| audiousername |
RDH4 was on Greg's (geek's) website somewhere. For some reason I can't find it now. When I do, I'll post the url.
EDIT: I feel like an idiot :( ... It was on the front page of his website. Here is a link
Thanks to Greg (Geek), Tim (Sch3mat1c) and Chocky (?) for making this happen :wave2:
They need mirrors desperately to share the load around (the entire book is around 77MB), so anyone with spare webspace and bandwidth... |
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| chrisb |
| quote: | Originally posted by chrisb
Alex, I hope my last post didn't sound petulant - that was not my intention.
While I'm at it, I should mention that the next scheduled revision is to change the input tube to an EF86 (once again courtesy of my "mystery" benefactor) Since I've got another 3 day weekend, I'll probably implement that before your reply.
cheers y'all
:drink: |
Well Dave, even tho I got a late start this evening, I did manage to get the EF86's installed - may need to add a little attenuation - rather a lot of gain. Also eliminated the last RC filter stage per Eddie's suggestion, perhaps prematurely; along with the intense gain we got some Lou back. I'll report further after a few hours of music. so far sounds promising. maybe I should stop now
"what, you're 'sposed to listen to them? Then how can you tell how good they are, if you're not comparing notes with the other geeks?
:xeye:
good night all |
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| planet10 |
| quote: | Originally posted by chrisb
along with the intense gain we got some Lou back. |
:^(
dave |
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| fdegrove |
Hi,
| quote: | | along with the intense gain we got some Lou back. |
Reed?
Cheers,;) |
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| planet10 |
| quote: | Originally posted by fdegrove
Reed? |
No... an inside joke. The Professor has a bit much in the hubris department. His breadboard system with some 80 pieces of iron tends to HUM....
dave |
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| fdegrove |
Hi,
| quote: | | His breadboard system with some 80 pieces of iron tends to HUM.... |
LOL....Inductive coupling from BC to LOUisiana, he?
Cheers,;) |
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| planet10 |
| quote: | Originally posted by fdegrove
LOL....Inductive coupling from BC to LOUisiana, he? |
More like from BS... :)
dave |
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| Alex Kitic |
Hi to all,
I missed the forum the last couple of days -- I have not even had the chance to go online.
First of all, I would like to comment on the RDH4 -- when I read that "we'll end up with RH" I got very interested, since I've never heard of the RDH4, and never read it, of course. But, what I saw was but a general schematics -- now it remains to be read (when I find it online) whether there is some concrete explanation how to do it. But I fear not, since it will most probably just address the feedback to be applied between anodes etc. So, for as much as I'm concerned, that is just another interesting text from the times of old when tubes glowed bold.
Furthermore, the RH6550 is slowly making progress... now the rectifier is an AX50, giving it the best sound yet. But, it is not the mercury vapor rectifier that is blessed with good sound -- I recon that is more about the fact that 6550, KT88, KT90 (Ei) are "ugly brutes" that should not be treated kindly. Insertion of the AX50 has risen the B+ to a value where there is 400V across the output tube and some 110mA drawn by the cathode... consequently, the dissipation is now reaching max. values - and the sound is improving (mostly) because of that -- although the output transformer arrangement that it has (momentarily) to work with is to say the least "ridiculous". Great bass, too.
Well, the schematics for RH2G is more resemblant to the mentioned John Broskie article. But, with all due respect to Mr. Broskie, and all other people who have contributed to tube design in the previous century :) I feel the need to give myself a little credit -- I'm self taught, meaning that I have no formal electronics training (economist and scientifical-technical translator). Therefore, I had to learn all that I know by reading and thinking... without direct tutors or anything. Furthermore, when someone writes a teoretical article on his idea, or whatever (i.e. some notion from an old and forgotten textbook) -- that is one pair of shoes. Implementing it in practice, knowing what and why to do in order to find the right values -- that is a different pair of shoes. At least to me. And should deserve some credit.
Finally, about the EF86 implementation: well, I have previously mentioned that instead of the ECC81 driver ECC83 could be directly substituted, with the previously mentioned consequences etc. BUT, substituting one tube for another is not necessarily leading to better results, no matter what the teory might imply. Unless these results are "above the theoretical plane" meaning that i.e. using a pentode (higher output impedance) current "source" might lead to better sound or something. Furthermore, just substituting anything for whatever, without further substitution of circuit parts is not necessarily a good option.
That's it for now... Actually, posting on the forum regularly is a bit difficult for me, because unlike most of you (I presume) I do not have ADSL or whatever 24hrs online access, but a mere dial-up, further worsened by years of monopoly in the state where I live (meaning that both telecommunications provider and internet provider are far from being good... and face no real competition, either because of signed agreements with the government (!) or because they where there first and now there is noone with enough starting capital to be able to surpass them on a massive scale...) -- therefore writing posts regularly is to say the least "challenging". So, feel free to contact me via e-mail.
Regards,
Aleksandar |
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| audiousername |
| quote: | Originally posted by Alex Kitic
Hi to all,
I missed the forum the last couple of days -- I have not even had the chance to go online. |
The forum went offline till a few hours ago, so you didn't miss anything :D
| quote: | Originally posted by Alex Kitic
So, for as much as I'm concerned, that is just another interesting text from the times of old when tubes glowed bold. |
The RDH4 was, and still is the most respected text for general information about valves and valve circuits. It is well worth a read.
I also read somewhere that this sort of plate-to-plate feedback was popular in the output stages of antique radios.
| quote: | Originally posted by Alex Kitic
I feel the need to give myself a little credit -- I'm self taught, meaning that I have no formal electronics training (economist and scientifical-technical translator). Therefore, I had to learn all that I know by reading and thinking... without direct tutors or anything. |
Same here. Completely self-taught..... So I come up with ideas which I think are original, only to find someone else beat me to it fifty years ago. Such is life. But it doesn't matter if it's been thought of before, it was an original idea to you and that is what matters (along with good music ;) )
| quote: | Originally posted by Alex Kitic
Actually, posting on the forum regularly is a bit difficult for me, because unlike most of you (I presume) I do not have ADSL or whatever 24hrs online access, but a mere dial-up, further worsened by years of monopoly in the state where I live (meaning that both telecommunications provider and internet provider are far from being good... and face no real competition, either because of signed agreements with the government (!) or because they where there first and now there is noone with enough starting capital to be able to surpass them on a massive scale...) -- therefore writing posts regularly is to say the least "challenging". So, feel free to contact me via e-mail. |
Alex, you're not alone. I am on dial-up too.... the 'horse and cart' version of the internet - or maybe I should say the valve version? :D (well they're both obsolete technologies). It took me about ten hours to download the RDH4. |
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| choky |
| quote: | Originally posted by Alex Kitic
Hi to all,
I missed the forum the last couple of days -- I have not even had the chance to go online.
First of all, I would like to comment on the RDH4 -- when I read that "we'll end up with RH" I got very interested, since I've never heard of the RDH4, and never read it, of course. But, what I saw was but a general schematics -- now it remains to be read (when I find it online) whether there is some concrete explanation how to do it. But I fear not, since it will most probably just address the feedback to be applied between anodes etc. So, for as much as I'm concerned, that is just another interesting text from the times of old when tubes glowed bold.
Regards,
Aleksandar |
send me a mail to my private addy (you know it) and I'll send ya RDH4 on CD |
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| Alex Kitic |
Hi, Choky...
I seem to recall having chatted with you before... but I cannot find your address. Please send me an e-mail to my address... and I will reply (if that's what you ment).
Regards,
Aleksandar
:) |
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| audiousername |
| Alex, there's that forum e-mail thinggy. You can click on the e-mail button under choky's post. |
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| choky |
| quote: | Originally posted by Alex Kitic
Hi, Choky...
I seem to recall having chatted with you before... but I cannot find your address. Please send me an e-mail to my address... and I will reply (if that's what you ment).
Regards,
Aleksandar
:) |
I send ya mail at "marketing............"
if that is not good enough,you can reach me via forum mail servicce or directly at
chokyATeunet.yu
hehe-I'm glad that you didn't try to translate "I mi konja za trku imamo " in our foreign affair minister's style ;)
cheers to all |
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| moamps |
| quote: | | "I mi konja za trku imamo " |
The right horse for the course. ;)
Pozdrav,
Milan |
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| choky |
| quote: | Originally posted by moamps
The right horse for the course. ;)
Pozdrav,
Milan |
:D |
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| choky |
| quote: | Originally posted by Alex Kitic
Hi, Choky...
I seem to recall having chatted with you before... but I cannot find your address. Please send me an e-mail to my address... and I will reply (if that's what you ment).
Regards,
Aleksandar
:) |
did you received my mail at your "marketing........" addy ? |
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| Alex Kitic |
Hi to everyone...
Nothing special happened on this thread for some time... is it dying? Should we start some other thread to cover "partial feedback issues"?
Thanks for the translation, Milan MoAmps... although it does not translate the feeling as it originally is. As a linguist, I was not eager to try and translate that... and repeat the errors already made by our government... :)
Thanks for the link (and invitation, I think), druze Yugovitz! I will attend shortly...
And, Audiousername... you could send me an e-mail. I think we could exchange more taughts that way.
Regards to everyone...
Aleksandar
PS
Come on, I expect to find all sorts of things on this thread by morning, when I will be watching it while I download various necessities... even foul language will do, just to keep it alive? :) Just kidding... |
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| choky |
seems I remember you sez that developing RH idea was happen' during one year ,when you were (jebes ga ,engleska vremena ce uvek ostati nepoznanica za mene ...hehe) unemployed ,when your primary
occupation was babysiting.... :clown:
after your mail ,in which you explained that things to me,I just dropped in all sorts of baaad and good things--my father died after long and bad period of illnes, my baby Isidora is born (now 10 months "old") etc.
those are the reasons why I can't put more efforts and time in hobby side of my audio and electronic activity.
I have dismantled one little Tesla stereo amp with 2x ECL82 (hehe-Teles...) waiting for da RH mode , but.........
I'm convinced that RH mode must be better than Triode or pentode mode , sollely based on my feeling for electronic (ya know ,I have that virus more than 20 yrs)
ok,stop with chating
you still didn't answered-did ya want that bloody RDH4 or not ;)
is your "marketing........." addy still valid?
cheers to all! |
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| Alex Kitic |
Choky...
Thank you very much for reminding me! Babysitting it is...
Sorry about your father -- and congratulations on your daughter!
The address marketing@... is invalid since jan2003 -- I quit that job and promised myself I would never again work as a manager or director or similia... since other jobs pay even less, I committed myself to being a free-lance professional... long story, better results, but in a country that as you know does not acknowledge the existence of free-lance professionals. When it comes to paying income taxes, I'm the first -- but when it comes to righs derived from employment (or self-employment) I'm the last. No wonder we will enter the EU somewhere in the 23rd century... but you know that story from your own point of view.
Yes, I do want the RDH4! And, my address is listed on my site... I'll try to e-mail you as soon as I return home, but that is probably going to be late evening :(
Regards to all,
Aleksandar |
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| audiousername |
Alex, It might be useful if you enable the forum e-mail thinggy (sorry, I don't know its proper name :) )
Click on 'user cp' at the top, 'edit options' and check 'no' under 'hide e-mail address?'
On the matter of RDH4, you can always set the computer to download it overnight... It is certainly worth it.
| quote: | Originally Posted by Alex Kitic
Should we start some other thread to cover "partial feedback issues"? |
Yes, that would be a most excellent idea. |
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| choky |
| quote: | Originally posted by audiousername
Alex, It might be useful if you enable the forum e-mail thinggy (sorry, I don't know its proper name :) )
Click on 'user cp' at the top, 'edit options' and check 'no' under 'hide e-mail address?'
On the matter of RDH4, you can always set the computer to download it overnight... It is certainly worth it.
Yes, that would be a most excellent idea. |
Alex is mebbe purposelly disabled this E-mail forum thingie ;)
regarding RDH4 ,it's easier that I send CD version to him,and preserve some valuable Greggggggggggggggggg's bandwith |
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| planet10 |
| quote: | Originally posted by choky
I have dismantled one little Tesla stereo amp with 2x ECL82 (hehe-Teles...) waiting for da RH mode , but......... |
I'll be very interested in this... it seems to me a good place to try RH. )i have a couple Roberts ECL82 amps...)
dave |
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| Andrewbee |
I can only say it works great with EL84's, so much so that I am buying 807's to do another amp this time not a retrofit but complete chassis.
Maybe I am a bit crazy to do this without first hearing the 807 version but this is the sound I like, very punchy and realistic (with EL84's anyway). I will try it as per Alexsanders original but also with the g2 fed from a voltage divider and perhaps also with tube regulation. I already ordered the parts which should be here on Wednesday. The only thing left to order is the opt of which I still have not decided on.
R.I.P. D.H.T.'s :devily:
Andrew |
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| planet10 |
| quote: | Originally posted by Andrewbee
so much so that I am buying 807's to do another amp |
I did note your inquiry on the JoeList. With a stash of 807s (& a Raytheon variant) i may well try it too.
My EL84 guinea pig is running now, and after i get some listening to it to get a reference i'll switch it from triode to RH.
dave |
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| audiousername |
| quote: | Originally posted by Andrewbee
R.I.P. D.H.T.'s :devily: |
But they were only recently revived from the dead! :(
What is the going rate for NOS 807 nowadays anyway? |
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| Andrewbee |
Dave,
yes I got 10 hopefully (they are being tested) coming which should last me the rest of my life. Or maybe one day I might get industrious and build a pp.
Audiousername,
They go on ebay for US$5 - US$10. each but you can get them from David Crittle at Retrovox for A$22.00. He has Sylvanias' in stock.
Or you could get the 12v 7 pin 1625 which is almost an 807 equivalent from A.E.S. for US$5;)
Andrew |
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| Alex Kitic |
Hi, guys!
I've been busy, as always... new developments on the RH field... RH6550 reaching a point where further thinking and trying is not necessary (except trying the pentode version)... and, I'm also working on a new RH with powerful tubes :)
But, regarding Andrewbee's confidence, I have to commit an indiscretion -- I have received a few days ago an email from a person who has finally completed his RH807... and am hereby quoting him in part:
| quote: | | It does sound very good, very close to my World Audio Design 300B PSE monoblocks. It has been built using good quality components, Tantalum resistors for signal,PIO coupling caps, Black gates for cathode bypass, Sowter SA02 output transformers, NOS RCA 807's. |
The amp looks nice, too... another reason why am I mentioning this is his suggestion for parts. What makes me a little sad is the fact that he did not state the RH807 outclassing the WAD300B PSE monoblocks... and I think that is due to a difference i power, mostly ;)
Regards to all,
Aleksandar |
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| Andrewbee |
Please keep the designs coming Alex, and I will test them for you:D
Andrew |
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| Andrewbee |
I just took a look at the Sowter SA02 and it looks to be on the small side for this application.
45mA Dc for the primary and 5Watts max @20 cycles.
I have not built so have not measured nor looked at the curves but looking at the RH807 I would the 807 think its pulling close to 60mA or so , correct me if I am wrong. So, if I am correct then that core must be more than saturated with so much current going through it.
Andrew |
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| audiousername |
Seeing as we're getting into other valves like 307A, EL34, 6550, 807 etc... I've started a new thread to continue the discussion.
This thread was originally meant for discussion of an EL84 SE design, but has grown wider than that. Having these ideas buried in another long thread makes it difficult to access for others.
Jason |
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| rickl |
I'm collecting parts for Alex's RH 84 SE. I recently picked up an old console and now have a chassis, 2 GE el84, 2 GE 12at7, and a Amperex EZ81 rectifier.
I'm sure I have a few passives in the junk box. I'll report back once I get it working.
BTW, I was able to get the existing 12ax7->el84 SE working but before I start tweaking it (removing tone controls, swap in better coupling caps, ...), just build something from scratch.
I assume this schematic is still correct.
rick |
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| planet10 |
On Saturday, we converted my Mulligan to an approximation of the RH84 using parts i had kicking around... this amp shows real promise (we had Chris' EF86/EL84 monobloks for comparison)... it is now on the bench for some fine tuning, and Chris is considering converting his monoblocks...
With Alex, Gary Pimm, & Pete Millet championing this kind of circuit it looks like the Pentode is starting to get some respect :)
I wonder now about a separate regulated supply for the screens?
dave |
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| chrisb |
| quote: | Originally posted by planet10
On Saturday, we converted my Mulligan to an approximation of the RH84 using parts i had kicking around... this amp shows real promise (we had Chris' EF86/EL84 monobloks for comparison)... it is now on the bench for some fine tuning, and Chris is considering converting his monoblocks...
With Alex, Gary Pimm, & Pete Millet championing this kind of circuit it looks like the Pentode is starting to get some respect :)
I wonder now about a separate regulated supply for the screens?
dave |
Since the "Mulligan Signature Series" consist of components from various vintage amp "organ donors" (FrankenAmp :cannotbe: ) , none of our power supply configurations will necessarily match Alex's exactly. In addition, we're playing with our own experiments on filtering options.
In any case, Dave could you retreive that cocktail napkin sketch from the paper recycle with your notes as to the revised R & C values for this particular specimen? |
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| Andrewbee |
Dave, et all,
After having built numerous versions of SE EL84 amps from triode connected to pentode to shunt feed and many variations on each theme in between, I can say that the RH mode works best of all to my ears.
I built one soon after the original thread began and have not looked back. I am not using any fancy parts, Hammond pwr trannie, solen I think coupling caps, 125ese opt's and a mixture of metal film and metal oxide resistors, basically what I had lying around.
I had my doubts about the screen supply using just a series resistor but methinks with sufficient B+ capacitance it works, as a matter of fact I know it works because I left it as is and bass is not a problem.
I was so impressed with it that I bought parts to build an 807 version including Lundahl 1663 opt's, dynamicaps, mills resistors, ASC caps in the P.S etc. I am going all out with this one. I only hope that with the fancy parts the sound does not deteriorate.
The RH 84 really is an excellent sounding amp.
Andrew |
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| rickl |
What kind of B+ are you running? I'm at 316v with about 338V at the plate of the el84.
I'm still seaching for a couple of .22uF coupling caps to complete the project. I'd really hate to spend money on this amp :D .
rick |
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| Andrewbee |
I don't remember exactly what I measured it at but am sure its within at least 5% of what is on the schematic, and am using a single 5? H choke with about 300uF. If you really want to know I will check it again but I am going to pull it apart soon to build the 807 version as I need the pwr trans :D
I usually measure the voltages and currents and write them on the schematics but did not do it this time, probably because I they were all okay and I did not intend to leave the amp as is on it recycled chassis. I pulled apart a 5v6 se amp and cut out a piece and added a plate on top for the tubes. Even the inputs connectors are still extra long and hanging out.
Andrew |
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| rickl |
Andrew,
Don't worry about the voltage values. I'll get close. I am using an existing console and I'll get the existing PS dialed in. It shouldn't be too hard.
rick |
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| Andrewbee |
Underneath, this style of wiring takes many many years of experience to accomplish so do not be disappointed if you fail to be as good as I am for many years.;)
I don't use a breadboard anymore I use this chassis instead. |
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| chrisb |
only an experienced and confident builder would trust his recycled treasure parts to wire nuts vs that pesky solder business
are those Jennifer Crock cryo-treated 6-9's silver connectors?
Seriously - I think we've all got a few projects under our belts that don't look this good under the skirt. |
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| rickl |
I like the hot glue gun work to hold down the wire. I'm always amazed at how nice some builders finish there gear.
rick |
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| Kyle K |
Can anyone tell me what the output impedance / damping factor is for the RH84? Similar to a SET?
Thanks,
Kyle |
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| Andrewbee |
Kyle,
I don't know what the output impedance is but this thing has bass, unlike your typical whimpy SET.:devilr:
It also does not suffer from that "all music sounds super smooth like a smoky jazz club" kind of washiness that the typical SET also suffers from;)
Build it and let us know what you think.
bohhwwwhahahahahahah.
Andrew |
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| planet10 |
| quote: | Originally posted by Andrewbee
Build it and let us know what you think. |
Mine Frugal-phile(tm) RH-84 is sitting sown in the car -- going to get it and hook it up to the tannoys (one with fresh tweeter also in the car)
dave |
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| Andrewbee |
Heya Dave,
sounds like a killer setup in the car :D
You should try it out in the house, its really a great amp, I've never heard Tannoys but heard much great stuff about them.
Andrew |
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| planet10 |
| quote: | Originally posted by Andrewbee
sounds like a killer setup in the car :D |
no AC doesn't play very loud... and the cable running up to the other speaker in the house restricts mobility.
| quote: | You should try it out in the house, its really a great amp, I've never heard Tannoys but heard much great stuff about them.
|
I've always wanted to listen to tannoys, so when i was offered a pair fairly cheap....
It is all hooked up and playing in the main system now... when i get my USB DAC this upcoming week, i'm going to try it directly into the RH84. BB iMac->RH84 -> Tannoy D50s.
Despite being rated at 92 dB, my 1st impression is that the 90 dB Fostex horns were more efficient.
dave |
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| Andrewbee |
Andrew| quote: | | no AC doesn't play very loud... and the cable running up to the other speaker in the house restricts mobility. |
LOL
I look forward to hearing your thoughts on the RH84 when you get your dac. I am now working on a RH807.
Is the Tannoy a multiway speaker and how does it sound?
Will you be using the BB as a music server?
I got a "new" G5 1.8GHZ from Hurricane Ivan, just needed to replace the PS and its been going since, good thing as my Flat Panel imac needs a logic bd and I was hoping to use the imac as a music server. One step forward, one step back, at least its not 2 steps back.
A mini mac would probably make a great music server, add a flat panel and a rodent, remotely administer it. Oops ! wrong forum, this should be about audio
:D |
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| planet10 |
| quote: | Originally posted by Andrewbee
Is the Tannoy a multiway speaker and how does it sound? |
8" dual concentric. I'm reserving judgement on them for awhile.
| quote: | | Will you be using the BB as a music server? |
Yes. Total cost so far $83 CAD.
| quote: | A mini mac would probably make a great music server, add a flat panel and a rodent, remotely administer it. Oops ! wrong forum, this should be about audio
:D |
Digital source -- that's audio :)
dave |
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| rickl |
I just finished building wood front and sides yesterday to my RH84. Attached is a pic. The speakers are from the same console. The backs are open.
Not sure where I'll use it but it was fun.
rick |
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| dunkelmann |
Im still working my way throgh this monster thead, but
here is my design for an EL84 Amp
http://www.solderingpoint.com/proje...6bq5compact.php
It has channel separated stabilized Mosfet Supply, no noise or hum is detectable and i think it sounds excellent.
I have made a PCB layout for it, so it can be built easily.
regards
MV |
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| Empee |
Hi !
i have a question and thought i should use this old thread as this one had the most discussion on the RH84SE design by Mr. Kitic.
Now I'm building this design as being my very first amp,
but unfortunatly I only have a pair of 10K OPT's, instead of the 5K OPT's recommended.
Is there a problem in using these ?
Cheers,
empee |
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| mach1 |
The plate curves of a pentode with approximately 10% local feedback (as per the RH84) look remarkably like those of a triode.
With a 10k opt you will therefore lose quite a lot of available power, however I imagine the amp will sound ok.
pm |
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| planet10 |
A lot of the german OPTs i've salvaged are 10k and they work fine from a sonics POV.
The ones that are in the RH84 variation i'm listening to now are 8K to 4 ohms. I'm using them with 8 ohm speakers so they are really 16k OPTs and i'm happy with how they sound (these same amps -- parafeed with trioded EF86 driver tubes), held their ground against a buddies set of AudioNote Conquerors).
dave |
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| Klimon |
| quote: | | A lot of the german OPTs i've salvaged are 10k and they work fine from a sonics POV. |
That has also been my experience + subjective power loss (volume setting) is much lower than calculations make you believe.
Simon |
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| ilimzn |
| quote: | Originally posted by kopite
Here is the best EL34 circuit, 8 watts in triode mode and sounds great. Will even drive your inefficient speakers.
http://www.lundahl.se/claus_b_se.html |
...Except it's not triode, but ultralinear... |
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| Alex Kitic |
Dear all,
Alex is back... at least for now. And, I could not stop myself from reacting to the "best circuit". Since when? And why? And according to whom?
Now that I am not bound to dial-up services any more, I might just read the rest of the thread before offending anyone or offending my own intelligence.
But,
whenever someone says "this is the best", I am almost certain that it is far from the truth.
This circuit is, as far as I have seen it, a common pentode in ultra-linear mode... so, what's new or best? The drivers asset? The power supply? The charisma of the author?
I am certain that it does not outperform any similar EL34 design! What about originality?
Regards to all,
Alex |
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| Empee |
Behold;
My very first "poweramp"
Thank you, Mr. Kitic, for the RH84SE design
and thank you all for the willingness to explain what and why.
Cheers,
Empee |
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| Akita |
| I found that you didt use the 5U4 as rectifier. Can i see your psu design? |
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| Empee |
hi there,
I guess you're not refering to my amp 'cause I usee a solid state rectifier bridge for this one.
With a transformer of sec. 250V with no centre tap this was the
easiest way to get to the 300V B+ asked for in the schematics.
I now get it to run at 297V
However,
I'm currently working on a new amp, my "model two",
which is going to have a double sec. tranny, both channels
each their own EZ81 rectifier and choke / cap.
How's that for channel seperation ?
:)
Cheers,
Empee |
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| Akita |
| What speaker you use? |
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| Empee |
Hi !
I run my little amp on various speakers,
actually I like to try every speaker I can get my hands on.
You'll be amazed how far these 5 Watts will get you !
Used it on Philips AD1065M's in open baffles (a 10" fullrange w. whizzer cone,
great on jazz), Yamaha NS10's, JBL 4208's, Eltac's and even a pair of
Fane Expanders (horn-loaded 3-way PA-monitors :smash: )
Currently I use it in my studio on a pair of Jean Marie Reynaud Menuet 1's.
Small, bookshelf-type speakers, 91dB sentitive. Great sound.
Last weekend I took my little amp to a friend and tested his Canton Ergo 1002DC's.
However only 89dB sensitive, I really got the windows shaking :devilr:
For all you bass-lovers;
Get Trentemöller's album "The Last Resort".
Track 2, "vamp".
deeeeeeeep bass
:D :D :D :D :D :D |
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| Akita |
| Thank, what a great review..! |
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| kegger |
I know it was asked if UL was tried in the RH 84 and was said no because didn't have outputs.
But if someone has SE-UL outputs, any issues implementing them on an RH 84 amp?
And what types of tweaks would one suggest to the schem to accommodate them if they will in fact workout here?
Thanks! |
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| Ty_Bower |
What are people using for the power supply choke in these RH84 amps? The schematic doesn't mention the DC resistance. The Hammond P-T158L, 15H, 75mA, 411 ohms, about $17 looks attractively priced.
Do you think I could substitute a 6CA4 for the rectifier? My power transformer has no 5 volt winding. Would I be likely to need any other component substitutions if went with a 6CA4? |
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| kegger |
A 6CA4 would be just fine, but that choke is a bit small in it's MA rating.
I wouldn't go any lower then one rated for 100ma, that resistance will knock your B+ down as well.
(For a stereo amp that is, for a mono amp 50ma should be fine)
Don't know what your power trannie is so it's hard to guess what B+ you'd get with a choke like that.
Download PSUDII power supply simulator (free, google search) plug in your values to get a good idea
of what you need to build the voltage output you desire.
But Yes a 6CA4 has more then the capabilities needed here. |
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| Empee |
The only thing I do not understand is why people choose
to use a direct heated rectifier tube on a indirect heated
tube amplifier ?
B+ will rise until the output tubes start conducting,
wich takes more time indirect heated,
putting stress on the PS caps
so you better use 450V-or-more DC rated caps,
or you might get into trouble.
Cheers,
Empee |
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| Ty_Bower |
6CA4 is indirectly heated...
only problem I might see is the effective plate resistance is about double the 5U4 (the tube recommended by Alex). |
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| mach1 |
| Could be: the 5755's high internal resistance would be well suited to this topology. |
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| vizion |
| how can we change sensitivity of the RH84 input from 1.5v to 2.0v ? |
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| rickl |
| quote: | Originally posted by Ty_Bower
6CA4 is indirectly heated...
only problem I might see is the effective plate resistance is about double the 5U4 (the tube recommended by Alex). |
I'm using a 6CA4 in my HR84. I haven't noticed any problems.
rick |
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| Empee |
looking good !!
Here's my latest version of the RH84.
The case used is from an army surplus,
in it was a 24V relais (a BIG one)
sound is brilliant, but it's the last time I use such a small housing
(I was cursing all the way through assembly!)
:-) |
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| Ty_Bower |
| Has anyone tried using a 12AZ7 tube on the front end of the RH84 amp? The schematic specifies an ECC81, but the operating characteristics of the two tubes appear very similar. |
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| ollebolle |
Here is my RH84 amp!
Thank you Alexandar for the schematic! Works great ;) |
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| Akita |
| Nice amp.....Ooop! where is your power transformer? |
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| alexg |
Newbie question:
How much current goes across the EL84 tube on this design?
Thanks. |
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| ollebolle |
| quote: | Originally posted by Akita
Nice amp.....Ooop! where is your power transformer? |
Actually, I have two of them :) Dual mono...
I had a couple of transformers taken from old tape recorders, so I thougt, why not dual mono ;)
They are mounted inside the chassi:
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| Akita |
| It look slim and firmly installed. great job! |
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| ollebolle |
Oh, by the way. My RH84 doesn't have the rh84 power supply.
My power supply uses semiconductor diodes, instead of the tube reflictor... |
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| ChrisMmm |
ollebolle,
I am looking at a RH84 build and interested in possibly using solid state PS as well. Could you possibly give details of your PS - voltages, circuit etc., I see 2 switches - some sort of standby?
Much appreciated, Chris |
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| ChrisMmm |
Completed my RH84 in the weekend, sounding good, Initially after voltage checks I hooked up to some speakers - it was SO quiet I though it wasn't working! This thing has no hum or hiss even with my 96db Fostex 208s - I paid a lot of attention to layout, keeping input wiring short and away from power supply. This is the quietest amp I have ever heard.
Power supply using FRED diodes rather than tube rectifier, tubes are Electro Harmonix and Brimar. Power and output transformers are Edcor
Couple of questions:
The B+ comes up at 281V, is there any value in tweaking the dropper resistors in the power supply to get closer to 300?
Power transformer gets fairly warm, is this unusual? Its 250-0-250v @ 250ma, 6.3v @ 4A should be plenty.
Thanks to Alex for a great design.
Cheers |
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| ChrisMmm |
Inside
No room to spare! |
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| blackeye*_0 |
ChrisMmm,
Thank you for sharing! It looks cozy inside. Did you build it as it is in the schematic? Also, perhaps you can post more impressions on the sonics when you and your amp get time.
I have some little Tannoy's that would probably do well with this design. I was looking for a simple little el84 single ended amp that I could build 4 of for biamping monoblocks. Might still be a fitting candidate....
cheers.
Mike. |
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| ChrisMmm |
Yes, other than trhe power supply followed the RH84 circuit exactly.
I initially tried them with some very old Celestion "C" speakers, much less efficient than the Fostex, still got plenty of clean sound from them.
I have been using T-amps for a couple of years, my latest one is capable of some 25watts. The RH drives the Fostex easily as loud. The bass with the RH seems fuller - have yet to decide if its as tight. Both amps have a very clean, dynamic, airy sound. Cost wise they are about the same and I prefer both to the 100watt Plinius amps I had, paired with the Fostex any way. |
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| Sheldon |
| quote: | Originally posted by ChrisMmm
The B+ comes up at 281V, is there any value in tweaking the dropper resistors in the power supply to get closer to 300?
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Unlikely.
| quote: | Originally posted by ChrisMmm
Power transformer gets fairly warm, is this unusual? |
No.
Sheldon |
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| ChrisMmm |
| Thanks Sheldon, I can get on and enjoy listening now! |
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| Empee |
Hi Sheldon,
Nice job !
I still listen to my RH84 daily, best single ended amp I build so far.
With regards to the heat in your powertranny,
I had simular problems until I tried Yeo's Da Block;
http://diyparadise.com/dablok.html
works like a charm !
I see you haven't got much space inside your amp but
you could always make a dedicated powersocket with
this DC-blocker installed (as I did....)
Cheers,
Empee |
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| ChrisMmm |
Hi,
Just made a second RH84 for a friend, again working perfectly first time!
Except - we are using a tube rectifier as per original circuit diagram this time and getting a B+ of 328V after it is full warmed up. I can add an RC filter after the LC filter to drop the voltage - do I need to? Is 328V going to damage the tubes?
Thanks. |
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| Akita |
Yes, you need to drop it to 300v, or a bit less 298v.
If your B+ is not regulated, it might shot up 10% more to around 360v when the incoming voltage fluctuation happen. For 328v to 360v, I think your el84 may not like it very much. |
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| Sheldon |
| quote: | Originally posted by ChrisMmm
Hi,
Just made a second RH84 for a friend, again working perfectly first time!
Except - we are using a tube rectifier as per original circuit diagram this time and getting a B+ of 328V after it is full warmed up. I can add an RC filter after the LC filter to drop the voltage - do I need to? Is 328V going to damage the tubes?
Thanks. |
If you are using a 5U4, you can try a 5R4 or a 5Y3. The R4 will reduce the voltage by 15-20V, the Y3, a little more.
Sheldon |
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| ChrisMmm |
Thanks guys.
Yes, using a 5UG so I will have a go with a different rectifier tube - see how that goes.
I realise now that the choke in the RH84 schematic is 20H/50ma (and I still don't understand why he had 50ma when the curcuit will pull around 100ma) but we used 15H/100ma. Its DCR is 256ohm whereas I imagine the 20H/50ma one would be twice that.
Cheers |
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| Sheldon |
| quote: | Originally posted by ChrisMmm
Thanks guys.
Yes, using a 5UG so I will have a go with a different rectifier tube - see how that goes.
I realise now that the choke in the RH84 schematic is 20H/50ma (and I still don't understand why he had 50ma when the curcuit will pull around 100ma) but we used 15H/100ma. Its DCR is 256ohm whereas I imagine the 20H/50ma one would be twice that.
Cheers |
It also depends on the DCR of the power transformer. You can plug the primary and secondary DCR, and the unloaded voltage into PSUD. With that and your choke DCR, you can get a very accurate simulation of the B+ with the program.
Sheldon |
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| ChrisMmm |
I let PSUD decide the trafo DCR as it wasn't specified. OTOH can I just put a meter across the secondary to get DCR?
Knowing the load is important too - I estimated based on 40ma x 2 for the EL84 and 10ma for the 12at7. I worked on 100ma.
Seems using a tube rectifier the voltage drop can vary by 20 volts or so.
That aside its a great tool. |
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