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 Post subject: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Fri 04, 2013 2:18 pm 
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Joined: Dec Tue 04, 2012 9:31 am
Posts: 93
Hello All!!

This maybe a bit off topic but i am aiming to make a very simple low power tube amp with ECC83 and 6L6 tubes which are available with a supplier here in India. My questions are
1. Is there a simple schematic somewhere that i can use to build one with these tubes?? even a mono audio amp would be ok as this will be my first time to assemble one of any kind. Point me to a schematic please if you know any with such tubes. I also have access to 6Y6 tubes of metal jacket type. Tube type UL 84 are also available. Sadly the supplier here doesn't have any EL84's( which i also wanted for my radio)
2 The aim is to make a simple good sounding amp.which is louder enough for a room of 15 feet by 15 feet. i am also open to use any combo of tubes and modern electronics to get tube sound. but my access is limited to only the above tube types.

3. I would like to connect my ipod /mobile to the input of such an amp.


4. On a different thought i am also toying with the idea of buying a small cheap transistor radio and simple hooking it to a tube amp rig that i want to make myself. is this worth doing??. could somebody point me out how to do it with a schematic?? i am not seeking audiophile sound but just good sound.

5. Is it possible to make a very simple low power amp with UL 84 and ECC83?? schematics??

6. My last question has to do with restoration. i have a radio with a bad ECC85 can i use some other tube in its place?? can an ECC83 be used with minor mods??

Thanks for reading. Would appreciate a quick reply with a scahematic if somebody is free now to do so as i am going tube and parts hunting tomorrow.


Warm Regards and a Happy New Year to ALL!!


Amit

India


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Sat 05, 2013 6:19 am 
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Because of it's 45v @ 100ma heater, the UL84 is going to be difficult to work with... On a 120v line one could use a pair in series with another pair of 18FY6 to build a small stereo amp... Another version could use one of the 18FY6 as phase inverter so outputs could be push-pull to approx double power output... Of course the main problem seems to be you are limited in tubes so apparently the UL84 is out...

A ECC81 is a closer match for the ECC85 than is the ECC83... Assuming the tube is in the tuner and access to socket connections is going to be difficult, it probably won't be practical to try to modify the heater circuit even if you had a ECC81... 6BK7 & 6DT8 are listed as subs for the ECC85 and American number is 6AQ8...

Assuming there isn't a customs issue, I could likely come up with a 6AQ8 or at least a good sub I could send you... PM me and we'll discuss this possibility...

As far as the 6L6 amp I'd think there are schematics on the net, I'll let someone else provide that info/links... A single 6L6 with 250/300v B+ will make more than enough audio to use in a 15' x 15' room...

Tom


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Sun 06, 2013 6:25 pm 
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Joined: Dec Tue 04, 2012 9:31 am
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Hello Tom,

Thanks! i will let you know what I finally decide to build based on what i have found. So far i have lots of old UCL82 and a few PL 84 and UL84's.

heres a link to a schematic of an amp that somebody already built with a UCL82. what do u think?? :)

http://kaizerpowerelectronics.dk/wp-con ... lifier.gif


Warm Regards

Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Mon 07, 2013 9:14 am 
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The 'amp' part's basic topology is a common single ended, with no feedback, design similar to what one finds on most commodity products of the period, like table radios, TV sets, tape recorders, record players, etc, but the use of grid leak bias on the input is odd (for an audio amp) and I see no good reason for it. Better would be bypassed cathode bias as is done on the output stage.

If the amp were 'a part of' something else, like a table radio, and self contained inside that device then the power supply would be okay but as a standalone amplifier it looks like a good way to make smoke. Circuit ground is riding on 50VAC, relative to AC neutral, which is why he warns to not connect it to AC neutral (or earth). But most audio devices will have their circuit ground earthed so unless the input is externally isolated it'll blow the auto transformer. If all you ever use with it is a battery powered device (isolated) then it would probably work but it's just begging for trouble.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Mon 07, 2013 10:03 am 
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an2727 wrote:
Thanks! i will let you know what I finally decide to build based on what i have found. So far i have lots of old UCL82 and a few PL 84 and UL84's.
The UCL82 and UL84 are interesting tubes both designed for a rather similar application, mainly 100mA series string audio amplifiers. The UCL82 was more common because of the integrated HiMu triode but the UL84 will do twice the power out at the same B+. The 'mating' triode for the UL84 is the 20EZ7, a 100mA heater version of the venerable 12AX7.

I built a little amp called "Tin Man" with the UL84 (45B5 in 'American' speak) http://flipper.cu.cc/Tin%20Man.htm

I was trying to get 'as much power as possible', hence the MOSFET cap multiplier filter that doesn't need an 'R' for the RC time constant, but a 'small' R with 'big cap' could be used as well. The power transformer has dual primaries so it could be wired for 220/240V in but a slight adjustment for the heater string might be needed since half 220 is a smidgen lower than the 120VAC on mine.

Typical spec for a UL84 is 1.9 Watts at 100V B+ because, after all is said and done, a 120VAC line ends up being about 100V B+ due to the old tube rectifiers. I get around 4 Watts because of the higher B+ with solid state rectification.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Mon 07, 2013 8:13 pm 
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Joined: Dec Tue 04, 2012 9:31 am
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Hello Flipperhome

Thanks for sharing the info and schematics.

I would like to know how i can mod the UCL82 schematic to make it safe. I can add an isolation transformer to do that?? i am a complete newbie to all this stuff and electronics is not my field..but willing to learn more out of curiosity and also the nostalgia of such things. I do not mind enclosing it in a box like a radio. only the tube part exposed( sort of in a cage like box)

Its hard for me to understand without looking at the moded schematic.Could u modify the UCL82 schematic as u think would be better.?? i could then follow the corrected circuit while building the amp. I have access to good work tools and stuff and cutting machines.


I will also do the UL84 amp also. my problem in both cases would be to identify the type of output transformers that i will need ..specially incase of the UCL82. any ideas for it? what would be the specs of the OPT to drive a 4 inch 4 ohm coaxial car speaker?? I thought of hunting out some high eficiency small speakers which are common and inexpensive. ( this is my learning period, no need for fancy stuff). I saw some car speakers claiming 91 or 92 db.
Coaxials of this type from blaupunkt were excellent in sound quality but sadly that company exists no more.



We get main supply here as 220Volts AC at 50HZ.

My goal is to gift one such amp to my daughter.

And build a couple of more SE amps for my self.I sort of liked the sound of SE more from the recordings i heard on them online.


Warm Regards

Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Tue 08, 2013 12:17 am 
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Adding an isolation transformer might work but it adds cost and, frankly, I don't know where one would get the autotransformer he shows either. The simplest way, and how it was used in American devices, would be to tweak my Tin Man schematic with the UCL82 triode replacing the 20EZ7 and a different value for the heater dropping resistor. The result would be an amp putting out half the power of Tin Man, which is why I chose the UL84 with 20EZ7.

The 'other way' would be to come up with some transformer arrangement that would power the heaters and end up with between 200V and 250V B+ but I don't have a good idea how to do that off hand. I've seen people push them to 300V but technically that's beyond the ratings and a Class A SE amp is the worst configuration in which to do it. Let's see, a dual winding 240V to dual winding 240V isolation transformer wired backwards might work. What I'm thinking is when run backwards the output is less so you'd have a 120V tap, running lower at, say, 100V, and the 240V end would be running low at 200. Heaters on the 100V tap and then the 200VAC would end up in the 250V B+ range. But since I don't need 240VAC transformers I don't know, off hand, where to get such a beast.

When I said "self contained inside" I didn't mean simply 'in an enclosure'. I meant electrically, like no 'input jack' that's going to get connected to earth. An example would be a table radio. There aren't any jacks and the input to the amp comes from the tuner section.

As for output transformers, the 4 ohm is potentially a problem because 8 is the norm these days. An old one might be 3.2 ohm, which would probably be close enough in these types, but if you're doing 'small' speakers you could just put two in series.

Tin Man uses an "All American Five" (AA5) OPT that was ubiquitous in millions of table radios, roughly 2k (2000) ohm plate impedance. The RDX-300 I used was a modem 'AA5 replacement' type but the company I got them from no longer carries them so it's moot.

I don't know what he used for an OPT but it was probably somewhere in the 5K to 6K ohm plate impedance range. The spec for 100V B+ is 3.6k so in a circuit like Tin Man 4k would probably be about right.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Tue 08, 2013 7:48 am 
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Joined: Dec Tue 04, 2012 9:31 am
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Hello again!

Thank you for taking the time to reply.

i think i will order an isolation transformer for the filament and also for the plate supply... cost is not a problem. i just have too many tubes of UCL82 . would like to see for myself how the first one sounds and if its good enough, i may go further.

I really have to find an equivalent of the EZ tube that you have in your schematic. what could be near to it?? i have a few PL 84's and a few PCL 84's as well and a lot of PCF 802's. are they of any use as pre amp tubes etc in conjunction with UCL82 or UL84's??


Warm regards
Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Tue 08, 2013 10:28 pm 
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an2727 wrote:
i think i will order an isolation transformer for the filament and also for the plate supply... cost is not a problem. i just have too many tubes of UCL82 . would like to see for myself how the first one sounds and if its good enough, i may go further.
The UCL82 is a nice tube and in 6BM8 ('American' speak) form a popular choice. Using two transformers is okay and getting around 250 B+ puts it in the same power range as Tin Man. The two types give similar results but an inexpensive AA5 OPT saved significant cost and is why I chose the 45B5.

There seem to be more 'American' schematics so try searching for 6BM8. The only difference will be the heater arrangement but I think you've settled that with the dual transformers. Here is one I think better than the other link and he provides a table for OPT impedances at differing B+. http://cool386.tripod.com/6bm8/6BM8.html First, he uses the cathode bias I mentioned and also wrapped some negative feedback around it like Tin Man. As you can see, it's basically Tin Man with a different tube. From 250V to 272V B+ the table suggests an 8K OPT but I'd discount his comments on using power and line transformers. You will want a 'real' OPT and 8k is a common value readily available either new, NOS, or used.

an2727 wrote:
I really have to find an equivalent of the EZ tube that you have in your schematic. what could be near to it?? i have a few PL 84's and a few PCL 84's as well and a lot of PCF 802's. are they of any use as pre amp tubes etc in conjunction with UCL82 or UL84's??
That's a double question. Within reason almost anything 'can be used' as a 'preamp tube' but that doesn't mean it's a 20EZ7 substitute. For example, the two you listed are pentode-triode pairs, not twin triodes. In addition they're "P" prefix, which in the European numbering system means 300 mA heaters, but the UL84, the "U" prefix, has a 100 mA heater. They just aren't going to series string well and, on top of that, they're different voltage so they don't parallel well either.

Unfortunately, I'm not aware of any direct substitute for the 20EZ7. It would be possible to use a 12AX7 but it's a 150mA heater so, to series string, you'd need to parallel each 45B5 with a 900 Ohm (say 910) resistor to absorb the 'extra' 50mA need to get 150mA through the 12AX7, and also change the top series resistor to absorb the extra 7.4 volt drop (to get the 20EZ7 20V down to 12.6V for the 12AX7). That, however, increases heater power by 6 Watts and would probably overload the single power transformer so instead of DC heater power it would need to go on the AC side of the bridge.

The alternate approach would be to use the 12AX7 (ECC83) and 6CW5 (EL86), which is a UL84 but with 6.3V heater. Then one would use a conventional 'dual secondary' tube transformer of 6.3(12.6) VAC and 120 VAC but, then, you don't have those tubes either.

Frankly, if you're going to do the UCL82 (at 250V B+) there's not much reason to do the UL84 because the end result is pretty much the same thing except, at least for me and what I can buy, more expensive.

As purely a matter of bragging :mrgreen: , the 6CW5, with 12AT7, is what I used to make my nephew's guitar amp. http://flipper.cu.cc/6CW5guitar.htm There I did use a power transformer as OPT because it's push pull (offsetting winding DC) and a guitar amp is in no way 'Hi-Fi', or even 'medium-Fi'. And I had one, which is about as 'inexpensive' as you can get, but the recording studio thought it was the greatest thing since sliced bread so it must have worked :mrgreen:

If I were to do it again I'd probably simplify the screen and bias supplies as I got a bit intimidated by stories of how 'sensitive' the 6CW5 was and went a bit overboard regulating things ‘just to make sure’.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Wed 09, 2013 4:50 am 
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Joined: Dec Tue 04, 2012 9:31 am
Posts: 93
Hello

thanks for sorting out my thoughts.

Thanks for sharing.That amp schematic looks doable but right now i dont have those tubes.

Btw in the mean time i have access to two other kinds of tubes

1.EBC81 ( AROUND 10 TUBES)
2. 6L6 ( AROUND 4 TUBES)
3.ECC88( around 4 tubes)

Can i build a nice sounding SE or pushpull amp with these??

Any schematics?


Warm Regards

Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Wed 09, 2013 6:24 pm 
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Joined: Dec Tue 04, 2012 9:31 am
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I have just got myself 4x ECC81 also and an EL84.
any use to make an SE amp??


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Wed 09, 2013 8:53 pm 
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In 'America speak' the ECC81 is a 12AT7, twin mu=60 triodes, and the EL84 is a 6BQ5, 12 plate Watt audio power pentode. At 250V B+ the 6BQ5 will do about 5 Watt with a 5k ohm plate impedance OPT.

The 6L6, using fixed bias (rather than cathode like the others), will do 11 Watt with 375 B+, 250 V Screen, and a 4k OPT.

Keep in mind that the bigger the B+ and power out the more expensive things get and, for a number of reasons (OPT cost for one), Push-Pull becomes more economical despite the increase in tube count.

I don't know what you meant in the previous post about "don’t have those tubes." The 6BM8 is the UCL82 with 6.3V instead of 50 V heater. The 'amp' part is identical and you have those (UCL82, or in 'American speak' 50BM8 [see? 50 vs 6 volt heater]}.

This link will let you look up tube datasheets. http://www.mif.pg.gda.pl/homepages/frank/vs.html


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Fri 11, 2013 7:36 am 
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Thank you for the link!!

I will do some reading

Btw, what would be the best possible price for a lot of 10 matched EL84 tubes?? Where should i order them??Are capacitors of of certain brand critical for good sound??
Is there a certain brand of speakers /drivers that i must try and use with a low power tube amp?? I am expecting around 2 watts of power from the UCL82 single tube amp.

As first step, I would like to use an easily available dual cone 8 ohm speaker.
I have a large number of EBC 81 tubes. Can they be used in a preamp section with good results or are they bad as preamps??


Warm regards

Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Fri 11, 2013 12:31 pm 
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an2727 wrote:
Thank you for the link!! I will do some reading
Since you like that one try this one for a gaggle of technical books. http://www.tubebooks.org/technical_books_online.htm

Radiotron Designer's Handbook, Fourth Edition, P. Langford Smith, 1953 is considered by many to be the ‘bible' of vacuum tubes.

an2727 wrote:
Btw, what would be the best possible price for a lot of 10 matched EL84 tubes?? Where should i order them??
Probably a Russian equivalent, like 6P14P, off Ebay.

an2727 wrote:
Are capacitors of of certain brand critical for good sound??
Lots of people swear by brand and type of capacitor but I am not one of them. Maybe the 'golden ears' can hear things I can't but as far as I'm concerned any decent film cap will do just as well as the other except for, perhaps, phono preamps but the tight tolerance needed probably automatically gets 'a better cap', if there is such a thing.

Don't get me wrong, I am not saying ALL capactitors are equal. I'm just saying there's no audible difference between good FILM caps.

an2727 wrote:
Is there a certain brand of speakers /drivers that i must try and use with a low power tube amp?? I am expecting around 2 watts of power from the UCL82 single tube amp. As first step, I would like to use an easily available dual cone 8 ohm speaker.
That opens an almost never ending can of worms as one man's nirvana might be junk to the other.

For 'low power' you'd like high efficiency speakers (high SPL) but that is difficult, and expensive, to find in modern speakers as they are now 'exotics'. They can be found in 'vintage' speakers but those are often open baffle and that creates another set of problems, namely large enclosures for bass response.

The dual cone idea is good but what used to be considered the 'poor man' Full Range Driver, the 8 inch Pioneer B20FU20-51FW, is discontinued and the alleged 'replacement', GRS 8FR-8, isn't. The listed Thiele parameters are way different and aren't even right at that. I've never tried one but from all I've read they only thing in common with the B20FU20 is physical appearance so, in short, if you find a good, inexpensive, dual cone full range driver let me know where.

If you've got money to spend then here is an example of a modern full range driver with good SPL.
http://www.madisoundspeakerstore.com/approx-8-fullrange/fostex-fe206en-8-full-range/

an2727 wrote:
I have a large number of EBC 81 tubes. Can they be used in a preamp section with good results or are they bad as preamps??
Should be okay. That's an audio triode with a couple of diodes thrown in to be used in AM radios. The triode is the 'first audio amp' that then goes to the output tube, In other words, it’s the preamp to the radio's SE audio amplifier. It's similar to the UCL82 triode section but in a separate bottle. Over here I'd use a 20EZ7, or 12AX7, or 12AT7 because there are two triodes, for stereo, and no need for the diodes but smoke 'em if you got 'em.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Fri 11, 2013 7:33 pm 
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Hello and Thanks for the headsup and link to the speaker website. I will have to order it and get it thru family coming back home from US. that speaker looks good. the woodwork looks like a maze though.i guess its more like a length of air volume all wound around in a box.??

Right now i am collecting tubes and getting a transformer built for the UCL82 single tube amp. the other parts for that amp have been wired together already.will have to wait for the transformers.There is transformer manufacturer here who will do a one off job for me.

Once i get more experience with the tube thingy, i will make a push pull amp with 6L6 metal tubes that i have.

btw what would the life of a tube in hours of use at 70% power??


Warm Regards

Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Sat 12, 2013 12:50 am 
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an2727 wrote:
Hello and Thanks for the headsup and link to the speaker website. I will have to order it and get it thru family coming back home from US. that speaker looks good. the woodwork looks like a maze though.i guess its more like a length of air volume all wound around in a box.??
Well, I didn't mean to say "that's the one to get." It might be what you want but I was just using it as an example. The enclosure is a folded horn to boost the low end response; otherwise you have a truly big, big thing (if making a straight horn).

The problem with any 'full range' (single) driver is keeping it small for high frequency response but simultaneously large for bass response. The contradictory goals necessitate compromise and, in this case, it's using a large horn, folded to keep space somewhat down at the expense of complexity, in order to amplify the low end. The enclosure is not easy to make (all that folding has to be air tight on both side walls) and they still recommend a tweeter because 8 inch, to get more bass, compromises the extreme top end.

I just noticed Parts Express has another 8 inch whizzer http://www.parts-express.com/pe/showdetl.cfm?partnumber=292-548 Now, I don't know a blessed thing about it other than that page, and there are no reviews, but at 92 dB it's 'reasonable' and they suggest a 1.05 CuFt enclosure with 42 Hz tuned port, which is a simple, 'convenient', size. No way it's going to equal a speaker 5 times the cost but I wonder about just how much to spend on a 2 Watt pentode SE.

Hmm, I just did a quick simulation and I don't know what they're smoking but 2 CuFt looks to me a minimum. WinISD's 'pick' for maximal flat response is 5.7 CuFt with a 34 hz port but 3 CuFt isn't bad. That speaker is 'new' and I'm tempted to try one.

Oh, if you have people over here then you might want to check some US tube sites. http://www.abcvacuumtubes.com/gridcaps_sockets_productlist.html and http://www.esrcvacuumtubes.com/ are two of the cheapest and I currently like to design things around 'dollar days' tubes.

an2727 wrote:
Right now i am collecting tubes and getting a transformer built for the UCL82 single tube amp. the other parts for that amp have been wired together already.will have to wait for the transformers.There is transformer manufacturer here who will do a one off job for me.
Having access to custom winding is nice. I presume they DO know the special interleave winding techniques needed for audio transformers?

an2727 wrote:
Once i get more experience with the tube thingy, i will make a push pull amp with 6L6 metal tubes that i have.
That's certainly doable but when checking schematics just be aware that the metal 6L6 is the 'original' 6L6 and not the higher power 6L6GC type

an2727 wrote:
btw what would the life of a tube in hours of use at 70% power?
I don't know.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Sun 13, 2013 7:30 pm 
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Hello again,

Its great to get suggestions from someone as knowledgeable as you :D

That speaker looks good and inexpensive but i was just wondering what you think would be the outcome from regular car speaker connected to that UCL82 single tube amp.. have a look at this link

http://www.indiajbl.com/CarAudioDesc.aspx?ID=113

The transformer manufacturer is a big transformer manufacturing company here.I will check with them about the the interleave thing. They will do a one off job as a favour. :wink:

I must admit being enlightened about the quality sound from low watts when i first used a simple ipod dock from altec. For the money its absolutely perfect in the sound department. IMT320. It does have a warm tone and i think its there on purpose. So i am assuming 2 watts for easy listening wont be bad if done the right way. Also i have a small Sony radio ICF-F10 that has beautiful smooth sound at just 800mW.

Now that you mentioned, i am aware of the lower power from the original 6L6 which i have.

Btw have you had the chance compare a tripath T amp( little chinese made Lepai amps) to a small SE amp??

Warm Regards
Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Mon 14, 2013 6:25 am 
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an2727 wrote:
That speaker looks good and inexpensive but i was just wondering what you think would be the outcome from regular car speaker connected to that UCL82 single tube amp.. have a look at this link

http://www.indiajbl.com/CarAudioDesc.aspx?ID=113
Holy smokes, 2 Ohm. Well, I suppose if your winder includes a 2 ohm tap it might work but an impedance that low means a larger winding multiplier, which also multiplies up any 'discrepancy' between what they claim and reality. Past that I don't know. I tried some 4 ohm car speakers and wasn't happy with them but they were different speakers so who knows?

an2727 wrote:
I must admit being enlightened about the quality sound from low watts when i first used a simple ipod dock from altec. For the money its absolutely perfect in the sound department. IMT320. It does have a warm tone and i think its there on purpose. So i am assuming 2 watts for easy listening wont be bad if done the right way. Also i have a small Sony radio ICF-F10 that has beautiful smooth sound at just 800mW.
Well, Watt, itself, doesn't really affect the 'quality', per see, unless you crank it to distortion trying to get volume. Or it's just a low quality amp to begin with, to make it cheap. But that, again, is not due to the Watt, per see.

People are often 'surprised' at 'how much volume' comes out with low Watt but that's because we tend to 'think' linearly while the ear is logarithmic. To the ear 200 Watt is 'barely' louder than 100 Watt and it works the same in reverse. A halving, or doubling, of perceived loudness is empirically determined to be about 10 dB and that's a power ratio of 10 to 1, so a 10 Watt amp sounds 'half as loud' as the 100 Watt. Now, that's significant but no where 1/10'th the volume, as our linear minds imagine it 'ought to be'. Okay, so 1 Watt is 1/4 the volume of a 100 Watt amp, but that's still a fair amount of perceived sound, especially since were speaking 'max power' and maybe we 'normally' use 1/2 turn on the 100 Watt amp's volume knob.

Of course, that's presuming the same speaker SPL and you can get 'more sound' by using more efficient speakers. I.E. increasing speaker SPL by 10 makes a 10 Watt amp, on the high SPL speakers, sound like 100 Watt, on the low SPL speakers. That's what people miss when feeling sorry for the poor folks 'stuck' with 15 Watt tube amps back in the old 'console' days. Those console speakers were often 6-10 dB more efficient than what's common today so that 'small' 15 Watt amp was doing some respectable ear pounding..

The problem I have with what I call my 'PC Speaker Class' amps (3 Watt range) is they sound so good by brother-in-law keeps wanting to crank it up to shake walls. :mrgreen: Well, it's fine for 'easy listening' but it isn't a wall shaker.

an2727 wrote:
Btw have you had the chance compare a tripath T amp( little chinese made Lepai amps) to a small SE amp??
No, but it seems to have mixed reviews.


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Mon 14, 2013 3:43 pm 
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Joined: Dec Tue 04, 2012 9:31 am
Posts: 93
Hello!

Interesting for me to note your observations . What kind of issues may arise regarding transformers and sound output if i was to use that JBL car speaker for my single tube SE amp using the UCL82 ??

I will search the local market here in delhi for some speakers incase this car speaker doesnt work.

Warm regards

Amit


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 Post subject: Re: DIY amp with ECC83 and 6L6 tubes
PostPosted: Jan Fri 25, 2013 3:32 pm 
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Joined: Dec Tue 04, 2012 9:31 am
Posts: 93
Hello Again

i completed the UCL82 single tube amp. It works but there is a major problem. There is loud hum even when it is not connected to any input signal. This hum gets louder and louder from zero within 30 seconds ..as the tube warms up after switching the amp on. Its was the same with another tube from the lot. what could be the posssible problems?? When i play music the hum is almost gone but definitely still there in the background. I am using a 93 dB dual cone 8 inch paper cone speaker for sound. To test, i am using a 3.5 jack on my cellphone to play music on this amp. The hum remains unchanged even when i cut off the stereo plug that goes into my fon!!
amp diagram is in this link:

http://kaizerpowerelectronics.dk/wp-con ... ifadvance!!

Let me know what could be wrong.What should i check?


Warm Regards

Amit


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