Hello guys. I dont want to repeat this question once again, but is stands against me.
I have homebuilt fullrange open baffle speakers with 93dB eficiency and I have used these with various single ended triodes like 45, 4P1L which can make only small power, 2 watts maximum.
I want the good SET sound, but with better bass and power in general. You will think that good option is to build bigger Se, for example with 300B or simillar power tube. I dont have this option because I have only small power OPT (from rema radio, 5k, 35mA, but these sounded actually pretty good).
With single ended triode, even this small power I get BEAUTIFUL, really GREAT soundstage and things like vocals, timbre, image are great.
Biggest problem is bass. The amp has these great things but at the same time lacks bass energy.
But I have push pull output transformers which were intended for EL34s in pentode. These can have 3.5-4k on each side of the primary.
I can be fine with 4 watts of power.
I have two most important questions:
1. Can I use these output transformers for, for example EL84s in triode or simillar valves?
2. I know that with pushpull I will have better bass, but what about the other things? Timbre, detail, soundstage, imagination... Wouldnt be these worse than with SE amp? This connects to another question which is what good pushpull circuit to use.
Thank you for your time and suggestions.
Best regards, Michal
I have homebuilt fullrange open baffle speakers with 93dB eficiency and I have used these with various single ended triodes like 45, 4P1L which can make only small power, 2 watts maximum.
I want the good SET sound, but with better bass and power in general. You will think that good option is to build bigger Se, for example with 300B or simillar power tube. I dont have this option because I have only small power OPT (from rema radio, 5k, 35mA, but these sounded actually pretty good).
With single ended triode, even this small power I get BEAUTIFUL, really GREAT soundstage and things like vocals, timbre, image are great.
Biggest problem is bass. The amp has these great things but at the same time lacks bass energy.
But I have push pull output transformers which were intended for EL34s in pentode. These can have 3.5-4k on each side of the primary.
I can be fine with 4 watts of power.
I have two most important questions:
1. Can I use these output transformers for, for example EL84s in triode or simillar valves?
2. I know that with pushpull I will have better bass, but what about the other things? Timbre, detail, soundstage, imagination... Wouldnt be these worse than with SE amp? This connects to another question which is what good pushpull circuit to use.
Thank you for your time and suggestions.
Best regards, Michal
Hi Michal,
I have the same "issue" as you. Just for fun I'm going to try something I did a while ago...and that is parallel single ended.
On your question 1. Yes you can use EL84...however you'll have to use 4 per channel. I.e. PushPull Parallel. (assuming you mean your EL34 output transformer) Because pp el84 prefers around 8k. In your case you have 3.5-4k hence you need 2 per "side" if you know what I mean.
2.) Try something easy like the poddwatt first. Often PP simply does not give you as big a soundstage.
I have the same "issue" as you. Just for fun I'm going to try something I did a while ago...and that is parallel single ended.
On your question 1. Yes you can use EL84...however you'll have to use 4 per channel. I.e. PushPull Parallel. (assuming you mean your EL34 output transformer) Because pp el84 prefers around 8k. In your case you have 3.5-4k hence you need 2 per "side" if you know what I mean.
2.) Try something easy like the poddwatt first. Often PP simply does not give you as big a soundstage.
These are what's limiting your bass performance.
Is the Sowter SA-02 in your budget? Do you have a budget for new iron?
You can try PP DHT. I've been running that for years now and to my ears sounds better than either SET or PP pentode, or PP pentodes in triode mode. My amp is a converted ST-70 running Sovtek 6B4G as the output tubes. Transformers are all original, but almost all of the rest had been modded in some way. Driver board and quad cap replacement is from Curcio, no negative feedback, original choke, bias supply not used as it uses cathode bias. I cannot remember why I converted to cathode bias, but it works.
Sound is big and powerful. No lack of bass from this beast.
I have a quad of Genalex 300B waiting to go into this amp. I've added dropping resistors for the filaments, and tube adapters for the 8 pin to 4 pin and took advantage of the extra unused pins on the 8 pin socket. The thing I'm a bit worried about with it is the filament current, I'd be drawing the same current as the original ST-70 would, but it is over what I believe to be the spec of the transformer. It will draw 3.45 amps, but the transformer is rated at 3amps, but 3 amps is what 2xEL34 would draw, and then the original also had the 7199 that took .45amps. I don't know what the story is on that.
Sound is big and powerful. No lack of bass from this beast.
I have a quad of Genalex 300B waiting to go into this amp. I've added dropping resistors for the filaments, and tube adapters for the 8 pin to 4 pin and took advantage of the extra unused pins on the 8 pin socket. The thing I'm a bit worried about with it is the filament current, I'd be drawing the same current as the original ST-70 would, but it is over what I believe to be the spec of the transformer. It will draw 3.45 amps, but the transformer is rated at 3amps, but 3 amps is what 2xEL34 would draw, and then the original also had the 7199 that took .45amps. I don't know what the story is on that.
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The recording itself has lots of information in it or not.
Added distortion gives the impression of more low level detail and more impact of percussive sounds. The reason of more impact is that, signal level and perceived loudness are 2 different things, more inner ear bands are activated.
Now I dont have money for a new iron....
Or.. Maybe when I wil try to make the bass best from the SE.... I can use paralelled tube rectifiers, and with class A2 I can maybe get 2.5-3 watts from one triode connected 4P1L. I dont want to use any feedback.
I know, a lot of things depends....
Have you heard some push pull amp that images really well?
Or.. Maybe when I wil try to make the bass best from the SE.... I can use paralelled tube rectifiers, and with class A2 I can maybe get 2.5-3 watts from one triode connected 4P1L. I dont want to use any feedback.
I know, a lot of things depends....
Have you heard some push pull amp that images really well?
I would wait until you do.
You could, but that won't make your output transformers any better.
Feedback would restore some of the bass lost in the OT, but putting feedback around a series feed output transformer can be a bit of a gamble.
I have several radio OPTs of varying ratios, usually for ECL86 or something of the kind.
Sadly most of these also have poor LF response, typically rolling off by 300Hz, but some even higher than that.
I wonder if parallel feed would ameliorate the bass response issues, if a suitably large coupling capacitor was used?
Of course, then you have a gapped OPT when you don't need the gap...but hopefully the HF response isnt too rough, or rolled off. It is at least an audio transformer...
I've read several times, and most recently in Elvee's recent thread, of using TV deflection transformers as OPTs.
It's an interesting idea, but I have yet to find any available to buy, or test, to know anything more about them.
I know you are avoiding FB, but even some local plate to grid FB would help with the bass response, a little.
All in my very limited experience, of course.
For comparison, my paralleled SE pentode amplifier, using 3 parallel 6P30B-R, makes good bass response down to 40Hz (being very conservative) and has a total DC bias of about 48mA. The OPT is rated for 60mA and 6W output. My amplifier delivers about 3W at about 1% THD. It uses lots of local feedback to lower gain and linearise the output stage in particular.
Triode strapped, I reckon it would output maybe 2 W. But then perhaps it would need less FB
The OPT is about the size of a 50VA power transformer. The core size is the cause of the poor bass response you have noted.
Parafeed would be a cheap experiment, provided you have the parts. Only a capacitor.
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So if you have some old radio OPT that's stacked and dipped in wax, you can pull it out of the channel frame and pull the lams out, clean all the wax off, then restack the transformer and eliminate the air gap. This is one of those things that's either incredibly easy or totally impossible depending on the transformer.
Once you have eliminated the airgap, the bass response will likely be just fine, then you can source an appropriate plate choke and off you go!
Once you have eliminated the airgap, the bass response will likely be just fine, then you can source an appropriate plate choke and off you go!
And of course the plate choke...unless you use a CCS...which I guess, needn't be solid state; if vacuum only is your goal
Not quite as simple as "just a capacitor" in my previous post. Sorry about that.
Hmm, parafeed output is a very interesting idea, but I have no idea how it will sound
I remember that Ive got pretty good bass with the same OPT, but this was with indirectly heated pentode 4654 strapped in triode...
Im a bit dissapointed.
The OPT is made for EL84 in pentode (5k, 25mA anode current, cca 250V anode voltage).
With 4654 (40-50mA and anode voltage of 270-280V) I have got pretty decent bass. It is not only about the bass whole response but also about the bass energy.
And now with 45 (lower than 250V b+ and 30-35mA current) Im not able to make good bass. I have 1k5 cathode resistor and 10uF paper in oil as bypass which should be absolutely enough (I increased it to 30uf but only very small increase in bass, almost nothing).
I am less well versed than many here, and have only built a handful of valve circuits, but I have noticed or learned some things.
I use the bypass capacitor value to set LF corner at the input stage, each stage after the bypass is for a higher frequency - I read somewhere about this practice, but my recall is awful.
In the output stage I use something like 1k8 to 2k2 cathode resistance, and bypass by 100uF. This is probably excessive as I was aiming for 1-2 Hz. So I could probably halve that value, say 47uF, and notice little effect.
But I have been in a similar situation, and that the circuit just liked working at X voltage and not at Y voltage.
Unscientific as that is...
Some just seem to have sweet spots...like the 6P30B-R liked the B+ real high, and the Vg2 about 40V lower. The trouble then is keeping current reasonable!
In triode, I would need to be at a similar plate voltage as in pentode (300V), or higher still. 350V is the VP at cutoff maximum value for the valve. So I still havent tried it!
My point being, with higher B+, the valve may 'like' to see the Primary Z its loaded with, but at lower B+ it really wants a lower primary Z. Instead of voltage headroom being a limit, it becomes current swing/headroom.
Also, changing circuit parameters like Vg2, if in pentode mode; or switching from pentode to triode, UL or variation of loading and it's going to change how suitable your transformer is as a load.
I think that's correct (as terrible as it reads) and perhaps it will help
I use the bypass capacitor value to set LF corner at the input stage, each stage after the bypass is for a higher frequency - I read somewhere about this practice, but my recall is awful.
In the output stage I use something like 1k8 to 2k2 cathode resistance, and bypass by 100uF. This is probably excessive as I was aiming for 1-2 Hz. So I could probably halve that value, say 47uF, and notice little effect.
But I have been in a similar situation, and that the circuit just liked working at X voltage and not at Y voltage.
Unscientific as that is...
Some just seem to have sweet spots...like the 6P30B-R liked the B+ real high, and the Vg2 about 40V lower. The trouble then is keeping current reasonable!
In triode, I would need to be at a similar plate voltage as in pentode (300V), or higher still. 350V is the VP at cutoff maximum value for the valve. So I still havent tried it!
My point being, with higher B+, the valve may 'like' to see the Primary Z its loaded with, but at lower B+ it really wants a lower primary Z. Instead of voltage headroom being a limit, it becomes current swing/headroom.
Also, changing circuit parameters like Vg2, if in pentode mode; or switching from pentode to triode, UL or variation of loading and it's going to change how suitable your transformer is as a load.
I think that's correct (as terrible as it reads) and perhaps it will help
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The solid state and glass state options drive the B+ voltage way up. Plate chokes are a reasonable choice.And of course the plate choke...unless you use a CCS...which I guess, needn't be solid state; if vacuum only is your goal
You're definitely not helping things. Try increasing to 100uF.
Still, radio output transformers are made to power radios. Lil Jon and the Eastside Boyz weren't around in the 60s when these transformers were made. They needed to be just barely good enough for what was available at the time (in terms of source material, broadcast quality, and speaker quality), so 100Hz-8kHz was completely reasonable. After all, you didn't want to bottom out the speaker in the radio, so throwing away most of the bass was a very sensible decision.
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It sounds to me as most likely that in using a OPT for pentode, 5k may not be a good load for EL84 in triode, though its often quoted for pentode. (I think)
It probably comes down to anode resistance, Ra (Rp).
Why not try with double the load R? Or Half? See what happens.
I'm assuming you have more than 1 secondary, which you may not.
It probably comes down to anode resistance, Ra (Rp).
Why not try with double the load R? Or Half? See what happens.
I'm assuming you have more than 1 secondary, which you may not.
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Or use the push-pull output transformers you already have.
Hi,
You wrote that you have used your Single-Ended output transformers with different triodes and that you already have a pair of push-pull output transformers with a primary of 3.5 - 4k.
Now I don't know how many and wich triodes you already have, but maybe it is possible to to make a push-pull amp with the triodes and the push-pull transformers you already have?
Things to look for this, are:
1) what are the secundairy connections on your 3.5 - 4k push-pull transformers you already have? Do these for instance have 4, 8 and 16 Ohm connections? Because that would give more opportunities.
2) what is the impedance of your loudspeakers?
Because in case your output transformers do have 4 Ohm connections and in case your loudspeakers have an impedance of 8 Ohm? In that case, you could use the 4 Ohm secundary connection of your push-pull output transformers and then the output-tubes will see an impedance of about 7 - 8k at the primary side.
In that case you could make a push-pull amp with tubes that need a push-pull transformer with a primary impedance of 7 - 8k.
That could be for instance the 45 triode or EL84 in Pentode. But if you want EL84 connected in triode you could even try these in push-pull class AB. And of course you can try several other tubes too.
Best regards,
Tubecase.
Hi,
You wrote that you have used your Single-Ended output transformers with different triodes and that you already have a pair of push-pull output transformers with a primary of 3.5 - 4k.
Now I don't know how many and wich triodes you already have, but maybe it is possible to to make a push-pull amp with the triodes and the push-pull transformers you already have?
Things to look for this, are:
1) what are the secundairy connections on your 3.5 - 4k push-pull transformers you already have? Do these for instance have 4, 8 and 16 Ohm connections? Because that would give more opportunities.
2) what is the impedance of your loudspeakers?
Because in case your output transformers do have 4 Ohm connections and in case your loudspeakers have an impedance of 8 Ohm? In that case, you could use the 4 Ohm secundary connection of your push-pull output transformers and then the output-tubes will see an impedance of about 7 - 8k at the primary side.
In that case you could make a push-pull amp with tubes that need a push-pull transformer with a primary impedance of 7 - 8k.
That could be for instance the 45 triode or EL84 in Pentode. But if you want EL84 connected in triode you could even try these in push-pull class AB. And of course you can try several other tubes too.
Best regards,
Tubecase.
SE vs PP articles attached.
The way I see it is the question of do you want finesse or do you want to go loud?
I've had them all and keep coming back to a small EL84 amplifier, building one at this moment, waiting for parts to arrive while in lockdown. With Russian tubes or those 6BQ5s' that have 14 Watt plate dissipation I'll get just 4 watt out of a SE using a 20% distributing load tap (aka Ultra Linear) - getting the most of the power of a pentode while retaining most of the characteristics of a triode. For me the 20% represented the best compromise between power and ultimate fidelity.
The way I see it is the question of do you want finesse or do you want to go loud?
I've had them all and keep coming back to a small EL84 amplifier, building one at this moment, waiting for parts to arrive while in lockdown. With Russian tubes or those 6BQ5s' that have 14 Watt plate dissipation I'll get just 4 watt out of a SE using a 20% distributing load tap (aka Ultra Linear) - getting the most of the power of a pentode while retaining most of the characteristics of a triode. For me the 20% represented the best compromise between power and ultimate fidelity.
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But these OPTs were quite good. The 60Hz rolloff can be truth, but I think it can be as low as 45Hz. Absolutely okay for me. And the high frequency is also good, it plays all the way to 20kHz. I dont see a problem here (althoughit can be better).
I see bigger problem that the OPT can not stand anymore than 40mA, which limits me to use only one 4P1L per channel, I cant go paralell in SE.
Hi Michal.
Two questions for you:
- Do you have any experience with DIY handwinding transformers?
- do you have good nerves?
I was DIYed myself OPTs for my "second" SET with 6C33C.
C cores, G10 (PCB material) bobin, insulation is a modern paper/mylar and teflon from russian teflon capacitors and Sowter principle of winding with 4 secondarys.
Very old and bad pic, sorry.
Two questions for you:
- Do you have any experience with DIY handwinding transformers?
- do you have good nerves?
I was DIYed myself OPTs for my "second" SET with 6C33C.
C cores, G10 (PCB material) bobin, insulation is a modern paper/mylar and teflon from russian teflon capacitors and Sowter principle of winding with 4 secondarys.
Very old and bad pic, sorry.
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