• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Grounded Grid Preamp

ray bronk

Member
2005-08-22 7:10 am
Hi Guys,

Well, considering the GGP preamp to build or maybe the one from Bottlehead. Also considering just buying the Symphony Plus and be done with it. I'm not to familiar with the "tube sound." But from what I have read so far, it seems like the 12A*7 family is fairly neutral and dynamic in its sound character. That 12B4 sounds even better. I don't have the skills, and because I am a person who is blind, can't see the pics. I can solder. So I'd have to have something built up for me. Anyhow, before I tackle getting anyone of these prees, I thought I'd get some of your thoughts. Bruce's GGP doesn't have a tube rectifier. Supposedly, that's suppose to make a big difference.

Thank you for any thoughts. What improvements can I make on that preamp or some of the others I have mentioned.

Much appreciated,
Ray
 

Gordy

Disabled Account
2006-11-02 6:15 pm
Hello Ray,

I'm not sure that there is actually a true 'tube sound'. Every preamp seems to be a little different to the next.

Although I have not heard the Grounded Grid preamp from Transcendent, I have heard good reports from those that have heard it. It also seems good value at $799 factory built, so that may be your best bet.
 
Hi Ray,

Like Gordy says, every preamp sounds a little different from the other, SS or tube. I have a factory wired grounded grid and a scratch build. The difference is on the power supply, the scratch build uses tube rectification instead of SS diode on the B+ side. Guess what, in A/B comparison, they do sound slightly different!!! The GG sound is on the natural and transparent side, very different from my Marantz 7C clone which has this kind of "tubey" sound most people talk about. I hope this will help. If not, feel free to ask.
 

ray bronk

Member
2005-08-22 7:10 am
Grounded Grid

Hi Fred,

That sounds really good. I have seen preamps out there with the 12A*7 configuration. It also has a tube rectification. Supposedly, the tube sounds better than solidstate rectivication. Don't know. I guess I'll just have to get one and see. Did you do any mods to your GGP?

Ray
 
Hi Ray,

It can be the tube rectification, or it can be because of I built it :) I do like the tube rectifier (6x4) version more. I neither used any exotic parts nor modified the original design. The differences are rather minor:
1. Tube rectification vs SS
2. My B+ transformer was from an old Eico tuner which also provide the filament winding.
3. My heater supply is 6.3VDC unregulated instead of regulated 12 as in the original schematic!!
4. The output caps are different brand. Factory came with Solen, I used CDE.
5. The factory build also has the optional attenuator, and my scratch build has a cheap carbon pot. The attenuator is a clear winner here. It is much more balanced at low volume!! My El Cheapo pot probably has a wrong log curve. It has too much output in the initial turn.
6. There is no source selector in my scratch build. It has only one input!!

Other members said John Broskie's Aikido sounded even better, but I haven't finish mine. So, I really can't say one way or the other for the moment.

Cheers,
 

ray bronk

Member
2005-08-22 7:10 am
Hi Fred,

Thanks for the info. So the GGP sounds better than your "scratch" unit? You used DCE caps? Why? Just curious. If you go up to the Audiogon, under tubes, this tuy has a Symphony V2R for 448 bucks with remote. Now, he just uses the Elps pot, with Phillips caps. He uses a 6X4 rectifier. That was why I was asking about the differences in rectification. Bottlehead makes there same one, with I think tube rectification and some other stuff too. So that's where I am. Unfortunately, I will have to have someone initially build the preamp. Why don't you just get another stepped atenuator like the one in the GGP and put it in your "scratch" unit? It will make things a bit closer in comparison.

Ray.
 
Hi Ray,

Technically speaking, both the factory wired and my scratch build are Grounded Grid Preamp. They have virtually the same schematic with the difference I mentioned previously. I prefer my scratch build's to the factory wired for a slightly larger sound stage and slightly lower noise floor. The differences are very subtle. I wouldn't notice that if I didn't do A/B comparison. Quite frankly, I can't say for sure it is the 6x4 a major factor. The output caps and the carbon pot can also contribute the variation. Why I use the CDE cap? Don't laugh, when I ordered the parts from digikey, I happened to see that one fit my wallet :) It is twice as expensive as the Solen that the factory used, but nothing exotic; however, the construction definitely looks better than the Solen - the size is almost twice as big either :) Seriously, I believe a good SS rectification is just as good. For example, the B- of my scratch build is SS rectification.

I didn't audition to the V2R, but I did audition another preamp from Audio Experience. I suspect that could be the same as the V2R without the remote. That AE preamp also used 3 12AX7's. The circuitry was very very similar to most of the Marantz 7c clone such as mine. It does have the "tubey" sound and is less transparent/natural than the GG. Comparing the 2, the GG definitely sound more lively and more dynamic. Assuming the V2R is a remote version of what I auditioned, it is not bad especially for that money with the remote feature and ready to play. If you can find some friend to help you to build from the kit, go for the GG, that will be my choice.
 
Hi Ray,

According to the production description, the kit includes PNP transistors which is for used as constant current source. If you want to use it as current sink, you will have to replace the PNP by NPN which are not included in the kit. Another thing to keep in mind, this is a generic kit. You will need to determine the resistors to dial to the desired current. The 28 pages manual will tell you the "how". I didn't try, but you probably can find out what resistor values to use by going through their forum. This has to be a very common use of the kit.
 
I would steer well clear of any linestage using 12AX7 tubes, especially three of them.

Have you considered scratchbuilding a simple one stage grounded cathode linestage with (say) a 5687 or a couple of 12B4 tubes? A quick search of the forum will give you plenty of possibilities to consider.
 

ray bronk

Member
2005-08-22 7:10 am
Hi Mach1,

Why do you suggest that I steer clear of 12AU7 tubes?

I'd love to build the 12B4, except for a couple things. I can't see the schematics. I can solder, but would have to have a verbal diagram of how to build one. No one is manufacturing a 12B4 line stage in a commercial vennue. At least this way, with the grounded Grid, I can find someone to build it for me. Plus admittedly, high voltages scare me a bit. I do understand that the 12B4 sounds better than the GGP, but that's where I'm stuck.

Ray
 
I actually suggested steering well clear of 12AX7 tubes, which the YS-audio linestage you linked uses.

However, since you raised the issue, I would not rate 12AU7 as a great choice either. The octal equivalent (6SN7) or the nine pin 6CG7 would be preferable on sonic grounds. However, from your reply, it would appear that there are other factors at play in your choice of linestages, and a Foreplay or GG may well be the best compromise in this instance