Have you tried the 5Y3 in choke input? Or cap not bigger than about 1uF? Should be an audibly better sound. This does mean you have to work out resistor size for critical inductance for the choke, or use a big choke value, since the 26 isn't going to use up much current. There's various formulas for critical inductance - I don't have it to hand but no doubt somebody else can provide the right information.
Andy
Andy
Hi All,
Although everything in an amp or preamp makes a difference, I think people focus way too much on rectifier tubes. I will write a post about this on my blog soon. There are many other things which have a much bigger impact on the sound than the rectifier. In fact for me it would be a sign that the design is marginal, if changing the rectifier has a big impact on sound. I know this sounds controversal to many, and it is just my experience.
Choice of basic circuit topology for example, then choice of good quality transformers, volume controls, caps. A good design isolates the signal circuit from the PSU.
Even within the PSU a well made power transformer has a bigger impact, choice between choke input and cap input and finally choice of rectifier circuit. I changed completely to full wave bridges with 4 tube diodes and prefer that over the regular FW rectifier with center tap. The cheapest TV damper tubes do it for me and I rather put the money into other parts than expensive rectifier tubes.
YMMV of cause!
Thomas
Although everything in an amp or preamp makes a difference, I think people focus way too much on rectifier tubes. I will write a post about this on my blog soon. There are many other things which have a much bigger impact on the sound than the rectifier. In fact for me it would be a sign that the design is marginal, if changing the rectifier has a big impact on sound. I know this sounds controversal to many, and it is just my experience.
Choice of basic circuit topology for example, then choice of good quality transformers, volume controls, caps. A good design isolates the signal circuit from the PSU.
Even within the PSU a well made power transformer has a bigger impact, choice between choke input and cap input and finally choice of rectifier circuit. I changed completely to full wave bridges with 4 tube diodes and prefer that over the regular FW rectifier with center tap. The cheapest TV damper tubes do it for me and I rather put the money into other parts than expensive rectifier tubes.
YMMV of cause!
Thomas
Hi Andy,
JC has written a good comment about the hybrid bridge a while ago about it beeing asymmetrical and he has a good point. I always went full tube bridge. I never spent much thought if I should go hybrid or all tube. I went all tube right away. JC provided an excellent reason, so no point for me to try the hybrid. Also as I wrote above there are so many other things which have a bigger impact. I rather experiment in those areas than in the PSU which will yield minor differences. Once the circuit is well done and the signal is isolated from the PSU, this becomes a rather boring topic. Of course it should be of good quality to begin with. TV dampers are so cheap, robust and have the lowest switching noise...
Thomas
JC has written a good comment about the hybrid bridge a while ago about it beeing asymmetrical and he has a good point. I always went full tube bridge. I never spent much thought if I should go hybrid or all tube. I went all tube right away. JC provided an excellent reason, so no point for me to try the hybrid. Also as I wrote above there are so many other things which have a bigger impact. I rather experiment in those areas than in the PSU which will yield minor differences. Once the circuit is well done and the signal is isolated from the PSU, this becomes a rather boring topic. Of course it should be of good quality to begin with. TV dampers are so cheap, robust and have the lowest switching noise...
Thomas
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Hi DHT maniacs,
I wonder how, in a SE amp, the signal can be isolated from the power supply. IMHO the power supply is in the signal path. Maybe with a regulated supply, but I doubt it.
Power supply components, yes the power transformer to start with, should be of very good quality not to have a negative influence on the amplifier as a whole, but no matter how good they are, you hear their character.
I wonder how, in a SE amp, the signal can be isolated from the power supply. IMHO the power supply is in the signal path. Maybe with a regulated supply, but I doubt it.
Power supply components, yes the power transformer to start with, should be of very good quality not to have a negative influence on the amplifier as a whole, but no matter how good they are, you hear their character.
Hi Pieter,
In a passively filtered supply it's mainly the last cap which remains in the signal path. The ultrapath concept is the best technique to isolate the impact of the supply imho. Still of course the supply has an impact, but it can be minimized and with a good choke input supply there are other aspects more worthwhile to explore.
Thomas
In a passively filtered supply it's mainly the last cap which remains in the signal path. The ultrapath concept is the best technique to isolate the impact of the supply imho. Still of course the supply has an impact, but it can be minimized and with a good choke input supply there are other aspects more worthwhile to explore.
Thomas
Peter,
Many people who build 26 preamps use cheap output transformers or even none and thus have a high output impedance, Would you seriously say it is worth trying chokes with different core materials before having the best possible ouptut transformer or optimize the caps in the signal path ?? I doubt that. Also the filament supply is by an order of magnitude more relevant than rectifiers or core materials in the B+ supply. That is what I mean by focussing on the wrong details. I'd first get all that to top grade and then it might be worthwhile to go into such PSU details. Albeit I'd probably move on and work on the power amp or some other aspect in the chain
Thomas
Many people who build 26 preamps use cheap output transformers or even none and thus have a high output impedance, Would you seriously say it is worth trying chokes with different core materials before having the best possible ouptut transformer or optimize the caps in the signal path ?? I doubt that. Also the filament supply is by an order of magnitude more relevant than rectifiers or core materials in the B+ supply. That is what I mean by focussing on the wrong details. I'd first get all that to top grade and then it might be worthwhile to go into such PSU details. Albeit I'd probably move on and work on the power amp or some other aspect in the chain
Thomas
I agree about the importance of the output transformer, though in my case I use a Hammond 126C in 1:1. That sounds good, but it needs a tube with lower plate resistance, which is why my preamp uses a 10Y instead of a 26. I have a Lundahl LL1660/5mA but since the 10y sounds so good I'm lazy to build the 26 version! Using the 10Y with the Hammond OPT was a big step up from 26 with cap output.
And of course the filament supply is crucial - especially with filament bias!
Andy
And of course the filament supply is crucial - especially with filament bias!
Andy
No certainly not!! We all know the "weakest link" thing, and I fully trust your engineering capabilities. Reading your blogs it is common sense that rules and that is a very good thing.
What I meant to say is that very often the focus is on components which are part of the amplifier, taking an often mediocre power supply design for granted.
On somewhat bigger scale, in my experience many DIY'ers are so much focused on building the popular 300B SE amp, forgetting that their 90 dB multiway loudspeakers might ask for something different..
Hi!
I tried it and I think the 1660 in 4.5:1 is much better. If you need higher step down ratios of course you can use the 1680, or the 1689
Thomas
I tried it and I think the 1660 in 4.5:1 is much better. If you need higher step down ratios of course you can use the 1680, or the 1689
Thomas
Hey Pieter,
Yes, we agree on that. I get many inquiries for 300B amps, but they shall be cheap and people are reluctant to move away from their low efficiency speakers.
It's quite pointless to spend the biggest part of the cost on just the tubes and compromise on the rest.
I fully agree with you on the PSU beeing very important. Yet I miss in all those PSU discussions coverage of different rectifier schemes. Also almost never the big advantage of screen windings between primary and secondary is mentioned. I get my power transformers wound with two independent screen windings and I found a big advantage of going to power transformers with grain oriented core material.
Best regards
Thomas
Yes, we agree on that. I get many inquiries for 300B amps, but they shall be cheap and people are reluctant to move away from their low efficiency speakers.
It's quite pointless to spend the biggest part of the cost on just the tubes and compromise on the rest.
I fully agree with you on the PSU beeing very important. Yet I miss in all those PSU discussions coverage of different rectifier schemes. Also almost never the big advantage of screen windings between primary and secondary is mentioned. I get my power transformers wound with two independent screen windings and I found a big advantage of going to power transformers with grain oriented core material.
Best regards
Thomas
You come to the 300b SET by a process of elimination!
1) you don't want push-pull or parallel SE
2) you don't want to build a power supply over about 450v
So the maximum quality and power you get from these choices is the 300b.
I did think about low voltage versions of 845 or 813, like around 450v, but frankly I couldn't see any advantage at that voltage.
And yes - my speakers are around 90db, but I have a smallish room and listen at lower volumes.
Am I missing something here?
Andy
1) you don't want push-pull or parallel SE
2) you don't want to build a power supply over about 450v
So the maximum quality and power you get from these choices is the 300b.
I did think about low voltage versions of 845 or 813, like around 450v, but frankly I couldn't see any advantage at that voltage.
And yes - my speakers are around 90db, but I have a smallish room and listen at lower volumes.
Am I missing something here?
Andy
Hi Andy,
Why? I don't get your reasoning at all. The 300B is a very expensive choice. And in my opinion if you want 300B sound go for the real thing, original WEs. Although current 300Bs got better, they are not more than surrogates in my opinion, it is like instant coffee compared with italian espresso
So the 300B for me is only an option if the funds are available to bring all parts of the amp on the same level. If the budget is not available I'd go for a different choice. As I wrote on my blog about the 6CB5A amp.
Quite a few people use such an amp now and some of them replaced quite expensive commercial 300B amps with them!
There are so many choices and possibilities.
All I want to say is that in order to get the maximum sonic qualities, it is important to balance each aspect of the amp. The tube is just one part of many.
Of course there might be good reasons for using that tube even if it is as simple as someone just likes the shape, by all means go ahead and use it and also play with rectifiers if it is fun for you, but don't assume that you get the best out of your amp or preamp by just using a particular tube or rectifier.
Best regards
Thomas
Why? I don't get your reasoning at all. The 300B is a very expensive choice. And in my opinion if you want 300B sound go for the real thing, original WEs. Although current 300Bs got better, they are not more than surrogates in my opinion, it is like instant coffee compared with italian espresso
So the 300B for me is only an option if the funds are available to bring all parts of the amp on the same level. If the budget is not available I'd go for a different choice. As I wrote on my blog about the 6CB5A amp.
Quite a few people use such an amp now and some of them replaced quite expensive commercial 300B amps with them!
There are so many choices and possibilities.
All I want to say is that in order to get the maximum sonic qualities, it is important to balance each aspect of the amp. The tube is just one part of many.
Of course there might be good reasons for using that tube even if it is as simple as someone just likes the shape, by all means go ahead and use it and also play with rectifiers if it is fun for you, but don't assume that you get the best out of your amp or preamp by just using a particular tube or rectifier.
Best regards
Thomas
Hey Thomas!
I'm glad you mentioned the 6CB5A since when I Googled it I came to this interesting site, which I enjoyed reading:
The Audio Eagle - Thomas Mayer Tube Amp Magic
I actually like the Chinese 300b tubes - I bought a few on ebay, waiting for good prices, and I didn't pay much. The trouble with buying on ebay is that the tubes are usually mid way through their lives, and you need to add a zero to the hours the owners "think" they've done. Bit like how much an alcoholic "thinks" he drinks. But yes, Chinese 300b's rock my particular boat. There are cheaper options like the 2E22 and 1624. I have some of those but haven't tried them yet. The 2a3 PP amps I've built did also sound very good indeed. I have plenty of 10Y but I haven't used them in the output of amps because I'd need much more sensitive speakers. I imagine they are flat out wonderful.
Andy
I'm glad you mentioned the 6CB5A since when I Googled it I came to this interesting site, which I enjoyed reading:
The Audio Eagle - Thomas Mayer Tube Amp Magic
I actually like the Chinese 300b tubes - I bought a few on ebay, waiting for good prices, and I didn't pay much. The trouble with buying on ebay is that the tubes are usually mid way through their lives, and you need to add a zero to the hours the owners "think" they've done. Bit like how much an alcoholic "thinks" he drinks. But yes, Chinese 300b's rock my particular boat. There are cheaper options like the 2E22 and 1624. I have some of those but haven't tried them yet. The 2a3 PP amps I've built did also sound very good indeed. I have plenty of 10Y but I haven't used them in the output of amps because I'd need much more sensitive speakers. I imagine they are flat out wonderful.
Andy
Hello Rod,
Thank's for the answar and also for supplying such and excellent description in the the pdf file you sent me along with the regulator board.
Regarding the B+ wiring and filament supply wiring. Do I read you correct when you suggest not putting HT and LT in the same umbilical?
Theo
I prefer them to be away from each other. Remember B+ noise comes from a low-impedance source. Cables close together, running for 1 metre, will give strong coupling, and the filament (in common-mode) has about the same voltage sensitivity as the grid.
OK, the regulator buffers this noise from the filament, but we should try not make extra work for the regulator to do!
Also, take care that the rectifier pulses from the filament transformer/rect/cap do not couple to the B+.... it may also happen with shared cable assembly.