Hey Kitic,
Didn´t you make yourself enough impopular in the Huey thread?
Fredrik has probably never heard the RH84 so how come you know what he likes? Must be your head is filled with.....you guess😉!. Its always so nice to read your posts, must be your politeness and fine manners! Can´t understand why you are always so ignorant and aggressive? Don´t waste your time to answer as you are on my "Ignore list" from now😀.
And for you guys who think it is so much harder to build a simple SE 6B4G. It is absolutely NOT! It is still only a difference of four schottkys and a cap on the output tube sockets. Same 125ESE, same driver(but preferably not ECC81) and same PSU can be used.
I also mentioned EL84s are cheaper but 5 or 20USD will not be the big cost in an amp.
Now to make me really impopular among the RH84 friends these are the words of Don in a reply to Kitic in the Huey-thread about RH84:
"Looking at the RH84 and RH34, I see 12AT7 and 12AU7 used as the driver tubes. The 12AT7 is listed as an RF mixer tube on the GE data sheet. This is a dead giveaway that a tube has high distortion, mixers don't even work unless they are non-linear. 12AU7 probably speaks for itself. Now it may be that the 12AT7 (or 12AU7) is close to square law, like a Mosfet, due to heavy g1 "island effect", this would work well for a mixer, and would largely produce only 2nd harmonic as a triode driver with heavy loading. The large un-bypassed driver cathode resistor used also helps linearize operation.
So, without measurement data available, I would guess that the driver is producing a fair amount of 2nd harmonic with a little extra 3rd harmonic. The 2nd harmonic is anti-phase to the 2nd harmonic produced by the output tube. So some 2 H cancellation is occuring. The resultant should be an amplifier with reduced 2nd harmonic and slightly increased 3rd harmonic. Now from previous FFT experience, I would guess that this produces an amplifier with some "punch" to its sound, as long as the 3rd is not too high. This may well sound pleasing to some listeners on some types of music.
Was that so painful? Why all the Voodoo cover-up? Real measurements would of course be more illuminating. They might even tell a different story, but we will never know until someone actually makes them."
Anyway Fredrik, if you want some advice about 125ESE and other irons don´t hesitate to contact Fuling, he knows a lot. Whatever tube amp you build, I am sure you will be caught of the musicality of it.
Re: rh84
The story you tell is very captivating, that makes it even more interesting to build. If the RH sounds good build from salvaged parts I feel more confident that even I could have a chance to make it produce some noise with my modest knowledge 🙂
Thanks for the tip. I´ve registered for membership a while ago but I think their approval process is all manual and can take quite some time.
I´ll listen to that and stick to the RH design. I´m already on deep water as it is 😉 If I change course too often all I´ll get done is chatting in forums and no building. Witch wouldn’t be a disaster though, this is pretty educational 🙂
I haven’t dared to check the Lundahl Transformers out. Assumed they were way too expensive. I do have e-mailed them now and asked for prices and suggestions on suitable transformers. The LL1682 is 5.5 kΩ is intended for 4 Ω speakers. Can I use an 8 Ω speaker with this OPT without loosing too much effect. Are there any other aspects on running a pair of 8 Ω speaker on an OPT marked for 4 Ω that I should consider?
/Fredrik
Alex Kitic said:
The story you tell is very captivating, that makes it even more interesting to build. If the RH sounds good build from salvaged parts I feel more confident that even I could have a chance to make it produce some noise with my modest knowledge 🙂
revintage said:
Thanks for the tip. I´ve registered for membership a while ago but I think their approval process is all manual and can take quite some time.
planet10 said:
I´ll listen to that and stick to the RH design. I´m already on deep water as it is 😉 If I change course too often all I´ll get done is chatting in forums and no building. Witch wouldn’t be a disaster though, this is pretty educational 🙂
JimW said:
I haven’t dared to check the Lundahl Transformers out. Assumed they were way too expensive. I do have e-mailed them now and asked for prices and suggestions on suitable transformers. The LL1682 is 5.5 kΩ is intended for 4 Ω speakers. Can I use an 8 Ω speaker with this OPT without loosing too much effect. Are there any other aspects on running a pair of 8 Ω speaker on an OPT marked for 4 Ω that I should consider?
/Fredrik
The LL1663 should suit you fine. But don´t invest that much money at the start of your first build. For this type of amp stay with the Hammond Fuling recommended. The RH84 will not crank out more than just above 3W so there will be no problem.
EDIT: You will have lots of diyer friends at the westcoast. Think Bardis who is building a 6B4G SE right now is from that area. Do you want me to ask the hififorum administrator about your upcoming membership?
EDIT: You will have lots of diyer friends at the westcoast. Think Bardis who is building a 6B4G SE right now is from that area. Do you want me to ask the hififorum administrator about your upcoming membership?
revintage said:
Thanks, I have read some of his posts at hififorum.nu. I saw that there is a small meeting where they show their DIY-project in my home town in mid April, could be interesting to attend.
/Fredrik
It is a pity. I was getting used to you
I was not under that impression 🙂
It's a pity you cannot comment something on your own and have to resort to others' comments.
I invite all interested to read the comments to that. In Serbia we say, literally, "the fool is proud of what the clever is ashamed of".
Yeah, right! You just do a bit of screwing and soldering and that's it. Particularly if you are "well guided". 🙂
I just could not resist mentioning this... is that some sort of reserved Country Club or some elite organization where you need the favors of well established members in order to be accepted?!?!?!?!
Fuling said:
Interesting. I didn´t want to use Hammond cause of the frequency response. In their data sheet they state it to be 100 Hz. - 15 Khz (at full rated power, +/- 1db max. - ref. 1 Khz). But with your measurements I have changed my mind. I think I’m going to use either Hammond 125ESE or Edcore depending of witch I can find nearest.
/Fredrik
That is probably the best choice for the first time builder. You can always decide later whether it is worth the additional investment needed for higher quality OTs.
I would also encourage you to try to find 2 (a pair) SE transformers from some old radio -- that way you will get the most bang for your buck!
Forsman: As Geek pointed out the the bandwidth probably decreases quite a bit at higher power levels but an 125ESE should still be much better than 100-15k at 3 or 4W.
Forsman said:
Here are the test results of the 125ESE as performed by Joseph Esmilla of JE Labs.
Hammond 125ESE
http://members.myactv.net/~je2a3/125ESE.htm
Test bench results for the Hammond 125ESE
http://members.myactv.net/~je2a3/OPTtestbench-1.htm
Enjoy,
That sounds good enough for me 🙂Fuling said:
Thanks, very interesting reading.korneluk said:
Regards
/Fredrik
I agree. I built my RH84 with some inexpensive guitar amp transformers and it sounded very good.Alex Kitic said:
When laying out your chassis, you might want to leave a little extra room around the OPTs, so that you can 'move up' to something bigger at a later time.
Or, just build another RH with the new OPTs and gift/sell your first one- this also works well and keeps the audio collection under control...
Cheers
John
rh84
Part of the fun is building with cheap parts and surpassing more expensive amps. I just built a rh84 with the 6au6 at the front (cheaper than the ecc's these days), both tubes in pentode of course, feedbackresistor = 220K. Result is very good.
By the way, I remember having used this 6au6 pentode driver for a 6B4G se amp in the past and this combination sounded also superb. I than tried the 12HG7 pentode as driver and I remember this was a success too. Perhaps a good idea to try this on the rh84.
I am thinking of regulating the power supply for the 6au6 and the screen of the el84 with a simple IRF820 regulator. Would this be a good idea ?
Part of the fun is building with cheap parts and surpassing more expensive amps. I just built a rh84 with the 6au6 at the front (cheaper than the ecc's these days), both tubes in pentode of course, feedbackresistor = 220K. Result is very good.
By the way, I remember having used this 6au6 pentode driver for a 6B4G se amp in the past and this combination sounded also superb. I than tried the 12HG7 pentode as driver and I remember this was a success too. Perhaps a good idea to try this on the rh84.
I am thinking of regulating the power supply for the 6au6 and the screen of the el84 with a simple IRF820 regulator. Would this be a good idea ?
Re: rh84
Indeed!
I've heard an RH84 totally pwn a far, far more expensive amp more than once.
The contest was made even more amusing by the RH84 looking like it was dredged up from a river 😀
Cheers!
Jaap said:
Indeed!
I've heard an RH84 totally pwn a far, far more expensive amp more than once.
The contest was made even more amusing by the RH84 looking like it was dredged up from a river 😀
Cheers!
Re: rh84
hey-Hey!!!,
The description I read of the RH amps shows why a pentode will work very well indeed. The higher plate Z triodes seem to get favour because 'triodes are better'. I would suggest some other pentodes; 6AC7, 12HL7, 12ZBY7, 6CL6, EF184. The RH connection can be simplified by sourcing the driver B+ from a screen tap on the OPT. Instead of having the FB set by the plate load/Fb resistor interaction( and with a triode, plate Z ), we get a set amount.
cheers,
Douglas
Jaap said:
hey-Hey!!!,
The description I read of the RH amps shows why a pentode will work very well indeed. The higher plate Z triodes seem to get favour because 'triodes are better'. I would suggest some other pentodes; 6AC7, 12HL7, 12ZBY7, 6CL6, EF184. The RH connection can be simplified by sourcing the driver B+ from a screen tap on the OPT. Instead of having the FB set by the plate load/Fb resistor interaction( and with a triode, plate Z ), we get a set amount.
cheers,
Douglas
I have done a rough draft of a parts list. Mostly because I didn’t knew anything about the parts in an amplifier a short while ago. I´m not saying that I know much now either, still a novice 🙂 I´m not sure whether I suggested suitable components or if I’m way of…
There is a resistor in the circuit (100 k Ω ) that connects the plates together marked “Rfb”. What does that mean? Is it just an abbreviation for the feedback or is it a special component and not just a resistor?
Draft parts list
/Fredrik
There is a resistor in the circuit (100 k Ω ) that connects the plates together marked “Rfb”. What does that mean? Is it just an abbreviation for the feedback or is it a special component and not just a resistor?
Draft parts list
/Fredrik
Fredrik-
I just had a very quick look at your parts list.
You have a typo (?)- the 5W cathode resistor is what you list as Res Type2.
Also, if you are wiring this up point-to-point using terminal (lug) strips, and wiring to the tube sockets, you will probably find axial-lead caps more convenient than radial lead(your type 2). For instance, the cathode bypass cap ('cap o') can be an axial electrolytic (your type 5/6).
Again, I would not worry much about any 'high-end' parts for your first RH84. As long as the caps are fresh and the resistors are the right value you will get a good-sounding amp.
Then later you can play with such things as Russian PIO caps in the cap 'f' position, if that interests you. (Leave a little extra space if you think you will be using bigger caps in the future.)
Cheers
John
I just had a very quick look at your parts list.
You have a typo (?)- the 5W cathode resistor is what you list as Res Type2.
Also, if you are wiring this up point-to-point using terminal (lug) strips, and wiring to the tube sockets, you will probably find axial-lead caps more convenient than radial lead(your type 2). For instance, the cathode bypass cap ('cap o') can be an axial electrolytic (your type 5/6).
Again, I would not worry much about any 'high-end' parts for your first RH84. As long as the caps are fresh and the resistors are the right value you will get a good-sounding amp.
Then later you can play with such things as Russian PIO caps in the cap 'f' position, if that interests you. (Leave a little extra space if you think you will be using bigger caps in the future.)
Cheers
John
Basically, I do not see why would it be a bad idea... it's an improvement, probably. Just like all the interest to replace ECC81 and similia with pentodes might be an improvement of the original design.
On the other hand, I like to keep things simple and reliable. If you apply a B+ of 315V, great. If the B+ is 250V, still great, but less powerful 🙂 I like to think of something built in that forgiving manner as "in-built reliability".
And, I am not a huge fan of regulation.
If all the above were not enough, I must add that I try to make all my designs look as if they could have been designed that way 60+ years ago, when there was no sand. Of course, caps were smaller (and you would not be able to make hybrid graetz-es)... but basically you can make the caps smaller and still obtain good results.
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