Amp Deal of the Century!

adam2434

Yeah, I used a Sharpie to put a reference dot on the bass and treble knobs.

I'm going to put the RS amp with a pair of the Insignia bookshelves (that I already have and am not using) in my daughter's bedroom. Source will be a Toshiba DVD player. Won't sound half bad for about $100 total - tons better than a cheap mini system or the boombox she currently has.

Then I'll also use this for a portable system for vacations if cargo space permits.

Thanks for the heads-up on this, Madmax.

engtaz

fredv wrote: »

Just received the NOS Amperex 6GM8 tubes, they are frame grid and are very similar to the 6DJ8 family, and best of all, only costed me $4 each. Time to figure out how to squeeze in the tube and the filament transformer in the 1.6" x 4" space :-)

Let us know how it goes. Please provide how to's and pics. Tube half sticking out the top would be neat.:D

engtaz

Got 1 today. Thanks for the info and I really want to know how the tube DIY project goes.

fredv

engtaz wrote: »

Let us know how it goes. Please provide how to's and pics. Tube half sticking out the top would be neat.:D

There are 2 approaches that I am considering:
1. Install the "tube board" in the place of the receiver board. That will need to
stick out an inches out from the top cover.
2. Install the "tube board" in between the preamp and the amp board - only
1.65" x 4" to work with; however, if I remove the preampboard completely,
I will have more width to work with. If I take this route, it is quite possible
that I can enclose the tubes inside the case.

This little amp seems to have a high fun factor to those want to tinker it

hearingimpared

fredv wrote: »

There are 2 approaches that I am considering:
1. Install the "tube board" in the place of the receiver board. That will need to
stick out an inches out from the top cover.
2. Install the "tube board" in between the preamp and the amp board - only
1.65" x 4" to work with; however, if I remove the preampboard completely,
I will have more width to work with. If I take this route, it is quite possible
that I can enclose the tubes inside the case.

This little amp seems to have a high fun factor to those want to tinker it

Fred you are a true, honest-to-goodness, tinkering, audiophile. I remember when I was like that. . . 20 years ago, no arthritis, infinite patience, steady hands, gimmicks, gadgets, and junk to make and mold thing from, tools galore, and oh yeah, 50 lbs lighter!!! LOL

fredv

hearingimpared wrote: »

oh yeah, 50 lbs lighter!!! LOL

Joe,
Same same here, that's why I have time to tinker instead of chasing chicks

hearingimpared

fredv wrote: »

Joe,
Same same here, that's why I have time to tinker instead of chasing chicks

WAAAAAAAAAAAAAAAA

engtaz

I have not worked with tubes so I have no knowledge of how to get started. Thanks for offer input.

Polk65

groups.google.com
google.com
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altavista.com
yahoo.com

fredv

engtaz wrote: »

I have not worked with tubes so I have no knowledge of how to get started. Thanks for offer input.

Tell you the truth, I am not half as good as I seem to be with electronics :-)
You will be surprised how simple that will be when I post the final product

ben62670

Any idea if the op amps are any good in these? Just the power supply alone is worth the $15. What do you guys think the max clean voltage out from the op amps is?
Thanks Ben

engtaz

fredv wrote: »

Tell you the truth, I am not half as good as I seem to be with electronics :-)
You will be surprised how simple that will be when I post the final product

I been working in electronic for over 20 years but it's all been in solidstate devices. I am not a proto type designer. Looking forward to your final product.


Thanks.
engtaz

madmax

I'm anxious to see what you come up with too!
madmax

fredv

As of now,
1. speaker connection is replaced with more friendly binding posts.
2. Input are more solid gold plate RCA jack.
3. Input wire are shielded.
4. Preamp board is gone.
5. Only a 100K pot is used in place of the preamp board.
Just the above mods, the amp is a lot quieter and neutral. I tried to bypass the preamp with the original board without much success, just too much noise.
See pic 1 for how it looks at the moment.

Since it is sort of like an amp now, I hook it up to my home brew Marantz 7c pre clone that was completed a week ago. I was totally floored. I have been listening to this combo for an hour, and I am seriously consider to leave it as it is because I doubt the 6GM8 will sound anything close to the 7c clone.
See pic2 for the junk looking 7c clone and my work bench over the floor. The
box below the 7c is a box of San Miguel, so never a dull time :-)

engtaz

Nice

madmax

I like it!
madmax

adam2434

Well, I got the little system set up in my 11 year-old daughter's bedroom yesterday. She loves it! Puts a smile on my face when she rocks out with it.

I ended up getting a DVD/VCR combo so she could have TV sound with the system and also plug her karaoke machine into the player's inputs, given the single input on the RS amp.

May have to find other speakers though. The Insignia's are not magnetically shielded and distort her TV, and the speakers need to flank the TV to work ideally from a space standpoint. Also, my wife was not too happy about the black speakers sitting on my daughter's white furniture next to her white TV. Got the old "you're not going to leave them there, are you" comment. So, need to try to find some inexpensive, white shielded speakers down the road. I believe RTi4's come in white, but they're a little pricey for this application.

Anyone know if the old M3's (wedge-shape) from the mid 90's are shielded?

Polk65

I just checked my M3's and the results on the TV were psychedelic.

adam2434

Polk65 wrote: »

I just checked my M3's and the results on the TV were psychedelic.

Yeah, Polk's description didn't mention shielding either. Thanks for checking.

madmax

You can always find bucking magnets and glue onto your existing speakers to shield them.
madmax

fredv

OK, just done to switch the pre from SS to tube, turned it on, no burning smell At the beginning, it had a noticeable hum/buzz. After playing the wire routing game, it is almost all gone unless I put my ear right next to the speakers. Since the tube is new, it needs some time to burn in. Initial impression was - mid was a signficant improvement over the stock amp, high is less harsh; however, doesn't sound tubey - can be a common characteristics of the 6DJ8 family. Anyhow, here are a couple pictures of how the new pre fits in. The remaining task is to figure out how to install the pot properly so that I can close the case.

engtaz

Looking great. Now you need to teach me so I can try to do it. Thanks for all the input.

cmy330go

Impressive!

Do you have a schematic by chance?

Yashu

JBL control 1 and control 5 are shielded and come in white. The control 5s are harder to find but I understand they sound great.

The control 1 is a great budget speaker that can fit almost anywhere (even comes with wall mounts) and if you truly need bass you can get a little sub.

I would say that this amp should drive them nicely, the control 5s I would be less sure about, but the 1s would sound fine.

Any harshness in the highs that you get with this amp are just going to be magnified 1000X through the RTi4s, but the jbl's tweeter should have a sweeter sound, much better tuned for rocking out to the kinds of music kids seem to like these days.

fredv

cmy330go wrote: »

Impressive!

Do you have a schematic by chance?

Yup, if it is to difficult to read, please let me know.
- B+ is the +15V
- the 6.3 heater transformer get the AC from where used to connected
to the receier board's AC.
- output's of the tube pre (pins 1 and 6) connect to the yellow and blue wires.
I used 0.1 uF/400V caps, but since the voltage is very low (12V), almost any
low voltage will do.

As of now, the gain is about 2.3, but it is still too much, I think the cathode
bypass caps can be remove to reduce the gain to something like 1.5.

The 6GM8 tube can be mounted in any position. I mount it horizontally so that I don't need to drill hole to the top.

madmax

It doesn't show up when I click on it.
madmax

hearingimpared

madmax wrote: »

It doesn't show up when I click on it.
madmax

Same here!

fredv

I uploaded the file to http://hometown.aol.com/fvu168/rs-sch.gif
Give that a try to see you can download it. If not, I will try to post again, not sure it has anything to do with it is a gif file or now. When I select save as jpeg, stupid Photoshop created a jpeg that was 5x times as bigger than the gif!!!

The additional pot is in place now. I cut some old foam and use hot glue to glue tham in place. To my surprise, the foam melted, and guess what? It became like a mold, when all cool down, the pot was very sturdy in it's place. Last step will be cut an openning in the front of the top case, then I can all all done!!

engtaz

would not work with opera or internet explorer but did work with firefox. Could I bother you for a parts list including where to get the tube and socket.

Thanks for all you help and the extra work you are doing to help us out,
engtaz

hearingimpared

fredv wrote: »

I uploaded the file to http://hometown.aol.com/fvu168/rs-sch.gif
Give that a try to see you can download it. If not, I will try to post again, not sure it has anything to do with it is a gif file or now. When I select save as jpeg, stupid Photoshop created a jpeg that was 5x times as bigger than the gif!!!

The additional pot is in place now. I cut some old foam and use hot glue to glue tham in place. To my surprise, the foam melted, and guess what? It became like a mold, when all cool down, the pot was very sturdy in it's place. Last step will be cut an openning in the front of the top case, then I can all all done!!

STill nothing there Fred!!!!