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    Building, troubleshooting and testing of these amplifiers should only be
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Used Tube Amps, second life..

This thread started elsewhere, in a thread called Used Full Range, second life

Sylver300B said:
I'm always surprise to come to realise that many "Full Range" fans have not discovered the magic of using an appropriate tube amp, wich these drivers were designed around.. as mates.

There is something magical about a good tube amp. Still trying SS thou... next up jason ls miniAs... just got the prototype RH34 connected thhou...

dave
 

BTW

Member
2002-11-03 11:52 pm
Singapore
planet10 said:


It's early days so far... better than when just triode strapped ... next one will be prettier, parafeed and with EF86s strapped in triode. I'm really interested to try these with a regulated screen supply.

dave


Thanks Dave, please keep us posted on the RH34......, IMO the RH mode should work great with more powerful tubes like the EL34, KT88, 6550s.....
 
RH34

Dave, for fun why not post a picture of the RH34 (no upksirts tho, it's not too pretty under there right now)

Even with 6DJ8 driver quite wonderful, and after the experience with parallel feed EL84 / EF86 drivers, I can't wait to try the same with '34's: put those Mullards to the test, that's for sure.




The next 3 or 4 will be a bit tidier

While I'm not technically savy enough to understand the significance of the circuit topology over your garden variety DIY friendly SE design, and was a bit skeptical about Alex's claims for the superiority of the RH84, after building several now, I'm a big fan. The fund is trying to space the sockets close enough to allow for component lead length only for the feedback R's


Next weekend's work party, the deck - over & under

Scottie, wanna get dirty?
 
Re: RH34

chrisb said:
Dave, for fun why not post a picture of the RH34 (no upksirts tho, it's not too pretty under there right now)

I might have to split this last bit into a new thread... since it has morphed into, used tube kit, second life....

Here is the proto RH34. The chassis plate, power trafo, and choke (underneath) were from an Organ, the OPTs from an east german EL84 amp (the largest EL84 OPTs i've ever seen... the 2 sections wired in series instead of parallel made them suitable for EL34), Mullard EL34s from a Dyna ST70. input tube recycled as well as as many other parts as we could easily find. We did buy new Solen fast caps for the power supply....

dave
 

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And the major donor for a PP RH84... i was looking at this as a transformer donor for the #2 RH34 but decided it would be a shame to separate the trafo from the chokes... and if that why not recycle the chassis. With all the 9 & 7 & octal sockets all i have to do is remove stuff to get the basic layout. Tridoe strapped 6AU6 for the front end (i can generate a matched quad of those out of my tube stash, something not possible with EF86s -- triode strapped 6AU6 was suggested as a sleeper by Bill @ PEARL). The trafo has 2 high voltage windings (450-0-450 & 175-0-175) with a choke for each so it will have separate supply for drivers + screens & outputs. I'll get a nice piece of plexi machined to replace the existing front panel.

dave
 

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Hi,

Maybe I am posting on a wrong thread, but I read that on a “Used Full Range drivers, second life” BTW says that Zenlite sounds more “SET-like” than ZEN v3….

I have built and I am using ZEN v3 with Fostex 206E in ML TL enclosure. From Nelson’s articles I understood that Zen V3 shouldn’t sound so different from ZenLite? Current source is just that, or not? I am becoming tempted to try Zenlite…

In fact, I disabled the “Aleph current source” (made it constant one) on ZEN v3 and it sounds smoother. Try this first on your V3, and then compare…..

FYI, I have built a GC as well. Sounds nice, but the ZEN is better.

Regards,

Vix
 
Vix said:
Hi,

Maybe I am posting on a wrong thread, but I read that on a “Used Full Range drivers, second life” BTW says that Zenlite sounds more “SET-like” than ZEN v3….

Regards,

Vix

Hi,

I wasn't refering to the Zen v3 , never heard one before. The Zenlite is much better than the GC in the midrange, however the battery GC are better in the Highs and Bass. So if one can combine the best of both, think we'll have a SOTA SS amplifer ;)
 
JUST A REMINDER

I was informed that something new was going on with RH amps, or better, interest for the topology etc.

Just as a reminder to anyone interested, if you need a PP version (frankly, there is no need for PP versions, except already having all the parts, especially OPTs), you just have to make 2x RHxx amp and add a phase splitter in front of it.

For operational purposes, a concertina or similar phase splitter should work just fine; for more serious builders, long tail is "de rigeur" -- finally, for those obsessed with perfection, the real alternative is a phase splitting input transformer... :)

And, by the way, when you build any of the RH amps -- you might visit my site again, look for my e-mail address, and let me know how do you like it (eventually, send a photo or some comments). To satisfy my curiosity.

Regards to all seriously involved real DIY,
Aleksandar

PS
"Phew" again to all armchair "know it all" theoretical experimenters... especially the bad mannered ones!
 
Hello Alexsander,
Its been awhile.
I have just started on my RH807 (finally) but using 6l6GC's instead since the chassis I am using already has octal sockets.

I am using Softone R core OPT's and the inductance is low (13H) but its what I have. Hopefully by the weekend I will have it playing. I also took a look at the KT88 RC coupled version, I like what you have done with Rfb and its dual purpose, very clever, that one is on my list but after listening to the RH84 do not know if I will enjoy the triode connected mode anymore, I really like the pentode / tetrode RH sound.

I looked up the 807 data sheet and with 500Vp and 200Vg2, the tube pulling ~50mA it will put out ~10W which would be similar to the KT88.
Yes, its running basically all out but the 807 is a tough old transmitting tube and will survive I think.
Keep up the good work.

Andrew
 
RH88 -- RH807 considerations

Hi, Andrewbee (and all others who I already know)...

Well, the RH88 has long since evolved into a 15W class pentode connected (tetrode actually, but the difference is unimportant in this case). The only alteration to be done in respect to the "original triode mode RH88" is to connect the g2 to the B+ above the transformer, via 3.3k resistor... and you get rewarded with additional power. Of course, there is an alteration to the sound, but it is very slight and positive -- I also prefer the pentode version, as more live etc.

Most important, it's a 15W class amp (just like classes of cruisers or destroyers) and it outperforms easily any 300B amp both in power and finesse (bass in particular, he, he) -- it's power contenders are the 211/VT4C amps (approx 15-18W), and they are much easier to beat in sonic terms (I personally do not consider 211/845 amps as the "last word" in SE audiphile pleasure)...

Finally, regarding the RH807 -- I would not force that one above max. anode dissipation. That is why on various occasions I have stated that whoever is interested in the "full power" version of the amp (higher B+, more power) should opt for tough versions of the 6L6.

Regards to all,
Aleksandar
 
Dave:
What i'm really interested in is an RH-style Class A PP amp... scoping out a chassis for an EL84 one last night (repurposing a military radio transmitter).

How do you make the PP a RH style amp? I just finished Alex's RH84 amp and it is working great. Thanks Andrewbee for the help :).

My next amp I want to make a 6l6gc PP with a 12at7 (or 12au7) driver. I have a OT with 4-8-16 ohm taps and a good PS. Any RH-style suggestions?

I'm giving an old Harmon Kardon PA amp a second life :D

Thanks,
rick
 
rickl said:
How do you make the PP a RH style amp?

Build another, connecting the anode of the other output valve to the opposite side of the PP OPT (which will have to have 4x greater reflected anode-to-anode primary impedance). An easy way to get an inverted drive signal for the other 'half' is to simply tie the cathodes of the input valve together and replace the cathode resistor with a solid state CCS.
 
I am building an RH84 SE amp and would like to know:
- 1) if I could use a Single ended transformer with the UL tap and connect the screen grid via a 330R resistor?

- 2) I am using a 5670 as driver; do I calculate the operating point taking the 100k feedback resistor in the equation, is it parallel with the load resistor?
Looking at the specs, and the available voltage, the 5670 can be biased at 4 to 6 ma.

Cheers.
 
I will be curious about UBT-3 circuit!

Andrewbee said:
Alexsander,
thanks for that. I am going to the U.S.A. next month for more training so will pick up a large Power transformer and a pair of probably One Electron UBT-3 opt's and give it a try.

Andrew

I have a pair of UBT-3's coming to me soon and considering using it for RH88 amp build.

Since the primary impedance is 3k I'm wondering if a 8 ohm speaker on the 4 ohm secondary tap will reflect the necessary 6k ohm back to the output tube okay or not????

Regards, Ron
 
Re: RH88 -- RH807 considerations

Alex Kitic said:
Hi, Andrewbee (and all others who I already know)...

Well, the RH88 has long since evolved into a 15W class pentode connected (tetrode actually, but the difference is unimportant in this case). The only alteration to be done in respect to the "original triode mode RH88" is to connect the g2 to the B+ above the transformer, via 3.3k resistor... and you get rewarded with additional power. Of course, there is an alteration to the sound, but it is very slight and positive -- I also prefer the pentode version, as more live etc.

Most important, it's a 15W class amp (just like classes of cruisers or destroyers) and it outperforms easily any 300B amp both in power and finesse (bass in particular, he, he) -- it's power contenders are the 211/VT4C amps (approx 15-18W), and they are much easier to beat in sonic terms (I personally do not consider 211/845 amps as the "last word" in SE audiphile pleasure)...


Regards to all,
Aleksandar

Alex,

Do you have the full schematic for the RH88 amp including all details of the power suppy displayed somewhere that could downloaded. All I could find was the RH34 simulation. I hate to assume everything would be the same, plus it would be nice to know I'm using all the correct values/parts.

I have some One Electron UBT-3 trannys coming soon. They are 3K primary and I thought that using 8 ohm speaker on the 4 ohm tap might give the desired 6k impedance reflected back to the output tube!

Thanks for all your info! I find it very interesting to find a simple circuit tube amp that does not require a large amount of parts to build!

Regards, Ron