new to tubes, heck new to hi fidelity.

[caferacer59]

So, after being depressed about being a 55 year old guy who loves music and was listening to a crappy play 3 sonos speaker I finally manned up and perused craiglists for a few weeks, I ended up buying a Pioneer SX-750, and then a pair of Klipsch KG-4's. Its a rocking combination, that could easily blow the stained glass out of my old 1899 house. BUT.... after a few weeks, there was something off to me, the higher frequencies were fatiguing, so I went and did the Bob Crites tweeters and crossovers and it was definitely an improvement. Still as much as I like to rock out to everything from Neil Young to Portis Head, there is also my soft side, think Art Blakey, Ornette Coleman, Bud Powell, Stan Getz and the like. That said, I get back on Craiglist and look at tubes but the Fishers, the Dynaco's etc in nice shape are out of my league, but this cool guy who moved here from the Balkans last year, is building little DIY tube amps so I bought one. Its a 10 watt PushPull with 6P6S /6V6- tubes. 6 tubes in total with 3 Edcor transformers. It was inexpensive and sounds nice with the KG-4, not loud but room filling, All of that being said, as nice as it sounds its still missing the sound stage and intimacy i would like to get, so my question is, will tube rolling and spending a decent amount of money (to me), lets say up to 250 dollars on tube upgrades possibly get me closer to what I want or is in not possible with a little DIY push pull. Thanks, new guy who knows nothing.

 

[triode17]

Welcome to AK. Tube changes probably won't do what you are looking for. But if you want to try, roll the two driver tubes, they will have a more profound effect on the sound than the power tubes, IMO. Can't speak for the amp. since it's DIY, but do you have a schematic you can post? I have built with Edcor transformers before and they are quite good. Soundstage and intimacy is more a function of the speaker/ room interactions. The KG-4s are meant to project sound out a good distance because of the horn tweeter and rather high efficiency. Experiment with other speaker placements if you can and avoid placing them near walls and corners.

 

[kward]

It is definitely possible to get glorious, intimate, feather like delicacy with a small push pull amp. I have done it, for example from an old Motorola tube amp pulled from a console and reworked/refurbished. Mine used 6V6's on the outputs similar to yours. I can't comment further because I know nothing about your particular amp, but in general, building a decent sounding PP amp requires some knowledge and skill do pull off and make sound good.

+1 on posting the schematic if that's doable and if won't violate any copyright of the builder/designer.

 

[toxcrusadr]

Good advice in the above posts.

What are you using for a source? CD, vinyl, mp3...?

 

[caferacer59]

I don't have a schematic and not sure it its cool to ask the guy for it since it seems a bit proprietary in my mind but in any event thanks for the above posts, i'll probably roll the Driver tubes just to do it. I listen largely to spotify streaming through a sonos connect box and vinyl on a lower end house of Marley TT with an entry level AT stylus. The streaming sounds better than the record player. Was thinking that a small upgrade to the stylus and perhaps a separate phono pre amp might be worth it. (I don;t use the built in turntable pre amp on the pioneer, but need to with the little tube amp.

 

[ScottFan355]

I don't have a schematic and not sure it its cool to ask the guy for it since it seems a bit proprietary in my mind but in any event thanks for the above posts, i'll probably roll the Driver tubes just to do it. I listen largely to spotify streaming through a sonos connect box and vinyl on a lower end house of Marley TT with an entry level AT stylus. The streaming sounds better than the record player. Was thinking that a small upgrade to the stylus and perhaps a separate phono pre amp might be worth it. (I don;t use the built in turntable pre amp on the pioneer, but need to with the little tube amp.

Well I’m no expert but I don’t think asking for a schematic should be a problem at all. If the amp ever needed to be repaired and he wasn’t around it would make things much easier.

 

[caferacer59]

good point, i just sent an email to ask.

 

[toxcrusadr]

That's right, and besides, any technician and many amateurs could trace it out anyway on a fairly simple amp, so it's not like he's giving away a lot of secrets.

 

[Dandy]

Welcome to AK. This is right place for music lovers on a tight budget.

What driver tubes are used? And what sort of phono preamp are you using?

I second the idea of getting the schematic. When you do, please post here. I think with the Edcor transformers you've got a good chance to get this one right.

 

[Poultrygeist]

If you want intimacy consider full range single driver speakers. Outstanding with tubes and highly recommended for the jazz you crave.

 

[caferacer59]

Thanks guys I will post it. He said it was in his head but will write it out and send it to me. The builders English’s is very limited but he said he was happy to do it

I have read about single driver speakers a little bit. This suggestion is intriguing. Any, recommendations for budget conscience candidate. (Under 600 ish)

 

[caferacer59]

In regard to the question on if I use a phono preamp the answer is just the built in pre amp in the turntable

 

[caferacer59]

Here is the schematics as sent.

 

[caferacer59]

I paid 300

 

[stoutblock]

What size and shape is your listening room? Have you experimented with speaker placement? I really like most klipsch speakers but they can often be unforgiving in a close intimate arrangement. They typically need some room.

Welcome to the journey...

 

[Dandy]

It would be worth asking the maker what Edcor output transformers he used. Or the model number might be printed somewhere on them.

Then you can check if the specs match the circuit. My guess is that they do. If the builder can build without a printed schematic, he's likely to be experienced.

This schematic might be useful for comparison: https://evilscienceaudio.com/2013/10/31/push-pull-6v6-amplifier/, and it gives a suggested value for a feedback resistor.

@6DZ7, why is the 6V6 so specific in its UL requirements? Assuming the OPTs have the correct primary impedance, should the position of the screen taps matter that much?

P.s. Re the built in phono stage, you will get better results with a tube phono stage.

 

[GordonW]

This amp has no feedback implementation. Also, the 6V6 tube has a fairly specific need for a 23% UL tapped output transformer which this one may not be... most "generic" UL taps are @40%. It would be good to find out if the proper OPT was used. Edcor has one, but is it on your amp?

Without FB you'll have more distortion, a less flat frequency response, higher output impedance and less damping. Different tubes won't fix it. If the UL tap is wrong it's not getting the full power, either.

.... so, was the amp inexpensive?

No feedback could explain the lack of image/soundstaging.

Without feedback, there's no gain normalization (it's easy for the gain to be different between the channels, due to tube and other component variations). Even small gain differences (to the level of 0.5dB) between channels will throw off imaging/soundstaging- and 1dB or more difference will absolutely ruin it, IME. Not only that- but small differences in frequency response (also easy to have happen without feedback to flatten the response) will also make the soundstage "wander about" (things seem to move around on the stage, unnaturally), as sounds move from one frequency to another.

I'd prefer to see that amp have feedback (10 to 12db should be plenty)- and use a tube preamp in front of it (another 6SN7 split between the channels would be fine- set it up to have as low of a gain as reasonably possible) to make up the gain that's lost. I'd bet it would have much better soundstaging afterward. I've built tube integrated amps very similar to this design, and they've worked very well...

Regards,
Gordon.

 

[caferacer59]

The builder has a photo hosting site that goes back to about 2005. He seems to have built at least a 100 amps from the looks of it. Interesting guy his daughter is at Johns Hopkins becoming a doc, he just got to the u.s. I’ll check on the output transformer. I didn’t understand maybe but when we were hanging out listening to the amp before I bought it. He seemed very proud to NOT use negative feedback. I wasn’t even sure what that was, getting closer now (haha). To those who asked about my room size it is about 16 by 15 with 12 foot ceilings. I have moved the speakers around a lot and I agree they are not built for smaller spaces. I currenly have them as far back from the chair I sit in and about 8 inches from the wall. I don’t want to mislead, so far with the money I have spent I feel my level of fidelity achieved isn’t bad. But.... I appear to be getting addicted to what tweak next is worth it. Uh oh. Here is a pic of the room

 

[caferacer59]

No it doesn’t right, right now if the music I am listening to demands more punch I use the pioneer mostly with a digital source, I switch the speakers to the tube amp where the turntable gets more use since I have a decent jazz record collection. I am interested in the suggestion regarding small, higher sensitivity singledriver speakers to hook up to the tube amp permanently. That idea is potentially interesting and I am going to start reading up on these type speakers.

 

[kward]

A little feedback is a good thing. You need some FB otherwise bass will sound mushy and you'll probably have some mid range bloat. Also without feedback, the amp could sound quite different depending on what speakers you use. Feedback will help to lessen those differences. Also if any of the tubes are microphonic, that will kill soncis also.

Nit picky, but the 1K grid stoppers on both frontend triodes should come between the socket pin and the grid leak resistor. Also the output on the cathode of the inverter/driver should connect to the junction of the self bias resistor, grid leak resistor, and lower cathode resistor. Like this:



These wiring changes probably won't make a difference with respect to the "flat" sound you are experiencing, though.

One last thing, if you're handy with a digital meter, check the voltages at the plates and cathodes of all tubes, and the power supply. Amp could sound off or anemic, or a few other adjectives, if the stages are not biased appropriately.