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CGV-300B Amp Results...Fun.

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A couple of months ago I bought an amp kit from Gabe and I must say that it's been a very enjoyable first tube hifi project. I'm using the amp with a set of Altec Valencia speakers in my basement studio as a secondary monitor setup as well as for listening enjoyment. This amp sounds amazingly good with great clarity and a full sound that's just right and never muddy, excellent.

Gabe did a great job of building a stereo 300b amp for a low price. I can't see how you could do it as a kit for really much less money. Due to the low price of the kit it makes getting into the sound of the SE 300b output tube reasonably inexpensive. It also gives me some budget to order some parts and to experiment trying some other tubes, filter and coupling caps. The circuit is so straightforward and simple changes while subtle are quite noticeable even though it sounds very good stock.

I was curious because of some of the stuff I've read so I changed the coupling caps from the stock orange drop types to Jensen foil. There are only 4 of them so I felt it was worth the price to experiment. Did it change the sound? Yes, in a subtle way that's quite pleasing it seems to make the overall sound smoother for lack of a better word. It doesn't seem as though the highs are reduced, just smoother.

I had some old Mullard 12AT7's on hand and I tried them in place of the Phillips JAN tubes which come with the amp. I guess I expected a bigger difference but after some experimentation and careful listening I found that I liked the JAN tubes better.

The amp is very quiet at idle, nearly dead silent. I changed the filter caps to the JJ clamp mount type which go on the top of the chassis. This gave the amp a neat appearance and freed up some room inside. Also I placed some washers between the baseplate and the chassis box to allow for some more airflow and I think this helped keep it running cooler.

The last mod I did was change the switch on the front from a power switch to a standby switch. Right now I turn the amp on and off with a switched outlet so that's not a problem. I think it's probably better to have the tubes on and warmed up before hitting them with B+ will this make a real difference?

Right now I'm driving the amp using a Mackie Big Knob controller that I use in my studio(very handy when switching between the nearfields and this setup). I would like to build a tube preamp with a phono input to use with this amp has anyone built the CGV-Pre1 kit that Gabe offers?

My amp came with EH Gold 300B output tubes. I think it sounds very good but experimenting with other ones which are available is a little costly. Has anyone done any testing comparing the Valve Art 300b to the EH Gold or the KR 300b which are much more expensive.
 
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The only other reasonably priced 300B I can think of would be the JJ. I have several pairs I have been using since about 2001 - sound great and are very reliable. I can't vouch for current production which may or may not be of comparable quality. Note filament current in the JJ is 1.5A as opposed to the more usual ~1.2A of most 300B.
 
I have read about the JJ's but I have not tried their 300b. I have used their E34L, 6L6 and ECC83's in guitar amps for years with great results. I have had a couple of problems with their 6L6's wanting to arc out on initial startup but if that doesn't happen they seem to sound good and to be very reliable.

Back when we were running the E34L's in the Marshall amps that we use with the band I would change them about every 6 months depending on how much we were playing out and using them, their cost was reasonable and they sounded very good. Now we're using the Saratov KT66 that Groove Tubes used to sell.

I've heard good and bad about the JJ 300b. Some folks seem to have good luck with them and like the sound, others say they are terrible, unreliable and rough sounding. I guess I should just buy a set and find out for myself.
 
I am using a JJ 300B now, and from the other I've tried (TJ, EH, Shuguang, Sovtek) I prefer the JJ. I have compared it with 1950's WE300B and 1990's 300B and while they sound a better on the mids, the JJ is value for money. It rocks! No harshness, no rough sound. Good out of the box already, give it a few days and it's even better.

Cheers!
 
I agree with the value for money assessment of the JJ. While it is probably somewhat circuit dependant, I have found the JJ to have a little more lower range dynamics than the EH. The EH is very listenable, however, and are what I do use in my pp 300b. The build quality of the older JJ 300b seemed to vary from tube to tube, however, the new examples I have seen looked very good. I have the JJ in a SE legacy amp, and have been very well pleased.
 
I think I'll continue to use these EH Golds for a while because they sound very good and I have them already. Later I think I'll give the JJ's a try because their price is quite reasonable. It's good to hear that their quality is going up but that's probably normal for it to take a while to get the kinks worked out on a new tube type.

That's one drawback to the 300b, getting a few types and trying them can be pretty expensive they do sound beautiful though so it's probably worth the cost.

I know in guitar amps that experimenting with various brands of output tubes has always paid off and they can sound WAY different. In this situation where the tube is being used in a linear manner are the difference much more subtle?
 
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