Aiqin/Oldchen Tube Amps

[mjw21a]

Hmmm, one thing I neglected to mention is I'm using a cheap Chinese 4 way RCA selector box.... Cuts the input signal by roughly half. I really should look at replacing with a quality one. I'd probably see a sound quality improvement and a very large sound quality increase. If I get an IR one or maybe a preamp I could probably use it to change channels and volume all in one and use a Logitech Harmony remote to control all devices (preamp, DAB radio, Marantz CD player, TV, Apple TV etc). Need to get a DAC sometime though as the output from the cheap TV's headphone port is truly horrendous. Thinking an S.M.S.L. SD-793II could be the go. Impressed with the one I use on the computer, and sounds better than the second gen S.M.S.L. Sanskrit to me.

Oh, I replaced the Chinese 6N9PJ tubes with NOS 6H9C tubes that a mate lent me which have improved body and tone of the amp considerably. The Chinese tubes while detailed, seem to simply be missing something. Once I've had my honeymoon I'll order some Melz 6H9C's for the amp and probably a new rectifier as well. I expect things will improve still further. This system is challenging my main system for sound quality at a very small fraction of its value presently. Very very happy with it. Seems the same old story with Chinese gear though. You need to upgrade the tubes for them to sound their best. I don't mind. Amazingly good value either way. Soviet era valves are cheap and far better sounding.

 

[Poultrygeist]

I've used several cheapo switch boxes as well as a better quality Niles but never experienced any loss of input signal. All performed the same.

You'll need a preamp with a remote to control the volume.

 

[mjw21a]

Yer, this one reduces signal by roughly half of what I get bypassing it. It's a cheap eBay push button jobbing.

 

[L-82]

Some one, should creat a list of replacement or alternative tubes that we can look out for or go out and by.
It would be fun to have a list of tubes and a small review of how they sound....

 

[mjw21a]

Well, I'm impressed with inexpensive NOS Soviet era tubes in this amp. I wasn't a fan of them in my Yaqin push/pull though they sound great in the Oldchen SEP. Nice enough that I can't be bothered looking for better like I wanted to with the stock tubes in there.

 

[Poultrygeist]

Well, I'm impressed with inexpensive NOS Soviet era tubes in this amp. I wasn't a fan of them in my Yaqin push/pull though they sound great in the Oldchen SEP. Nice enough that I can't be bothered looking for better like I wanted to with the stock tubes in there.

Those Russian tubes sold by eBay vendors located in former bloc countries are excellent. I've used them in several amps and preamps and found them to sound better than some expensive vintage tubes. I go with the ones designated with an extra p and ev which denote a more robust tube specified for military applications.

Best yet they are dirt cheap. The only downside is they can take over a month to ship to the US.

 

[mjw21a]

Yeah, I get the -E, - EV, -EB, -ER long life versions. Typically as good as a tube gets and definitely dirt cheap

 

[rlaudio]

I'm interested in somehow adding remote control volume and some additional line inputs to my amp. Not sure what the best bang for the buck solution is. I don't want to mess with the simple design of just going straight to the Aiqin/Oldchen, as that was part of the draw in the first place. But I would love to be able to connect my turntable and perhaps CD player in addition to my DAC/computer setup. Schiit makes a nice inexpensive preamp that would solve the multiple input issue, but alas, it has no remote. Any thoughts?

 

[mjw21a]

Yes, a preamp would be the way to go I think

 

[Tom Bombadil]

Interesting thread. Certainly a single-ended EL34 amp for this price is attractive. That is, if it has any quality to it.

Also interesting that they run this in ultralinear mode instead of triode.

Any more experiences to report? Did that buzzing ever stop, it sounded like it was a bit more audible than one would like.

 

[bubba42]

Interesting thread. Certainly a single-ended EL34 amp for this price is attractive. That is, if it has any quality to it.

Also interesting that they run this in ultralinear mode instead of triode.

Any more experiences to report? Did that buzzing ever stop, it sounded like it was a bit more audible than one would like.

I didn't have a buzz at all.

What does ultralinear mode mean? I'm unfamiliar with that term. It seems to be a good thing https://en.wikipedia.org/wiki/Ultra-linear

 

[mjw21a]

No buzz on mine. It's dead silent at max volume unless I have my Little Bear T10 connected. The T10 is the source of noise on mine. Truly wonderful sounding amp.

My main system is push/pull due to running existing inefficient speakers. If getting an all new system though with new speakers the Oldchen amp + efficient speakers are certainly a better choice for the money.

 

[Tom Bombadil]

No buzz on mine. It's dead silent at max volume unless I have my Little Bear T10 connected. The T10 is the source of noise on mine. Truly wonderful sounding amp.

My main system is push/pull due to running existing inefficient speakers. If getting an all new system though with new speakers the Oldchen amp + efficient speakers are certainly a better choice for the money.

I'm driving 90dB speakers with a 4 wpc amp (and a small powered subwoofer) and I'm getting all of the volume I need, and more. I don't turn it up to max ... too loud. This is in my smaller system. In my primary system, I've driving 91dB speakers with an 18 wpc amp, in a large room. Again more volume than I need.

 

[mjw21a]

I'm driving 90dB speakers with a 4 wpc amp (and a small powered subwoofer) and I'm getting all of the volume I need, and more. I don't turn it up to max ... too loud. This is in my smaller system. In my primary system, I've driving 91dB speakers with an 18 wpc amp, in a large room. Again more volume than I need.

The only reason I've ever cranked up the volume was to see how noisy the amp was..... I wasn't, its surprisingly very quiet. On the other hand, which phono cartridge I run determines how much I need to turn the amp up. If the source level is lower, you need to turn your amp up more. Simple as that.

 

[bubba42]

Wow, I hooked up more efficient speakers to this and it makes a huge difference. The 93db Infinity Primus p363 worked fine, but the more efficient 98db Klipsch RF3-II really make a difference. They even get too loud with my 3.5 watt MiniWatt/TubeCube.

 

[mjw21a]

Yeah, I imagine that those would be insanely loud. My Dayton USA PS220-8's are too loud (96.5 db/w) so it's necessary to turn down the gain at the source. Thankfully my EAR 834P copy has variable gain, and my Marantz CD player also has volume control.

I no longer run my cheapo RCA selector as I found it introduced a harshness to the systems sound. Looking into a 3 way rotary switch so I can mod the amp for more inputs or possibly build a switch box now.

 

[JFRACE]

I have had 2 of these amps and have had one of them redone with caps and resistors,and then re-wired to run in triode mode only. The second one was done at the factory in triode mode only. When in their original wiring they put out about 10.5 wpc, and in triode just under 4 wpc.

On tube upgrades I've done 5U4B for the rectifier, 6CA7 for the EL34-B, and 6SN7GT (AND VARIANTS) for the 6N9P. NOS tubes were Sylvanis, RCA, Mullard and they definitely gave a different sound than the Chinese tubes.

I also have a Yaqin MC-10L and liked the sound of the SET over it. I was using Klipsch Forte II speakers and just sold them to get Vandersteen 2Ci speakers, so I wound up selling the amp as it doesn't have enough power to push these.

These are nice entry level amps that can be upgraded to hang with some of the better amps out there.

 

[mjw21a]

I have had 2 of these amps and have had one of them redone with caps and resistors,and then re-wired to run in triode mode only. The second one was done at the factory in triode mode only. When in their original wiring they put out about 10.5 wpc, and in triode just under 4 wpc.

On tube upgrades I've done 5U4B for the rectifier, 6CA7 for the EL34-B, and 6SN7GT (AND VARIANTS) for the 6N9P. NOS tubes were Sylvanis, RCA, Mullard and they definitely gave a different sound than the Chinese tubes.

I also have a Yaqin MC-10L and liked the sound of the SET over it. I was using Klipsch Forte II speakers and just sold them to get Vandersteen 2Ci speakers, so I wound up selling the amp as it doesn't have enough power to push these.

These are nice entry level amps that can be upgraded to hang with some of the better amps out there.

The Yaqin to my ears, is a bit bright . Sounds best with warm, laid back vintage speakers .

I'm running my MC10T to B&W DM16 speakers (1981) with a Wharfedale SW150 sub . This combination can make literally anything sound spectacular .

The Oldchen sounds fantastic with uncoloured, revealing and modern sounding speakers. The downside to that is that a poor recording sounds terrible . . . A good recording on the other hand will completely blow away my Yaqin system in the living room.

Then again , I picked up some lovely Pioneer CS-88A speakers (1971) the other day. They're 96.5db/w sensitivity. Sound incredible on the little T amp I tried them on. I really need to hook them up to the Oldchen for a listen. I suspect they'll sound fantastic though you never know until you try them. I've found not every speaker gets along with every amp. It's a case of mix and match.

 

[FlaCharlie]

Missed that. Sorry. I just didn't want you to send it back because of the tubes.



Speaking of tube rolling, has anyone else done any? I tried a pair of Sylvania JAN CHS 6SL7WGT preamp tubes, which seem to be, from my research, the ones that have the most 3D-like sound, which is what I am going for. They have not given me a huge leap over the stock tubes, but they do project a bit wider soundstage and have more air between the instruments. I also tried some RCA 6SL7 (clear glass) tubes. They have a very lush sound with some spectacular bass. Good tube for rock but not as refined as the JAN CHS 6SL7WGT. According to the seller, the 6SN7, not the 6SL7, is the exact replacement of the 6N9P, although he confirmed that the 6SL7 works fine. Does anyone know the difference? It seems like the 6SL7 has a tad less gain than the stock 6N9P.

I have also tried a Sylvania 5U4G for the rectifier. I did seem to dig a little deeper than the Chinese rectifier, but I didn't notice that much of an improvement.

I know I need to try many more tubes, but I wouldn't run out right away to get new tubes. I found the Oldchen itself improved my sound over the APPJ Miniwatt by about 30%; the tube upgrades only got me about 5% more at best.

Seems like lots of people on here are interested in the Chinese amps. As a result I got curious and started poking around to learn some more about some of them and came across this thread. All my experience is with vintage and DIY tube gear.

In reading some of these threads it's obvious that many of the posters are new to tubes, which is wonderful! Those of you who are tube newbies might want to check out one of the online tube data sites such as Frank's: http://tubedata.milbert.com/index.html

To my surprise they even have some of the Chinese tubes listed. They are of course, hard to decipher unless you know Chinese. The sheet for the 6N9P: http://tubedata.milbert.com/sheets/095/6/6N9P.pdf Despite the advice mentioned above from the "seller", the data sheet seems to indicate an amplification factor of 70, which is the same as a 6SL7. The 6SN7 has the same pinout and will plug into the socket but it only has a gain of 20. Sometimes two tubes can be interchanged without damage but the substitute will not operate optimally since it was designed to use different voltages and bias points.

Another very important consideration is the current draw of the tube heaters. This is probably especially critical in some of the Chinese amps since I've read claims that, in some cases, their power transformers are not particularly stout. Using tubes that draw more heater current than the originals might push them too hard and result in transformer failure. The 6SL7 draws the same heater current as the stock tube, so no problem. Heater current is one of the main things to watch out for when changing rectifiers since there is sometimes a big difference. The 5U4 family seems to be a good substitute for the 5Z3P since they both draw 3 amps.

But in the case of these amps I would suggest replacing the stock 5Z3P with a 5U4GB rectifier. Why? After looking at the data sheets of both the Chinese 5Z3P http://tubedata.milbert.com/sheets/095/5/5Z3P.pdf and the American 5Z3 http://tubedata.milbert.com/sheets/127/5/5Z3.pdf I noticed the recommendation for using a 4uf input capacitor. The schematic I saw for this amp (if accurate - perhaps one of you can confirm this) shows a 47uf input cap. Using that large a cap with the stock rectifier might lead to internal arcing and premature failure. The 5U4GB is rated at 40uf and should be much more reliable. They are very common and I find that used examples often test as new so I'd suggest just getting a couple that test strong on eBay. No need to pay a premium price.

 

[mjw21a]

Yes, I'm running all NOS Russian tubes. Good value for money.

6P3S-E for the power tubes, 6H8C for signal tubes and 5C3S for the rectifier tube. Sounds great and is cheap.