So - new scenario. I have a gain of around 40 to 45 when I drive it with a 4P1L. The sound is great - two DHTs (the 4P1L in triode). Nothing better I know of in audio for the two output stages. This leaves me with a gap in gain. I need to add a gain of 2.5 or 3. Several ways of doing this which we've discussed already - step-up transformers, pentodes, another tube stage.
So this is where I put in a simple NE5532 and get the best sound I've yet had in my system. Now I know very little about solid state being self-taught at building with tubes. But it seems rather clear to me that solid state is very good at handling small signals. It also moves and evolves very quickly. DAC chips get better and better, op-amps get better and better. So I think what stopped me seeing that is the convention that you get 2v out of a SE DAC. I just left it there and didn't question it. But if you change the convention and get 5-7 volts out you solve the gain problem. Even a humble NE5532 is a device of choice for a gain of x3. I've now heard it and it works.
These days there's a lot of talk about a "new normal". My provisional position - and what isn't provisional in audio - is to start with two DHT output stages and not be tempted by a high mu indirectly heated tube. I don't want that compromise. And then to make up the gain using solid state in the small signal stages. This has given me the best sound I've had so far in my system. That's my new normal. I don't know what you guys think of that.
So - new scenario. I have a gain of around 40 to 45 when I drive it with a 4P1L. The sound is great - two DHTs (the 4P1L in triode). Nothing better I know of in audio for the two output stages. This leaves me with a gap in gain. I need to add a gain of 2.5 or 3. Several ways of doing this which we've discussed already - step-up transformers, pentodes, another tube stage.
So this is where I put in a simple NE5532 and get the best sound I've yet had in my system. Now I know very little about solid state being self-taught at building with tubes. But it seems rather clear to me that solid state is very good at handling small signals. It also moves and evolves very quickly. DAC chips get better and better, op-amps get better and better. So I think what stopped me seeing that is the convention that you get 2v out of a SE DAC. I just left it there and didn't question it. But if you change the convention and get 5-7 volts out you solve the gain problem. Even a humble NE5532 is a device of choice for a gain of x3. I've now heard it and it works.
These days there's a lot of talk about a "new normal". My provisional position - and what isn't provisional in audio - is to start with two DHT output stages and not be tempted by a high mu indirectly heated tube. I don't want that compromise. And then to make up the gain using solid state in the small signal stages. This has given me the best sound I've had so far in my system. That's my new normal. I don't know what you guys think of that.
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looking at your history with tubes amps , constant changes are your "new normal" seems the same for many of us 🙂
or a line stage with them ? 🙂
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300B (A1 to A2 region) requires 140-160Vpp grid swing (depends of operating point).
The "standard" 2V RMS input has 5.64Vpp swing.
The required gain is even 28.
Without stepup (or another stage - Hi Andy, the NE5532 is the third stage! 😛pp -) only EML30 (or 841) fulfils this condition.
The "standard" 2V RMS input has 5.64Vpp swing.
The required gain is even 28.
Without stepup (or another stage - Hi Andy, the NE5532 is the third stage! 😛pp -) only EML30 (or 841) fulfils this condition.
euro21: Thanks for the calculations. I'm not sure how, but I'm getting something different
DAC output = 2vRMS = 5.6vpp
Gain of 3 in NE5532 = 6vRMS = 17vPP
Gain of 10 (maybe even 11) in 4P1L stage = 60vRMS = 170vpp
Operating point of 300b at present -50v.
Am I going wrong somewhere here?
DAC output = 2vRMS = 5.6vpp
Gain of 3 in NE5532 = 6vRMS = 17vPP
Gain of 10 (maybe even 11) in 4P1L stage = 60vRMS = 170vpp
Operating point of 300b at present -50v.
Am I going wrong somewhere here?
I would run my 300B with a voltage of 400V - 420V and a - Ug between - 95 to 103V, so your swing is a bit at the low side, but OK. The 300B hates positive grid voltage as you know...
Quiet a novel approach trying to avoid another tube stage and do this with an opamp stage... this is what I call innovative
Quiet a novel approach trying to avoid another tube stage and do this with an opamp stage... this is what I call innovative
Blitz: Yes, I am indeed running the 300b very cool at the moment, just because my PSU was designed for a 250v operating point with the PSE 4P1L. I can change that, of course, but in my smallish room I don't need much more power than I have at present. I don't see the bias going above -60v anyway. I could take the B+ up to 350v. I've read that 300bs sound best hot and I've equally read that they sound best cool! It's a long time since I used a 300b so I'm not too familiar with desirable operating points.
I'm not going to be tempted by an EML tube, guys. Well out of my price range. And the challenge is to use standard components and still get a good result. Not much cheaper than a 4P1L and a NE5532, and the money goes into plate chokes and OPTs which never wear out.
I'm not going to be tempted by an EML tube, guys. Well out of my price range. And the challenge is to use standard components and still get a good result. Not much cheaper than a 4P1L and a NE5532, and the money goes into plate chokes and OPTs which never wear out.
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